Joint structure, semiconductor device, method for manufacturing a joint structure, and method for manufacturing a semiconductor device

Abstract

The objective is to prevent surrounding heat-resistant components from degrading due to heat when the joining material between the first conductor and the second conductor is melted and joined, and to ensure a uniform joint. [Solution] The joint structure comprises a first conductor (110) and a second conductor (2), and a laminated jointing material (3) disposed between the first conductor and the second conductor to join the first conductor and the second conductor. The laminated jointing material (3) comprises a first jointing material layer (310) joined to the first conductor, a second jointing material layer (320) joined to the second conductor, and an auxiliary conductor plate (300) disposed between the first jointing material layer and the second jointing material layer, having a higher melting point than the first jointing material layer and the second jointing material layer. The second conductor (2) has laser (6) irradiation marks on the back surface of the surface facing the auxiliary conductor plate.

Description

Technical Field

[0001] The present invention relates to a bonding structure, a semiconductor device, a method for manufacturing a bonding structure, and a method for manufacturing a semiconductor device.

Background Art

[0002] As one method of electrically connecting a first conductor and a second conductor in a semiconductor device or the like, there is a method of melting and bonding a bonding material such as solder provided between the first conductor and the second conductor with a laser (for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] When melting the bonding material between the first conductor and the second conductor, if there are members with low heat resistance around the first conductor or the second conductor, the members with low heat resistance will deteriorate due to the heat when the bonding material is melted. Further, when irradiating a laser to melt the bonding material, the entire bonding material may not be heated to a uniform temperature, and there is a risk of non-uniform bonding.

[0005] One object of the present invention is to prevent members with low heat resistance around from deteriorating due to heat when melting and bonding the bonding material between the first conductor and the second conductor, and to perform uniform bonding.

Means for Solving the Problems

[0006] A bonding structure according to one embodiment comprises a first conductor and a second conductor, and a laminated bonding material disposed between the first conductor and the second conductor to bond the first conductor and the second conductor. The laminated bonding material comprises a first bonding material layer bonded to the first conductor, a second bonding material layer bonded to the second conductor, and an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer, having a melting point higher than the first bonding material layer and the second bonding material layer. The second conductor has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate. [Effects of the Invention]

[0007] According to the above-described embodiment, when the joining material between the first conductor and the second conductor is melted and joined, it is possible to prevent the surrounding heat-resistant components from deteriorating due to heat and to achieve a uniform joint. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1A is a plan view illustrating a joint structure according to the first embodiment, and Figure 1B is a cross-sectional view illustrating a cross-sectional configuration along the dashed line A-A' in Figure 1A. [Figure 2] Figures 2A and 2B illustrate a first method for manufacturing a jointed structure according to the first embodiment. [Figure 3] Figures 3A and 3B illustrate how heat is transferred when the bonding layer of a laminated bonding material is heated. [Figure 4] Figure 4 illustrates the thickness relationship of each layer in a laminated bonding material. [Figure 5] Figures 5A to 5C are tables illustrating examples of preferred relationships between the thickness of the auxiliary conductor plate and the bonding material layer. [Figure 6] Figure 6 is a table illustrating another example of a preferred relationship between the thickness of the auxiliary conductor plate and the bonding layer. [Figure 7] Figure 7 is a cross-sectional view illustrating a second method for manufacturing the joint structure according to the first embodiment. [Figure 8]Figures 8A and 8B are cross-sectional views illustrating a third method for manufacturing the joint structure according to the first embodiment. [Figure 9] Figure 9 is a diagram that supplements the dimensional relationship between the members to be joined and the laminated joining material in the joining structure of the first embodiment. [Figure 10] Figure 10A is a plan view illustrating a modified example of the laminated bonding material according to the first embodiment, and Figure 10B is a cross-sectional view illustrating a cross-sectional configuration along the dashed line C-C' in Figure 10A. [Figure 11] Figure 11 is a diagram illustrating an example of the configuration of a semiconductor device according to the second embodiment. [Figure 12] Figure 12 is a cross-sectional view illustrating the cross-sectional configuration along the dashed line D-D' in Figure 11. [Figure 13] Figure 13 is a circuit diagram illustrating an inverter circuit formed in a semiconductor device. [Figure 14] Figure 14 is a cross-sectional view illustrating an example of the configuration of a semiconductor device according to the third embodiment. [Figure 15] Figure 15 is a cross-sectional view illustrating an example of the configuration of a semiconductor device according to the fourth embodiment. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below with reference to the drawings. The X, Y, and Z axes in the referenced drawings are shown for the purpose of identifying the relationships between identical components shown in different drawings, such as their planes and directions. The X, Y, and Z axes are orthogonal to each other and form a right-handed system. In the following description, the direction parallel to the X axis will be referred to as the X direction, the direction parallel to the Y axis will be referred to as the Y direction, and the direction parallel to the Z axis will be referred to as the Z direction. Furthermore, when relating the X, Y, and Z directions to the directions of the arrows (positive and negative) on the illustrated X, Y, and Z axes, they will be labeled as "positive side" or "negative side."

[0010] In this specification, the Z direction may be referred to as the up and down direction. In this specification, "up" or "above" means the positive Z direction relative to a reference surface, member, position, etc., and "down" or "below" means the negative Z direction relative to a reference surface, member, position, etc. For example, when it is stated that "member B is placed on member A," member B is placed on the positive Z direction relative to member A. Also, when it is stated that "the top surface of member A," that surface includes the surface located at the positive Z end of member A and facing the positive Z direction. These directions and the names of the surfaces associated with them are used only for the sake of explanation. Depending on the mounting orientation of the semiconductor device described as an example, the correspondence with the X, Y, and Z axes may change. For example, the surface referred to as the "top surface" in this specification may be referred to as the "bottom surface" or "side surface," etc., and the names of other surfaces may change accordingly.

[0011] The aspect ratios of each component and the relative sizes of components in each figure are represented schematically and do not necessarily correspond to the actual relationships between components in semiconductor devices manufactured. For the sake of explanation, the relative sizes of components may be exaggerated, or the representation may differ from the actual external shapes of components used in semiconductor devices. Furthermore, some of the cross-sectional diagrams show the cross-sectional configuration of a structure cut by a hypothetical cutting line that cannot be accurately shown in the diagram of the semiconductor device structure, for the sake of explanation. In addition, some of the cross-sectional diagrams show only a portion of the cross-sectional configuration of a semiconductor device structure to which the present invention is applied.

[0012] The descriptions such as "not shown", "not illustrated", and "not depicted" in this specification are intended to mean that the components to which these descriptions are attached, or the reference numerals and leader lines clearly indicating those components, are not shown in the figures. For example, "a conductor not shown" means both that the part (e.g., a figure or a line) representing the conductor is not shown in the figure and that the reference numerals and leader lines clearly indicating the part corresponding to the conductor in the figure are not described in the figure. Which is intended depends on the context. Also, the reference numerals underlined in the figure indicate the entire component including a plurality of parts distinguished by a plurality of reference numerals.

[0013] (First Embodiment: Bonding Structure) FIG. 1A is a plan view illustrating a bonding structure according to the first embodiment, and FIG. 1B is a cross-sectional view illustrating a cross-sectional configuration along the dashed-dotted line A-A' in FIG. 1A. The term "bonding structure" in this specification is intended to mean a structure composed of a plurality of conductors as bonded members and a laminated bonding material 3 inserted between the bonded members and bonded to the bonded members. FIGS. 1A and 1B illustrate a bonding structure in which a conductor pattern 110 and a lead terminal 2 are used as bonded members and are bonded through the laminated bonding material 3. The laminated bonding material 3 in the illustrated bonding structure includes an auxiliary conductor plate 300, a first bonding material layer 310 laminated on the lower surface of the auxiliary conductor plate 300, and a second bonding material layer 320 laminated on the upper surface of the auxiliary conductor plate 300.

[0014] The conductor pattern 110 is a flat-shaped joined member that is laminated and disposed on the upper surface of the insulating substrate 100 in the wiring board 1 and joined to the first joining material layer 310 of the laminated joining material 3. The lead terminal 2 is one of the wiring members and is a joined member disposed above the conductor pattern 110 via the laminated joining material 3. The illustrated lead terminal 2 has a joined portion 200, a rising portion 201, and a routing portion 202. The joined portion 200 is a portion that contacts the laminated joining material 3 and is joined to the second joining material layer 320 of the laminated joining material 3. The rising portion 201 is a portion that extends in a direction opposite to the conductor pattern 110 (the +Z direction) from the end of the joined portion 200 in a plane parallel to the lower surface of the joined portion 200. The routing portion 202 is a portion between the upper end of the rising portion 201 and another joined portion or terminal portion (not shown). The shape of the routing portion 202 is not limited to a specific shape. By having a bent portion as a connection portion between the joined portion 200 and the rising portion 201 and using it for the lead terminal 2 that can be laser-irradiated with respect to the joined portion 200, the joining property (for example, joining strength, positioning accuracy, etc.) can be improved. Note that the conductor pattern 110 is an example of the first conductor (the first joined member) laminated and disposed on the insulating layer, and the lead terminal 2 is an example of the second conductor (the second joined member) electrically connected to the first conductor by the laminated joining material 3. The joining structure according to the present embodiment is applied to, for example, a semiconductor device described later with reference to FIGS. 11 to 15 and the like. The joined members in the semiconductor device are not limited to the combination of the conductor pattern 110 and the lead terminal 2 described above. The joined members in the semiconductor device may be, for example, a combination of the upper surface electrode of the semiconductor element and the lead terminal 2. Further, the joined members in the joining structure according to the present embodiment may be, for example, a combination of an external terminal of the semiconductor device (the outer terminal portion of the lead terminal) and a bus bar or the like connected to the external terminal of the semiconductor device. Further, the application target of the joining structure according to the present embodiment is not limited to the semiconductor device. Note that the conductor pattern 110 may be called the first conductor and the lead terminal 2 may be called the second conductor.

[0015] The wiring board 1 may be a laminate including an insulating substrate 100, a conductor pattern 110 disposed on the upper surface of the insulating substrate 100, and a heat dissipation layer 190 disposed on the lower surface of the insulating substrate 100. Another conductor pattern, separate from the conductor pattern 110, may be disposed on the upper surface of the insulating substrate 100. The conductor pattern 110 and the heat dissipation layer 190 may be disposed in contact with the insulating substrate 100, or they may be bonded to the insulating substrate 100 via a bonding material such as brazing material. The wiring board 1 may be, but is not limited to, a DCB (Direct Copper Bonding) substrate or an AMB (Active Metal Brazing) substrate. The conductor pattern 110 and the heat dissipation layer 190 may be called circuit conductors.

[0016] The insulating substrate 100 may be a ceramic substrate formed from a ceramic material such as aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), or a composite material of aluminum oxide (Al2O3) and zirconium oxide (ZrO2). The insulating substrate 100 may also be a substrate formed from an insulating resin such as epoxy resin in a sheet shape, a substrate impregnated with an insulating resin onto a base material such as glass fiber, or a substrate in which the surface of a flat metal core is coated with an insulating resin.

[0017] The conductor pattern 110 may be, for example, a wiring member for electrically connecting the lead terminal 2 to the electrodes of a semiconductor element arranged on the wiring board 1. The electrodes of the semiconductor element electrically connected to the lead terminal 2 via the conductor pattern 110 may be upper or lower electrodes, and may be, for example, the collector or emitter electrode of an IGBT (Insulated Gate Bipolar Transistor) element formed on the semiconductor element. The heat dissipation layer 190 is used as a heat dissipation component that conducts the heat generated by the semiconductor element arranged on the wiring board 1 to the heat sink 4. The conductor pattern 110 and the heat dissipation layer 190 are formed from metal foil made of a conductive metal such as copper (Cu) or a copper alloy, or aluminum (Al) or an aluminum alloy. The conductor pattern 110 and the heat dissipation layer 190 may also be made by using the above-mentioned metal foil as a base material and forming a coating film of nickel (Ni) or a nickel alloy on the surface of the base material, for example by plating. In other words, the conductor pattern 110 and the heat dissipation layer 190 are not limited to being formed from a single metal material, but may also have layers of multiple distinct metal materials. Furthermore, the members to be joined by the laminated joining material 3 of this embodiment are not limited to those formed from a specific metal material or having a specific structure. The heat sink 4 may be a metal plate such as copper or aluminum, and the heat sink 4 and the heat dissipation layer 190 are joined by a joining material 5 such as solder. The heat sink 4 may be one of multiple components constituting a cooler, or it may be a cooler itself.

[0018] As described above, the lead terminal 2 has a joined portion 200, a rising portion 201, and a routing portion 202. The lead terminal 2 has another joined portion or terminal portion, etc., which is not shown, at the end of the routing portion 202 in the +X direction as shown in Figures 1A and 1B. The lead terminal 2 is formed using a metal plate made of a conductive metal such as copper or copper alloy, aluminum or aluminum alloy. The lead terminal 2 may be made using the above-mentioned metal plate as the base material, with a coating film of nickel or nickel alloy formed on the surface of the base material to prevent oxidation. The coating film of nickel or nickel alloy can be formed, for example, by dry process such as sputtering, or by wet process such as wet plating. The nickel coating film contains 98 wt% or more nickel and may contain unavoidable impurities other than nickel. The nickel alloy coating film is formed (deposited) by electroless plating and may contain 2-15 wt% phosphorus (P) or boron (B). Furthermore, when at least one of the first bonding material layer 310 and the second bonding material layer 320 of the laminated bonding material 3 is a tin (Sn)-based bonding material layer, the surface material of the member to be bonded to the tin-based bonding material is preferably copper or a copper alloy that readily solid-solves with tin, or nickel or a nickel alloy, and more preferably copper or a copper alloy. A copper alloy is an alloy containing 60% or more copper, and a nickel alloy is an alloy containing 60% or more nickel. In addition, the base material of the member to be bonded, such as the lead terminal 2 and the conductor pattern 110, may be a conductive member including the metal plate or metal foil described above and a coating film covering it. In other words, the conductor as the member to be bonded is also called the base material and may include a coating film. Furthermore, as described later, the upper surface of the bonded portion 200 of the lead terminal 2 may be irradiated with a laser and have irradiation marks as a result.

[0019] The laminated bonding material 3 is a bonding member that electrically connects the conductor pattern 110 of the wiring board 1 and the portion to be bonded 200 of the lead terminal 2, and includes a first bonding material layer 310, a second bonding material layer 320, and an auxiliary conductor plate 300. In the laminated bonding material 3 illustrated in Figure 1B, the first bonding material layer 310, the auxiliary conductor plate 300, and the second bonding material layer 320 are laminated in this order from the upper surface of the conductor pattern 110 of the wiring board 1 toward the portion to be bonded 200 of the lead terminal 2. In other words, the auxiliary conductor plate 300 is positioned between the first bonding material layer 310 and the second bonding material layer 320 of the laminated bonding material 3. The first bonding material layer 310 and the second bonding material layer 320 are conductive layers made of a low-melting-point metal, which will be described later and can be used as a bonding material. The auxiliary conductor plate 300 is formed of a conductive metallic material with a higher melting point than the first bonding layer 310 and the second bonding layer 320. The first bonding layer 310 is bonded to the conductor pattern 110 of the wiring board 1 and the auxiliary conductor plate 300, and the second bonding layer 320 is bonded to the bonded portion 200 of the lead terminal 2 and the auxiliary conductor plate 300. In this specification, "bonding layer" includes an alloy layer of a low-melting-point metallic material used as a bonding material and the surface material of the member to be bonded. In other words, although the first bonding layer 310 and the second bonding layer 320 are each shown as a single layer in Figure 1B, after bonding, an alloy layer of the material of the member to be bonded and the bonding material is actually formed at the bonding interface with the member to be bonded. For example, at the bonding interface between the first bonding material layer 310 and the conductor pattern 110, an alloy layer is formed of a low-melting-point metal material used to form the first bonding material layer 310 and the surface material of the conductor pattern 110.

[0020] The materials for the first bonding layer 310 and the second bonding layer 320 can be selected from metal materials such as brazing material or solder material that melt when the members to be joined are irradiated with a laser and can be used for joining with the members to be joined. However, if the members to be joined become hot due to Joule heating when the laser is irradiated, damage to the insulating material near the members to be joined, deformation of the members to be joined, etc. may occur. For example, the joining of the conductor pattern 110 and the lead terminal 2 by the laminated bonding material 3 shown in Figures 1A and 1B is performed by irradiating the upper surface of the joined portion 200 of the lead terminal 2 from above (see Figure 2B). In this example, if the conductor pattern 110 and the insulating substrate 100 (e.g., ceramic substrate, insulating resin substrate, etc.) facing the lower surface of the conductor pattern 110 become hot when the laser is irradiated, the insulating substrate 100 may be damaged, and deformation of the lead terminal 2 may also occur. Furthermore, if one of the members to be joined is the top electrode of a semiconductor element, there is a risk that the semiconductor element may be damaged due to the top electrode becoming hot. From this viewpoint, the materials for the first bonding layer 310 and the second bonding layer 320 are preferably conductive metal materials with a melting point in the range of 100°C to 400°C, and more preferably in the range of 100°C to 300°C, in order to reduce damage to other surrounding members due to the temperature rise during laser irradiation. Such metal materials will be referred to as "low-melting-point metals" below. In addition, the low-melting-point metals used as materials for the first bonding layer 310 and the second bonding layer 320 may have a lower melting point than, for example, the insulating resin in contact with the members to be joined, if other members present around the members to be joined during laser irradiation, such as the insulating substrate 100 facing the lower surface of the conductor pattern 110, are made of insulating resin. For example, if the insulating substrate 100 is an epoxy resin substrate, its melting point (heat resistance temperature) is approximately 260°C. Therefore, if the insulating substrate 100 is an epoxy resin substrate, a low-melting-point metal may be selected as the material for the first bonding layer 310 and the second bonding layer 320, which is conductive, has a melting point in the range of 100°C to 250°C, and has good bonding properties with the conductor pattern 110 and the surface material of the lead terminals 2 of the wiring board 1 (more specifically, the surface material of the lower surface of the part to be bonded 200).

[0021] When the surface materials of the conductor pattern 110 and lead terminal 2, which are the members to be joined, are copper (Cu) or nickel (Ni), lead-free solder can be used for the first joining layer 310 and the second joining layer 320, and specifically, tin (Sn) or a tin-containing alloy (hereinafter referred to as "tin alloy") can be used. Tin contains 99 wt% or more of tin and unavoidable impurities. The tin alloy may be an alloy containing 30 wt% or more of tin, such as a tin-copper alloy, a tin-silver (Ag) alloy, a tin-bismuth (Bi) alloy, a tin-antimony (Sb) alloy, a tin-indium (In) alloy, etc., and may also contain unavoidable impurities. Table 1 shows some specific examples of the composition and melting point of tin alloys applicable to the first joining layer 310 and the second joining layer 320. [Table 1]

[0022] Furthermore, it is preferable to select low-melting-point metals for the materials of the first bonding layer 310 and the second bonding layer 320 that will not melt or soften due to the heat that may be applied to these bonding layers after bonding. When reliability testing (e.g., high-temperature storage test) of a semiconductor device to which the laminated bonding material 3 is applied is performed at 150°C, the melting point of the low-melting-point metal used for the first bonding layer 310 and the second bonding layer 320 is preferably 150°C or higher, and more preferably 200°C or higher. Also, from the viewpoint of bonding strength, the materials for the first bonding layer 310 and the second bonding layer 320 are preferably tin-silver alloys or tin-copper alloys. The first bonding layer 310 and the second bonding layer 320 may have the same composition or different compositions.

[0023] The auxiliary conductor plate 300 is a component for suppressing the direct conduction of heat generated when a laser is irradiated onto one of the members to be joined to the other member to be joined through the joining material layer, and for heating the first joining material layer 310 and the second joining material layer 320 to a uniform temperature. The auxiliary conductor plate 300 is formed of a metal or alloy that has a higher melting point and higher thermal conductivity and electrical conductivity than the first joining material layer 310 and the second joining material layer 320. The shape of the auxiliary conductor plate 300 is preferably foil-like or plate-like with a predetermined thickness. The auxiliary conductor plate 300 may have through holes, etc., as described later with reference to Figures 10A and 10B, within a range that can suppress the direct conduction of heat generated in one of the members to be joined to the other member to be joined, and can heat the first joining material layer 310 and the second joining material layer 320 to a uniform temperature. Furthermore, the auxiliary conductor plate 300 is positioned between the first bonding material layer 310 and the second bonding material layer 320, but the width of the auxiliary conductor plate 300 may be larger from the viewpoint of thermal uniformity. Conversely, the width of the auxiliary conductor plate 300 may be smaller, and the first bonding material layer 310 and the second bonding material layer 320 may be in contact around the auxiliary conductor plate 300. Also, multiple foil-shaped or plate-shaped auxiliary conductor plates 300 may be positioned between the first bonding material layer 310 and the second bonding material layer 320.

[0024] The material of the auxiliary conductor plate 300 is preferably a material that is electrically conductive, has high thermal conductivity, and has good bonding properties with the first bonding material layer 310 and the second bonding material layer 320. When the first bonding material layer 310 and the second bonding material layer 320 are tin alloys, the material of the auxiliary conductor plate 300 can be selected from, for example, copper or copper alloy, nickel or nickel alloy, silver or silver alloy, aluminum or aluminum alloy, tungsten (W), and molybdenum (Mo). These materials may also be combined, and for example, a nickel film may be coated on the surface of copper or the like by plating. Preferably, at least the surface of the auxiliary conductor plate is copper or copper alloy, nickel or nickel alloy, which readily solid-solves with tin or tin alloy used as a bonding material, and more preferably copper or copper alloy. The materials of the first bonding material layer 310 and the second bonding material layer 320 may be selected based on the material of the auxiliary conductor plate 300.

[0025] (First method for manufacturing a jointed structure according to the first embodiment) Figures 2A and 2B illustrate a first method for manufacturing a bonded structure according to the first embodiment. Figures 3A and 3B illustrate how heat is transferred when heating the bonding material layer of a laminated bonding material. The cross-sections illustrated in Figures 2A and 2B correspond to the cross-section in Figure 1B. Figure 3B may be a cross-sectional view illustrating a cross-sectional configuration along the dashed line B-B' in Figure 3A, but the hatching indicating that it is a cross-section has been omitted. Here, a first method for manufacturing a bonded structure using the conductor pattern 110 and lead terminals 2 of a wiring board 1 as members to be bonded is described, but the combination of members to be bonded is not limited to this. The combination of members to be bonded may be the electrodes on the upper surface of a semiconductor element and lead terminals, as described later with reference to Figures 11 and 12, or the external terminals and busbars of a semiconductor device, as described later with reference to Figure 15. In addition, in the first manufacturing method, multiple bonded structures may be manufactured in succession.

[0026] The first method for manufacturing the bonded structure includes an arrangement step and a joining step. The arrangement step in the first manufacturing method may be a step of stacking the first joining material sheet 311, the auxiliary conductor plate 300, the second joining material sheet 321, and the portion to be joined 200 of the lead terminal 2 on top of the conductor pattern 110 of the wiring board 1, as illustrated in Figure 2A. The first joining material sheet 311 and the second joining material sheet 321 correspond to the first joining material layer 310 and the second joining material layer 320, and may be sheets (conductor foils) made of a low-melting-point metal used as a joining material, such as tin or a tin alloy, as described above. The first joining material sheet 311, the auxiliary conductor plate 300, and the second joining material sheet 321 may be stacked separately in this order, or they may be stacked in a laminated state in which the first joining material sheet 311 and the second joining material sheet 321 are pressed onto the auxiliary conductor plate 300 in advance. The laminate formed by pressing the first bonding material sheet 311 and the second bonding material sheet 321 onto the auxiliary conductor plate 300 is an example of a laminated bonding material 3 formed by bonding the first bonding material layer, the auxiliary conductor plate 300, and the second bonding material layer together to form an integrated structure. Alternatively, a laminate formed by pressing either the first bonding material sheet 311 or the second bonding material sheet 321 onto the auxiliary conductor plate 300 may be laminated with the other of the first bonding material sheet 311 or the second bonding material sheet 321. The laminate of the first bonding material sheet 311, the auxiliary conductor plate 300, and the second bonding material sheet 321 may, for example, have the upper surface of the second bonding material sheet 321 pressed (closely attached) to the lower surface of the part 200 to be bonded to the lead terminal 2 before the arrangement process. Furthermore, the back surface of the upper surface of the conductor pattern 110 facing the auxiliary conductor plate 300, that is, the back surface of the conductor pattern 110, may be in direct contact with the insulating layer (insulating substrate 100), or it may be joined to the insulating layer by a brazing material or the like.

[0027] In the joining process, which follows the placement process, as illustrated in Figure 2B, a laser 6 is irradiated from above the portion 200 to be joined on the lead terminal 2 toward the upper surface of the portion 200 to be joined, heating and melting the second joining material sheet 321 and the first joining material sheet 311. In other words, the laser 6 is irradiated onto the back surface of the surface of the lead terminal 2 facing the auxiliary conductor plate 300, that is, the upper surface of the portion 200 to be joined on the lead terminal 2. Preferably, the irradiation conditions of the laser 6 satisfy the conditions for thermal conduction welding, in which the second joining material sheet 321 and the first joining material sheet 311 are melted and the lead terminal 2 and the conductor pattern 110 are joined via the laminated joining material 3. Thermal conduction welding is a welding method that joins by melting only the joining material, such as a low-melting-point metal, without melting the members to be joined. Preferred examples of the irradiation conditions of the laser 6 will be described later.

[0028] In the joining process, the laser is irradiated onto an irradiation area 600 corresponding to the irradiation diameter of the laser 6 within the entire upper surface of the part 200 to be joined of the lead terminal 2. The irradiation area 600 is not limited to a circle, but may also be elliptical or the like. In the part 200 to be joined of the lead terminal 2 illustrated in Figure 3A, the laser 6 is irradiated onto each of the two irradiation areas 600 under predetermined irradiation conditions that result in heat conduction welding. When the laser 6 is irradiated onto the part 200 to be joined of the lead terminal 2, the temperature within the irradiation area 600 on the part 200 rises, and heat is conducted from the part 200 to the second joining material sheet 321 of the laminated joining material 3, as illustrated by the arrows in Figure 3B. Some of the heat conducted to the second joining material sheet 321 melts the second joining material sheet 321, and the remaining heat is conducted to the auxiliary conductor plate 300. The heat conducted to the auxiliary conductor plate 300 is absorbed by the auxiliary conductor plate 300 and conducts to the first bonding material sheet 311 while diffusing within the auxiliary conductor plate 300 to the outside of the irradiation area 600, thereby melting the first bonding material sheet 311. In other words, by placing the auxiliary conductor plate 300, which has a higher melting point and better thermal conductivity than the bonding material sheets, between the first bonding material sheet 311 and the second bonding material sheet 321, it is possible to suppress the direct conduction of heat generated at the lead terminal 2 by laser irradiation to the first bonding material sheet 311 in a localized manner. Furthermore, by conducting heat within the auxiliary conductor plate 300 to the outside of the irradiation area 600, the temperature difference between the parts of the first bonding material sheet 311 and the second bonding material sheet 321 that are inside the irradiation area 600 and the parts that are outside the irradiation area 600 in a plan view can be reduced. In other words, according to the first manufacturing method of the bonded structure of this embodiment, it is possible to suppress localized excessive temperature rises in the first bonding material sheet 311 and the second bonding material sheet 321, and to uniformly heat and melt the entire first bonding material sheet 311 and the second bonding material sheet 321.

[0029] When the lead terminals 2, the second bonding sheet 321, and the auxiliary conductor plate 300 are heated and the second bonding sheet 321 melts, the surface material of the lead terminals 2 and the material of the second bonding sheet 321, and the material of the second bonding sheet 321 and the material of the auxiliary conductor plate 300, which are in contact with each other, form alloys in their respective interface layers, solidify, and are firmly bonded. Similarly, when the auxiliary conductor plate 300, the first bonding sheet 311, and the conductor pattern 110 are heated and the first bonding sheet 311 melts, the material of the auxiliary conductor plate 300 and the material of the first bonding sheet 311, and the material of the first bonding sheet 311 and the surface material of the conductor pattern 110, which are in contact with each other, form alloys in their respective interface layers, solidify, and are firmly bonded. Therefore, when the laminated bonding material 3 is heated uniformly, the alloy composition, grain size, and distribution also become uniform, resulting in good bonding performance. In contrast, if the bonding material between the members to be joined is heated unevenly, as in the case where there is no auxiliary conductor plate 300, some of the alloy formed by the surface material of the members to be joined and the bonding material material may become coarser or finer, and the distribution of each alloy also becomes uneven, resulting in a decrease in bonding performance (bonding strength). Therefore, the first manufacturing method, which allows the first bonding material sheet 311 and the second bonding material sheet 321 to be heated and melted uniformly, can achieve uniform bonding performance (e.g., bonding strength, positional accuracy, etc.) compared to conventional manufacturing methods for bonded structures that melt bonding material without the auxiliary conductor plate 300.

[0030] Furthermore, in the first manufacturing method described above, since each bonding material sheet 311, 321 is heated uniformly, the generation of voids within the bonding material layers 310, 320 during the process in which each bonding material sheet 311, 321 melts and then solidifies to become each bonding material layer 310, 320 (see Figure 1B) can be suppressed. Each bonding material layer 310, 320 includes an alloy layer formed at the bonding interface with the member to be bonded, consisting of the material of the bonding material sheets 311, 321 and the member to be bonded. For this reason, for example, a uniform alloy layer can be formed across the entire plane between the first bonding material layer 310 and the conductor pattern 110 of the wiring board 1 (bonding interface), thereby improving the bonding strength between the conductor pattern 110 and the first bonding material layer 310. Similarly, the bonding strength between the first bonding material layer 310 and the auxiliary conductor plate 300, the bonding strength between the auxiliary conductor plate 300 and the second bonding material layer 320, and the bonding between the second bonding material layer 320 and the bonded portion 200 of the lead terminal 2 are all improved. Therefore, the bonded structure manufactured by the first manufacturing method described above can improve the reliability of the bond between the conductor pattern 110 and the lead terminal 2 compared to a structure bonded with a bonding material that does not have an auxiliary conductor plate 300.

[0031] Furthermore, in the first manufacturing method described above, the laser output required to melt the second bonding material sheet 321 and the first bonding material sheet 311 can be reduced, preventing deformation, damage, etc., of the bonded portion 200 of the lead terminal 2 due to laser irradiation of the upper surface of the bonded portion 200. In addition, since the second bonding material sheet 321 and the first bonding material sheet 311 can be uniformly melted with a relatively small laser output, excessive temperature rise of the conductor pattern 110 of the wiring board 1 can be suppressed. For this reason, when an insulating substrate 100 is placed below the conductor pattern 110, which is the bonded member, as illustrated in Figure 3A, it is possible to prevent thermal damage to the insulating substrate 100, such as a decrease in adhesion between the conductor pattern 110 and the insulating substrate 100 due to the heat generated to melt the first bonding material sheet 311.

[0032] The joining of the conductor pattern 110 and the lead terminal 2 using the laminated joining material 3 according to the first embodiment is performed by irradiating the laser 6 under irradiation conditions such that the second joining material sheet 321 and the first joining material sheet 311 melt and become a heat conduction type weld, as described above. When using the laminated joining material 3, the diffusion of heat within the auxiliary conductor plate 300 allows the entire first joining material sheet 311, including the portion outside the irradiation area 600 of the laser 6, to be uniformly heated and melted. Furthermore, it is preferable that the joining material does not ablate and scatter or become depleted during this process.

[0033] Furthermore, the irradiation conditions of the laser 6 may be such that, when joining a joining material that does not include the auxiliary conductor plate 300 by melting it, a melting phenomenon may not occur in a part of the first joining material sheet 311 (the part outside the irradiation area 600). In addition, the irradiation conditions of the laser 6 may be such that a keyhole type weld may occur in part (locally). Keyhole type welding is a type of welding characterized by a high thermal energy density of the irradiated laser, which causes a depression to form on the laser-irradiated metal surface due to ablation or the like. When this depression becomes deep and forms a cavity, it is called a "keyhole," but when a keyhole is present, the joining strength becomes uneven, so it is preferable that the irradiation conditions of the laser 6 be such that the entire joined structure becomes a heat conduction welding type.

[0034] Furthermore, after laser irradiation, the upper surface of the joined portion 200 of the lead terminal 2, which is the irradiated surface, may have irradiation marks. Irradiation marks are those with a shape approximately equal to the shape of the laser irradiation area (irradiated surface shape), and are surface discoloration caused by laser irradiation, shallow depressions of several tens of micrometers in depth of 100 μm or less, melt marks, etc., and may be rougher than the flat surface other than the irradiated area. Irradiation conditions of the laser 6 such that the average depth of the irradiation marks (depressions) is greater than 100 μm may cause shape deformation near the irradiated area of ​​the joined member (lead terminal 2). For this reason, while some of the irradiation marks may be deeper than 100 μm, it is preferable that the average depth be 100 μm or less, and more preferably 50 μm or less. In other words, it is preferable that the irradiation conditions of the laser 6 be such that even if irradiation marks (depressions, melt marks) occur on the irradiated surface, their average depth is 100 μm or less (more preferably 50 μm or less).

[0035] The laser 6 used in the bonding process may, in one example, be an Nd:YAG laser with a wavelength of 1064 nm, belonging to the near-infrared region. When an Nd:YAG laser is used, the light absorption rate for copper (Cu) used in the conductor pattern 110, lead terminals 2, and auxiliary conductor plate 300 is approximately 1.5% for the fundamental wave at a wavelength of 1064 nm, and approximately 35.6% for the second harmonic at a wavelength of 532 nm. In other words, when an Nd:YAG laser is used, the light absorption rate at the lead terminals 2 is significantly improved (by approximately 24 times) by irradiating the lead terminals 2 with a laser 6 that has been shortened by wavelength conversion (in other words, the second harmonic). Therefore, when the conductors such as lead terminals 2 to be bonded by the laminated bonding material 3 are made of copper or have a coating film of nickel or the like formed on the copper surface, bonding can be performed more efficiently by using a green laser with the second harmonic (wavelength 532 nm) as the Nd:YAG laser irradiated in the bonding process. Note that the laser 6 used in the bonding process is not limited to the Nd:YAG laser described above. The wavelength of the laser 6 used in the bonding process is preferably a wavelength that has a high light absorption rate for the material of the member to be bonded, such as the lead terminal 2. For example, the wavelength of the laser 6 is preferably less than 1100 nm, and particularly preferably within the range of 500 nm to 550 nm. The laser 6 is not limited to the green laser described above, but may also be a blue laser with a wavelength of 450 nm, or a laser with yet another wavelength.

[0036] Furthermore, the laser used in the joining process may be a pulsed laser. In heat conduction welding using a pulsed laser, the maximum output energy of the laser is in the range of 900 J / Pulse to 3000 J / Pulse, and it is particularly preferable to set it to 1800 J / Pulse or higher. Note that the pulsed laser irradiated onto the member to be joined, such as the lead terminal 2, is not limited to a laser with a specific pulse width. In heat conduction welding using a pulsed laser, the longer the pulse width, the more the irradiation energy is dispersed over time, the lower the maximum temperature reached within the irradiation area 600 on the base material, and the higher the light absorption rate. The pulse width may be, for example, 2.4 ms to 4.0 ms. The laser irradiation diameter can be from 0.2 mm to 15 mm and is selected according to the joining area, but 0.3 mm to 3 mm is preferable from the viewpoint of uniform heat distribution. Furthermore, from the viewpoint of uniform heat distribution, it is preferable that the laser irradiation diameter be 1 / 10 to 1 / 2 of the length of the short side of the upper surface of the part to be joined 200. The laser 6 is circular or elliptical on the irradiation surface (i.e., the shape of the irradiation surface is circular or elliptical), and the irradiation diameter is, for example, the diameter of the laser 6 irradiated onto the upper surface of the joined portion 200 of the lead terminal 2, which is the irradiation surface, if the laser 6 is circular, and the length of its major axis if it is elliptical.

[0037] When joining members to be joined using the laminated bonding material 3 of this embodiment, the irradiation conditions of the laser 6 in the joining process can be set based on, for example, the composition and thickness of the members to be joined (e.g., the conductor pattern 110 and the lead terminal 2), the first bonding material sheet 311, the second bonding material sheet 321, the auxiliary conductor plate 300, and the composition and thickness of the insulating member placed below the members to be joined. Furthermore, the temperature of the laminated bonding material 3 during laser irradiation is preferably between T1m+5°C and T1m+30°C, and more preferably between T1m+10°C and T1m+20°C, where T1m is the melting point of the second bonding material sheet 321.

[0038] (Examples) Hereinafter, the present invention will be described in more detail with reference to embodiments of the present invention. However, the present invention is not limited to the scope of the following embodiments. FIG. 4 is a diagram illustrating the thickness relationship of each layer of the laminated bonding material. In FIG. 4, only the portions of the lead terminal 2 and the conductor pattern 110 of the wiring board 1, which are the members to be joined, that are joined by the laminated bonding material 3 are shown. As illustrated in FIG. 4, in the laminated bonding material 3 in the bonding structure of the first embodiment, it is preferable that the thickness T1 of the auxiliary conductor plate 300 is larger than the thickness T21 of the first bonding material layer 310 and the thickness T22 of the second bonding material layer 320. The thickness T1 of the auxiliary conductor plate 300 can be, for example, 0.05 mm ≦ T1 ≦ 0.5 mm. The thicknesses T21 of the first bonding material layer 310 and T22 of the second bonding material layer 320 can be 0.005 mm ≦ T21 ≦ 0.2 mm and 0.005 mm ≦ T22 ≦ 0.2 mm, respectively, and it is possible that T21 < T1 and T22 < T1. Among the relationships of the thicknesses T1, T21, and T22 of each layer satisfying such conditions, particularly preferable relationships will be described with reference to FIGS. 5 and 6. FIGS. 5A to 5C are tables explaining examples of preferable relationships between the thickness of the auxiliary conductor plate and the bonding material layer. FIG. 6 is a table explaining another example of a preferable relationship between the thickness of the auxiliary conductor plate and the bonding material layer.

[0039] The table in Figure 5A shows the combinations of the thickness T1 of the auxiliary conductor plate 300 and the thickness T2 of the bonding material layer in each of Examples 1 to 11 of the present invention. In Examples 1 to 11, the thickness T21 of the first bonding material layer 310 and the thickness T22 of the second bonding material layer 320 are the same (T21=T22=T2). The table in Figure 5B shows the results of investigating the bonding reliability for each of the 11 combinations of Examples 1 to 11, when the thickness of the lead terminal 2 irradiated with the laser 6 during the bonding process is 1.2 mm (see Figure 4). Specifically, the bonding reliability between members to be bonded by each of the laminated bonding materials 3A to 3D in the semiconductor device 10 illustrated in Figures 11 and 12, and between other similar members to be bonded was investigated. The members to be bonded were irradiated with the aforementioned 532 nm wavelength green laser at 1800 J / Pulse with an irradiation diameter of 2 mm. Furthermore, to evaluate the presence of voids or unjointed areas between the joined portion 200 of the lead terminal 2 and the conductor pattern 110, electrical resistance can be measured.

[0040] The table in Figure 5B shows the evaluation results of void fraction R(%), defined from electrical resistance, and HC (Heat Cycle) withstand capability (number of cycles) as examples of values ​​associated with joint reliability. Void fraction R(%) is the void occupancy rate within the bonding material layer, derived, for example, from electrical resistance and ultrasonic testing, and is a value indicating joint reliability. The bondability and reliability as a semiconductor module were evaluated for a bonded structure consisting of lead terminals 2, laminated bonding material 3, and conductor pattern 110. HC withstand capability (number of cycles) is the number of temperature cycles until the conductor pattern 110 and lead terminals 2 become electrically insulated (open) when a temperature load is repeatedly applied, and is a value indicating the reliability of the semiconductor module. Specifically, the HC withstand capability was defined as the number of cycles in which the resistance increased by 20% above a predetermined resistance. The temperature load was repeatedly applied in the order of 25°C, -40°C, 125°C, and 25°C, with each cycle being considered one cycle. As a result, the results shown in the table in Figure 5B were obtained for all bond locations. In the table in Figure 5B, Examples 1 to 11 are arranged in ascending order of ratio T2 / T1 to facilitate understanding the relationship between the ratio T2 / T1 (the ratio of the thickness T1 of the auxiliary conductor plate 300 to the thickness T2 of the bonding material layer) and bonding reliability. Furthermore, the meanings of "A," "B," and "C" in the table in Figure 5B, which indicate the evaluation results of the void fraction R and HC tolerance, are as shown in the table in Figure 5C. Specifically, an evaluation of "C" indicates that the required connection reliability is at least met, and an evaluation of "B" indicates that the connection reliability is within a preferred range higher than that of evaluation "C." An evaluation of "A" indicates that the connection reliability is within an even more preferred range, higher than that of evaluation "B." The comparative example in the table in Figure 5B may be a case where the conductor pattern 110 and the lead terminal 2 are joined with a single bonding material (for example, a bonding material with the same composition as the first bonding material layer 310). An evaluation of "×" for the void fraction R and HC tolerance in the comparative example indicates that the required connection reliability is not met.

[0041] From the table in Figure 5B, it was found that there is a reliable range for the ratio T2 / T1 between the thickness T1 of the auxiliary conductor plate 300 and the thickness T2 of the bonding layer. Specifically, when the thickness T21 of the first bonding layer 310 and the thickness T22 of the second bonding layer 320 are the same T2, setting the ratio within the range of 0.0125 ≤ T2 / T1 ≤ 0.6 reduces voids in the joint and improves reliability by more than 60%, thereby improving joint reliability. Furthermore, setting the ratio within the range of 0.025 ≤ T2 / T1 ≤ 0.375 further increases joint reliability, and setting it within the range of 0.06 ≤ T2 / T1 ≤ 0.125 further increases joint reliability. Moreover, the terminal temperature for the combination of thicknesses T1 and T2 where the void ratio R is evaluated as "B" is approximately 100°C, and the terminal temperature for the combination of thicknesses T1 and T2 where the void ratio R is evaluated as "A" is approximately 80°C (see Figure 5C). Therefore, by applying a combination of thicknesses T1 and T2 such that the void ratio R is rated "B" or "A", the rise in terminal temperature can be suppressed, and the effect of the heat generated during the bonding process on the surrounding insulating material can be reduced.

[0042] In addition, in the laminated bonding material 3 according to the first embodiment, the thickness T21 of the first bonding material layer 310 and the thickness T22 of the second bonding material layer 320 may be different. The table in Figure 6 shows the evaluation results of the void ratio R (%) and HC tolerance (number of cycles) for Examples 12 to 17 in which the thickness T21 of the first bonding material layer 310 and the thickness T22 of the second bonding material layer 320 are different. Examples 12 and 13 correspond to Example 6 in which the thickness T21 of the first bonding material layer 310 and the thickness T22 of the second bonding material layer 320 are the same thickness T2 (=0.005 mm), and are examples in which either the thickness T21 of the first bonding material layer 310 or the thickness T22 of the second bonding material layer 320 is thicker than the thickness T2. In other words, the ratio of the thickness of the thinner of the two bonding layers, the first bonding layer 310 and the second bonding layer 320, to the thickness T1 of the auxiliary conductor plate 300 in Examples 12 and 13 (T21 / T1 in Example 12 and T22 / T1 in Example 13) is the same as the T2 / T1 in Example 6. The evaluation results for the void fraction R and HC tolerance in Examples 12 and 13 are the same as the evaluation result for Example 6, which is "C". In addition, the evaluation results for Examples 14 and 15, which correspond to Example 7 where the evaluation results for the void fraction R and HC tolerance are expressed as "B", were also evaluated as "B", in which either the thickness T21 of the first bonding layer 310 or the thickness T22 of the second bonding layer 320 was made thicker than the thickness T2 in Example 7. Furthermore, the evaluation results for Examples 16 and 17, which correspond to Example 1 in which the evaluation results for void fraction R and HC tolerance were evaluated as "A", were also evaluated as "A", in which either the thickness T21 of the first bonding layer 310 or the thickness T22 of the second bonding layer 320 was made thicker than the thickness T2 of Example 1. In other words, the evaluation results illustrated in the table in Figure 6 suggest that even if the thickness T21 of the first bonding layer 310 and the thickness T22 of the second bonding layer 320 are different, if the ratio T2s / T1 of the thickness T2s of the thinner bonding layer to the thickness T1 of the auxiliary conductor plate 300 is within the range of T2 / T1 described above, equivalent connection reliability can be obtained regardless of the thickness of the thicker bonding layer. However, if the thicker bonding layer is too thick, it becomes difficult to uniformly melt the bonding layer during the bonding process, which may reduce the bonding reliability. For this reason, it is preferable that the thickness of the thicker bonding layer be 0.2 mm or less.

[0043] (Other manufacturing methods for the joint structure according to the first embodiment) The manufacturing method of the bonded structure according to the first embodiment is not limited to the first manufacturing method described above. Other manufacturing methods of the bonded structure according to the first embodiment will be described with reference to Figure 7, and Figures 8A and 8B. Figure 7 is a cross-sectional view illustrating a second manufacturing method of the bonded structure according to the first embodiment. Figures 8A and 8B are cross-sectional views illustrating a third manufacturing method of the bonded structure according to the first embodiment. The cross-sections illustrated in Figure 7, and Figures 8A and 8B correspond to the cross-section of Figure 2A (Figure 1B), respectively. Here, a second and third manufacturing method of a bonded structure using the conductor pattern 110 and lead terminals 2 of a wiring board 1 as members to be bonded will be described, but the combination of members to be bonded is not limited thereto. The combination of members to be bonded may be the electrodes on the upper surface of a semiconductor element and lead terminals, as described later with reference to Figures 9 and 10, or the external terminals of a semiconductor element and a busbar. Furthermore, in the second and third manufacturing methods, multiple bonded structures may be manufactured in succession.

[0044] The second method for manufacturing the bonded structure includes a placement step and a joining step, similar to the first method. In the placement step of the second method, instead of stacking the first bonding material sheet 311, auxiliary conductor plate 300, and second bonding material sheet 321 as described above, an auxiliary conductor plate 300, on which a bonding material layer of a low melting point metal is formed (film-formed) by plating or the like, is placed. That is, in the placement step of the second method, as illustrated in Figure 7, a laminate (laminated bonding material 3) is formed by integrating the first bonding material layer 312 and the second bonding material layer 322 on the lower and upper surfaces of the auxiliary conductor plate 300, and is placed between the conductor pattern 110 of the wiring board 1 and the lead terminal 2. After placing the auxiliary conductor plate 300 on which the first bonding material layer 312 and the second bonding material layer 322 are formed and the lead terminal 2 in the placement step, the joining step is performed. In the joining process, as described above, a laser 6 is irradiated from the upper surface of the part 200 to be joined of the lead terminal 2 under irradiation conditions that result in a heat conduction welding type, uniformly heating and melting the second joining material layer 322 and the first joining material layer 312, thereby joining the conductor pattern 110 and the lead terminal 2.

[0045] The first bonding material layer 312 and the second bonding material layer 322 can be formed (film-formed) not only by well-known plating methods, but also by ion plating, sputtering, or other methods that grow a film of a low-melting-point metal (e.g., tin or a tin alloy) used as a bonding material on the lower and upper surfaces of the auxiliary conductor plate 300, respectively. By using an auxiliary conductor plate 300 with the bonding material layers formed and integrated in this way, it is possible to prevent bonding defects in the subsequent bonding process due to misalignment between the bonding material and the auxiliary conductor plate 300 during the placement process. Each bonding material layer 312, 322 can be, for example, tin-plated (plating with 99 wt% or more tin) or tin-copper-based plating. In the case of tin-copper-based plating, the copper content is preferably 1 wt% to 12 wt%, and more preferably 2 wt% to 10 wt%. The thickness of each bonding material layer 312, 322 is not limited to a specific thickness, but the ratio T2s / T1 between the thickness T2s of the thinner bonding material layer 310, 320 after the bonding process and the thickness T1 of the auxiliary conductor plate 300 should be within the range of T2 / T1 described above. Furthermore, the second manufacturing method may be combined with the first manufacturing method. In other words, the first bonding material layer 312 may include a bonding material film formed on the lower surface of the auxiliary conductor plate 300 and a bonding material sheet disposed on the lower surface of the bonding material film. Similarly, the second bonding material layer 322 may include a bonding material film formed on the upper surface of the auxiliary conductor plate 300 and a bonding material sheet disposed on the upper surface of the bonding material film.

[0046] The third manufacturing method for the joint structure according to the first embodiment also includes a placement step and a joining step, similar to the first and second manufacturing methods. In the placement step of the third manufacturing method, a layer of low-melting-point metal to be used as a joining material (joining material layer) is placed on the surface of the member to be joined that faces the auxiliary conductor plate 300. That is, the placement step of the third manufacturing method includes the step of placing the joining material layer 313 on the upper surface of the conductor pattern 110 of the wiring board 1 and the step of placing the joining material layer 323 on the lower surface of the part to be joined 200 of the lead terminal 2, as illustrated in Figure 8A. The joining material layer 313 on the upper surface of the conductor pattern 110 may be a low-melting-point metal with the same composition as the first joining material sheet 311 placed on the lower surface of the auxiliary conductor plate 300. The joining material layer 323 on the lower surface of the lead terminal 2 may be a low-melting-point metal with the same composition as the second joining material sheet 321 placed on the upper surface of the auxiliary conductor plate 300. The bonding material layer 313 on the upper surface of the conductor pattern 110 and the bonding material layer 323 on the lower surface of the bonded portion 200 of the lead terminal 2 may be arranged by pressing or other means using sheet-like bonding material, or the first bonding material layer 312 and the second bonding material layer 322 used in the second manufacturing method may be formed (film-formed) and arranged. Furthermore, the first bonding material sheet 311 and the second bonding material sheet 321 may be laminated on the lower and upper surfaces of the auxiliary conductor plate 300, or the first bonding material layer 312 and the second bonding material layer 322 used in the second manufacturing method may be formed (film-formed). The auxiliary conductor plate 300 may have a bonding material layer formed on either the lower or upper surface, and a bonding material sheet arranged on the other. After the arrangement process, the bonding process is performed. In the joining process, as described above, a laser 6 is irradiated from the upper surface of the part 200 to be joined of the lead terminal 2 under irradiation conditions that result in a heat conduction welding type, uniformly heating and melting the joining material layer 323 and the second joining material sheet 321, as well as the first joining material sheet 311 and the joining material layer 313, thereby joining the conductor pattern 110 and the lead terminal 2.

[0047] The bonding material layer 313 on the upper surface of the conductor pattern 110 and the bonding material layer 323 on the lower surface of the lead terminal 2 are formed by deposition by plating, sputtering, or by pressing a sheet material, respectively. The thickness T41 of the bonding material layer 313 on the upper surface of the conductor pattern 110 and the thickness T31 of the first bonding material sheet 311 (or first bonding material layer 312) on the lower surface of the auxiliary conductor plate 300 are set so that the thickness T21 of the first bonding material layer 310 after the bonding process illustrated in Figure 8B satisfies the above-mentioned conditions. The thickness T42 of the bonding material layer 323 on the lower surface of the lead terminal 2 and the thickness T32 of the second bonding material sheet 321 (or second bonding material layer 322) on the upper surface of the auxiliary conductor plate 300 are set so that the thickness T22 of the second bonding material layer 320 after the bonding process illustrated in Figure 8B satisfies the above-mentioned conditions.

[0048] In the third manufacturing method described above with reference to Figures 8A and 8B, the first bonding material sheet 311 (or first bonding material layer 312) and the bonding material layer 313 on the upper surface of the conductor pattern 110 are preferably made of low-melting-point metals with the same composition from the viewpoint of uniformly heating and melting both, but their compositions may be different. Similarly, the second bonding material sheet 321 (or second bonding material layer 322) and the bonding material layer 323 on the lower surface of the lead terminal 2 are preferably made of low-melting-point metals with the same composition, but their compositions may be different. Furthermore, when forming (depositing) the bonding material layer 313 on the upper surface of the conductor pattern 110 by plating or the like, for example, the bonding material layer 313 may be formed on the upper surface of the conductor pattern 110 in the manufacturing process of the wiring board 1. The surface material of the conductor pattern 110 on which the bonding material layer 313 is formed may be, for example, copper or a copper alloy, or nickel or the like that coating the surface of the copper. Similarly, when forming (depositing) a bonding material layer 323 on the lower surface of the lead terminal 2 by plating or the like, for example, the bonding material layer 323 may be formed on the lower surface of the lead terminal 2 during the manufacturing process of the lead terminal 2. The surface material of the lead terminal 2 on which the bonding material layer 323 is formed may be, for example, copper or a copper alloy, or nickel or the like that coating the surface of copper. In the third manufacturing method, only one of the bonding material layer 313 on the conductor pattern 110 of the wiring board 1 and the bonding material layer 323 on the lead terminal 2 may be formed (deposited). Furthermore, if the bonding material layer 313 is formed on the conductor pattern 110, the first bonding material sheet 311 etc. on the lower surface of the auxiliary conductor plate 300 may be omitted, and if the bonding material layer 323 is formed on the lead terminal 2, the second bonding material sheet 321 etc. on the upper surface of the auxiliary conductor plate 300 may be omitted.

[0049] The manufacturing method of the joint structure according to the first embodiment is not limited to the first to third manufacturing methods described above. The joint structure may be manufactured by pre-arranging the joining material layer and auxiliary conductor plate 300 on one of the members to be joined, and then joining it with the other member to be joined on which the joining material layer has been formed. For example, first, the joining material layer 323 and auxiliary conductor plate 300 are placed (temporarily bonded) on the lower surface of the part to be joined 200 of the lead terminal 2 by pressing or heating, and the auxiliary conductor plate 300 is joined to the lead terminal 2 via the joining material layer 323. Meanwhile, the joining material layer 313 is also placed on the upper surface of the conductor pattern 110 of the wiring board 1 by pressing or film formation. Then, the lower surface of the lead terminal 2 on which the joining material layer 323 and auxiliary conductor plate 300 are laminated and the conductor pattern 110 of the wiring board 1 on which the joining material layer 313 has been formed are placed and joined. In this example, the joining material layer 313 and auxiliary conductor plate 300 may be pre-laid on the upper surface of the conductor pattern 110 of the wiring board 1.

[0050] (Supplementary information regarding the dimensions of the joint structure in the first embodiment) Figure 9 is a diagram that supplements the dimensional relationship between the members to be joined and the laminated joining material in the joining structure of the first embodiment.

[0051] In the first embodiment, it is preferable that the laminated bonding material 3 is sized such that the entire bonding surface of the member with the smaller bonding surface area among the two members to be bonded is bonded to the bonding material layer of the laminated bonding material 3. In this specification, "bonding surface" refers to the entire surface of a member to be bonded, including the bonding region with the bonding material layer of the laminated bonding material 3. There are cases where the entire bonding surface is the bonding region, and cases where the bonding surface includes the bonding region and the surrounding non-bonding region. In the example of the lead terminal 2 shown in Figure 1B, the bonding surface is the lower surface of the bonding portion 200, and the entire bonding surface is a bonding region where it is bonded to the second bonding material layer 320. Also, in the example of the conductor pattern 110 shown in Figure 1B, the bonding surface is the upper surface, and includes a bonding region where it is bonded to the first bonding material layer 310 and the surrounding non-bonding region. In the comparison between the conductor pattern 110 of the wiring board 1 shown in Figure 1B, etc., and the joined portion 200 of the lead terminal 2, the joined portion 200 of the lead terminal 2 has a smaller joined surface area. For this reason, it is preferable that the laminated bonding material 3 be sized such that the entire lower surface of the joined portion 200 of the lead terminal 2 becomes the joining area with the second bonding material layer 320. However, the dimensions of such a laminated bonding material 3 are not limited to the dimensions shown in Figure 1B, etc., where the upper surface of the second bonding material layer 320 and the lower surface of the joined portion 200 of the lead terminal 2 have substantially the same area.

[0052] The dimensions of the laminated bonding material 3 may, for example, be such that the dimension W3 of the auxiliary conductor plate 300 is larger than the dimension W2 of the joined portion 200 of the lead terminal 2, as shown in Figure 9. In such a laminated bonding material 3, the dimensions W3 of the first bonding material sheet 311 or first bonding material layer 312 and the second bonding material sheet 321 or second bonding material layer 322 before being melted by laser are also substantially the same as the dimension W3 of the auxiliary conductor plate 300 and are larger than the dimension W2 of the joined portion 200 of the lead terminal 2. For this reason, for example, even if a displacement occurs in the position of the joined portion 200 of the laminated bonding material 3 and the lead terminal 2 in a plan view of the upper surface of the conductor pattern 110 when the laminated bonding material 3 and the lead terminal 2 are placed on the conductor pattern 110 of the wiring board 1, the entire joined surface (lower surface) of the joined portion 200 of the lead terminal 2 can be joined with the second bonding material layer 320. Therefore, variations in electrical characteristics, bonding strength, etc., caused by variations in bonding area for each product (for example, for each semiconductor device 10 described later) can be suppressed. However, increasing the dimension W3 of the laminated bonding material 3 (auxiliary conductor plate 300) may lead to increased material costs and hinder miniaturization. For this reason, it is preferable that the difference between the dimension W3 of the laminated bonding material 3 (auxiliary conductor plate 300) and the dimension W2 of the bonded portion 200 of the lead terminal 2 (2 × ΔW = W3 - W2) be within the range of, for example, 0 mm to 10 mm. Although Figure 9 only illustrates the dimensional difference in the Y direction, a similar dimensional difference may also exist in the X direction.

[0053] (Modified example of the laminated bonding material of the first embodiment) Figure 10A is a plan view illustrating a modified example of the laminated bonding material according to the first embodiment, and Figure 10B is a cross-sectional view illustrating the cross-sectional configuration along the dashed line C-C' in Figure 10A. Note that in Figure 10B, hatching indicating that each component is a cross-section has been omitted.

[0054] The laminated bonding material 3 according to the first embodiment suppresses direct and localized heat conduction to the first bonding material sheet 311, etc., by diffusing the heat conducted from the lead terminals 2 to the auxiliary conductor plate 300 via the second bonding material sheet 321, etc., within the auxiliary conductor plate 300. In other words, the auxiliary conductor plate 300 of the laminated bonding material 3 only needs to have a shape that can suppress direct and localized heat conduction to the first bonding material sheet 311, etc., and is not limited to the shape with flat top and bottom surfaces exemplified in Figure 1B, etc. For example, the auxiliary conductor plate 300 may have a through hole 301 that penetrates from the top surface to the bottom surface, as shown in Figures 10A and 10B. Furthermore, it is preferable to make the hole diameter R2 of the through hole 301 smaller than the dimensions of the laser irradiation area 600 (irradiation diameter R1), so that a portion of the heat in the irradiation area 600 is conducted to the auxiliary conductor plate 300 and diffused within the auxiliary conductor plate 300. The diameter R2 of the through hole 301 is preferably within the range of R1 / 10 to R1 / 2. Within this range, direct and local heat conduction to the first bonding material sheet 311 or the first bonding material layer 312 can be suppressed. Therefore, compared to the case where the auxiliary conductor plate 300 is not placed, direct and local heat conduction to the part of the bonding material close to the bonding interface with the conductor pattern 110 of the wiring board 1 is suppressed. Furthermore, as the bonding material placed above and below the auxiliary conductor plate 300 melts and enters the through hole 301, after the bonding process, the first bonding material layer 310 and the second bonding material layer 320 become integrated by the bonding material 330 in the through hole 301 of the auxiliary conductor plate 300. Therefore, although it has inferior heat uniformity compared to an auxiliary conductive plate that does not have plate-shaped through holes, it makes it less likely for delamination to occur at the interface between the first bonding material layer 310 and the auxiliary conductor plate 300, or at the interface between the second bonding material layer 320 and the auxiliary conductor plate 300.

[0055] The position of the through-hole 301 is not limited to a position within the laser irradiation area 600 as illustrated in Figures 10A and 10B. When using an auxiliary conductor plate 300 with a through-hole 301, for example, if the through-hole 301 is formed at a position offset from the center of the laser irradiation area 600 so that it does not partially or completely overlap with the irradiation area 600 in a plan view, it is preferable to suppress direct and local heat conduction to the first bonding material sheet 311, etc. Alternatively, instead of a through-hole 301, a notch may be provided at a position that is the end of the auxiliary conductor plate 300 (for example, a corner) in a plan view, and the first bonding material layer 310 below the auxiliary conductor plate 300 and the second bonding material layer 320 above it may be integrated by a bonding material 330 along the notch. The auxiliary conductor plate 300 is primarily intended to suppress direct and localized heat conduction from one joined member (lead terminal 2) to the other joined member (conductor pattern 110), and to uniformly heat the joining material (low melting point metal) by heat diffusion within the auxiliary conductor plate 300. Therefore, a laminated joining material 3 using a cloth-like or mesh-like member containing metal fibers as the auxiliary conductor plate 300 does not have a significant effect in suppressing direct and localized heat conduction to the first joining material sheet 311 or the first joining material layer 312 compared to a configuration using a flat plate-shaped auxiliary conductor plate 300, or a flat plate with small through holes or notches in a portion thereof.

[0056] The laminated bonding material 3 in the bonding structure of the first embodiment is not limited to the three-layer structure described above. The laminated bonding material 3 may have a configuration in which a plurality of auxiliary conductor plates 300 are alternately laminated with the bonding material layers between the first bonding material layer 310 and the second bonding material layer 320. In this example, the plurality of auxiliary conductor plates 300 may be the same in material and shape (thickness), or two or more types of auxiliary conductor plates with different materials or shapes may be combined. Furthermore, the first bonding material layer 310 and the second bonding material layer 320 in the laminated bonding material 3 are not limited to the same material, but may be made of different materials depending on, for example, the surface material of the member to be joined to the first bonding material layer 310 and the surface material of the member to be joined to the second bonding material layer 320.

[0057] The bonded structure and its manufacturing method described in the first embodiment can be applied, for example, to semiconductor devices and their manufacturing methods used in power conversion devices such as inverter devices for vehicles or other industrial applications. Examples of semiconductor devices to which the bonded structure according to the first embodiment can be applied are described below as the second to fourth embodiments. In this specification, "semiconductor device" refers to a semiconductor element, sometimes called a semiconductor chip or die, sealed with an insulating material, and may also be called a "semiconductor module," etc. Furthermore, the second to fourth embodiments described below are merely examples of semiconductor devices to which the bonded structure according to the first embodiment can be applied. The bonded structure and its manufacturing method described in the first embodiment can be applied to various semiconductor devices, or other devices or structures, that have a bonded structure in which members to be joined are joined by thermal conduction welding using a bonding material, and which are not described in detail in this specification.

[0058] (Second embodiment: Semiconductor device) Figure 11 is a plan view illustrating an example of the configuration of a semiconductor device according to the second embodiment. Figure 12 is a cross-sectional view illustrating a cross-sectional configuration along the dashed line D-D' in Figure 11. Figure 13 is a circuit diagram illustrating an inverter circuit formed in the semiconductor device. In the following description of the second embodiment, a detailed explanation of the components described in the first embodiment will be omitted.

[0059] The semiconductor device 10 according to the second embodiment includes a wiring board 1, lead terminals 2A and 2B, laminated bonding materials 3A to 3D, a heat sink 4, semiconductor elements 7A and 7B, and a case 8, as illustrated in Figures 11 and 12. The semiconductor device 10 in Figures 11 and 12 has a half-bridge inverter circuit 11 as illustrated in Figure 13 formed thereon.

[0060] The wiring board 1 has a first conductor pattern 110, a second conductor pattern 120, and a third conductor pattern 130 arranged on the upper surface of an insulating substrate 100, which is an insulating layer, and a heat dissipation layer 190 arranged on the lower surface of the insulating substrate 100. The insulating substrate 100 may be a ceramic substrate, but it may also be a resin insulating substrate. The wiring board 1 is placed on the upper surface of the heat sink 4, and the heat dissipation layer 190 of the wiring board 1 and the heat sink 4 are joined by a bonding material 5A. In addition, a first semiconductor element 7A is placed on the upper surface of the first conductor pattern 110, and a second semiconductor element 7B is placed on the upper surface of the second conductor pattern 120. The first semiconductor element 7A and the second semiconductor element 7B may be, for example, RC (Reverse Conducting)-IGBT elements, which integrate an IGBT (Insulated Gate Bipolar Transistor) element 711 and a diode element 712 connected in antiparallel to the IGBT element 711, as shown in Figure 13. The diode element 712 could be, for example, a FWD (Free Wheeling Diode) element. However, it is not limited to these.

[0061] Collector electrodes 701, which function as the collector of the IGBT element 711 and the cathode of the diode element 712, are positioned on the lower surfaces of the first semiconductor element 7A and the second semiconductor element 7B. The collector electrode 701 of the first semiconductor element 7A is bonded to the first conductor pattern 110 of the wiring board 1 by a bonding material (not shown). The collector electrode 701 of the second semiconductor element 7B is bonded to the second conductor pattern 120 of the wiring board 1 by a bonding material 5B. The collector electrode 701 is sometimes called the back electrode. Also, when the collector electrode 701 faces the conductor pattern of the wiring board 1 as shown in the figure, it is sometimes called the bottom electrode or bottom surface electrode.

[0062] An emitter electrode 702, which functions as the emitter of the IGBT element 711 and the anode of the diode element 712, and a gate electrode 703, which functions as the gate of the IGBT element 711, are arranged on the upper surfaces of the first semiconductor element 7A and the second semiconductor element 7B. The emitter electrode 702 of the first semiconductor element 7A is electrically connected to the second conductor pattern 120 of the wiring board 1 via a lead terminal 2A. The lead terminal 2A has two jointed portions; one jointed portion is joined to the emitter electrode 702 of the first semiconductor element 7A by a multilayer bonding material (not shown), and the other jointed portion is joined to the second conductor pattern 120 of the wiring board 1 by another multilayer bonding material (not shown). The emitter electrode 702 of the second semiconductor element 7B is electrically connected to the third conductor pattern 130 of the wiring board 1 via a lead terminal 2B. The lead terminal 2B has two jointed portions, one of which is joined to the third conductor pattern 130 by a laminated bonding material 3A, and the other jointed portion is joined to the emitter electrode 702 of the second semiconductor element 7B by another laminated bonding material 3B. When the emitter electrode 702 is positioned on the side opposite to the side facing the conductor pattern of the wiring board 1 in the semiconductor elements 7A and 7B (i.e., the top surface), as shown in the figure, it is sometimes called the upper electrode or top surface electrode.

[0063] The semiconductor device 10 illustrated in Figures 11 and 12 has a ring-shaped case 8 on the upper surface of the heat sink 4, with its upper and lower ends open and surrounding the wiring board 1 in a plan view of the upper surface of the heat sink 4. The case 8 comprises a ring-shaped case body 800 formed of an insulating material such as epoxy resin or polyphenylene sulfide (PPS) resin, and lead terminals 810, 820, 830, 840, and 850 integrated with the case body 800. Each of the lead terminals 810, 820, 830, 840, and 850 has an inner terminal portion that is electrically connected to a conductor in the space enclosed by the case body 800, and an outer terminal portion that extends upward from the upper surface of the case body 800 and functions as an external terminal of the semiconductor device 10. The first lead terminal 810, the second lead terminal 820, and the third lead terminal 830 are main terminals through which current converted from DC to AC by an inverter circuit flows. The first lead terminal 810 and the second lead terminal 820 are, for example, input terminals in an inverter circuit connected to the positive and negative terminals of an external DC power supply, respectively. The inner terminal portion of the first lead terminal 810 is joined to the first conductor pattern 110 of the wiring board 1 by a laminated bonding material (not shown). The inner terminal portion of the second lead terminal 820 is joined to the third conductor pattern 130 of the wiring board 1 by a laminated bonding material 3C. The third lead terminal 830 is, for example, an output terminal in an inverter circuit connected to a load. The inner terminal portion of the third lead terminal 830 is joined to the second conductor pattern 120 of the wiring board 1 by a laminated bonding material 3D. The fourth lead terminal 840 and the fifth lead terminal 850 are control terminals that apply a control signal to the gate electrode 703 of the first semiconductor element 7A, and control terminals that apply a control signal to the gate electrode 703 of the second semiconductor element 7B, respectively. The inner terminal portion of the fourth lead terminal 840 is electrically connected to the gate electrode 703 of the first semiconductor element 7A by wire 9A, and the inner terminal portion of the fifth lead terminal 850 is electrically connected to the gate electrode 703 of the second semiconductor element 7B by wire 9B. The semiconductor device 10 may also be equipped with auxiliary control terminals and the like, which are not shown in Figures 11 and 12.

[0064] In the semiconductor device 10 illustrated in Figures 11 and 12, the bonded portions of lead terminals 2A and 2B, and the inner terminal portions (bonded portions) of the first lead terminal 810, second lead terminal 820, and third lead terminal 830 of the case 8, all have their upper surfaces exposed before the sealing resin is filled into the space surrounded by the case body portion 800, allowing for laser irradiation. Therefore, each of the bonded portions of the lead terminals 2A, 2B, 810, 820, and 830 described above can be bonded to a bonding partner (bonded member) using the laminated bonding material 3 described in the first embodiment.

[0065] The conductor pattern 110 of the wiring board 1 and the first lead terminal 810 of the case 8 are joined by a laminated bonding material (not shown), forming a joint structure similar to the joint structure described in the first embodiment where the conductor pattern 110 of the wiring board 1 and the joined portion 200 of the lead terminal 2 are joined by a laminated bonding material 3. The joint structure where the third conductor pattern 130 of the wiring board 1 and the lead terminal 2B are joined by a laminated bonding material 3A, and the joint structure where the third conductor pattern 130 and the second lead terminal 820 are joined by a laminated bonding material 3C, are similar to the joint structures described in the first embodiment. The joint structure where the second conductor pattern 120 of the wiring board 1 and the third lead terminal 830 are joined by a laminated bonding material 3D is also similar to the joint structure described in the first embodiment. The emitter electrode 702 of semiconductor element 7A and the lead terminal 2A are joined by a multilayer bonding material (not shown), forming a bonding structure in which the conductor pattern 110 in the bonding structure described in the first embodiment is replaced with the upper electrode (emitter electrode 702) of semiconductor element 7A. The bonding structure in which the emitter electrode 702 of semiconductor element 7B and the lead terminal 2B are joined by a multilayer bonding material 3B is a structure in which the conductor pattern 110 in the bonding structure described in the first embodiment is replaced with the upper electrode (emitter electrode 702) of semiconductor element 7B. Multiple multilayer bonding materials within one semiconductor device 10, including the illustrated multilayer bonding materials 3A to 3D, may all have the same combination of materials and the same lamination configuration, or they may not. For example, the multilayer bonding material 3A that joins the lead terminal 2B and the conductor pattern 130 as exemplified in Figure 12, and the multilayer bonding material 3B that joins the lead terminal 2B and the emitter electrode 702 of semiconductor element 7B, may have the same combination of materials but different combinations of layer thicknesses.

[0066] In addition, in the semiconductor device 10 of the second embodiment, some of the four laminated bonding materials 3A to 3D shown in Figure 12 may be electrically connected in a different form without using the laminated bonding material 3. For example, in the semiconductor device 10, the upper electrode (emitter electrode 702) of the semiconductor element and the conductor pattern of the wiring board 1 may be electrically connected by a wire instead of the lead terminal 2. In the semiconductor device 10, for example, a plurality of semiconductor elements may be arranged on the first conductor pattern 110 and the second conductor pattern 120 of the wiring board 1, respectively. The plurality of semiconductor elements arranged on one conductor pattern may include, for example, semiconductor elements that function as switching elements such as IGBT elements and semiconductor elements that function as diode elements such as FWD elements.

[0067] The first lead terminal 810, the second lead terminal 820, and the third lead terminal 830 of case 8 may each have their outer terminal portions bent in a direction along the upper surface of the case body 800. Case 8 may be provided with additional lead terminals other than the lead terminals 810, 820, 830, 840, and 850 illustrated in Figure 11. The additional lead terminals may include, for example, a lead terminal electrically connected to the emitter electrode 702 of semiconductor element 7A and functioning as a first auxiliary control terminal, and a lead terminal electrically connected to the emitter electrode 702 of semiconductor element 7B and functioning as a second auxiliary control terminal. The first auxiliary control terminal may be connected via a fourth lead terminal 840 to a gate drive circuit that generates a control signal to be applied to the gate of IGBT element 711, and the second auxiliary control terminal may be connected via a fifth lead terminal 850 to a gate drive circuit that generates a control signal to be applied to the gate of IGBT element 711.

[0068] The heat sink 4 may be a plate-shaped metal plate, have fins extending downward from its bottom surface, or have a cooler with a water jacket having fins. In other words, the heat sink 4 may be one of the components constituting the cooler 12 located below (shown by a dashed line in Figure 12), or it may be a separate component from the cooler 12 that is attached to the cooler 12. The cooler 12 cools the semiconductor elements 7A and 7B by dissipating the heat conducted from them through the wiring board 1 and the heat sink 4. The heat sink 4 or the cooler 12 may be such that multiple semiconductor devices 10, which may have a planar configuration as shown in Figure 12, can be arranged in parallel (for example, in the Y direction). The cooler 12 is not limited to a specific cooling method and structure. Also, the heat sink 4 itself may function as a cooler, and the cooler 12 may be omitted.

[0069] (Method of manufacturing semiconductor devices) The manufacturing process for the semiconductor device 10 according to the second embodiment includes, for example, a first arrangement step, a first bonding step, a second arrangement step, and a second bonding step. The first arrangement step may be a step of arranging bonding material 5A, a wiring board 1, bonding material 5B, and semiconductor elements 7A and 7B on the upper surface of the heat sink 4. Bonding materials 5A and 5B may be, for example, sheet solder. The first bonding step may be a step of heating and melting bonding materials 5A and 5B to bond the heat sink 4 and the heat dissipation layer 190 of the wiring board 1, and to bond the conductor pattern of the wiring board 1 to the collector electrodes 701 of the semiconductor elements 7A and 7B. The first bonding step may be the same as a well-known reflow step. Bonding materials 5A and 5B may also be bonding materials having a silver sintered material.

[0070] The second placement step includes, for example, the steps of placing the laminated bonding material 3 on the conductor pattern of the wiring board 1 and on the emitter electrodes 702 of the semiconductor elements 7A and 7B, placing the lead terminals 2A and 2B, and placing the case 8. The step of placing the case 8 may include, for example, the step of bonding the case body portion 800 of the case 8 to the upper surface of the heat sink 4 with an adhesive. In the second placement step, the auxiliary conductor plate 300 constituting the laminated bonding material 3 and the bonding material layers above and below it are placed, for example, by any of the three methods described in the first embodiment and other implementable methods. In the second joining step, a laser is irradiated to each part of the members to be joined by the laminated bonding material 3 in the manner described in the first embodiment to form a joined structure joined by thermal conduction welding. Furthermore, the manufacturing method of the semiconductor device 10 in the second embodiment may include, after the second bonding step, a step of filling the recess surrounded by the case body portion 800 of the case 8 with sealing resin, or a step of closing the opening at the upper end of the case body portion 800 with a lid member.

[0071] In this way, by using the laminated bonding material 3 having the auxiliary conductor plate 300 and applying irradiation conditions that allow joining by thermal conduction welding, the laser is irradiated from above onto the part to be joined of the lead terminal 2A, etc. This prevents the insulating substrate 100 located below the laser irradiation area from being directly and locally heated to a high temperature. Therefore, it is possible to prevent the insulating substrate 100 from suffering thermal damage, and for example, it is possible to prevent a decrease in the reliability of the semiconductor device 10 due to a decrease in the adhesion between the conductor patterns 120, 130, etc. and the insulating substrate 100, and to prevent the heat conduction to the heat sink 4 via the wiring board 1 from being inhibited. Furthermore, as described in the first embodiment, by using the laminated bonding material 3, the members to be joined can be joined uniformly, so the reliability of the joint, such as the joint strength, is improved, and the variation in the electrical characteristics of the joint structure of each semiconductor device 10 can be reduced.

[0072] (Third embodiment: Semiconductor device) Figure 14 is a cross-sectional view illustrating an example of the configuration of a semiconductor device according to the third embodiment. The cross-section in Figure 14 corresponds to the cross-section in Figure 12. In other words, the cross-sectional configuration in Figure 14 may be the cross-sectional configuration at the position of the dashed line D-D' in the semiconductor device 10 of Figure 11. The semiconductor device 10 illustrated in Figure 14 can be considered, in one respect, as the semiconductor device 10 described in the second embodiment with the heat sink 4 located below the wiring board 1 omitted. The wiring board 1 in the semiconductor device 10 of the third embodiment includes a metal base 191 corresponding to the heat sink layer 190 of the second embodiment, an insulating layer 101 disposed on the upper surface of the metal base 191, and a conductor pattern disposed on the insulating layer 101. The conductor pattern disposed on the insulating layer 101 includes the second conductor pattern 120 and the third conductor pattern 130 illustrated in Figure 14, and a first conductor pattern 110 not shown in Figure 14. The metal base 191 may be a metal plate such as copper or aluminum, and the insulating layer 101 may be a resin insulating material. The insulating layer 101 is formed, for example, by applying an uncured thermosetting resin to the upper surface of the metal base 191, or by placing a sheet of semi-cured thermosetting resin and then curing the thermosetting resin. The conductor pattern on the upper surface of the insulating layer 101 is, for example, placed on the upper surface of the thermosetting resin used to form the insulating layer 101 when the thermosetting resin is in a semi-cured state, and then brought into close contact with the insulating layer 101 during the curing process of the semi-cured thermosetting resin. In the third embodiment, the laminate of the metal base 191, insulating layer 101, and conductor patterns 120 and 130, referred to as the wiring board 1, may be referred to by other terms. For example, the wiring board 1 in the semiconductor device 10 of Figure 14 can be described, in another respect, as a laminate in which the insulating layer 101 and conductor patterns 120 and 130 are laminated on the upper surface of the heat sink 4.

[0073] The semiconductor device 10 of the third embodiment is manufactured by a manufacturing method that includes four steps, similar to the semiconductor device 10 of the second embodiment: a first placement step, a first bonding step, a second placement step, and a second bonding step.

[0074] (Fourth embodiment: Semiconductor device) Figure 15 is a cross-sectional view illustrating an example of the configuration of a semiconductor device according to the fourth embodiment. The cross-sectional view in Figure 15 is intended to facilitate understanding of the characteristic configuration of the semiconductor device of this embodiment, and includes parts that do not accurately represent the cross-sectional view of an actual semiconductor device. The semiconductor device 10 illustrated in Figure 15 has a configuration in which a portion of the outer terminal portion (bonded portion) 814 of the first lead terminal 810 provided on the case 8 and a portion of the outer terminal portion (bonded portion) 824 of the second lead terminal 820 are bonded together with an insulating layer 860. Such a first lead terminal 810 and second lead terminal 820 are sometimes called laminate terminals. Laminate terminals are manufactured by well-known methods, and the insulating material used as the insulating layer 860, the thickness of the insulating layer 860, etc., are selected according to the electrical characteristics required in the semiconductor device 10 to which the laminate terminal is applied.

[0075] In Figure 15, the outer terminal portion 824 of the second lead terminal 820, the insulating layer 860, and the outer terminal portion 814 of the first lead terminal 810 are stacked in this order on the upper surface 801 of the case body 800. However, the arrangement of the outer terminal portion 824 of the second lead terminal 820 and the outer terminal portion 814 of the first lead terminal 810 may be reversed. The first lead terminal 810 and the second lead terminal 820 are not limited to terminals for a specific function in a circuit formed on the semiconductor device 10. For example, the first lead terminal 810 and the second lead terminal 820 may be input terminals (P terminal and N terminal) in the inverter circuit 11 described above with reference to Figure 13.

[0076] The inner terminal portion of the first lead terminal 810 is a portion that extends upward from the inner circumferential wall surface of the case body portion 800 to the wiring board 1, and includes a joined portion 811, a rising portion 812, and a routing portion 813. Similarly, the inner terminal portion of the second lead terminal 820 is a portion that extends upward from the inner circumferential wall surface of the case body portion 800 to the wiring board 1, and includes a joined portion 821, a rising portion 822, and a routing portion 823. The joined portion 811 of the first lead terminal 810 is joined to the conductor pattern 104 of the wiring board 1 by a laminated bonding material 3E, and the joined portion 821 of the second lead terminal 820 is joined to the conductor pattern 105 of the wiring board 1 by a laminated bonding material 3F. The laminated bonding material 3E and the laminated bonding material 3F may be any of the configurations described in the first embodiment. A semiconductor device 10 having a bonded structure including a laminated bonding material 3E and a bonded structure including a laminated bonding material 3F is manufactured by applying either the manufacturing method described in the first embodiment to the second arrangement step and the second bonding step in the manufacturing method described in the second embodiment. In Figure 15, the routing portion 813 of the first lead terminal 810 is shown to pass above the bonded portion 821 of the second lead terminal 820, but in an actual semiconductor device, it passes in a position that does not obstruct laser irradiation to the upper surface of the bonded portion 821 of the second lead terminal 820. That is, the first lead terminal 810 has a planar shape in which the routing portion 813 does not overlap with the upper surface of the bonded portion 821 of the second lead terminal 820 in an XY planar view.

[0077] Furthermore, in the semiconductor device 10 illustrated in Figure 15, the outer terminal portion 814 of the first lead terminal 810 is joined to a busbar 15 by a laminated bonding material 3G. The busbar 15 may be a conductive plate such as the terminal of an external power supply connected to the inverter circuit 11 of the semiconductor device 10, or the terminal of a smoothing capacitor connected in parallel to the inverter circuit 11. In this specification, for convenience, it is referred to as "busbar 15," but the conductor designated with reference numeral 15 is not limited to what is called a "busbar." Although not shown in Figure 15, the outer terminal portion 824 of the second lead terminal 820 has a joined portion that does not overlap with the insulating layer 860 and the outer terminal portion 814 of the first lead terminal 810 in an XY plan view. The joined portion of the outer terminal portion 824 of the second lead terminal 820 is joined to a busbar (not shown) by a laminated bonding material (not shown). The bonded structure formed by joining the outer terminal portion 814 of the first lead terminal 810 and the busbar 15 with a laminated bonding material 3G is the same structure as the bonded structure described in the first embodiment. Therefore, in the semiconductor device 10 of this embodiment, the first lead terminal 810 and the busbar 15 can be joined uniformly and firmly. Furthermore, when a laser is irradiated onto the upper surface of the busbar 15, it is possible to prevent heat from being directly and locally conducted from the busbar 15 to the outer terminal portion 814 of the first lead terminal 810. Therefore, for example, it is possible to prevent thermal damage to the insulating layer 860 between the outer terminal portion 814 of the first lead terminal 810 and the outer terminal portion 824 of the second lead terminal 820, which would otherwise lead to insulation degradation. In addition, by joining the outer terminal portion 824 of the second lead terminal 820 and a busbar (not shown) with a laminated bonding material, it is possible to prevent thermal damage to the case body portion 800 located below the outer terminal portion 824 of the second lead terminal 820. Furthermore, although not shown in Figure 15, in the semiconductor device 10 of the fourth embodiment, the third lead terminal 830 (see Figures 11 and 12) may also be joined to the busbar by a laminated bonding material.

[0078] Furthermore, the first lead terminal 810 and the second lead terminal 820 in the semiconductor device 10 manufactured using the laminated bonding material 3 described above may have a planar shape in which the outer terminal portion 814 and the outer terminal portion 824 do not overlap each other, and they may not be laminate terminals. In other words, the outer terminal portion 814 of the first lead terminal 810 and the outer terminal portion 824 of the second lead terminal 820 connected to the busbar 15 may be formed by bending the portion that extends upward from the upper surface of the case body portion 800 in the semiconductor device 10 illustrated in Figure 11 in a direction along the upper surface of the case body portion 800. In this case as well, the outer terminal portions 814 and 824 can be joined to the busbar by the laminated bonding material 3, thereby achieving a uniform and strong bond.

[0079] Furthermore, in conventional semiconductor devices of this type, for example, one method of connecting lead terminals 810, 820, and 830 provided on the case 8 to a busbar is to form through holes in the outer terminal portions of the lead terminals and connect the lead terminals and the busbar with bolts and nuts. However, such a connection method requires forming through holes in the lead terminals and busbars, which imposes constraints on the shape and structure of the lead terminals and busbars. In addition, since the connection between the outer terminal portions of the lead terminals and the busbar using bolts and nuts is by contact, the current that can flow is limited by contact resistance, making it difficult to increase the current of the semiconductor device 10. Moreover, because it is a mechanical fastening, there is a possibility of poor conductivity due to deformation during fastening or loosening due to vibration after fastening. In contrast, in the semiconductor device 10 of the fourth embodiment, the flat upper surface of the outer terminal portions of the lead terminals 810, 820, and 830, which do not have through holes, and the flat lower surface of the busbar 15, which does not have through holes, are joined by a laminated bonding material 3 having an auxiliary conductor plate 300. Since this joint is made by thermal conduction welding as described in the first embodiment, deformation, damage, and other thermal damage to the joint structure and surrounding insulating material can be prevented when the upper surface of the busbar 15 is irradiated with a laser to join the busbar 15 and the outer terminal portion of the lead terminal. Furthermore, since the entire joint interface is uniformly joined by the laminated joint material 3 having the auxiliary conductor plate 300, the constraints on the current that can flow between the busbar 15 and the lead terminal are relaxed compared to when the busbar 15 and the lead terminal are in contact, making it possible to increase the current of the semiconductor device 10. Moreover, since the entire joint interface is uniformly joined by the laminated joint material 3, poor conductivity between the busbar 15 and the lead terminal is less likely to occur.

[0080] (Supplementary information on semiconductor devices) The second, third, and fourth embodiments described above are merely examples of semiconductor devices to which the bonding structure described in the first embodiment is applied. The semiconductor devices to which the bonding structure described in the first embodiment is applied are not limited to the exemplified semiconductor devices. For example, in a semiconductor device to which the bonding structure is applied, as described above, the outer terminal portion 814 of the first lead terminal 810 and the outer terminal portion 824 of the second lead terminal 820 may be arranged along the upper surface 801 of the case body portion 800 and without overlapping each other in an XY plan view. The arrangement of the outer terminal portion 814 of the first lead terminal 810 and the outer terminal portion 824 of the second lead terminal 820 on the upper surface 801 of the case body portion 800 is not limited to the arrangement aligned in the Y direction as exemplified in Figure 11, but may also be arranged in the X direction.

[0081] In the inverter circuit 11 shown in Figure 13, the IGBT element 711 and the diode element 712, which are shown as being formed on a single semiconductor element (for example, semiconductor element 7A), may be formed on separate semiconductor elements. The switching element in the inverter circuit 11 is not limited to the IGBT element 711, but may also be a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a BJT (Bipolar Junction Transistor), or the like. The diode element 712 in the inverter circuit 11 is not limited to an FWD element, but may also be an SBD (Schottky Barrier Diode), a JBS (Junction Barrier Schottky) diode, an MPS (Merged PN Schottky) diode, a PN diode, or the like. The semiconductor device may, for example, consist only of the portion (upper arm) of the inverter circuit 11 illustrated in Figure 13, which includes the first lead terminal 810, the first semiconductor element 7A, the fourth lead terminal 840, and the third lead terminal 830, or it may consist only of the portion (lower arm) of the third lead terminal 830, the second semiconductor element 7B, the fifth lead terminal 850, and the second lead terminal 820. The semiconductor device may also have an inverter circuit with a different circuit configuration than the inverter circuit 11 illustrated in Figure 13, or it may have a circuit other than the inverter circuit.

[0082] The semiconductor device may not have a case 8 with lead terminals integrally formed on it. Specifically, the semiconductor device may be a resin-encapsulated semiconductor device, sometimes called a semiconductor package, which is manufactured by mounting semiconductor elements on a lead frame and then encapsulating the semiconductor elements using transfer molding or the like.

[0083] The following summarizes the key features of the embodiment described above. The bonding structure according to the above-described embodiment comprises a first conductor and a second conductor, and a laminated bonding material disposed between the first conductor and the second conductor to bond the first conductor and the second conductor, wherein the laminated bonding material comprises a first bonding material layer bonded to the first conductor, a second bonding material layer bonded to the second conductor, and an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer and having a higher melting point than the first bonding material layer and the second bonding material layer, wherein the second conductor has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate.

[0084] In the bonding structure according to the above embodiment, the first conductor is arranged on the insulating layer such that the back surface of the surface facing the auxiliary conductor plate faces the insulating layer.

[0085] In the joint structure according to the above embodiment, the ratio T2 / T1 between the thickness T2 of the thinner of the first joint material layer and the second joint material layer and the thickness T1 of the auxiliary conductor plate is within the range of 0.0125 ≤ T2 / T1 ≤ 0.6.

[0086] In the joint structure according to the above embodiment, the first joint material layer and the second joint material layer are metals or alloys having a melting point in the range of 100°C to 300°C.

[0087] In the joint structure according to the above embodiment, the first joint material layer and the second joint material layer are tin or a tin-containing alloy.

[0088] In the joint structure according to the above embodiment, the first conductor and the second conductor are copper, a copper-containing alloy, nickel, or a nickel-containing alloy.

[0089] In the joining structure according to the above embodiment, the auxiliary conductor plate is one of the following: copper or an alloy mainly composed of copper, nickel or an alloy mainly composed of nickel, silver or an alloy mainly composed of silver, aluminum or an alloy mainly composed of aluminum, tungsten, and molybdenum.

[0090] The semiconductor device according to the above-described embodiment comprises a wiring board having an insulating layer and a conductor pattern disposed on a first surface of the insulating layer, a lead terminal bonded to the conductor pattern by a laminated bonding material, and a semiconductor element having an electrode electrically connected to the conductor pattern of the wiring board, wherein the laminated bonding material comprises a first bonding material layer bonded to the conductor pattern, a second bonding material layer bonded to the lead terminal, and an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer and having a higher melting point than the first bonding material layer and the second bonding material layer, and the lead terminal has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate.

[0091] The semiconductor device according to the above-described embodiment comprises a semiconductor element and a lead terminal joined to the electrode of the semiconductor element by a multilayer bonding material, wherein the multilayer bonding material comprises a first bonding material layer joined to the electrode of the semiconductor element, a second bonding material layer joined to the lead terminal, and an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer and having a higher melting point than the first bonding material layer and the second bonding material layer, and the lead terminal has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate.

[0092] The semiconductor device according to the above-described embodiment comprises a semiconductor element sealed by an insulating member, a lead terminal having an outer terminal portion electrically connected to the electrode of the semiconductor element and exposed from the insulating member, and a conductor plate joined to the outer terminal portion of the lead terminal by a laminated bonding material, wherein the laminated bonding material comprises a first bonding material layer joined to the lead terminal, a second bonding material layer joined to the conductor plate, and an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer and having a higher melting point than the first bonding material layer and the second bonding material layer, and the conductor plate has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate.

[0093] In the semiconductor device according to the above embodiment, the lead terminal includes a first lead terminal and a second lead terminal, and the first lead terminal and the second lead terminal are laminate terminals in which a part of the first lead terminal and a part of the second lead terminal are bonded together with an insulating layer in between.

[0094] The method for manufacturing the bonded structure according to the above-described embodiment includes an arrangement step of arranging the first bonded material layer, the auxiliary conductor plate, the second bonded material layer, and the second conductor on the first conductor in the order of stacking the first bonded material layer, the auxiliary conductor plate, the second bonded material layer, and the second conductor; and a bonding step of irradiating the back surface of the second conductor facing the auxiliary conductor plate with a laser to heat the second bonded material layer and the first bonded material layer, thereby bonding the first conductor and the second conductor, wherein the auxiliary conductor plate is made of a conductive material with a higher melting point than the first bonded material layer and the second bonded material layer.

[0095] In the method for manufacturing a bonded structure according to the above embodiment, the wavelength of the laser is in the range of 500 nm to 550 nm.

[0096] In the method for manufacturing a bonded structure according to the above embodiment, in the arrangement step, a laminated bonded material, in which the first bonded material layer, the auxiliary conductor plate, and the second bonded material layer are integrated, is placed on the first conductor.

[0097] In the method for manufacturing a bonded structure according to the above embodiment, the laminated bonded material is formed by bonding the first bonded material layer, the auxiliary conductor plate, and the second bonded material layer together.

[0098] In the method for manufacturing the bonded structure according to the above embodiment, the laminated bonded material has a first bonded material layer formed on the lower surface of the auxiliary conductor plate and a second bonded material layer formed on the upper surface of the auxiliary conductor plate.

[0099] In the method for manufacturing a bonded structure according to the above embodiment, the first bonded material layer and the second bonded material layer arranged in the arrangement step include, in the first bonded material layer, a bonded material layer arranged or formed on the upper surface of the first conductor and a bonded material layer arranged or formed on the lower surface of the auxiliary conductor plate, or in the second bonded material layer, a bonded material layer arranged or formed on the upper surface of the auxiliary conductor plate and a bonded material layer arranged or formed on the lower surface of the second conductor.

[0100] In the method for manufacturing a joined structure according to the above embodiment, the joining step involves irradiating the laser under irradiation conditions such that the second joining material layer and the first joining material layer are melted and an alloy is formed at the interface between the second conductor and the second joining material layer, and at the interface layer between the first conductor and the first joining material layer, thereby joining the first conductor and the second conductor.

[0101] In the method for manufacturing a joined structure according to the above embodiment, the first joining material layer and the second joining material layer are tin or a tin-containing alloy.

[0102] In the method for manufacturing the joint structure according to the above embodiment, the auxiliary conductor plate is one of the following: copper or an alloy mainly composed of copper, nickel or an alloy mainly composed of nickel, silver or an alloy mainly composed of silver, aluminum or an alloy mainly composed of aluminum, tungsten, and molybdenum.

[0103] The method for manufacturing a semiconductor device according to the above-described embodiment includes: a first arrangement step of arranging a semiconductor element on a wiring board having an insulating layer and a conductor pattern arranged on a first surface of the insulating layer; a second arrangement step of arranging the first bonding material layer, the auxiliary conductor plate, the second bonding material layer, and the lead terminals on the conductor pattern of the wiring board so that they are stacked in this order; and a bonding step of irradiating the back surface of the lead terminal facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer and bonding the conductor pattern of the wiring board and the lead terminals, wherein the auxiliary conductor plate is made of a conductive material with a higher melting point than the first bonding material layer and the second bonding material layer.

[0104] The method for manufacturing a semiconductor device according to the above-described embodiment includes: a first arrangement step of arranging a semiconductor device on a wiring board having an insulating layer and a conductor pattern arranged on a first surface of the insulating layer; a second arrangement step of arranging a first bonding material layer, an auxiliary conductor plate, a second bonding material layer, and a lead terminal on the electrodes of the semiconductor device so that they are stacked in this order; and a bonding step of irradiating the back surface of the lead terminal facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer, thereby bonding the electrodes of the semiconductor device and the lead terminal, wherein the auxiliary conductor plate is made of a conductive material with a higher melting point than the first bonding material layer and the second bonding material layer.

[0105] The method for manufacturing a semiconductor device according to the above-described embodiment includes an arrangement step of arranging a first bonding material layer, an auxiliary conductor plate, a second bonding material layer, and a conductor plate in such order on the first surface of the outer terminal portion of a lead terminal having an outer terminal portion exposed from the insulating member and electrically connected to the electrodes of a semiconductor element sealed by an insulating member; and a bonding step of irradiating the back surface of the conductor plate facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer, thereby bonding the lead terminal and the conductor plate, wherein the auxiliary conductor plate is made of a conductive material with a higher melting point than the first bonding material layer and the second bonding material layer.

[0106] Furthermore, the present invention is not limited to the embodiments described above, and may be modified, substituted, or transformed in various ways without departing from the spirit of the technical idea. In addition, if the technical idea can be realized in a different way by advances in the technology or by other derived technologies, it may be implemented by that method. Accordingly, the claims cover all embodiments that may fall within the scope of the technical idea. [Industrial applicability]

[0107] As described above, the present invention has the effect of preventing the deterioration of surrounding heat-resistant components due to heat when the bonding material between the first conductor and the second conductor is melted and joined, and is particularly useful when applied to semiconductor devices for industrial or vehicle use, such as power conversion devices. [Explanation of symbols]

[0108] 1 Wiring board 100 Insulating substrate 101 Insulating layer 110, 120, 130 Conductor Patterns 190 Heat dissipation layer 2, 2A, 2B lead terminals 200 Part to be joined 3, 3A~3G laminated bonding material 300 Auxiliary Conductor Plate 310, 320, 312, 322, 313, 323 Bonding material layer 311, 321 Bonding material sheet 4 Heat sink 5, 5A, 5B Bonding material 6 lasers 600 irradiation area 7A, 7B Semiconductor Devices 701 Collector electrode 702 Emitter electrode 8 cases 800 Case body 810, 820, 830, 840, 850 lead terminals 860 Insulating layer 10 Semiconductor Devices

Claims

1. A first conductor and a second conductor, The device comprises a laminated bonding material disposed between the first conductor and the second conductor, which joins the first conductor and the second conductor, The aforementioned laminated bonding material is The first bonding material layer bonded to the first conductor, The second bonding material layer bonded to the second conductor, The device comprises an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer, the auxiliary conductor plate having a melting point higher than the first bonding material layer and the second bonding material layer, The second conductor has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate. bonded structure.

2. The bonding structure according to claim 1, wherein the first conductor is arranged on the insulating layer such that the back surface of the surface facing the auxiliary conductor plate faces the insulating layer.

3. The bonding structure according to claim 1, wherein the ratio T2 / T1 of the thickness T2 of the thinner bonding layer among the first bonding layer and the second bonding layer to the thickness T1 of the auxiliary conductor plate is within the range of 0.0125 ≤ T2 / T1 ≤ 0.

6.

4. The joint structure according to claim 1, wherein the first joint layer and the second joint layer are metals or alloys having a melting point in the range of 100°C to 300°C.

5. The joint structure according to claim 4, wherein the first joint layer and the second joint layer are tin or a tin-containing alloy.

6. The joint structure according to claim 5, wherein the first conductor and the second conductor are copper, a copper-containing alloy, nickel, or a nickel-containing alloy.

7. The bonding structure according to any one of claims 1 to 6, wherein the auxiliary conductor plate is made of copper or an alloy mainly composed of copper, nickel or an alloy mainly composed of nickel, silver or an alloy mainly composed of silver, aluminum or an alloy mainly composed of aluminum, tungsten, and molybdenum.

8. A wiring board having an insulating layer and a conductor pattern arranged on a first surface of the insulating layer, A lead terminal joined to the conductor pattern by a laminated bonding material, The circuit board comprises a semiconductor element having electrodes electrically connected to the conductor pattern of the circuit board, The aforementioned laminated bonding material is A first bonding material layer bonded to the aforementioned conductor pattern, A second bonding material layer bonded to the lead terminal, The device comprises an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer, the auxiliary conductor plate having a melting point higher than the first bonding material layer and the second bonding material layer, The lead terminal has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate. Semiconductor equipment.

9. Semiconductor elements and The semiconductor element is bonded to a lead terminal by a laminated bonding material, The aforementioned laminated bonding material is A first bonding material layer bonded to the electrode of the semiconductor element, A second bonding material layer bonded to the lead terminal, The device comprises an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer, the auxiliary conductor plate having a melting point higher than the first bonding material layer and the second bonding material layer, The lead terminal has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate. Semiconductor equipment.

10. A semiconductor element sealed with an insulating material, A lead terminal having an outer terminal portion that is electrically connected to the electrode of the semiconductor element and exposed from the insulating member, The device comprises a conductor plate joined to the outer terminal portion of the lead terminal by a laminated bonding material, The aforementioned laminated bonding material is The first bonding material layer bonded to the lead terminal, A second bonding material layer bonded to the aforementioned conductor plate, The device comprises an auxiliary conductor plate disposed between the first bonding material layer and the second bonding material layer, the auxiliary conductor plate having a melting point higher than the first bonding material layer and the second bonding material layer, The conductor plate has laser irradiation marks on the back surface of the surface facing the auxiliary conductor plate. Semiconductor equipment.

11. The lead terminals include a first lead terminal and a second lead terminal, The semiconductor device according to claim 10, wherein the first lead terminal and the second lead terminal are laminate terminals formed by bonding a portion of the first lead terminal and a portion of the second lead terminal together with an insulating layer in between.

12. Arrangement step of arranging the first bonding material layer, the auxiliary conductor plate, the second bonding material layer, and the second conductor so that they are stacked on the first conductor in this order, The process includes a bonding step of irradiating the back surface of the second conductor facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer, thereby bonding the first conductor and the second conductor, The auxiliary conductor plate is formed of a conductive material with a higher melting point than the first bonding layer and the second bonding layer. A method for manufacturing a bonded structure.

13. The method for manufacturing a bonded structure according to claim 12, wherein the wavelength of the laser is in the range of 500 nm to 550 nm.

14. The method for manufacturing a bonded structure according to claim 12, wherein in the arrangement step, a laminated bonded material in which the first bonded material layer, the auxiliary conductor plate, and the second bonded material layer are integrated is arranged on the first conductor.

15. The method for manufacturing a bonded structure according to claim 14, wherein the laminated bonded material is formed by bonding together the first bonded material layer, the auxiliary conductor plate, and the second bonded material layer.

16. The method for manufacturing a bonded structure according to claim 14, wherein the laminated bonded material has a first bonded material layer formed on the lower surface of the auxiliary conductor plate and a second bonded material layer formed on the upper surface of the auxiliary conductor plate.

17. The first bonding material layer and the second bonding material layer arranged in the above arrangement step are The first bonding layer includes a bonding layer disposed or formed on the upper surface of the first conductor and a bonding layer disposed or formed on the lower surface of the auxiliary conductor plate, or The second bonding layer includes a bonding layer disposed or formed on the upper surface of the auxiliary conductor plate and a bonding layer disposed or formed on the lower surface of the second conductor. A method for manufacturing a jointed structure according to claim 12.

18. The method for manufacturing a joined structure according to claim 12, wherein the joining step involves irradiating the laser under irradiation conditions such that the first conductor and the second conductor are joined by thermal conduction welding, which melts the second joining material layer and the first joining material layer and forms an alloy at the interface between the second conductor and the second joining material layer and at the interface layer between the first conductor and the first joining material layer.

19. The method for manufacturing a bonded structure according to claim 12, wherein the first bonded material layer and the second bonded material layer are tin or a tin-containing alloy.

20. The method for manufacturing a joint structure according to any one of claims 12 to 19, wherein the auxiliary conductor plate is made of copper or an alloy mainly composed of copper, nickel or an alloy mainly composed of nickel, silver or an alloy mainly composed of silver, aluminum or an alloy mainly composed of aluminum, tungsten, and molybdenum.

21. A first arrangement step of arranging a semiconductor element on a wiring board having an insulating layer and a conductor pattern arranged on the first surface of the insulating layer, A second arrangement step involves arranging the first bonding material layer, the auxiliary conductor plate, the second bonding material layer, and the lead terminals on the conductor pattern of the wiring board in such order: The bonding step includes irradiating the back surface of the lead terminal facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer, thereby bonding the conductor pattern of the wiring board to the lead terminal, The auxiliary conductor plate is formed of a conductive material with a higher melting point than the first bonding layer and the second bonding layer. A method for manufacturing a semiconductor device.

22. A first arrangement step of arranging a semiconductor element on a wiring board having an insulating layer and a conductor pattern arranged on the first surface of the insulating layer, A second arrangement step involves arranging the first bonding material layer, the auxiliary conductor plate, the second bonding material layer, and the lead terminals on the electrodes of the semiconductor element in such order: The bonding step includes irradiating the back surface of the lead terminal facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer, thereby bonding the electrode of the semiconductor element to the lead terminal, The auxiliary conductor plate is formed of a conductive material with a higher melting point than the first bonding layer and the second bonding layer. A method for manufacturing a semiconductor device.

23. A configuration step of arranging the first bonding material layer, the auxiliary conductor plate, the second bonding material layer, and the conductor plate on the first surface of the outer terminal portion of a lead terminal having an outer terminal portion exposed from the insulating member, such that the first bonding material layer, the auxiliary conductor plate, the second bonding material layer, and the conductor plate are stacked in this order. The bonding step includes irradiating the back surface of the conductor plate facing the auxiliary conductor plate with a laser to heat the second bonding material layer and the first bonding material layer, thereby bonding the lead terminal and the conductor plate. The auxiliary conductor plate is formed of a conductive material with a higher melting point than the first bonding layer and the second bonding layer. A method for manufacturing a semiconductor device.

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