Semiconductor device and method for manufacturing the same

Abstract

To keep the solder thickness at which constant heat dissipation can be maintained.SOLUTION: A semiconductor device includes a metal base plate 30 in which an arrangement region is set on a front surface apart from a center line CL, and a ceramic circuit board 21 provided in the arrangement region through solders 25a and 25b. Here, the thickness of the solders 25a and 25b at an end apart from the center line CL is larger than the thickness thereof at an end part close to the center line CL. In a region outside the solders 25a and 25b, generation of shrinkage cavity is suppressed. By such a manufacturing method, the increase in thermal resistance of the solders 25a and 25b is suppressed and the decrease in heat dissipation of the semiconductor device 10 is also suppressed while the increase in quantity of the solders 25a and 25b is suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device. [Background technology]

[0002] The semiconductor device includes a plurality of substrates, semiconductor elements mounted on the substrates, and a metal base plate to which the substrates are bonded on the front surface. The substrate includes a ceramic substrate, a metal plate provided on the rear surface of the ceramic substrate, and a circuit pattern provided on the front surface of the ceramic substrate. The semiconductor elements are provided on the circuit pattern of the substrate. The semiconductor elements are power devices. The power devices are, for example, IGBTs (Insulated Gate Bipolar Transistors) and power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). A plurality of substrates each provided with such semiconductor elements are provided on a metal base plate via solder. In the semiconductor device, heat from the semiconductor elements is conducted from the substrate to the metal base plate and dissipated. In order to improve the heat dissipation of the semiconductor device, it is desirable to thin the solder between the substrate and the metal base plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-170826 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in semiconductor devices, if the solder is made too thin, cavities (shrinkage cavities) will occur inside the solder. If shrinkage cavities occur in the solder, the thermal conductivity of the solder will decrease. As a result, the heat dissipation ability of the semiconductor device will decrease, leading to a decrease in characteristics. On the other hand, if the solder is made thicker to prevent shrinkage cavities from occurring, it will not be possible to improve heat dissipation.

[0005] The present invention has been made in consideration of these points, and aims to provide a semiconductor device and a method for manufacturing a semiconductor device in which a solder thickness is maintained to maintain a constant heat dissipation property. [Means for solving the problem]

[0006] According to one aspect of the present invention, a metal base plate having an arrangement area set on its front surface, spaced apart from a center, and a first protrusion formed in a first formation position on the arrangement area closer to the center and a second protrusion formed in a second formation position on a side farther from the center than the first formation position; and a substrate provided in the arrangement area via solder, wherein the first protrusion abuts against a rear surface of the substrate, the second protrusion has a length substantially equal to that of the first protrusion, the second protrusion is spaced apart from the rear surface of the substrate, and the thickness of the solder at an end away from the center is thicker than the thickness of the end close to the center; A semiconductor device is provided.

[0007] According to another aspect of the present invention, a metal base plate having an arrangement area set on its front surface away from a center, and a substrate provided in the arrangement area via solder, the arrangement area of ​​the metal base plate being set in a plurality of areas along a predetermined direction from the center, the substrate being provided in each of the arrangement areas via the solder, and the thickness of the solder in the outermost arrangement area along the predetermined direction from the center is greater at an end away from the center than at an end closer to the center; A semiconductor device is provided. According to another aspect of the present invention, there is provided a method for manufacturing the above semiconductor device. Effect of the Invention

[0008] According to the disclosed technology, a solder thickness that can maintain a certain level of heat dissipation can be maintained, enabling stable operation. [Brief description of the drawings]

[0009] [Figure 1] 1 is a plan view of a semiconductor device according to a first embodiment. [Diagram 2] 1 is a cross-sectional view of a semiconductor device according to a first embodiment. [Diagram 3] 4 is a flowchart of a first semiconductor device manufacturing method. [Figure 4] FIG. 13 is a diagram for explaining a setting for a solder bonding apparatus in the first semiconductor device manufacturing method. [Diagram 5] FIG. 2 is a diagram for explaining heating by a solder bonding apparatus in the first semiconductor device manufacturing method. [Figure 6] FIG. 11 is a diagram for explaining cooling in a solder bonding apparatus in the first semiconductor device manufacturing method. [Figure 7] FIG. 11 is a cross-sectional view of a semiconductor device according to a second embodiment. [Figure 8] 13 is a flowchart of a second semiconductor device manufacturing method. [Figure 9] FIG. 13 is a diagram for explaining a setting for a solder bonding apparatus in the second semiconductor device manufacturing method. [Figure 10] FIG. 13 is a plan view of a semiconductor device according to a third embodiment. [Figure 11] FIG. 11 is a cross-sectional view of a semiconductor device according to a third embodiment. [Figure 12] FIG. 13 is a plan view of a semiconductor device according to a fourth embodiment. [Figure 13] FIG. 13 is a cross-sectional view of a semiconductor device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiment will be described with reference to the drawings. In the following description, the terms "front surface" and "upper surface" refer to the surface facing upward in the semiconductor device 10 of FIG. 2. Similarly, "upper" refers to the upward direction in the semiconductor device 10 of FIG. 2. The terms "rear surface" and "lower surface" refer to the surface facing downward in the semiconductor device 10 of FIG. 2. Similarly, "lower" refers to the downward direction in the semiconductor device 10 of FIG. 2. Similar orientations are used in other drawings as necessary. The terms "front surface", "upper surface", "upper", "rear surface", "lower surface", "lower", and "side surface" are merely convenient expressions for specifying relative positional relationships and do not limit the technical idea of ​​the present invention. For example, "upper" and "lower" do not necessarily mean the vertical direction with respect to the ground. In other words, the directions of "upper" and "lower" are not limited to the direction of gravity.

[0011] [First embodiment] A semiconductor device according to a first embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a plan view of the semiconductor device according to the first embodiment, and Fig. 2 is a cross-sectional view of the semiconductor device according to the first embodiment. In Fig. 1, the positions at which protrusions 32a-35a and protrusions 32b-35b are formed are indicated by dashed lines. Fig. 2 shows a cross-sectional view taken along dashed line XX in Fig. 1.

[0012] The semiconductor device 10 includes two semiconductor units 20a, 20b and a metal base plate 30 on which the semiconductor units 20a, 20b are provided via solders 25a, 25b. In the following description, the semiconductor units 20a, 20b will be referred to as the semiconductor unit 20 unless otherwise specified.

[0013] The semiconductor unit 20 includes a ceramic circuit board 21 and semiconductor chips 28a and 28b arranged on the ceramic circuit board 21 via solder. The ceramic circuit board 21 is rectangular in plan view. The ceramic circuit board 21 includes an insulating plate 22, a metal plate 23 provided on the back surface of the insulating plate 22, and circuit patterns 24a to 24d provided on the front surface of the insulating plate 22. The insulating plate 22 and the metal plate 23 are rectangular in plan view. The corners may be chamfered in an R shape or a C shape. The size of the metal plate 23 is smaller than the size of the insulating plate 22 in plan view, and is formed inside the insulating plate 22. The insulating plate 22 is made of ceramics with good thermal conductivity. Examples of such ceramics include aluminum oxide, aluminum nitride, and silicon nitride. The metal plate 23 is made of a metal with excellent thermal conductivity. Examples of such metals include aluminum, iron, silver, copper, or an alloy containing at least one of these. The thickness of the metal plate 23 is 0.1 mm or more and 2.0 mm or less. The surface of the metal plate 23 may be plated to improve corrosion resistance. In this case, the plating material used is, for example, nickel, a nickel-phosphorus alloy, or a nickel-boron alloy. The circuit patterns 24a to 24d are made of a metal having excellent electrical conductivity. Such a metal is, for example, silver, copper, nickel, or an alloy containing at least one of these. The thickness of the circuit patterns 24a to 24d is 0.5 mm or more and 1.5 mm or less. The surface of the circuit patterns 24a to 24d may be plated to improve corrosion resistance. In this case, the plating material used is, for example, nickel, a nickel-phosphorus alloy, or a nickel-boron alloy. Such circuit patterns 24a to 24d are obtained by forming a metal layer on the front surface of the insulating plate 22 and performing a process such as etching on the metal layer. Alternatively, the circuit patterns 24a to 24d cut out in advance from the metal layer may be pressure-bonded to the front surface of the insulating plate 22. 1 are merely examples. The number, shape, size, and other factors of the circuit patterns can be appropriately selected as necessary.For example, a direct copper bonding (DCB) substrate or an active metal brazed (AMB) substrate can be used for the ceramic circuit board 21 that is configured with such components.

[0014] The semiconductor chip 28a includes a switching element. The switching element is, for example, an IGBT or a power MOSFET. When the semiconductor chip 28a is an IGBT, it has a collector electrode as a main electrode on the back surface, and a gate electrode and an emitter electrode as a main electrode on the front surface. When the semiconductor chip 28a is a power MOSFET, it has a drain electrode as a main electrode on the back surface, and a gate electrode and a source electrode as a main electrode on the front surface. The back surface of the semiconductor chip 28a is bonded to the circuit patterns 24b and 24c by solder (not shown). Wiring members are electrically and mechanically connected to the main electrode and gate electrode on the front surface of the semiconductor chip 28a as appropriate. The wiring members are, for example, bonding wires, lead frames, pin-shaped or ribbon-shaped members.

[0015] The semiconductor chip 28b also includes a diode. The diode is, for example, an FWD (Free Wheeling Diode) such as an SBD (Schottky Barrier Diode) or a PiN (P-intrinsic-N) diode. Such a semiconductor chip 28b has an output electrode (cathode electrode) as a main electrode on the back surface and an input electrode (anode electrode) as a main electrode on the front surface. The back surface of the semiconductor chip 28b is joined to the circuit patterns 24b and 24c by solder (not shown). Wiring members are also electrically and mechanically connected appropriately to the main electrodes on the front surface of the semiconductor chip 28b. The wiring members are, for example, bonding wires, lead frames, or pin-shaped or ribbon-shaped members. Note that, instead of the semiconductor chips 28a and 28b, IGBTs and FWDAlternatively, a reverse-conducting (RC)-IGBT having both the functions may be used. FIG. 1 merely shows a case where two sets of semiconductor chips 28a, 28b are provided. The number of sets is not limited to two, and may be set according to the specifications of the semiconductor device 10. If necessary, electronic components may be arranged on the circuit patterns 24b, 24c according to the specifications of the semiconductor device 10. The necessary number of electronic components are bonded to the circuit patterns 24b, 24c via solder. The electronic components are appropriately selected so that the semiconductor device 10 can perform the desired functions. Such electronic components are, for example, a control integrated circuit (IC), a thermistor, a capacitor, and a resistor.

[0016] Lead-free solder is used for the solder that joins the semiconductor chips 28a, 28b and the circuit patterns 24b, 24c. The lead-free solder mainly contains at least one of the following alloys: an alloy of tin-silver-copper, an alloy of tin-zinc-bismuth, an alloy of tin-copper, and an alloy of tin-silver-indium-bismuth. Furthermore, the solder may contain additives. The additives are, for example, nickel, germanium, cobalt, or silicon. By containing additives, the solder can have improved wettability, gloss, and bonding strength, thereby improving reliability.

[0017] The metal base plate 30 is made of a metal having excellent thermal conductivity. Such metals are, for example, aluminum, iron, silver, copper, or an alloy containing at least one of these. In addition, a plating process may be performed on the surface of the metal base plate 30 to improve corrosion resistance. In this case, the plating material used is, for example, nickel, a nickel-phosphorus alloy, or a nickel-boron alloy. In addition, the metal base plate 30 has a larger thermal expansion coefficient than the ceramic circuit board 21. The metal base plate 30 may be rectangular in a plan view. In addition, the corners may be chamfered into an R shape or a C shape. Such a metal base plate 30 includes a heat sink 31 and protrusions 32a to 35a, 32b to 35b formed on the front surface of the heat sink 31. The heat sink 31 is a part of the metal base plate 30 that forms a flat plate shape. As shown in FIG. 2, the heat sink 31 is warped downward in a convex shape. That is, the short and long sides of the heat sink 31 are warped upward from the center so that the center is on the lower side. This is due to heating performed during the manufacturing process of the semiconductor device 10, as described later. The average thickness of the entire heat sink 31 is 1 mm or more and 10 mm or less. In addition, the heat sink 31 has arrangement areas 36a and 36b set symmetrically with the center as the center. The semiconductor units 20a and 20b are arranged in the arrangement areas 36a and 36b, as described later. The metal base plate 30 (heat sink 31) is warped downward and convexly from the center. For this reason, the arrangement areas 36a and 36b are not set at the center of the heat sink 31, but are set symmetrically with respect to the center line CL of the heat sink 31. Specifically, in the case of FIG. 1, the arrangement areas 36a and 36b are set on the left and right sides, respectively, of the center line CL that passes through the center of the heat sink 31 and is parallel to the short side direction. If necessary, mounting holes are formed in the corners of the heat sink 31. The metal base plate 30 is attached to a predetermined location by screwing into the mounting holes, and a cooler, which will be described later, is also attached.

[0018] Moreover, the metal base plate 30 has the protrusions 32a to 35a and 32b to 35b integrally formed at the corners of the arrangement areas 36a and 36b of the heat sink 31. The arrangement areas 36a and 36b of the heat sink 31 may be located opposite the semiconductor units 20a and 20b. That is, the arrangement areas 36a and 36b of the heat sink 31 may be located opposite the rear surface of the metal plate 23 of the ceramic circuit board 21. Therefore, the protrusions 32a to 35a and 32b to 35b may be located opposite the corners of the semiconductor units 20a and 20b. Furthermore, they may be located opposite the corners of the rear surface of the metal plate 23 of the ceramic circuit board 21. In the first embodiment, the protrusions 32a to 35a and 32b to 35b have the same height. The height is, for example, 0.05 mm or more and 0.5 mm or less. The diameter of the protrusions 32a to 35a, 32b to 35b is, for example, 50 μm or more and 500 μm or less. The protrusions 32a to 35a, 32b to 35b are not limited to the rod-like shape shown in FIG. 2. The protrusions 32a to 35a, 32b to 35b may be, for example, hemispherical, semi-elliptical, or cubic. Alternatively, the protrusions 32a and 34a may be connected to each other to form a convex shape along the side of the ceramic circuit board 21. Similarly, the protrusions 33b and 35b, the protrusions 33a and 35a, and the protrusions 32b and 34b may be connected to each other to form a convex shape along the side of the ceramic circuit board 21.

[0019] A cooler (not shown) may be attached to the back surface of the metal base plate 30 via solder or silver solder. At this time, the mounting holes of the metal base plate 30 and the cooler are screwed. This improves the heat dissipation of the metal base plate 30. The cooler in this case is made of, for example, a metal with excellent thermal conductivity. Such metals are, for example, aluminum, iron, silver, copper, or an alloy containing at least one of these. In addition, as the cooler, a heat sink composed of fins or multiple fins, a water-cooled cooling device, or the like can be applied. In addition, the metal base plate 30 may be integrated with such a cooler. In this case, it is also made of a metal with excellent thermal conductivity. Such metals are, for example, aluminum, iron, silver, copper, or an alloy containing at least one of these. Then, a plating process may be performed on the surface of the cooler integrated with the metal base plate 30 in order to improve corrosion resistance. In this case, the plating material used is, for example, nickel, a nickel-phosphorus alloy, or a nickel-boron alloy.

[0020] The semiconductor units 20a, 20b are provided in the arrangement regions 36a, 36b of the metal base plate 30 via the solders 25a, 25b. At this time, as shown in Fig. 2, the solders 25a, 25b are formed between the front surface of the metal base plate 30 and the rear surface of the metal plate 23 of the ceramic circuit board 21. This bonds the front surface of the metal base plate 30 to the rear surface of the metal plate 23 of the ceramic circuit board 21. The solders 25a, 25b form fillets that smoothly flare outward from the ends of the metal plate 23.

[0021] 2, the thickness of the ends of the solders 25a, 25b away from the center line CL (center) of the metal base plate 30 is thicker than the thickness of the ends of the solders 25a, 25b close to the center line CL. It is preferable that the thickness of the ends of the solders 25a, 25b away from the center line CL (center) of the metal base plate 30 is 10% or more and 400% or less thicker than the thickness of the ends of the solders 25a, 25b close to the center line CL. For example, the thickness of the ends of the solders 25a, 25b away from the center line CL (center) is 0.40 mm, and the thickness of the ends of the solders 25a, 25b close to the center line CL is 0.25 mm. Here, the thickness of the ends of the solders 25a, 25b may be the thickness of the solders 25a, 25b formed between the rear surface of the end of the metal plate 23 formed on the ceramic circuit board 21 and the front surface of the heat sink 31 excluding the protrusions 32a-35a, 32b-35b of the metal base plate 30. The solders 25a, 25b may be thicker as they move away from the center line CL of the metal base plate 30. Alternatively, depending on the warping of the metal base plate 30, the solders 25a, 25b may have a portion between the end close to the center line CL and the end away from the center line CL that is thinner than the end away from the center line CL.

[0022] In addition, the tips of the protrusions 32a, 34a and the protrusions 33b, 35b on the side closer to the center line CL of the metal base plate 30 are in contact with the back surface of the semiconductor units 20a, 20b. On the other hand, the protrusions 33a, 35a and the protrusions 32b, 34b away from the center line CL are all separated from the back surface of the semiconductor units 20a, 20b with gaps 26a, 26b therebetween, including their tips. Note that FIG. 2 only shows the protrusions 32a, 33a and the protrusions 32b, 33b side. The same is true for the protrusions 34a, 35a and the protrusions 34b, 35b side. That is, the semiconductor units 20a, 20b are joined by the solders 25a, 25b in an inclined state such that the end closer to the center line CL of the metal base plate 30 is lower than the end farther from the center. Therefore, the thickness of the solders 25a, 25b is greater at the ends away from the center line CL (center) of the metal base plate 30 than at the ends close to the center line CL. Also, the amount of the solders 25a, 25b protruding from the ends of the metal plate 23 on the front surface of the metal base plate 30 is greater at the ends away from the center line CL (center) than at the ends close to the center line CL. Therefore, the fillets of the solders 25a, 25b at the ends away from the center line CL of the metal base plate 30 are greater than the fillets at the ends close to the center line CL.

[0023] In the first embodiment, although not shown, the semiconductor device 10 may be sealed with a sealing resin. In this case, the sealing member contains a thermosetting resin such as an epoxy resin, a phenolic resin, or a maleimide resin, and a filler contained in the thermosetting resin. An example of the sealing member is an epoxy resin containing a filler. An inorganic filler is used as the filler. Examples of the inorganic filler include silicon oxide, aluminum oxide, boron nitride, and aluminum nitride.

[0024] Next, a method for manufacturing such a semiconductor device 10 will be described with reference to Figs. 3 to 6. Fig. 3 is a flow chart of the first semiconductor device manufacturing method. Fig. 4 is a diagram for explaining a setting in a solder bonding apparatus in the first semiconductor device manufacturing method, and Fig. 5 is a diagram for explaining heating in the solder bonding apparatus in the first semiconductor device manufacturing method. Fig. 6 is a diagram for explaining cooling in the solder bonding apparatus in the first semiconductor device manufacturing method. Figs. 4 to 6 are cross-sectional views at a position corresponding to the dashed dotted line XX in Fig. 1.

[0025] First, components of the semiconductor device 10, such as the semiconductor chips 28a and 28b, the ceramic circuit board 21, the metal base plate 30, and the solder plate, are prepared (step S1). Note that the metal base plate 30 has the protrusions 32a to 35a and the protrusions 32b to 35b formed in advance in the set placement areas 36a and 36b, respectively.

[0026] Next, the metal base plate 30 is set in a predetermined area of ​​the solder bonding device 50. The center of the metal base plate 30 may be warped upward in a convex shape. That is, the center of the metal base plate 30 may be warped upward from the short side and the long side. The solder plates 27a and 27b are set so as to be supported by the protrusions 32a to 35a and the protrusions 32b to 35b formed in the arrangement areas 36a and 36b of the metal base plate 30. The solder plates 27a and 27b are plate-shaped and made of the same composition as the solders 25a and 25b. The solder plates 27a and 27b are sized so that the corners of the solder plates 27a and 27b are supported by the protrusions 32a to 35a and the protrusions 32b to 35b, respectively, in a plan view. The thickness of the solder plates 27a and 27b is configured to be approximately the same as or several percent higher than the height of the protrusions 32a to 35a and the protrusions 32b to 35b. The ceramic circuit board 21 is set on the solder plates 27a and 27b, and the semiconductor chips 28a and 28b are set on the circuit patterns 24b and 24c of the ceramic circuit board 21 via solder plates (not shown) (step S2). The solder plates are also of the same type as the solder plates 27a and 27b. In step S2, a jig that can be aligned with the arrangement areas 36a and 36b of the metal base plate 30 is used. Such a jig is flat and has the same size as the metal base plate 30 in a plan view, and has openings that are slightly larger than the size of the arrangement areas 36a and 36b in the areas corresponding to the arrangement areas 36a and 36b. The jig is also configured from a material with excellent heat resistance. Such a material is, for example, a composite ceramic material or carbon. In the openings of a jig set on a metal base plate 30, the solder plates 27a and 27b, the ceramic circuit board 21, the solder plates, and the semiconductor chips 28a and 28b are set.

[0027] Next, as shown in FIG. 4, weights 41a and 41b are respectively set on the center line CL side of the metal base plate 30 of the ceramic circuit board 21 (step S3). The weights 41a and 41b are, for example, rectangular in plan view. Such weights 41a and 41b are provided on the outer edge of the ceramic circuit board 21 along the opposing sides of the ceramic circuit board 21. For example, the weights 41a and 41b are preferably located above the protrusions 32a and 34a and the protrusions 33b and 35b in side view. Note that such weights 41a and 41b are also made of a material having excellent heat resistance. Such a material is, for example, a composite ceramic material or carbon.

[0028] Next, the soldering device 50 is driven to heat the solder plates 27a and 27b via the metal base plate 30 (step S4). The heat generated by the soldering device 50 is conducted to the rear surface of the metal base plate 30. When the metal base plate 30 is heated, it is warped so that the center is convex downward. In other words, the metal base plate 30 is warped so that the short and long sides are higher than the center. Therefore, the rear surface of the metal base plate 30 is heated by the soldering device 50 from the center (center line CL) of the rear surface of the metal base plate 30 to the outer edge of the metal base plate 30 (heat sink 31) along the dashed arrow in FIG. 5. The heat is conducted to the protrusions 32a to 35a and the protrusions 32b to 35b via the heat sink 31. Then, the solder plates 27a and 27b supported by the protrusions 32a to 35a and the protrusions 32b to 35b are heated and melted. The molten solders 27a1, 27b1 melted from the solder plates 27a, 27b are pressed toward the arrangement regions 36a, 36b by the ceramic circuit board 21. At this time, the ceramic circuit board 21 is pressed toward the arrangement regions 36a, 36b by the weights 41a, 41b, and the end of the ceramic circuit board 21 far from the center line CL is raised above the side pressed by the weights 41a, 41b. In this state, the thickness of the end of the molten solders 27a1, 27b1 completely melted from the solder plates 27a, 27b far from the center line CL of the metal base plate 30 is thicker than the thickness of the end close to the center line CL, as shown in FIG. The protrusions 32a to 35a and the protrusions 32b to 35b are rod-shaped. Therefore, the molten solder 27a1, 27b1 melted from the solder plates 27a, 27b can easily flow down the protrusions 32a-35a and the protrusions 32b-35b to the arrangement regions 36a, 36b. The protrusions 32a-35a and the protrusions 32b-35b are rod-shaped and provided at the corners of the arrangement regions 36a, 36b. Therefore, the molten solder 27a1, 27b1 is unlikely to be hindered from spreading to the arrangement regions 36a, 36b. The protrusions 32a, 34a and the protrusions 33b, 35b on the side closer to the center line CL of the metal base plate 30 are in contact with the rear surfaces of the semiconductor units 20a, 20b at least at their tips.On the other hand, the protrusions 33a, 35a and the protrusions 32b, 34b far from the center line CL are separated from the rear surface of the semiconductor units 20a, 20b at all points including their tips by leaving gaps 26a, 26b. In addition, the ceramic circuit board 21 may be pressed with a weight, and a resist material may be applied parallel to the center line CL to the outside of the side far from the center line CL of the arrangement areas 36a, 36b so that the molten solders 27a1, 27b1 have the shape shown in FIG. 6. The resist material can prevent the molten solders 27a1, 27b1 from flowing outward from the center line CL. This ensures that the thickness of the end of the molten solders 27a1, 27b1 far from the center line CL of the metal base plate 30 is thicker than the end of the molten solders close to the center line CL.

[0029] Next, the operation of the soldering device 50 is stopped to cool the molten solders 27a1 and 27b1 (step S5). When the heat generation of the soldering device 50 is stopped, the metal base plate 30 (heat sink 31) is cooled from the center (center line CL) toward the outer edge of the metal base plate 30 (heat sink 31) along the dashed arrow shown in FIG. 6. Accordingly, the molten solders 27a1 and 27b1 are also cooled from the center line CL toward the outside. The outer regions of the molten solders 27a1 and 27b1 that are cooled in this manner last are condensed and the volume shrinks. At this time, as the outer regions of the molten solders 27a1 and 27b1 shrink, the volume of the surroundings is further condensed to compensate for the volume of the shrinkage. At this time, if there is not enough volume to compensate, a space is formed and a shrinkage cavity is generated. However, in the first embodiment, as shown in FIG. 6, the thickness of the molten solder 27a1, 27b1 at the end away from the center line CL of the metal base plate 30 is thicker than the thickness of the end close to the center line CL. Therefore, as the outer regions of the molten solder 27a1, 27b1 shrink, the volume of the shrinkage can be compensated for, and the occurrence of shrinkage cavities can be suppressed. In this way, the molten solder 27a1, 27b1 is cooled and solidified to become the solder 25a, 25b. As a result, the semiconductor unit 20a, 20b is bonded to the metal base plate 30 by the solder 25a, 25b, and the semiconductor device 10 is manufactured. The semiconductor device 10 is removed from the solder bonding device 50, and the semiconductor device 10 shown in FIG. 2 is obtained. In the flowchart of FIG. 3, weights 41a, 41b are used to tilt the ceramic circuit board 21. However, the present invention is not limited to this case, and a part or a jig having a function of pressing the center line CL side of the ceramic circuit board 21 when melting the solder plates 27a and 27b may be used.

[0030] In this manner, the semiconductor device 10 places the ceramic circuit board 21 in the arrangement regions 36a, 36b of the metal base plate 30 via the solder plates 27a, 27b, and melts the solder plates 27a, 27b while pressing the side of the front surface of the ceramic circuit board 21 close to the center line CL of the metal base plate 30 toward the metal base plate 30, thereby joining the ceramic circuit board 21 to the arrangement regions 36a, 36b. By melting the solder plates 27a, 27b while pressing the side of the front surface of the ceramic circuit board 21 close to the center line CL of the metal base plate 30 toward the metal base plate 30, the thickness of the end of the molten solder 27a1, 27b1 away from the center line CL becomes thicker than the thickness of the end close to the center line CL. Therefore, as the region outside the molten solder 27a1, 27b1 shrinks, the volume of the shrinkage can be compensated for, and the occurrence of shrinkage cavities can be suppressed.

[0031] The semiconductor device 10 thus manufactured includes a metal base plate 30 having arrangement regions 36a, 36b on its front surface, spaced apart from the center line CL, and a ceramic circuit board 21 provided in the arrangement regions 36a, 36b via solders 25a, 25b. In this case, the thickness of the ends of the solders 25a, 25b away from the center line CL is greater than the thickness of the ends close to the center line CL. The generation of shrinkage cavities is suppressed in the regions outside the solders 25a, 25b. This manufacturing method suppresses an increase in the amount of the solders 25a, 25b, while also suppressing an increase in the thermal resistance of the solders 25a, 25b, and prevents a decrease in the heat dissipation performance of the semiconductor device 10. Therefore, the semiconductor device 10 is prevented from decreasing in reliability and operates stably.

[0032] [Second embodiment] A semiconductor device 10a according to a second embodiment will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view of the semiconductor device according to the second embodiment. FIG. 7 is a cross-sectional view of a portion corresponding to the dashed dotted line XX in FIG. 1. The semiconductor device 10a has the same plan view as FIG. 1. The same reference numerals are used to designate the same components as the semiconductor device 10 according to the first embodiment, and detailed descriptions thereof will be simplified or omitted.

[0033] The protrusions 32a-35a and protrusions 32b-35b formed in the arrangement regions 36a, 36b of the metal base plate 30 of the semiconductor device 10a are formed so that the protrusions 33a, 35a and protrusions 32b, 34b on the outer side of the center line CL are higher than the protrusions 32a, 34a and protrusions 33b, 35b on the center line CL side. The heights of the protrusions 33a, 35a and protrusions 32b, 34b are 50% or more and 400% or less higher than the heights of the protrusions 32a, 34a and protrusions 33b, 35b. For example, the heights of the protrusions 33a, 35a and protrusions 32b, 34b are 0.35 mm, and the heights of the protrusions 32a, 34a and protrusions 33b, 35b are 0.10 mm. The protrusions 32a-35a and the protrusions 32b-35b on the side closer to and the side farther from the center line CL of the metal base plate 30 are in contact with the rear surfaces of the semiconductor units 20a and 20b at their tips. Note that FIG. 7 only shows the protrusions 32a, 33a and the protrusions 32b, 33b. The protrusions 34a, 35a and the protrusions 34b, 35b are similar. The thickness of the end of the solder 25a, 25b away from the center line CL (center) of the metal base plate 30 is thicker than the thickness of the end of the solder 25a, 25b close to the center line CL. Here, the thickness of the end of the solder 25a, 25b may be the thickness of the solder 25a, 25b formed between the rear surface of the end of the metal plate 23 formed on the ceramic circuit board 21 and the front surface of the heat sink 31 excluding the protrusions 32a-35a, 32b-35b of the metal base plate 30. That is, the ends of the semiconductor units 20a and 20b near the center line CL of the metal base plate 30 are center line CLThe solder 25a and 25b are joined in a slanted state so that the end portion is lower than the end portion farther from the center line CL. The amount of the solder 25a and 25b protruding from the end portion of the metal plate 23 on the front surface of the metal base plate 30 is greater at the end portion farther from the center line CL (center) than at the end portion closer to the center line CL. Therefore, the fillets of the solder 25a and 25b at the end portion farther from the center line CL of the metal base plate 30 are larger than the fillets at the end portion closer to the center line CL. The semiconductor device 10a may also have a convex shape in which the projections 32a and 34a are connected to each other and extend along the sides of the ceramic circuit board 21. The projections 33b and 35b, the projections 33a and 35a, and the projections 32b and 34b may also have a convex shape in which the projections 33a and 35a are connected to each other and extend along the sides of the ceramic circuit board 21. The projections 33a and 35a are connected to each other and are higher than the projections 32a and 34a. The protrusions 32b to 35b have the same height.

[0034] A method for manufacturing such a semiconductor device 10a will be described with reference to Figs. 8 and 9. Fig. 8 is a flowchart of a method for manufacturing a second semiconductor device. Fig. 9 is a diagram for explaining a set for a solder bonding apparatus in the method for manufacturing a second semiconductor device. In the flowchart of Fig. 8, detailed descriptions of the same steps as those in the flowchart of Fig. 3 are simplified or omitted. Fig. 9 is also a cross-sectional view at a position corresponding to the dashed dotted line XX in Fig. 1, and corresponds to Fig. 4 of the first embodiment.

[0035] First, like the first embodiment, components of the semiconductor device 10a, such as the semiconductor chips 28a, 28b, the ceramic circuit board 21, the metal base plate 30, the solder plate, etc., are prepared (step S1). The metal base plate 30 is prepared as shown in Fig. 7. That is, the metal base plate 30 is prepared in advance such that the protrusions 33a, 35a and the protrusions 32b, 34b on the outer side of the center line CL are higher than the protrusions 32a, 34a and the protrusions 33b, 35b on the center line CL side in the arrangement regions 36a, 36b.

[0036] Next, the metal base plate 30 is set in a predetermined area of ​​the solder bonding device 50. The center of the metal base plate 30 may also be warped upward to some extent. That is, the center of the metal base plate 30 may be warped upward from the short and long sides. The solder plates 27a and 27b are set so as to be supported by the protrusions 32a to 35a and protrusions 32b to 35b formed in the arrangement areas 36a and 36b of the metal base plate 30. The solder plates 27a and 27b are supported by the protrusions 32a to 35a and protrusions 32b to 35b of different heights, and are inclined so that the center line CL side is lower than the outside away from the center line CL. As shown in FIG. 9, the ceramic circuit board 21 is placed on the solder plates 27a and 27b, and the semiconductor chips 28a and 28b are placed on the circuit patterns 24b and 24c of the ceramic circuit board 21 via solder plates (not shown) (step S2).

[0037] In steps S3 and S4, the same processes as steps S4 and S5 in the flowchart of FIG. 3 are performed. That is, the solder bonding device 50 is driven to heat the solder plates 27a and 27b via the back surface of the metal base plate 30 (step S3). As a result, the center of the metal base plate 30 is warped in a downward convex shape. Then, the molten solders 27a1 and 27b1 melted from the solder plates 27a and 27b spread between the back surface of the ceramic circuit board 21 and the arrangement areas 36a and 36b. Even in this case, in order to prevent the molten solders 27a1 and 27b1 from spreading too much, a resist material may be applied parallel to the center line CL to the outside of the sides farther from the center line CL of the arrangement areas 36a and 36b.

[0038] In addition, when the protrusions 33a, 35a and the protrusions 32b, 34b are higher than the protrusions 32a, 34a and the protrusions 33b, 35b by, for example, 100 μm or more, the molten solders 27a1, 27b1 may be thinner at the end farther from the center line CL of the ceramic circuit board 21 than at the end closer to the center line CL. On the other hand, when the protrusions 33a, 35a and the protrusions 32b, 34b are sufficiently higher than the protrusions 32a, 34a and the protrusions 33b, 35b, the molten solders 27a1, 27b1 may not fill the end farther from the center line CL of the ceramic circuit board 21. In this case, the entire end of the solders 25a, 25b solidified from the molten solders 27a1, 27b1 in the subsequent process farther from the center line CL of the ceramic circuit board 21 will not be supported by the fillet. On the other hand, when protrusions 33a, 35a and protrusions 32b, 34b are approximately 100 μm taller than protrusions 32a, 34a and protrusions 33b, 35b, molten solder 27a1, 27b1 can reliably fill up to the end farther from center line CL of ceramic circuit board 21. As a result, the thickness of molten solder 27a1, 27b1 at the end farther from center line CL of metal base plate 30 is greater than the thickness of the end closer to center line CL.

[0039] Next, the molten solders 27a1, 27b1 melted from the solder plates 27a, 27b are cooled (step S4). In this manner, the molten solders 27a1, 27b1 are cooled and solidified to become the solders 25a, 25b. The solders are then removed from the solder bonding device 50, and as shown in FIG. 7, the ceramic circuit board 21 is fixed to the metal base plate 30, thereby obtaining the semiconductor device 10a.

[0040] In this manner, in the semiconductor device 10a, the ceramic circuit board 21 is placed on the protrusions 32a, 34a, 33b, 35b and the protrusions 33a, 35a, 32b, 34b formed in the arrangement regions 36a, 36b of the metal base plate 30 via the solder plates 27a, 27b, and the solder plates 27a, 27b are melted to bond the ceramic circuit board 21 to the arrangement regions 36a, 36b. As a result, the thickness of the end of the molten solder 27a1, 27b1 away from the center line CL is thicker than the end of the molten solder 27a1, 27b1 close to the center line CL. Therefore, as the region outside the molten solder 27a1, 27b1 shrinks, the volume of the shrinkage can be compensated for, and the occurrence of shrinkage cavities can be suppressed. Therefore, compared to the first embodiment, a pressing process (by weights 41a, 41b) is not required, and the manufacturing cost is reduced. Furthermore, the semiconductor device 10a uses the protrusions 32a, 34a, 33b, and 35b, and the protrusions 33a, 35a, 32b, and 34b that are taller than the protrusions 32a, 34a, 33b, and 35b. Therefore, the thickness of the ends of the solders 25a and 25b that are farther from the center line CL is thicker than the thickness of the ends that are closer to the center line CL. Therefore, it is possible to form a fillet that is thicker at the ends that are farther from the center line CL than at the ends that are closer to the center line CL more reliably than the first embodiment.

[0041] The semiconductor device 10a thus manufactured includes a metal base plate 30 having arrangement regions 36a, 36b on its front surface, spaced apart from the center line CL, and a ceramic circuit board 21 provided in the arrangement regions 36a, 36b via solders 25a, 25b. At this time, the thickness of the ends of the solders 25a, 25b away from the center line CL is thicker than the thickness of the ends close to the center line CL. The outside regions of the solders 25a, 25b are prevented from generating shrinkage cavities. This manufacturing method prevents an increase in the amount of the solders 25a, 25b, while also preventing an increase in the thermal resistance of the solders 25a, 25b, and prevents a decrease in the heat dissipation performance of the semiconductor device 10a. The protrusions 32a-35a and the protrusions 32b-35b all support the rear surfaces of the semiconductor units 20a, 20b. Therefore, the adhesion of the solders 25a, 25b to the metal base plate 30 is higher than that in the first embodiment, and the bonding between the metal base plate 30 and the semiconductor units 20a, 20b is improved. Therefore, the semiconductor device 10a is prevented from decreasing in reliability and operates stably.

[0042] [Third embodiment] A semiconductor device 10b according to the third embodiment will be described with reference to Figs. 10 and 11. Fig. 10 is a plan view of the semiconductor device according to the third embodiment, and Fig. 11 is a cross-sectional view of the semiconductor device according to the third embodiment. Fig. 11 is a cross-sectional view taken along dashed line XX in Fig. 10. In the third embodiment, the same components as those in the first and second embodiments are denoted by the same reference numerals. The description thereof will be simplified or omitted.

[0043] The semiconductor device 10b includes four semiconductor units 20c, 20d, 20e, and 20f, and a metal base plate 30 on which the semiconductor units 20c, 20d, 20e, and 20f are provided via solder (solder 25c for the semiconductor unit 20c). In the following description, the semiconductor units 20c, 20d, 20e, and 20f will be referred to as the semiconductor unit 20 unless otherwise specified.

[0044] Metal base plate 30 has heat sink 31 and protrusions 32c-35c, 32d-35d, 32e-35e, and 32f-35f formed on the front surface of heat sink 31. In addition, in Fig. 10, the positions where these protrusions 32c-35c, 32d-35d, 32e-35e, and 32f-35f are formed are indicated by dashed lines.

[0045] The heat sink 31 has rectangular arrangement regions 36c, 36d, 36e, and 36f set symmetrically about the center CP in a plan view. Specifically, the arrangement regions 36c and 36f are set point-symmetrically about the center CP. The arrangement regions 36d and 36e are set point-symmetrically about the center CP. Moreover, the arrangement regions 36c and 36d and the arrangement regions 36e and 36f are each line-symmetrical about a straight line (not shown) that passes through the center CP and is parallel to the short side. Furthermore, the arrangement regions 36c and 36e and the arrangement regions 36d and 36f are each line-symmetrical about a straight line (not shown) that passes through the center CP and is parallel to the long side.

[0046] At the corners of the arrangement regions 36c, 36d, 36e, and 36f, protrusions 32c to 35c, 32d to 35d, 32e to 35e, and 32f to 35f are integrally formed, respectively. The heights of these protrusions 32c to 35c, 32d to 35d, 32e to 35e, and 32f to 35f are configured to be higher in the protrusions farther from the center CP than in the protrusions closer to the center CP. For example, the case of the arrangement region 36c will be described. As shown in FIG. 11, among the protrusions 32c to 35c, the protrusion 32c closest to the center CP is the lowest, and the protrusion 35c farthest from the center CP is the highest. The heights of the protrusions 33c and 34c (the protrusion 33c is not shown in FIG. 11) are intermediate between them. In FIG. 11, the position of the protrusion 34c is indicated by a dashed line. By forming the protrusions 32c to 35c in this manner, when the ceramic circuit board 21 is placed in the placement area 36c via the solder 25c according to the flowchart of Fig. 8, the thickness of the end of the solder 25c away from the center CP is thicker than the thickness of the end of the solder 25c close to the center CP. 32c ~ 35c10, the thickness of the solder 25c formed between the semiconductor unit 20c and the front surface of the heat sink 31 excluding the area Fc. In this case, as shown in FIG. 10, the thickness of the solder 25c in the area Fc surrounded by the dashed line of the semiconductor unit 20c is thicker than the area Nc surrounded by the dashed line close to the center CP. Similarly, in the other arrangement areas 36d, 36e, 36f, among the protrusions 32d to 35d, 32e to 35e, 32f to 35f, the height of the protrusions 32d, 32e, 32f closest to the center CP is the lowest, and the height of the protrusions 35d, 35e, 35f farthest from the center CP is the highest. The heights of the protrusions 33d, 34d, 33e, 34e, 33f, 34f are intermediate between them. According to the flow chart of FIG. 8, when the ceramic circuit board 21 is placed in the arrangement areas 36d, 36e, and 36f via solder (not shown), the solder thickness at the end far from the center CP is thicker than the solder thickness at the end close to the center CP. In these cases, as shown in FIG. 10, the solder thickness at the areas Fd, Fe, and Ff surrounded by the dashed lines of the semiconductor units 20d, 20e, and 20f is thicker than the areas Nd, Ne, and Nf surrounded by the dashed lines close to the center CP. In addition, the amount of solder protruding from the end of the metal plate 23 on the front surface of the metal base plate 30 is larger at the end far from the center CP than at the end close to the center CP. Therefore, the fillet at the end far from the center CP of the metal base plate 30 is larger than the fillet at the end close to the center CP. In the following, the solder for joining the semiconductor units 20c, 20d, 20e, and 20f to the metal base plate 30 will be simply referred to as solder.

[0047] Such a semiconductor device 10b has a metal base plate 30 with arrangement areas 36c, 36d, 36e, and 36f set on the front surface away from the center CP, and a ceramic circuit board 21 provided via solder in the arrangement areas 36c, 36d, 36e, and 36f. In this case, the thickness of the end of the solder away from the center CP is thicker than the thickness of the end of the solder close to the center CP. The generation of shrinkage cavities is suppressed in the area outside the solder. With this manufacturing method, an increase in the amount of solder is suppressed, and an increase in the thermal resistance of the solder is also suppressed, and a decrease in the heat dissipation property of the semiconductor device 10b is also prevented. Therefore, the semiconductor device 10b is suppressed from decreasing in reliability and operates stably.

[0048] In addition, when the heights of the protrusions 32c-35c, 32d-35d, 32e-35e, and 32f-35f are all uniform in the semiconductor device 10b, the semiconductor device 10b is manufactured according to the flowchart of FIG. 3. In this case, in step S3, weights are set on the regions Nc, Nd, Ne, and Nf shown in FIG. 10, respectively. Alternatively, one weight may be set including the regions Nc, Nd, Ne, and Nf shown in FIG. 10. As a result, the back surface of the ceramic circuit board 21 is supported by the protrusions 32c, 33d, 34e, and 35f that are closest to the center CP. In addition, the back surface of the ceramic circuit board 21 is separated from the tips of the protrusions 35c, 34d, 33e, and 32f that are farthest from the center CP with a gap therebetween.

[0049] [Fourth embodiment] In the fourth embodiment, a case where a plurality of semiconductor units are linearly arranged on a metal base plate will be described with reference to Figs. 12 and 13. Fig. 12 is a plan view of the semiconductor device of the fourth embodiment, and Fig. 13 is a cross-sectional view of the semiconductor device of the fourth embodiment. Fig. 13 is a cross-sectional view taken along the dashed line XX in Fig. 12. In the fourth embodiment, the same components as those in the first to third embodiments are given the same reference numerals. The description of these components will be simplified or omitted. The semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l have the same configuration as the semiconductor unit 20. For this reason, the reference numerals for the components of the semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l are omitted in Figs. 12 and 13. Furthermore, in Fig. 12, the arrangement of the semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l is represented by a square. In FIG. 12, the positions of the protrusions are indicated by dashed lines and the reference numerals are omitted.

[0050] The semiconductor device 10c includes a plurality of semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l, and a metal base plate 30 on which the semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l are arranged. The semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l are electrically connected to each other by bonding wires as appropriate. Electronic components are also arranged on the metal base plate 30. The electronic components are electrically connected to the semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l by bonding wires as appropriate. The metal base plate 30 has arrangement regions 36g, 36h, and 36i and arrangement regions 36j, 36k, and 36l each set in a straight line across the center line CL. The semiconductor units 20g, 20h, 20i, 20j, 20k, and 20l are arranged in the arrangement regions 36g, 36h, 36i, 36j, 36k, and 36l via solder, respectively. In addition, protrusions of the same height are integrally formed at the corners of the arrangement regions 36g, 36h, 36i, 36j, 36k, and 36l, respectively, as in the first embodiment.

[0051] 13, in the semiconductor units 20g, 20l (ceramic circuit board 21) farthest from the center line CL (center) of the metal base plate 30, the thickness of the end of the solder 25g, 25l far from the center line CL (center) of the metal base plate 30 is thicker than the thickness of the end of the solder 25g, 25l close to the center line CL. Here, the thickness of the end of the solder 25g, 25l may be the thickness of the solder 25g, 25l formed between the back surface of the end of the metal plate 23 formed on the ceramic circuit board 21 and the front surface of the heat sink 31 excluding the protrusions 32g, 33g, 32l, 33l of the metal base plate 30. In addition, the amount of the solder 25g, 25l protruding from the end of the metal plate 23 on the front surface of the metal base plate 30 is larger at the end far from the center line CL (center) than at the end close to the center line CL. Therefore, the fillets of the solders 25g, 25l at the ends farther from the center line CL of the metal base plate 30 are larger than the fillets at the ends closer to the center line CL. Also, the tips of the protrusions 32g, 33l on the side closer to the center line CL of the metal base plate 30 are in contact with the rear surface of the semiconductor units 20g, 20l (ceramic circuit board 21). Meanwhile, the rear surfaces of the semiconductor units 20g, 20l (ceramic circuit board 21) are separated from the protrusions 33g, 32l farthest from the center line CL by gaps 26g, 26l.

[0052] Furthermore, as shown in FIG. 13, in the semiconductor units 20h to 20k located inside, other than the semiconductor units 20g and 20l furthest from the center line CL (center) of the metal base plate 30, the thickness of the solder end of each solder end farther from the center line CL (center) of the metal base plate 30 may be thinner than the thickness of the solder end close to the center line CL. Also, the amount of solder protruding from the end of the metal plate 23 on the front surface of the metal base plate 30 may be smaller at the end farther from the center line CL (center) than at the end close to the center line CL. Therefore, the fillet of the end of the solder farther from the center line CL of the metal base plate 30 may be smaller than the fillet of the end close to the center line CL. Also, the tip of the protrusion on the side close to the center line CL of the metal base plate 30 may be separated from the back surface of the semiconductor units 20h to 20k with a gap. Meanwhile, the back surface of the semiconductor units 20h to 20k may be abutted against the protrusion farthest from the center line CL.

[0053] Such a semiconductor device 10c is manufactured according to the flowchart shown in Fig. 3. In this case, in step S3, a weight is set on the end portion on the center line CL side of the semiconductor units 20g, 20l (ceramic circuit boards 21) that are farthest (outermost) from the center line CL on the metal base plate 30. The weight used in this case may have the same shape and material as in the first embodiment.

[0054] After that, in step S4, when such a metal base plate 30 is placed on the soldering device 50, heat propagates from the center (center line CL) of the metal base plate 30 to the outside. Therefore, the solder plate at the end farthest from the center line CL of the semiconductor units 20g, 20l (ceramic circuit board 21) farthest from the center line CL of the metal base plate 30 (outermost) is melted last. Then, in step S5, the operation of the soldering device 50 is stopped, and the molten solder melted from the solder plate is cooled. At this time, too, it is cooled from the center (center line CL) toward the outer edge of the metal base plate 30. When the molten solder is cooled, as described above, the outer region that is cooled last is coagulated and the volume is reduced. For this reason, shrinkage cavities are likely to occur in the solder at the end farthest from the center line CL of the outermost semiconductor units 20g, 20l among the semiconductor units 20g, 20h, 20i, 20j, 20k, 20l. Therefore, in manufacturing the semiconductor device 10c, in the metal base plate 30 on which the multiple arrangement regions 36g, 36h, 36i, 36j, 36k, 36l are arranged, weights are set on the outermost arrangement regions 36g, 36l closer to the center line CL of the ceramic circuit board 21. In the semiconductor device 10c manufactured in this way, as shown in FIG. 13, the solders 25g, 25l of the semiconductor units 20g, 20l farthest from the center line CL are thicker at the end farther from the center line CL than at the end closer to the center line CL. Since the generation of shrinkage cavities is suppressed in the outer regions of the solders 25g, 25l, the increase in the amount of the solders 25g, 25l is suppressed, while the increase in the thermal resistance of the solders 25g, 25l is also suppressed, and the deterioration of the heat dissipation of the semiconductor device 10c is also prevented. Therefore, the deterioration of the reliability of the semiconductor device 10c is suppressed, and the semiconductor device 10c operates stably.

[0055] In the semiconductor device 10c, the semiconductor units 20g, 20l furthest from the center line CL (center) of the metal base plate 30 can be formed like the protrusions 32a, 33a, 32b, 33b in the second embodiment and shown in FIG. 7. The protrusions 33g, 32l on the outer side of the center line CL are formed higher than the protrusions 32g, 33l on the center line CL side. The protrusions on the sides closer to and farther from the center line CL of the metal base plate 30 32g , 33g , 32l , 33l The tips of the contact members 20a and 20b are in contact with the rear surfaces of the semiconductor units 20g and 20l, respectively.

[0056] In this case, the semiconductor device 10c can be manufactured according to the flow chart shown in FIG. 8. In this case, the height of the protrusions (protrusions 33g, 32l in FIG. 13) farther from the center line CL of the outermost arrangement regions 36g, 36l among the arrangement regions 36g, 36h, 36i, 36j, 36k, 36l of the metal base plate 30 is made higher than the protrusions (protrusions 32g, 33l in FIG. 13) closer to the center line CL. As a result, as in the solders 25g, 25l shown in FIG. 13, the thickness of the end farther from the center line CL becomes thicker than the thickness of the end closer to the center line CL. In this case, the outer regions of the solders 25g, 25l are also prevented from generating shrinkage cavities, so that the increase in the amount of the solders 25g, 25l is suppressed, while the increase in the thermal resistance of the solders 25g, 25l is also suppressed, and the deterioration of the heat dissipation of the semiconductor device 10c is also prevented. Therefore, the deterioration of the reliability of the semiconductor device 10c is suppressed, and the semiconductor device 10c operates stably.

[0057] Furthermore, in consideration of the fourth embodiment, when four or more semiconductor units 20 are linearly installed on the metal base plate 30, it is preferable that at least the thickness of the solder end away from the center line CL of the metal base plate 30 in the outermost semiconductor unit 20 is made thicker than the thickness of the solder end close to the center line CL. Also, in consideration of the fourth embodiment, in the third embodiment as well, when three or more semiconductor units 20 are arranged vertically and horizontally on the metal base plate 30, it is preferable that at least the thickness of the solder end away from the center of the metal base plate 30 in the outermost semiconductor units 20 in each of the vertical and horizontal directions is made thicker than the thickness of the solder end close to the center. [Explanation of symbols]

[0058] 10, 10a, 10b, 10c Semiconductor device 20, 20a, 20b, 20c, 20d, 20e, 20f, 20g, 20h, 20i, 20j, 20k, 20l Semiconductor unit 21 Ceramic circuit board 22 Insulating plate 23 Metal plate 24a, 24b, 24c, 24d Circuit patterns 25a, 25b, 25c, 25g, 25l solder 26a,26b,26g,26l gap 27a, 27b Solder plate 27a1, 27b1 Molten solder 28a, 28b Semiconductor chip 30 Metal base plate 31 Heat sink 32a~35a,32b~35b,32c~35c,32d~35d,32e~35e,32f~35f,32g,33g,32l,33l Projection 36a,36b,36c,36d,36e,36f,36g,36h,36i,36j,36k,36l placement area 41a,41b Weight 50 Soldering equipment

Claims

1. a metal base plate having an arrangement area on its front surface spaced apart from a central portion, the arrangement area having a first protrusion formed at a first formation position closer to the central portion and a second protrusion formed at a second formation position farther from the central portion than the first formation position; a substrate provided in the placement area via solder; having the first protrusion is in contact with the rear surface of the substrate, the second protrusion has a length substantially equal to that of the first protrusion, and the second protrusion is spaced apart from the rear surface of the substrate; The thickness of the solder at an end away from the center is greater than the thickness of the solder at an end closer to the center. Semiconductor device.

2. The metal base plate is warped in a convex shape such that the central portion protrudes toward the opposite side to the front surface. The semiconductor device according to claim 1 .

3. The arrangement area of ​​the metal base plate is set symmetrically around the center, The substrates are provided in the placement regions, 3. The semiconductor device according to claim 1 or 2.

4. A metal base plate having an arrangement area on a front surface thereof spaced apart from a center portion; a substrate provided in the placement area via solder; having a plurality of the arrangement regions of the metal base plate are set along a predetermined direction from the center, and the substrates are respectively provided in the arrangement regions via the solder; a thickness of an end portion of the solder in the outermost arrangement region from the center along the predetermined direction from the center portion is greater than a thickness of an end portion of the solder in the outermost arrangement region from the center portion. Semiconductor device.

5. a preparation step of preparing a convex metal base plate having an arrangement area set on a front surface thereof away from a center portion, the center portion protruding toward the front surface side, and a substrate; a placement step of placing the substrate in the placement area via solder; a joining step of melting the solder while pressing a side of the front surface of the substrate close to the center toward the metal base plate to join the substrate to the arrangement area; A method for manufacturing a semiconductor device having the above structure.

6. a first protrusion formed at a first forming position on the side closer to the center in the arrangement region and a second protrusion formed at a second forming position on the side farther from the first forming position, The method for manufacturing a semiconductor device according to claim 5 .

7. The first protrusion and the second protrusion have approximately the same length, After the bonding step, the first protrusion is in contact with the rear surface of the substrate, The second protrusion is spaced from the rear surface of the substrate. The method for manufacturing a semiconductor device according to claim 6 .

8. The second protrusion is longer than the first protrusion, After the bonding step, the first protrusion is in contact with the rear surface of the substrate, The second protrusion abuts against the rear surface of the substrate. The method for manufacturing a semiconductor device according to claim 6 .

9. In the bonding step, a weight is placed on a side of the front surface of the substrate close to the center, and the substrate is pressed against the metal base plate. The method for manufacturing a semiconductor device according to claim 5 .

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