Plating method for silver sinter bonding, plating film for silver sinter bonding, power module substrate and semiconductor device

Abstract

To provide a plating method for silver sintering joining, having excellent initial bonding strength and heat resistance, capable of suppressing warpage and cracking of a member to be joined such as a substrate, a plating film for silver sintering joining, a substrate for a power module equipped with a plating film, and a semiconductor device including the substrate for a power module.SOLUTION: A plating method for silver sintering joining includes a barrier layer forming step for forming a cobalt plating film or a platinum plating film on an upper side of a surface to be plated and a topmost layer forming step for forming a silver plating film on the topmost surface of a plated surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plating method for silver sinter bonding, a plating film for silver sinter bonding, a power module substrate, and a semiconductor device. [Background technology]

[0002] Traditionally, Si (silicon) semiconductors have been used as power semiconductors. In recent years, the use of SiC (silicon carbide) semiconductors and GaN (gallium nitride) semiconductors, which can operate at higher temperatures than Si semiconductors, has been increasing. As a result, the operating temperature of semiconductors is expected to rise to over 200°C, and heat resistance is becoming necessary for the die bond parts that bond semiconductor elements to substrates. One bonding technology that has attracted attention is silver sintering bonding. On the other hand, silver sintering bonding requires surface treatment of the substrate and other components to be bonded, and the film formed by this surface treatment also needs to be heat resistant.

[0003] For example, Patent Document 1 discloses that a coating consisting of a nickel plating film as a base layer and a specific alloy plating film formed on the nickel plating film improves the heat resistance reliability of a die attach portion, which is the joint between a semiconductor element and a support. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-46276 A Summary of the Invention [Problem to be solved by the invention]

[0005] The substrate is provided with a circuit formed of copper or aluminum on a base material. When silver sintering is used to bond a semiconductor element to the circuit, a silver plating film may be used on the outermost layer of the circuit that comes into contact with the silver sintered layer in order to ensure good bonding strength. Although the silver plating film provides good initial bonding strength, it is easily permeable to oxygen, and may cause oxidation of the underlying metal such as copper or aluminum, particularly under high temperature conditions, thereby reducing the bonding strength, and tends to have poor heat resistance. To solve this problem, it is necessary to further provide an oxidation barrier layer for the underlying metal.

[0006] As a result of intensive research by the present inventors, it was found that in conventional techniques, a thick nickel plating film of 3 μm or more is used as a barrier layer to prevent oxidation of the underlying metal, but when a thick nickel plating film of 3 μm or more is used together with a silver plating film, this thick nickel plating film causes problems such as warping and cracking of the members to be joined, such as substrates.

[0007] The present invention aims to solve the above-mentioned problems newly discovered by the inventors, and to provide a plating method for silver sinter bonding, which has good initial bonding strength and heat resistance and can suppress warping and cracking of members to be bonded, such as substrates, a plating film for silver sinter bonding, a power module substrate provided with the plating film, and a semiconductor device provided with the power module substrate. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that even if a cobalt plating film or platinum plating film is thin (for example, even if the film thickness is 1.0 μm or less), it can function as a barrier layer against oxygen, provide good heat resistance, and suppress the occurrence of warping and cracking in the member to be joined, such as a substrate, and further, that by providing a silver plating film on the uppermost surface layer thereof, sufficient initial bonding strength with a silver sintered material can be obtained, and the film has good initial bonding strength and heat resistance, and can suppress warping and cracking in the member to be joined, such as a substrate, and have completed the present invention. That is, the present invention relates to a plating method for silver sinter bonding, which includes a barrier layer forming step of forming a cobalt plating film or a platinum plating film on the upper side of a surface to be plated, and an outermost layer forming step of forming a silver plating film on the outermost layer of the surface to be plated.

[0009] The cobalt plating film or the platinum plating film preferably has a thickness of 1.0 μm or less.

[0010] It is preferable that the barrier layer formation step is a step of forming a cobalt plating film on the upper side of the surface to be plated, and further includes an intermediate layer formation step of forming a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film.

[0011] It is preferable that the barrier layer forming step is a step of forming a cobalt plating film on the upper side of the surface to be plated, and further includes an intermediate layer forming step of forming a platinum plating film on the upper side of the cobalt plating film.

[0012] It is preferable that the barrier layer forming step is a step of forming a cobalt plating film on the upper side of the surface to be plated, and that the cobalt plating film contains a transition metal element of Group 5 and / or Group 6 of the periodic table.

[0013] The content of transition metal elements of Group 5 and / or Group 6 of the periodic table in the cobalt plating film is preferably 3 to 70 mass %.

[0014] In the plating method for silver sinter bonding, it is preferable that the total thickness of the plating film is 15 μm or less.

[0015] The present invention also relates to a plating film (plating film laminate) for silver sinter bonding, which has a cobalt plating film or a platinum plating film and, as an outermost layer, a silver plating film.

[0016] The cobalt plating film or the platinum plating film preferably has a thickness of 1.0 μm or less.

[0017] It is preferable that the plated metal layer has a cobalt plating film and has a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film.

[0018] It is preferable that the plated metal layer has a cobalt plating film and a platinum plating film is provided on the upper side of the cobalt plating film.

[0019] It is preferable that the cobalt plating film is provided, and that the cobalt plating film contains a transition metal element of Group 5 and / or Group 6 of the periodic table.

[0020] The content of transition metal elements of Group 5 and / or Group 6 of the periodic table in the cobalt plating film is preferably 3 to 70 mass %.

[0021] The plating film preferably has a total thickness of 15 μm or less.

[0022] The present invention also relates to a power module substrate comprising a substrate, a circuit formed on the substrate, and the plating film formed on a surface of the circuit.

[0023] The circuit is preferably made of copper and / or aluminum.

[0024] The surface of the plating film is preferably a silver sintered bonding surface.

[0025] The present invention also relates to a semiconductor device comprising the power module substrate and a semiconductor element, wherein a surface of the plating film of the power module substrate and the semiconductor element are bonded by silver sintering bonding. Effect of the Invention

[0026] According to the present invention, the plating method for silver sinter bonding includes a barrier layer formation step of forming a cobalt plating film or a platinum plating film on the upper side of the surface to be plated, and an outermost layer formation step of forming a silver plating film on the outermost layer of the surface to be plated, so that the method has good initial bonding strength and heat resistance and can suppress warping and cracking of the members to be bonded, such as substrates.

[0027] Furthermore, according to the present invention, the plating film (plating film laminate) for silver sinter bonding has a cobalt plating film or a platinum plating film and, as the outermost layer, a silver plating film, so that it has good initial bonding strength and heat resistance and can suppress warping and cracking of the members to be bonded, such as substrates.

[0028] Furthermore, according to the present invention, a power module substrate includes a base material, a circuit formed on the base material, and a specific plating film (plating film laminate) formed on a surface of the circuit, and therefore has good initial bonding strength and heat resistance, and can suppress warping and cracking of the substrate.

[0029] Furthermore, according to the present invention, a semiconductor device is provided which includes a specific power module substrate and a semiconductor element, and the surface of the plating film of the power module substrate and the semiconductor element are bonded by silver sintering bonding. This provides good initial bonding strength and heat resistance, and suppresses warping and cracking of the substrate, making this a highly reliable semiconductor device. [Brief description of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view showing an outline of a plating film according to one embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view showing an outline of a plating film according to one embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view showing an outline of a plating film according to one embodiment of the present invention. [Figure 4] 1 is a cross-sectional view showing an outline of a plating film according to one embodiment of the present invention. [Diagram 5] 1 is a cross-sectional view showing an outline of a power module substrate according to an embodiment of the present invention. [Figure 6] 1 is a cross-sectional view showing an outline of bonding between a power module substrate according to an embodiment of the present invention and a semiconductor element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The plating method for silver sinter bonding of the present invention includes a barrier layer formation step of forming a cobalt plating film or a platinum plating film on the upper side of the surface to be plated, and an outermost layer formation step of forming a silver plating film on the outermost layer of the surface to be plated. The plating film (plating film laminate) for silver sinter bonding of the present invention has a cobalt plating film or a platinum plating film, and a silver plating film as the outermost layer. This provides good initial bonding strength and heat resistance, and can suppress warping and cracking of the members to be bonded, such as substrates.

[0032] The reason why the above-mentioned effects are obtained by the plating method and the plating film (plating film laminate) is presumed to be as follows. As described above, even if the cobalt plating film and platinum plating film are thin (for example, even if the film thickness is 1.0 μm or less), they function sufficiently as a barrier layer against oxygen, and can provide good heat resistance while also making it possible to suppress the occurrence of warping and cracks in members to be joined, such as substrates. Furthermore, by providing a silver plating film as the outermost layer on the upper side of the cobalt plating film or platinum plating film, sufficient initial bonding strength with the silver sintered material can be obtained. Furthermore, the synergistic effect of the cobalt plating film or platinum plating film and the silver plating film provides good initial bonding strength and heat resistance, and can suppress warping and cracking of members to be bonded, such as substrates. As described above, the plating method and the plating film laminate have a silver plating film as the outermost layer, and therefore have good initial bonding strength and also good heat resistance, and can suppress warping and cracking of members to be joined, such as substrates, and are therefore suitably applicable to silver sinter bonding.

[0033] <Plating method> The plating method for silver sinter bonding of the present invention includes the following steps: a barrier layer forming step of forming a cobalt plating film or a platinum plating film on the upper side of the surface to be plated; a top layer forming process for forming a silver plating film on the top layer of the plated surface; Includes.

[0034] In this specification, the surface to be plated means the surface on which a plating film is formed. For example, when a plating film is formed on a circuit formed on a substrate, the surface to be plated is the circuit surface.

[0035] In this specification, the upper side of the surface to be plated is not particularly limited as long as it is located above the surface to be plated, and may be the surface of the surface to be plated, i.e., the bottommost layer of the plating film, or a layer other than the bottommost layer of the plating film. Thus, in this specification, forming a cobalt plating film or a platinum plating film on the upper side of the surface to be plated is not particularly limited as long as a cobalt plating film or a platinum plating film is formed on the upper side of the surface to be plated (excluding the outermost layer of the plating film), and includes not only an embodiment in which a cobalt plating film or a platinum plating film is formed on the surface of the surface to be plated, i.e., as the lowermost layer of the plating film, but also an embodiment in which a cobalt plating film or a platinum plating film is formed as a layer other than the lowermost layer of the plating film (excluding the outermost layer of the plating film), for example, after forming one or more plating films on the surface of the surface to be plated. In this specification, other similar expressions, for example, the upper side of the cobalt plating film, have the same meaning. In this specification, the surface of a surface to be plated means on the surface to be plated, and other similar expressions, such as the surface of a cobalt plating film, also have the same meaning and mean on the cobalt plating film.

[0036] In this specification, forming a silver plating film on the outermost layer of a surface to be plated means forming a silver plating film as the outermost layer of a plating film (plating film laminate) provided on the surface to be plated.

[0037] <<Barrier layer formation process>> In the barrier layer formation step, a cobalt plating film or a platinum plating film is formed on the upper side of the plated surface. This makes it possible to form a cobalt plating film or a platinum plating film that functions sufficiently as a barrier layer against oxygen even if it is thin (for example, even if the film thickness is 1.0 μm or less), and it is possible to obtain good heat resistance and also to suppress the occurrence of warping and cracks in the members to be joined, such as substrates.

[0038] The barrier layer forming step is preferably a step of forming a cobalt plating film on the upper side (preferably the front surface) of the surface to be plated, which provides better heat resistance and is also advantageous in terms of cost.

[0039] It is important to form a cobalt plating film or a platinum plating film as the barrier layer, and the method of forming the plating film is not particularly limited. The method of forming the plating film is not particularly limited, and examples thereof include electroless plating, electroplating, hot-dip plating, vacuum plating (PVD), and vapor phase plating (CVD). These may be used alone or in combination of two or more. Among them, electroless plating and electroplating are preferred, and electroless plating is more preferred, for reasons of low cost, simplicity of equipment, and productivity.

[0040] The method of electroless plating is not particularly limited, and it is sufficient to precipitate a metal in a plating solution using a reducing agent, and a person skilled in the art can appropriately carry out the method according to known methods.

[0041] The reducing agent is not particularly limited as long as it is a water-soluble compound capable of reducing the water-soluble metal compound in the plating solution to metal, and examples of the reducing agent that can be used include hydrazine derivatives, formaldehyde compounds, hydroxylamines, sugars, phosphorous acid, formic acid, boron hydride compounds, hypophosphites, dimethylamine borane, ascorbic acid, etc. These may be used alone or in combination of two or more kinds.

[0042] The thickness of the cobalt plating film or platinum plating film formed by the barrier layer forming step is preferably 1.0 μm or less, more preferably 0.8 μm or less, even more preferably 0.6 μm or less, particularly preferably 0.5 μm or less, and most preferably 0.4 μm or less, and is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. Within the above ranges, the effect tends to be more favorably obtained.

[0043] The cobalt-plated film or platinum-plated film (particularly the cobalt-plated film) formed in the barrier layer-forming step may be an alloy film of cobalt and platinum, or may be an alloy film containing other metals.

[0044] The other metal is not particularly limited, and examples thereof include transition metal elements of Group 5 or Group 6 of the periodic table, such as tungsten, molybdenum, niobium, tantalum, and vanadium. The other metal may also include phosphorus and boron derived from the reducing agent, and carbon, nitrogen, oxygen, and sulfur derived from the additive. The other metal may be used alone or in combination of two or more. Among them, transition metal elements of Group 5 or Group 6 of the periodic table are preferred, and elements of the fifth to sixth periods of the transition metal elements of Groups 5 to 6 of the periodic table are more preferred, with tungsten and niobium being even more preferred, and tungsten being particularly preferred.

[0045] The transition metal elements of Group 6 of the periodic table, including tungsten, and the transition metal elements of Group 5 of the periodic table, such as niobium, are transition metal elements with adjacent group numbers, and have the same crystal lattice structure in the single metal. Therefore, by including a naturally occurring transition metal element of Group 5 and / or Group 6 of the periodic table (preferably excluding chromium from the viewpoint of environmental load) as the other metal in the cobalt plating film or platinum plating film, the heat resistance can be improved more suitably as in the case of including tungsten shown in the examples. Among them, tungsten, molybdenum, niobium, and tantalum have similar chemical properties, such as having close lattice constants, being completely dissolved in each other, and forming acidic oxides together. Therefore, by including an element of the fifth to sixth periods of the transition metal elements of Groups 5 to 6 of the periodic table as the other metal in the cobalt plating film or platinum plating film (particularly, the cobalt plating film), the above-mentioned favorable effects can be obtained. Furthermore, tungsten and niobium have large cohesive energy, and therefore are believed to be capable of more suitably improving heat resistance.

[0046] The content of transition metal elements of Group 5 and / or 6 of the periodic table in the cobalt plating film or platinum plating film (preferably the cobalt plating film) is preferably 3 mass% or more, more preferably 4 mass% or more, even more preferably 5 mass% or more, particularly preferably 10 mass% or more, and is preferably 70 mass% or less, more preferably 65 mass% or less, even more preferably 60 mass% or less, particularly preferably 55 mass% or less. Within the above ranges, the effects tend to be more favorably obtained. Here, when a plurality of transition metal elements of Group 5 and / or Group 6 of the periodic table are contained, the above content means the total content.

[0047] The cobalt content in the cobalt plating film is preferably 30% by mass or more, more preferably 35% by mass or more, even more preferably 40% by mass or more, and is preferably 99% by mass or less, more preferably 97% by mass or less, even more preferably 96% by mass or less, and particularly preferably 95% by mass or less. When it is within the above range, the effect tends to be more suitably obtained.

[0048] The platinum content in the platinum plating film is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, and may be 100% by mass. When it is within the above range, the effects (particularly heat resistance) tend to be more favorably obtained.

[0049] In this specification, the content of each metal in the plating film is measured by an inductively coupled plasma (ICP) optical emission spectrometer, specifically, by the method described in the Examples.

[0050] <<Outermost layer formation process>> In the outermost layer forming step, a silver plating film is formed on the outermost layer of the plated surface. That is, in the outermost layer forming step, a silver plating film is formed as the outermost layer of the plating film (plating film laminate) to be provided on the plated surface. This allows the silver plating film to be formed on the outermost layer above the cobalt plating film or platinum plating film, and sufficient initial bonding strength with the silver sintered material is obtained.

[0051] It is important to form a silver plating film as the outermost layer of the plated surface (the outermost layer of the plating film provided on the plated surface), and the method for forming the plating film is not particularly limited. The method for forming the plating film is the same as that for the barrier layer formation process, including preferred embodiments.

[0052] The thickness of the silver plating film formed in the outermost layer forming step is preferably 3.0 μm or less, more preferably 2.5 μm or less, even more preferably 2.0 μm or less, particularly preferably 1.5 μm or less, and is preferably 0.2 μm or more, more preferably 0.3 μm or more, and even more preferably 0.4 μm or more. When it is within the above range, the effect tends to be more favorably obtained.

[0053] The silver plating film formed in the outermost layer forming step may be an alloy film containing other metals, such as the same metals as described above, which may be used alone or in combination of two or more kinds.

[0054] The silver content in the silver plating film formed by the outermost layer forming step is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, and may be 100% by mass. When it is within the above range, the effect (particularly, initial bonding strength) tends to be more favorably obtained.

[0055] <<Other processes>> The plating method for silver sinter-bonding of the present invention may include other steps as long as it includes the barrier layer forming step and the outermost layer forming step. That is, the plating method for silver sinter-bonding of the present invention may include other steps as long as it forms a silver plating film on the outermost layer of the plated surface while forming a cobalt plating film or a platinum plating film on the upper side of the plated surface.

[0056] As other steps, in addition to a step of forming another plating film such as a step of forming a nickel plating film, a cleaner step, an etching step, a pickling step, an activator step, a post-dip step, a dismuting step, a zincate step, etc. may be performed as necessary. The chemicals used in the cleaner step, the etching step, the pickling step, the activator step, the post-dip step, the dismuting step, and the zincate step can be appropriately selected from known chemicals.

[0057] <<<Intermediate layer formation process>>> The barrier layer forming step is a step of forming a cobalt plating film on an upper side of a surface to be plated, It is preferable to further include an intermediate layer forming step of forming a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film, and it is more preferable to further include an intermediate layer forming step of forming a platinum plating film on the upper side of the cobalt plating film. This makes it possible to obtain the desired effect. By providing a nickel plating film as the intermediate layer, the adhesion with other films tends to be improved. Furthermore, by providing a platinum plating film as the intermediate layer, the heat resistance tends to be further improved.

[0058] It is important to form a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film, and the method for forming the plating film is not particularly limited. The method for forming the plating film is the same as that in the barrier layer formation step, including preferred embodiments.

[0059] The thickness of the nickel plating film or platinum plating film formed on the upper side of the cobalt plating film in the intermediate layer forming step is preferably 1.0 μm or less, more preferably 0.5 μm or less, even more preferably 0.3 μm or less, particularly preferably 0.2 μm or less, and is preferably 0.01 μm or more, more preferably 0.03 μm or more, and even more preferably 0.05 μm or more. When the thickness is within the above range, the effect tends to be more favorably obtained.

[0060] The nickel plating film or platinum plating film (particularly the nickel plating film) formed in the intermediate layer forming step may be an alloy film containing other metals. The other metals, including preferred embodiments, are the same as those of the cobalt plating film or platinum plating film formed in the barrier layer forming step.

[0061] The nickel content in the nickel plating film is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, and is preferably 99.5% by mass or less, and more preferably 99% by mass or less. When it is within the above range, the effect tends to be more suitably obtained.

[0062] The platinum content in the platinum plating film is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 98% by mass or more, and may be 100% by mass. When it is within the above range, the effects (particularly heat resistance) tend to be more favorably obtained.

[0063] The total thickness of the plating film (plating film laminate) formed by the plating method of the present invention is preferably 15 μm or less, more preferably 10 μm or less, even more preferably 7 μm or less, particularly preferably 5 μm or less, most preferably 3 μm or less, even more preferably 2 μm or less, even more preferably 1.5 μm or less, particularly most preferably 1 μm or less, and is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.4 μm or more, and particularly preferably 0.6 μm or more. When it is within the above range, the effect tends to be more favorably obtained.

[0064] In this specification, the thickness and total thickness of the plating film are the average values ​​of measurements taken at five points using an X-ray fluorescence spectrometer, and are specifically measured by the method described in the Examples.

[0065] The plating method of the present invention preferably includes only a barrier layer forming step and an outermost layer forming step as steps for forming a plating film, and more preferably the barrier layer forming step is a step for forming a cobalt plating film on the upper side of the plated surface. This makes it possible to form a plating film with a smaller total thickness, and while having good initial bonding strength and heat resistance, it is possible to more suitably suppress warping and cracking of the members to be bonded, such as a substrate.

[0066] The plating method of the present invention further comprises the steps of: A barrier layer forming step of forming a cobalt plating film on the upper side (preferably the front surface) of the surface to be plated; an intermediate layer forming step of forming a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film; a top layer forming process for forming a silver plating film on the top layer of the plated surface; It is also preferred that It is also more preferable that the intermediate layer forming step is a step of forming a platinum plating film on the upper side of the cobalt plating film, It is further preferable that the intermediate layer forming step is a step of forming a platinum plating film on a surface of the cobalt plating film, It is also particularly preferable that the outermost layer forming step is a step of forming a silver plating film on the surface of the platinum plating film. This provides good initial bonding strength and heat resistance, and can suppress warping and cracking of the members to be bonded, such as substrates, and is particularly excellent in heat resistance.

[0067] The plating method of the present invention further comprises the steps of: A barrier layer forming step of forming a cobalt plating film on the upper side (preferably the front surface) of the surface to be plated; an intermediate layer forming step of forming a nickel plating film on the upper side (preferably the surface) of the cobalt plating film; an intermediate layer forming step of forming a platinum plating film on the upper side (preferably the surface) of the nickel plating film; a surface layer forming step of forming a silver plating film on the surface layer of the plated surface (preferably the surface of the platinum plating film); may include:

[0068] The plating method of the present invention further comprises the steps of: forming a nickel plating film on a surface to be plated; a barrier layer forming step of forming a platinum plating film on the upper side (preferably the surface) of the nickel plating film; a surface layer forming step of forming a silver plating film on the surface layer of the plated surface (preferably the surface of the platinum plating film); may include: In electroless plating, when the surface to be plated is copper or aluminum, it is difficult to form a platinum plating film on the surface to be plated, but the above method forms a nickel plating film on the surface to be plated, so that it is possible to form a platinum plating film as a barrier layer even in electroless plating. Note that, in the case of methods other than electroless plating, such as electroplating, PVD, CVD, etc., it is possible to form a platinum plating film on the surface to be plated, even if the surface to be plated is copper or aluminum.

[0069] The material of the plated surface is not particularly limited, and examples thereof include copper, aluminum, iron, nickel, etc. The material of the plated surface may be an alloy of these. Among these, copper, aluminum, Fe-Ni alloys, and copper alloys such as brass are preferred, and copper and aluminum are more preferred.

[0070] The plating method for silver sintering of the present invention can be applied to any member that can be used for silver sintering. The member that can be used for silver sintering is not particularly limited, and examples thereof include substrates such as ceramic substrates and printed circuit boards; semiconductor elements, heat sinks, heat sinks, chips, lead frames, and copper plates. Among these, substrates (particularly ceramic substrates), heat sinks, heat sinks, and chips, which are members having a base metal, are preferred, and substrates (particularly ceramic substrates) are more preferred, because they can prevent oxidation of the base metal and improve heat resistance.

[0071] <Plating film (plating film laminate)> The plating film (plating film laminate) for silver sinter bonding of the present invention is A cobalt plating film or a platinum plating film, The outermost layer is a silver plating film. has. The plating film of the present invention is, for example, a plating film provided on a plated surface formed by the plating method of the present invention. Therefore, each film of the plating film of the present invention is similar to each film explained in the plating method of the present invention, including preferred aspects. Other explanations are also similar, including preferred aspects.

[0072] The plating film (plating film laminate) of the present invention may have a cobalt plating film or a platinum plating film, and a silver plating film as the outermost layer of the plating film, and may have a film other than a cobalt plating film, a platinum plating film, or a silver plating film.

[0073] <<Barrier layer>> The plating film (plating film laminate) of the present invention has a cobalt plating film or a platinum plating film as a barrier layer. The barrier layer may be located above the surface to be plated, but is preferably formed on the surface of the surface to be plated. Even if the cobalt plating film or platinum plating film is thin (for example, even if the film thickness is 1.0 μm or less), it can function sufficiently as a barrier layer against oxygen, thereby providing good heat resistance and making it possible to suppress the occurrence of warping and cracks in members to be joined, such as substrates.

[0074] The barrier layer is preferably a cobalt plating film, which provides better heat resistance and is also advantageous in terms of cost.

[0075] The thickness of the cobalt plating film or platinum plating film is preferably 1.0 μm or less, more preferably 0.8 μm or less, even more preferably 0.6 μm or less, particularly preferably 0.5 μm or less, and most preferably 0.4 μm or less, and is preferably 0.05 μm or more, more preferably 0.1 μm or more, and even more preferably 0.2 μm or more. When the thickness is within the above range, the effect tends to be more favorably obtained.

[0076] The cobalt plating film or platinum plating film (particularly, the cobalt plating film) may be an alloy film of cobalt and platinum, or may be an alloy film containing other metals. The other metals, including preferred embodiments, are the same as those of the cobalt plating film or platinum plating film formed by the barrier layer formation step. The content of the transition metal elements of Group 5 and / or Group 6 of the periodic table in the cobalt plating film or platinum plating film (preferably the cobalt plating film) is also the same as that of the cobalt plating film or platinum plating film formed by the barrier layer formation step. The content of cobalt in the cobalt plating film and the content of platinum in the platinum plating film are also the same as those of the cobalt plating film or platinum plating film formed by the barrier layer formation step.

[0077] <<Top layer>> The plating film (plating film laminate) of the present invention has a silver plating film as the outermost layer of the plating film provided on the plated surface. Since the silver plating film is provided as the outermost layer on the upper side of the cobalt plating film or platinum plating film, sufficient initial bonding strength with the silver sintered material can be obtained.

[0078] The thickness of the silver plating film is preferably 3.0 μm or less, more preferably 2.5 μm or less, even more preferably 2.0 μm or less, particularly preferably 1.5 μm or less, and is preferably 0.2 μm or more, more preferably 0.3 μm or more, and even more preferably 0.4 μm or more. Within the above ranges, the effect tends to be more favorably obtained.

[0079] The silver plating film formed by the outermost layer forming step may be an alloy film containing other metals. Examples of the other metals include the same metals as those mentioned above, and they may be used alone or in combination of two or more. The silver content in the silver plating film is also the same as that of the silver plating film formed by the outermost layer forming step.

[0080] <<Other layers>> The plating film of the present invention only needs to have a cobalt plating film or a platinum plating film and, as the outermost layer of the plating film, a silver plating film, and may have other layers.

[0081] The other layer is not particularly limited, and examples thereof include a nickel plating film and a palladium film.

[0082] The barrier layer has a cobalt plating film on the upper side of the plated surface, It is preferable that a nickel plating film and / or a platinum plating film is provided on the upper side of the cobalt plating film, and it is more preferable that a platinum plating film is provided on the upper side of the cobalt plating film, whereby the effect can be more suitably obtained.

[0083] The nickel plating film and platinum plating film provided on the upper side of the cobalt plating film are similar to the nickel plating film and platinum plating film formed in the intermediate layer forming step, including preferred aspects.

[0084] The total thickness of the plating film (plating film laminate) of the present invention is preferably 15 μm or less, more preferably 10 μm or less, even more preferably 7 μm or less, particularly preferably 5 μm or less, most preferably 3 μm or less, even more preferably 2 μm or less, even more preferably 1.5 μm or less, particularly most preferably 1 μm or less, and is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.4 μm or more, and particularly preferably 0.6 μm or more. Within the above range, the effect tends to be more favorably obtained.

[0085] The plating film (plating film laminate) of the present invention preferably has only a cobalt plating film or a platinum plating film and a silver plating film, and more preferably has only a cobalt plating film and a silver plating film. That is, it is preferable to have a cobalt plating film or a platinum plating film on the surface of the surface to be plated and only a silver plating film on the surface of the film, and more preferably to have a cobalt plating film on the surface of the surface to be plated and only a silver plating film on the surface of the cobalt plating film. This makes it possible to form a plating film with a smaller total thickness, which has good initial bonding strength and heat resistance, and can more suitably suppress warping and cracking of the members to be bonded, such as a substrate. A plating film 1 according to one embodiment of the present invention has a cobalt plating film 2 formed on a surface 6 to be plated, and a silver plating film 3 formed on the cobalt plating film 2, as shown in FIG.

[0086] In addition, the plating film (plating film laminate) of the present invention is A cobalt plating film on the upper side (preferably the front side) of the surface to be plated; A nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film; The outermost layer is a silver plating film. It is also preferred that A cobalt plating film on the upper side (preferably the front side) of the surface to be plated; A platinum plating film is provided on the upper side (preferably the surface) of the cobalt plating film; The outermost layer is a silver plating film. It is also more preferred to have A cobalt plating film on the upper side (preferably the front side) of the surface to be plated; A platinum plating film is provided on the upper side (preferably the surface) of the cobalt plating film; The top layer is a platinum plating film, and the other layer is a silver plating film. It is further preferred that the compound has the following structure: This provides good initial bonding strength and heat resistance, and can suppress warping and cracking of the members to be bonded, such as substrates, and is particularly excellent in heat resistance. As shown in FIG. 2 , a plating film 1 according to one embodiment of the present invention has a cobalt plating film 2 formed on a surface 6 to be plated, a platinum plating film 4 formed on the cobalt plating film 2, and a silver plating film 3 formed on the platinum plating film 4.

[0087] In addition, the plating film (plating film laminate) of the present invention is A cobalt plating film on the upper side (preferably the front side) of the surface to be plated; A nickel plating film is provided on the upper side (preferably the surface) of the cobalt plating film, A platinum plating film on the upper side (preferably the surface) of the nickel plating film, The outermost layer (preferably the surface of the platinum plating film) is a silver plating film and may have the following structure: As shown in FIG. 3 , a plating film 1 according to one embodiment of the present invention has a cobalt plating film 2 formed on a surface 6 to be plated, a nickel plating film 5 formed on the cobalt plating film 2, a platinum plating film 4 formed on the nickel plating film 5, and a silver plating film 3 formed on the platinum plating film 4.

[0088] In addition, the plating film (plating film laminate) of the present invention is A nickel plating film is formed on the surface of the plated surface. A platinum plating film is formed on the upper side (preferably the surface) of the nickel plating film, The outermost layer (preferably the surface of the platinum plating film) is a silver plating film and may have the following structure: In electroless plating, when the surface to be plated is copper or aluminum, it is difficult to form a platinum plating film on the surface to be plated, but with the above method, a nickel plating film is formed on the surface to be plated, so that even in electroless plating, a platinum plating film can be formed as a barrier layer. Note that, with methods other than electroless plating, such as electrolytic plating, PVD, CVD, etc., it is possible to form a platinum plating film on the surface to be plated, even if the surface to be plated is copper or aluminum. As shown in FIG. 4 , a plating film 1 according to one embodiment of the present invention has a nickel plating film 5 formed on a surface 6 to be plated, a platinum plating film 4 formed on the nickel plating film 5, and a silver plating film 3 formed on the platinum plating film 4.

[0089] The plating film (plating film laminate) for silver sinter bonding of the present invention can be applied to any member for which silver sinter bonding is to be performed, without any particular limitation. The member for which silver sinter bonding is to be performed is the same as the member described in the plating method of the present invention, including preferred aspects. The material of the plated surface is also the same as the material described in the plating method of the present invention, including preferred aspects.

[0090] <Power module substrate> As described above, the plating film (plating film laminate) of the present invention can be suitably applied to substrates, and below, a power module substrate will be described as an example of a substrate using the plating film of the present invention. The power module substrate of the present invention is A substrate; A circuit formed on the substrate; and A plating film formed on the circuit surface, The plating film is the plating film (plating film laminate) of the present invention. In this specification, the power module substrate means a substrate used in a power module, specifically, the substrate exemplified below. In this specification, the power module substrate is a concept including a lead frame and a spacer used in a power semiconductor.

[0091] The substrate having a base material and a circuit formed on the base material is not particularly limited, and examples thereof include DBC substrates, DBA substrates, AMB substrates, etc. Here, DBC stands for Direct Bonded Copper, DBA stands for Direct Bonded Aluminum, and AMB stands for Active Metal Brazing.

[0092] Hereinafter, a heat-resistant power module substrate according to one embodiment of the present invention will be described with reference to the drawings. The power module substrate 100 according to one embodiment of the present invention is a substrate for mounting a power semiconductor that generates high heat. As shown in Fig. 5, the power module substrate 100 according to one embodiment of the present invention includes a base material 10, a circuit 20 formed on the base material directly or via a brazing material, and a plating film (plating film laminate) 1 formed on a surface of the circuit.

[0093] The base material 10 used in the power module substrate 100 according to one embodiment of the present invention is not particularly limited, and examples thereof include aluminum oxide, aluminum nitride, silicon nitride, and the like. These may be used alone or in combination of two or more. Among these, aluminum oxide, aluminum nitride, and silicon nitride are preferred because of their excellent cost, heat dissipation, strength, and the like.

[0094] As shown in Fig. 5, a circuit 20 is formed on a substrate 10. At this time, the circuit 20 may be formed on the substrate 10 by a direct method, or the circuit 20 may be formed via a brazing material (not shown). The circuit 20 is usually made of copper and / or aluminum. Here, the copper and aluminum may be alloys.

[0095] The method for forming the circuit 20 may be any known method and is not particularly limited, but in the direct method, one side of a copper plate, which is a circuit member, may be oxidized and bonded to the substrate 10, and unnecessary parts other than the circuit may be etched away. Aluminum has excellent ductility, and copper has excellent heat dissipation properties. These metals are also superior in terms of cost compared to other metals, and therefore are used for power module substrates.

[0096] The plating film 1 formed on the surface of the circuit 20 is the plating film of the present invention. The surface of the plating film is silver sinter-bonded to, for example, a semiconductor element, so that the surface of the plating film forms a silver sinter-bonded surface, which has good initial bonding strength and heat resistance and can suppress warping and cracks of the board. In FIG. 6, the surface of the plating film 1 formed on the surface of the circuit 20 is silver sinter-bonded to the semiconductor element 30. That is, the surface of the plating film 1 is bonded to the semiconductor element 30 via the silver sintered body layer 40.

[0097] In the present invention, the method of silver sinter bonding is not particularly limited, and a person skilled in the art can appropriately carry out the method according to a known method. For example, a paste in which silver particles are dispersed in an organic solvent is used as a silver sintering material, the organic solvent is volatilized by heating or the like to bring the silver particles into contact with each other, and a bonding layer is formed by sintering.

[0098] <Semiconductor device> The power module substrate of the present invention can be suitably applied to a semiconductor device, and an example of a semiconductor device using the power module substrate of the present invention will be described below. The semiconductor device of the present invention comprises: A power module substrate according to the present invention and a semiconductor element are provided, The surface of the plating film of the power module substrate and the semiconductor element are joined by silver sintering bonding.

[0099] In this specification, the surface of the plating film of the power module substrate and the semiconductor element being silver sinter-bonded may mean that the entire surface of the plating film is silver sinter-bonded to the semiconductor element, or a part of the surface of the plating film is silver sinter-bonded to the semiconductor element. For example, when the plating film is formed on the front and back surfaces of the substrate, only the surface of the plating film formed on one of the surfaces may be silver sinter-bonded to the semiconductor element. In this case, the surface that is silver sinter-bonded to the semiconductor element may be the entire surface of the plating film or only a part of the surface. In other words, only a part of the surface of the plating film formed on one of the surfaces may be silver sinter-bonded to the semiconductor element. In addition, in this specification, it is sufficient that at least one of the semiconductor elements included in a substrate is silver sinter-bonded to the surface of the plating film of the power module substrate, and all of the semiconductor elements may be silver sinter-bonded to the surface of the plating film of the power module substrate.

[0100] In the semiconductor device of the present invention, the surface of the plating film of the present invention and the semiconductor element are silver sintered-bonded, so that the surface of the plating film forms a silver sintered bonding surface, which has good initial bonding strength and heat resistance and can suppress warping and cracks in the substrate, making it a highly reliable semiconductor device.

[0101] The semiconductor element is not particularly limited, and examples thereof include power semiconductor elements such as Si (silicon) semiconductor elements, SiC (silicon carbide) semiconductor elements, and GaN (gallium nitride) semiconductor elements. These may be used alone or in combination of two or more. Among them, power semiconductor elements are preferred because they are particularly required to have heat resistance, and SiC semiconductor elements and GaN semiconductor elements are more preferred.

[0102] The semiconductor device of the present invention can be used in various electronic components. Examples of electronic components include those used in home appliances, in-vehicle devices, power transmission systems, transport equipment, and communication equipment, and more specifically, power modules such as air conditioners, elevators, electric vehicles, hybrid vehicles, trains, and power control units for power generation devices, general home appliances, and personal computers. Among these, power modules are preferred because they are particularly required to have heat resistance. EXAMPLES

[0103] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0104] According to the conditions shown in Tables 1 and 2, each plating was applied to a substrate to form a plating film laminate. A Cu bulk material (25×60×3 mm) was used as the base substrate to be plated. The obtained plating film laminate and the substrate on which the plating film laminate was provided were evaluated by the following method. The evaluation results are shown in Table 1.

[0105] <Measurement of plating film thickness> The thickness of the plating film was calculated as the average value of measurements taken at five locations using an X-ray fluorescence spectrometer (manufactured by Hitachi High-Tech Science Corporation, product name: SFT-9550).

[0106] <Analysis of plating film composition> After the plating film was formed, the composition was analyzed. Specifically, the plating film was dissolved in nitric acid, and the resulting solution was quantitatively analyzed for each element using an inductively coupled plasma (ICP) emission spectrometer (manufactured by HORIBA, product name: Ultima Expert). The content of each component in the film was calculated from the mass of the dissolved plating film.

[0107] <Silver sintered bonding evaluation> (Preparation of evaluation samples) A base substrate (Cu bulk material; 25 x 60 x 3 mm) and a simulated chip (Cu bulk material processed to chip size; 5 x 5 x 1 mm) were used as the objects to be plated. Each plating was applied according to the conditions shown in Tables 1 and 2, and then the base substrate and the simulated chip (both forming the same film laminate) were connected to each other using a silver sintering material (MAX102: manufactured by Nihon Handa Co., Ltd.) and heat-treated for 10 minutes at 250°C in air without pressure to form a silver sintered bond, and a sample for evaluation was prepared. (Measuring the bonding strength) For the evaluation samples, the silver sinter-bonded chips were sheared sideways, and the strength at the time of breakage was measured using a bond tester (manufactured by Nordson DAGE, product name: 4000Plus) to determine the bond strength (initial bond strength). Further, the evaluation sample was subjected to a heat treatment at 300° C. for 500 hours, and the bonding strength (bonding strength after heat treatment) of the heat-treated evaluation sample was measured in the same manner as described above. The measured initial bonding strength and bonding strength after heat treatment are shown in Table 1. Furthermore, the silver sintered bonding was evaluated according to the following criteria. ◎: No problem (bonding strength after heat treatment: 30Mpa or more) 〇: Strength slightly decreased by heat treatment (bonding strength after heat treatment: less than 20-30MPa) △: Strength decreased due to heat treatment (bonding strength after heat treatment: less than 20 MPa) ×: Not bonded

[0108] <Warping (cracks)> An Al-Cu wafer (100 x 10 mm, thickness 0.2 mm) was plated according to the conditions shown in Tables 1 and 2, and it was confirmed whether warping occurred.

[0109] The method of producing the plating film laminate and the substrate provided with the plating film laminate in each of the examples and comparative examples will be described in detail below.

[0110] Comparative Example 1 An electroless CoWP plating film (Co: 83% by mass, W: 12% by mass, P: 5% by mass) was formed in a single layer with a thickness of 0.3 μm on the surface of the Cu bulk material to be plated, using an Epitas HWP-5 manufactured by Uemura Kogyo Co., Ltd.

[0111] Comparative Example 2 An electroless CoWB plating film (Co: 49% by mass, W: 50% by mass, B: 1% by mass) was formed in a single layer with a thickness of 0.3 μm on the surface of the Cu bulk material to be plated, using Epitas HWB-31 manufactured by Uemura Kogyo Co., Ltd.

[0112] Comparative Example 3 An electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed in a single layer with a thickness of 0.3 μm on the surface of the Cu bulk material to be plated, using Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd.

[0113] Comparative Example 4 An electroless NiP plating film (Ni: 94% by mass, P: 6% by mass) was formed to a thickness of 0.3 μm on the surface of the Cu bulk material to be plated using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and then an electroless Pt plating film was formed on the surface of the NiP plating film to a thickness of 0.1 μm using a TGM-21 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.4 μm.

[0114] Comparative Example 5 An electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm on the surface of the Cu bulk material to be plated using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and then an electroless Au plating film was formed on the surface of the NiP plating film (Ni: 94 mass%, P: 6 mass%) to a thickness of 0.3 μm using a Gobright TWX-40 manufactured by Uemura Kogyo Co., Ltd., to a thickness of 0.15 μm, forming a plating film laminate with a total thickness of 0.45 μm.

[0115] Comparative Example 6 On the surface of the Cu bulk material to be plated, an electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Pd plating film was formed to a thickness of 0.1 μm using an Altarea TPD-30 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Au plating film was formed to a thickness of 0.15 μm using a Gobright TWX-40 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.55 μm.

[0116] Comparative Example 7 An electroless Ag plating film was formed in a single layer with a thickness of 0.5 μm on the surface of the Cu bulk material to be plated, using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd.

[0117] Comparative Example 8 On the surface of the Cu bulk material, which was the surface to be plated, an electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Pd plating film was formed to a thickness of 0.1 μm using an Altarea TPD-30 manufactured by Uemura Kogyo Co., Ltd., and on this surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.9 μm.

[0118] Comparative Example 9 An electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm on the surface of the Cu bulk material to be plated using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and then an electroless Ag plating film was formed on the surface of the NiP plating film to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.8 μm.

[0119] Comparative Example 10 An electroless NiB plating film (Ni: 99% by mass, B: 1% by mass) was formed to a thickness of 0.3 μm on the surface of the Cu bulk material to be plated using BEL Nickel manufactured by Uemura Kogyo Co., Ltd., and then an electroless Ag plating film was formed on the surface of the NiB plating film to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.8 μm.

[0120] Comparative Example 11 An electroless NiWP plating film (Ni: 84 mass%, W: 11 mass%, P: 5 mass%) was formed to a thickness of 0.3 μm on the surface of the Cu bulk material to be plated using Trialloy NWP manufactured by Uemura Kogyo Co., Ltd., and then an electroless Ag plating film was formed on the surface of the NiWP plating film to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.8 μm.

[0121] Comparative Example 12 On the surface of the Cu bulk material to be plated, an electroless NiWB plating film (Ni: 89 mass%, W: 10 mass%, B: 1 mass%) was formed to a thickness of 0.3 μm using a plating solution of BEL nickel manufactured by Uemura Kogyo Co., Ltd. with added tungsten components, and on that surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.8 μm.

[0122] Comparative Example 13 An electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 10.0 μm on the surface of the Cu bulk material to be plated using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and then an electroless Ag plating film was formed on the surface of the NiP plating film to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 10.5 μm.

[0123] Example 1 On the surface of the Cu bulk material to be plated, an electroless CoP plating film (Co: 95 mass%; P: 5 mass%) was formed to a thickness of 0.3 μm using a plating solution made by removing the tungsten component from Epitas HWP-5 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.8 μm.

[0124] Example 2 On the surface of the Cu bulk material to be plated, an electroless CoB plating film (Co: 99 mass%, B: 1 mass%) was formed to a thickness of 0.3 μm using a plating solution made by removing the tungsten component from Epitas HWB-31 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.8 μm.

[0125] Example 3 On the surface of the Cu bulk material to be plated, an electroless CoP plating film (Co: 95% by mass, P: 5% by mass) was formed to a thickness of 0.3 μm using a plating solution made by removing the tungsten component from Epitas HWP-5 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Pt plating film was formed to a thickness of 0.1 μm using TGM-21 manufactured by Uemura Kogyo Co., Ltd., and on this surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.9 μm.

[0126] Example 4 On the surface of the Cu bulk material to be plated, an electroless CoB plating film (Co: 99% by mass, B: 1% by mass) was formed to a thickness of 0.3 μm using a plating solution made by removing the tungsten component from Epitas HWB-31 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Pt plating film was formed to a thickness of 0.1 μm using TGM-21 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.9 μm.

[0127] Example 5 An electroless CoWP plating film (Co: 83 mass%, W: 12 mass%, P: 5 mass%) was deposited to a thickness of 0.3 μm on the surface of the Cu bulk material (the surface to be plated) using an Epitas HWP-5 manufactured by Uemura Kogyo Co., Ltd., and then an electroless Ag plating film was deposited on the surface of the CoWP plating film to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.8 μm.

[0128] Example 6 An electroless CoWB plating film (Co: 49 mass%, W: 50 mass%, B: 1 mass%) was formed to a thickness of 0.3 μm on the surface of the Cu bulk material to be plated using an Epitas HWB-31 manufactured by Uemura Kogyo Co., Ltd., and then an electroless Ag plating film was formed on the surface of the CoWB plating film to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., to form a plating film laminate with a total thickness of 0.8 μm.

[0129] Example 7 On the surface of the Cu bulk material, which was the surface to be plated, an electroless CoWP plating film (Co: 83 mass%, W: 12 mass%, P: 5 mass%) was formed to a thickness of 0.3 μm using an Epitas HWP-5 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and on this surface, an electroless Pt plating film was formed to a thickness of 0.1 μm using a TGM-21 manufactured by Uemura Kogyo Co., Ltd., and on this surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 1.2 μm.

[0130] Example 8 On the surface of the Cu bulk material, which was the surface to be plated, an electroless CoWB plating film (Co: 49 mass%, W: 50 mass%, B: 1 mass%) was formed to a thickness of 0.3 μm using an Epitas HWB-31 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and on this surface, an electroless Pt plating film was formed to a thickness of 0.1 μm using a TGM-21 manufactured by Uemura Kogyo Co., Ltd., and on this surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 1.2 μm.

[0131] Example 9 On the surface of the Cu bulk material to be plated, an electroless NiP plating film (Ni: 94 mass%, P: 6 mass%) was formed to a thickness of 0.3 μm using a Nimden NPR-4 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Pt plating film was formed to a thickness of 0.1 μm using a TGM-21 manufactured by Uemura Kogyo Co., Ltd., and on that surface, an electroless Ag plating film was formed to a thickness of 0.5 μm using an Argento RSD-4 manufactured by Uemura Kogyo Co., Ltd., forming a plating film laminate with a total thickness of 0.9 μm.

[0132] [Table 1]

[0133] [Table 2]

[0134] From Table 1, it is found that the examples having a cobalt plating film or a platinum plating film and a silver plating film as the outermost layer have good initial bonding strength and heat resistance, and can suppress warping and cracking of the members to be bonded, such as a substrate. Therefore, the plating method and plating film of the present invention are suitable for use in silver sinter bonding. [Explanation of symbols]

[0135] 1. Plating film (plating film laminate) 2 Cobalt plating film 3. Silver plating film 4 Platinum plating film 5 Nickel plating film 6 Surface to be plated 10 Base material 20 Circuit 30 Semiconductor elements 40 Silver sintered layer 100 Power module substrate

Claims

1. a barrier layer forming step of forming a cobalt plating film or a platinum plating film on the upper side of the surface to be plated; a top layer forming process for forming a silver plating film on the top layer of the plated surface; 2. A plating method for silver sintered bonding comprising:

2. 2. The plating method according to claim 1, wherein the thickness of the cobalt plating film or the platinum plating film is 1.0 μm or less.

3. The barrier layer forming step is a step of forming a cobalt plating film on an upper side of a surface to be plated, 3. The plating method according to claim 1, further comprising an intermediate layer forming step of forming a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film.

4. The barrier layer forming step is a step of forming a cobalt plating film on an upper side of a surface to be plated, 3. The plating method according to claim 1, further comprising an intermediate layer forming step of forming a platinum plating film on the upper side of the cobalt plating film.

5. The barrier layer forming step is a step of forming a cobalt plating film on an upper side of a surface to be plated, 5. The plating method according to claim 1, wherein the cobalt plating film contains a transition metal element of Group 5 and / or Group 6 of the periodic table.

6. 6. The plating method according to claim 5, wherein the content of transition metal elements of Group 5 and / or Group 6 of the periodic table in the cobalt plating film is 3 to 70 mass %.

7. The plating method according to any one of claims 1 to 6, wherein the total thickness of the plating film is 15 µm or less.

8. A cobalt plating film or a platinum plating film, The outermost layer is a silver plating film. With silver plating film for sintered bonding.

9. 9. The plating film according to claim 8, wherein the cobalt plating film or the platinum plating film has a thickness of 1.0 μm or less.

10. The cobalt plating film is provided.

10. The plating film according to claim 8, further comprising a nickel plating film and / or a platinum plating film on the upper side of the cobalt plating film.

11. The cobalt plating film is provided.

10. The plating film according to claim 8, further comprising a platinum plating film on the upper side of the cobalt plating film.

12. The cobalt plating film is provided. The plating film according to any one of claims 8 to 11, wherein the cobalt plating film contains a transition metal element of Group 5 and / or Group 6 of the periodic table.

13. The plating film according to claim 12, wherein the content of a transition metal element of Group 5 and / or Group 6 of the periodic table in the cobalt plating film is 3 to 70 mass %.

14. The plating film according to any one of claims 8 to 13, wherein the total thickness is 15 µm or less.

15. A substrate; A circuit formed on the substrate; and A power module substrate having a plating film formed on the circuit surface, The power module substrate, wherein the plating film is the plating film according to any one of claims 8 to 14.

16. 16. The power module substrate according to claim 15, wherein the circuit is made of copper and / or aluminum.

17. 17. The power module substrate according to claim 15, wherein a surface of the plating film is a silver sintered bonding surface.

18. A power module substrate according to any one of claims 15 to 17, comprising a semiconductor element, A semiconductor device in which the surface of the plating film of the power module substrate and the semiconductor element are bonded by silver sintering.

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