JP2008227331A - Semiconductor module, circuit board used therefor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a semiconductor module having both high heat radiation performance and high durability over a thermal stock cycle. <P>SOLUTION: In this semiconductor module 1, a circuit board 2 is joined to a heat radiation member 3 via a solder layer 4. The circuit board 2 consists of a ceramic board 5, a metal circuit board 6 joined to both sides thereof, and a heat radiation plate 7, and a brazing material firmly joins the metal circuit board 6 to the ceramic board 5 and the metal heat radiation plate 7 to the ceramic board 5. A heat radiation member joining region 11 having a plurality of uneven portions is provided on the surface of the heat radiation member 3 (surface of side to be joined to the metal circuit board 7). In the heat radiation member joining region 11, linear uneven portions parallel to each other are formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention mainly relates to a semiconductor module on which a semiconductor chip that operates with high power is mounted, and a structure of a circuit board used therefor. Moreover, it is related with the manufacturing method of this circuit board.

  In recent years, power semiconductor modules (for example, IGBT modules) capable of high voltage and large current operation have been used as inverters for electric vehicles. As such a semiconductor module, a semiconductor module is used in which a semiconductor chip is bonded to a circuit board having high electrical insulation and thermal conductivity and high mechanical strength. A cross-sectional view of an example of this structure is shown in FIG. Here, in the semiconductor module 51, the circuit board 52 and the semiconductor chip 53 are joined by the first solder layer 54. The circuit board 52 is composed of a ceramic circuit board 55 and a metal circuit board 56 and a metal heat radiating board 57 bonded to both sides thereof. Between the metal circuit board 56 and the ceramic board 55, and between the metal heat radiating board 57 and the ceramic board 55, It is firmly joined by a brazing material (not shown). The metal circuit board 56 is formed in a pattern to be a wiring, and the semiconductor chip 53 is bonded thereon via a solder layer 54. The metal heat radiating plate 57 is formed over almost the entire surface of the ceramic substrate 55 in order to enhance the heat dissipation of the circuit board 52. The ceramic substrate 55 is, for example, silicon nitride ceramics having a high thermal conductivity and excellent electrical insulation and strength. The metal circuit board 56 and the metal heat sink 57 are both formed of a metal having a high thermal conductivity such as copper or aluminum. Is done. On the other side of the semiconductor chip 53, a heat radiating member 58 is joined to the metal heat radiating plate 57 by a second solder layer 59 in order to further improve the heat radiating property. The heat radiating member 58 also serves as a support substrate in the semiconductor module 51, and is made of, for example, copper and / or aluminum. Here, for joining the ceramic substrate 55 and the metal circuit board 56 and joining the ceramic substrate 55 and the metal heat radiating plate 57, brazing which has a high joining strength but requires a high temperature (600 ° C. or more) is used. . On the other hand, since the semiconductor chip 53 cannot withstand high temperatures, the bonding between the semiconductor chip 53 and the metal circuit board 56 has low bonding strength but does not require high temperature (a temperature higher than 350 ° C.) for bonding. Is used. Since the joining of the metal heat radiating plate 57 and the heat radiating member 58 is performed after the semiconductor chip 53 is joined to the circuit board 52 or simultaneously with this joining, solder is similarly used.

When the device including such a semiconductor module 51 is ON, the semiconductor chip 53 becomes high temperature due to its own heat generation. On the other hand, when the device including the semiconductor module 51 is OFF, this heat generation is eliminated, so that the semiconductor chip 53 becomes equal to the cooling water temperature or the ambient temperature to which the module is exposed. Therefore, in normal use, the semiconductor module 51 is subjected to a number of cooling and heating cycles. The thermal expansion coefficient at room temperature of the components constituting the semiconductor module 51 is, for example, 3.0 × 10 ⁻⁶ / K for silicon constituting the semiconductor chip 53, and 3.0 for silicon nitride constituting the ceramic substrate 55. × ^{10 -6} / K or less, copper constituting the metal circuit plate 56, a metal radiating plate 57 differs from the 16.7 × ^{10 -6} / K approximately. For this reason, when these are joined, warpage due to this difference in thermal expansion occurs in the semiconductor module 51 during this cooling cycle. The magnitude and direction of the warp change during this cycle. At the time of this warping, crack propagation and peeling may progress to the solder joint (the first solder layer 54 and the second solder layer 59) having the smallest mechanical strength in the above configuration. In particular, in the second solder layer 59 having a large area, since the amount of warpage due to the thermal cycle is large, a crack is generated from the end portion of the metal heat radiating plate, and the second solder layer 59 is often peeled by the progress toward the inside. Therefore, in such a high-power semiconductor module, high heat dissipation and high durability against a cooling cycle are required at the same time.

  Increasing the thickness of the solder layer to reduce the shear strain or equivalent plastic strain generated in the solder layer is effective for suppressing crack propagation at the joint. However, the thermal conductivity of solder is about 30 to 40 W / m / K at the highest, and is much smaller than metal circuit boards, metal heat sinks and ceramic substrates. Thermal resistance increases and heat dissipation becomes worse. Also, it is difficult to obtain a solder material having a large thermal conductivity as described above. Therefore, it has been difficult to achieve both high heat dissipation and durability in a circuit board or semiconductor module.

  For this reason, various structures have been proposed in which the concentration of stress on the solder joint (solder layer) is suppressed, the fracture of the solder joint is suppressed, and the reliability is improved. For example, Patent Document 1 describes that in a bonded metal heat dissipation plate, the thickness of a portion not bonded to a ceramic substrate is partially reduced. Patent Document 2 describes a structure in which a step is provided on the outer periphery of a metal circuit board and a metal heat sink, and Patent Document 3 describes a structure in which a groove or the like is partially provided in the metal circuit board. ing. In these structures, the stress is concentrated on the stepped portion and the groove portion, and the stress is not concentrated on the solder layer. In Patent Document 4, the stress applied to the entire circuit board is adjusted by optimizing the thickness of the solder layer, the thickness of the metal circuit board and the metal heat sink, and the mechanical strain applied to the solder layer is minimized. It is described that. Thereby, a circuit board in which the solder layer was not easily broken was obtained.

JP 2000-101203 A JP 10-4156 JP-A-10-84059 JP2003-204020A

  However, in the techniques described in Patent Documents 1 to 3, the main purpose is to prevent stress concentration on the joint (solder layer). For this reason, it is inevitable that this stress is concentrated on the components other than the solder layer instead, and the components are easily broken. For example, in the technique described in Patent Document 1, there is a problem in the durability of a ceramic substrate with which a partially thinned metal heat sink is in contact. Further, in the methods described in Patent Documents 2 and 3, the stepped portion and the groove portion on the outer periphery of the metal circuit board are easily broken. Although the effect on the operation of the semiconductor module is less when these parts break than when the solder joint breaks, it is still preferable for reliability because the circuit board is not partially broken. There is no impact.

  On the other hand, in the technique described in Patent Document 4, specifically, for example, it is described that the thickness of the solder layer is increased or the metal heat dissipation plate is increased. Lower. Therefore, it is clear that it is difficult to obtain a structure that achieves both durability and heat dissipation.

  Therefore, it has been difficult to obtain a semiconductor module having both high heat dissipation properties and high durability against a cooling cycle.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above problems, the present invention has the following configurations.
The gist of the first invention of this application is that a semiconductor chip is mounted on a circuit board in which a metal circuit board and a metal heat sink are respectively formed on both surfaces of a ceramic substrate, and the metal heat sink is bonded to a heat dissipation member via a solder layer. A heat dissipation member bonding region having a plurality of irregularities formed on a surface of the heat dissipation member on a side in contact with the metal heat dissipation plate, wherein the heat dissipation member is formed of the metal in the heat dissipation member bonding region. It exists in the semiconductor module characterized by joining via the heat sink and the solder layer.

  It is preferable that linear concavo-convex patterns formed in parallel to each other are formed in the heat dissipation member bonding region.

  A plurality of arranged convex patterns or concave patterns may be formed in the heat dissipation member bonding region.

  In 1st invention, the heat sink joining area | region in which the unevenness | corrugation used as the shape fitted to the said heat radiating member joining area | region was provided in the surface at the side which contacts the said heat radiating member in the said metal heat sink, The said heat sink It is preferable that a joining area | region and the said heat radiating member joining area | region are joined via a solder layer.

  The gist of the second invention of this application is that a semiconductor chip is mounted on a circuit board in which a metal circuit board and a metal heat sink are respectively formed on both surfaces of a ceramic substrate, and the metal heat sink is bonded to a heat dissipation member via a solder layer. A heat sink joining region in which a plurality of projections and depressions are formed on a surface of the metal heat sink that is in contact with the heat dissipation member, and the metal heat sink is formed in the heat sink joint region. It exists in the semiconductor module characterized by joining through the heat radiating member and the solder layer.

  It is preferable that linear concavo-convex patterns formed in parallel to each other are formed in the heat sink joint region.

  A plurality of arranged convex patterns or concave patterns may be formed in the heat sink joint area.

  The gist of the third invention of the present application is a circuit board in which a metal circuit board and a metal heat radiating plate are formed on both surfaces of the ceramic substrate, respectively, and a plurality of surfaces are provided on a surface opposite to the surface in contact with the ceramic substrate in the metal heat radiating plate. The present invention resides in a circuit board characterized in that a heat sink joining region in which the unevenness is formed is provided.

  It is preferable that linear concavo-convex patterns formed in parallel to each other are formed in the heat sink joint region.

  A plurality of arranged convex patterns or concave patterns may be formed in the heat sink joint area.

  The gist of the fourth invention of the present application is a manufacturing method of a semiconductor module in which a circuit board having a metal circuit board and a metal heat sink formed on both sides of a ceramic substrate is joined to a heat dissipation member, A semiconductor module comprising: a heat sink joining region having a plurality of projections and depressions on a surface in contact with the heat sink; and joining the heat sink joining region and the heat sink in the heat sink via a solder layer. Exist in the manufacturing method.

  On the surface of the heat radiating member on the side in contact with the metal heat radiating plate, a heat radiating member bonding region having irregularities to be fitted to the heat radiating plate bonding region is formed, and the heat radiating plate bonding region and the heat radiating member bonding region, In a method for manufacturing a semiconductor module, characterized in that bonding is performed through a solder layer.

  The subject matter of the fifth invention of the present application is a method of manufacturing a semiconductor module in which a circuit board having a metal circuit board and a metal heat sink formed on both sides of a ceramic substrate is joined to a heat sink, and the metal in the heat sink A semiconductor device comprising: a heat dissipating member joining region having a plurality of projections and depressions on a surface in contact with the heat dissipating plate; and joining the heat dissipating member joining region of the heat dissipating member and the metal heat dissipating plate through a solder layer. It exists in the manufacturing method of a module.

  Since this invention is comprised as mentioned above, the semiconductor module which has high heat dissipation and high durability with respect to a thermal cycle can be obtained.

  The present invention will be described below with reference to specific embodiments. However, the present invention is not limited to these embodiments.

(First embodiment)
FIG. 1 is an assembly perspective view showing the configuration of the semiconductor module according to the first embodiment. In the semiconductor module 1, the circuit board 2 and the heat radiating member 3 are joined by the solder layer 4. The circuit board 2 is composed of a ceramic substrate 5, a metal circuit board 6 (upper side in FIG. 1) and a metal heat sink 7 (lower side in FIG. 1), and the metal circuit board 6 and the ceramic substrate. 5 and the metal heat radiating plate 7 and the ceramic substrate 5 are firmly joined by a brazing material (not shown). The metal circuit board 6 is formed in a pattern to be a wiring, and a semiconductor chip 8 is bonded thereon. The metal heat sink 7 is formed over almost the entire surface of the ceramic substrate 5 in order to improve the heat dissipation of the circuit board 2. The heat radiating member 3 is joined to the metal heat radiating plate 7 by a solder layer 4 in order to further improve the heat radiating performance. The heat radiating member 3 also serves as a support substrate in the semiconductor module 1.

  In manufacturing this semiconductor module, first, the circuit board 2 in which the ceramic substrate 5, the metal circuit board 6, and the metal heat sink 7 are joined is manufactured. Next, the semiconductor chip 8 is joined and mounted on the circuit board 2 by a solder layer (not shown). Since the above process is the same as the circuit board manufacturing method that is normally performed, detailed description is omitted. Next, the circuit board 2 on which the semiconductor chip 8 is mounted is joined to the heat dissipation member 3 by the solder layer 4.

  Here, the mounted semiconductor chip 8 is a power semiconductor element such as an IGBT (insulated gate bipolar transistor) formed of silicon, for example. When this semiconductor module is used, heat is generated because a large current flows through the semiconductor chip 8. The circuit board 2 and the heat dissipation member 3 perform this heat dissipation.

  In the circuit board 2, the ceramic substrate 5 is an insulating material having a high thermal conductivity, for example, silicon nitride ceramics (thermal conductivity: 90 W / m / K) having a thickness of about 0.32 mm.

  Since the metal circuit board 6 serves as a wiring in the circuit board 2, copper (thermal conductivity: about 390 W / m / K) is used as a material having both high thermal conductivity and low electrical resistivity. A predetermined pattern for wiring is formed. In addition, you may use a copper alloy, aluminum (thermal conductivity: about 230 W / m / K), and these alloys. The thickness is appropriately selected from the range of 0.1 to 3.0 mm in consideration of the overall thermal resistance value in consideration of the pattern and size of the metal circuit board 6 in the semiconductor module 1.

  The material of the metal heat sink 7 is the same as that of the metal circuit board 6, and the thickness thereof is preferably 0.1 to 3.0 mm, similarly to the metal circuit board 6. However, although the thickness of the metal circuit board 6 and the metal heat sink 7 depends on the pattern shape of the metal circuit board 6, in general, the thickness of the metal circuit board 6 and the metal heat sink 7 is equal, or the metal circuit board. 6 is used so as to be thicker than the thickness of the metal heat sink 7. Thereby, generally the curvature of the circuit board 2 becomes small. Further, since the metal heat radiating plate 7 is provided in order to increase heat dissipation, the metal heat radiating plate 7 generally has a larger area than the metal circuit plate 6 and is formed over almost the entire surface of the ceramic substrate 5.

  Here, in the circuit board 2, the bonding of the ceramic substrate 5 and the metal circuit board 6 and the bonding of the ceramic substrate 5 and the metal heat sink 7 are brazed with high bonding strength, for example, a brazing material to which an active metal is added. Bonding using is used. This joining requires a high temperature (600 ° C. or higher). As the brazing material, for example, a silver (Ag) -copper (Cu) -titanium (Ti) based active metal brazing material can be used, and these can be joined at 700 ° C. or higher. Further, the thickness of the brazing material after joining is about 10 to 20 μm, which is negligible compared to the metal circuit board 6 and the like, and Cu and Ag diffuse after joining. For this reason, the heat conduction (thermal resistance) of the brazing material does not become a problem.

  The heat radiating member 3 serves as a heat radiating base and a substrate for the semiconductor module 1. As the material, copper having a thickness of about 2 to 5 mm is used. Alternatively, aluminum or an alloy thereof may be used. The heat generated from the semiconductor chip finally flows into the heat radiating member 3 via the circuit board 2, and the heat radiating member 3 or the cooling fin fixed to the heat radiating member radiates the heat to the atmosphere or cooling water. Thereby, the temperature rise (especially junction temperature) of this semiconductor element and the temperature rise of the whole semiconductor module 1 are suppressed.

  On the other hand, since the semiconductor chip 8 to be mounted cannot withstand high temperatures, solder that does not require high temperature is used for bonding between the semiconductor chip 8 and the metal circuit board 6. As the solder, for example, lead (Pb) -tin (Sn) -based solder material, tin (Sn) -silver (Ag) -lead (Pb) -based solder material, and Pb-free Sn-silver considering the recent environmental response An (Ag) -based, Sn-Ag-copper (Cu) -based, Sn-zinc (Zn) -based, Sn-indium (In) -based solder material, or the like can be used. Although the temperature required for these joining is as low as about 200-400 degreeC, the joining strength is small compared with the said brazing material. Since the joining of the metal heat radiating plate 7 and the heat radiating member 3 is often performed after the semiconductor chip 8 is joined to the circuit board 2, the solder layer 4 has a similar solder having a lower melting point, such as 40 Pb-Sn. Crystalline solder is used. Moreover, the thermal conductivity of these solder materials is about 20-40 W / m / K, and is small compared with the ceramic substrate 5, the metal heat sink 7, etc. For this reason, if the solder layer 4 is thick, the thermal resistance of the part will become large and heat dissipation will worsen.

  In this semiconductor module 1, a heat radiating member bonding region 11 in which a plurality of irregularities are formed is provided on the surface of the heat radiating member 3 (the surface to be bonded to the metal heat radiating plate 7). In the heat radiating member bonding region 11, linear irregularities parallel to each other are formed. This unevenness can be formed by, for example, pressing. In addition to the above press processing, it is possible to perform cutting after continuous formation in rolling if the groove is processed by a processing machine, or is formed by wet etching, or if the unevenness is a simple shape with a straight line It is.

  On the other hand, in the metal heat radiating plate 7 in the circuit board 2, the surface to be joined to the heat radiating member 3 is flat. Therefore, FIG. 2 is a cross-sectional view of these joint interfaces in the direction AA in FIG. 1 after they are joined via the solder layer 4. At this bonding interface, copper or the like, which is a material of the heat dissipation member 3, and solder alternately exist according to the uneven pattern. Since solder is a material that is more easily plastically deformed than copper, and copper is also easily deformed laterally in the cross-sectional shape shown in FIG. 2, this joint interface is deformed against the stress in the lateral direction in FIG. It becomes easy to do. On the other hand, since the solder layer is supported by entering the concave portion in the heat radiation member joining region 11, no breakage occurs even in this deformation. Therefore, this bonding interface can be a strain relaxation layer against thermal expansion of the circuit board 2.

  By adopting this structure, the thickness of the solder layer 4 is not uniform, and as shown in FIG. 2, the concave portion in the heat radiation member bonding region 11 is thick and the convex portion is thin. Accordingly, since the thickness of the solder layer 4 is substantially thicker than that when no unevenness is provided, the thermal resistance of the solder layer 4 itself is increased. However, since the unevenness is provided on the heat dissipation member 3, the effective surface areas of the heat dissipation member 3 and the solder layer 4 are increased. Therefore, the heat dissipation capability of the heat dissipation member 3 itself is improved. Therefore, as a result, the thermal resistance from the metal heat radiating plate 7 side to the heat radiating member 3 side is not deteriorated as compared with the case where the unevenness is not formed, that is, the case where the heat radiating member bonding region 11 is not provided.

  Therefore, the semiconductor module 1 having this structure has both high heat dissipation and high durability against a cooling cycle.

(Second Embodiment)
In the semiconductor module according to the second embodiment, the basic configuration is substantially the same as that of the semiconductor module according to the first embodiment, and the lower surface of the metal heat radiating plate 8 (the surface to be joined to the heat radiating member 3). The form of is changing.

  In this semiconductor module, a heat sink joint region 12 is provided on the lower surface of the metal heat sink 7. In the heat radiating plate bonding region 12, linear concavo-convex parallel to each other are formed so as to fit into the concavo-convex of the heat radiating member bonding region 11. Similar to the heat radiating member bonding region 11, it is also possible to form the unevenness by, for example, press molding. In this case, however, care must be taken not to cause cracks in the ceramic member. Thereafter, similarly to the first embodiment, the metal heat radiating plate 7 and the heat radiating member 3 are joined via the solder layer 4. Under the present circumstances, it joins in the form which the unevenness | corrugation of the heat radiating member junction area | region 11 and the unevenness | corrugation of the heat sink joining area | region 12 fit.

  FIG. 3 is a cross-sectional view of the bonding interface between the metal heat radiating plate 8 and the heat radiating member 3 after the bonding. This figure corresponds to FIG. 2 in the first embodiment. At the joint interface, the unevenness of the heat dissipation member bonding area 11 and the unevenness of the heat dissipation plate bonding area 12 are fitted, so that the thickness of the solder layer 4 is almost uniformly thin and there is a thick portion. do not do. Therefore, the thermal resistance of the solder layer 4 itself can be reduced. In addition, due to the unevenness in the heat sink joint region 12, the effective areas of the metal heat sink 7, the solder layer 4, and the heat sink 3 are increased. Therefore, particularly high heat dissipation can be obtained.

  On the other hand, in the cross-sectional shape of FIG. 3, copper is easily deformed in the lateral direction. On the other hand, since the solder is supported by entering the fitted uneven pattern, the solder layer 4 does not break even during this deformation.

  Therefore, the semiconductor module with this structure also has high heat dissipation and high durability against the cooling and heating cycle.

(Third embodiment)
The basic configuration of the semiconductor module according to the third embodiment is substantially the same as that of the semiconductor module according to the first embodiment, except that an uneven pattern is provided only on the metal heat sink 7.

  In this semiconductor module, a heat sink joint region 12 is provided on the lower surface of the metal heat sink 7. In the heat radiating plate bonding region 12, linear unevenness parallel to each other is formed. FIG. 4 is a sectional view after the joining. Since the structure of this bonding interface is a structure in which the vertical relationship is reversed from that in the case of the first embodiment, it is obvious that the same effect as that of the first embodiment can be obtained also in this structure. . In addition, the method of forming the unevenness in the heat sink bonding area 12 is the same as that in the first embodiment.

(Fourth embodiment)
The basic configuration of the semiconductor module according to the fourth embodiment is substantially the same as that of the semiconductor module according to the first embodiment, but the uneven pattern is different. This assembly perspective view is shown in FIG. Since the circuit board 2 and the semiconductor chip 8 in the semiconductor module 21 are the same as those in the first embodiment, description thereof is omitted. The same applies to the material of the solder layer 4 and the heat dissipation member 3.

  In the heat radiating member joining region 31 in the heat radiating member 3 used here, as shown in the enlarged view on the right side of FIG. 5, a plurality of convex patterns (upper right of FIG. 5) or concave patterns (lower right of FIG. 5) are formed. It is arranged and formed. For example, the unevenness can be formed by pressing.

  Since the structure of the bonding interface in this structure is the same as that in FIG. 2, the same effect can be obtained. However, in the first embodiment, only the cross section in the direction of AA in FIG. 1 is the form in FIG. 2, whereas in the semiconductor module 21, the same is true in the direction perpendicular thereto. It becomes the form. Therefore, the circuit board 2 or the heat radiating member 3 is easily deformed at the time of thermal expansion and hardly breaks in both directions. Moreover, it is the same as that of 1st Embodiment about the point provided with high heat dissipation.

  Therefore, the semiconductor module having this structure has both high heat dissipation and high durability against a cooling cycle.

  In the above example in the fourth embodiment, the surface of the metal heat radiating plate 7 is flat and the heat radiating member joining region 31 is provided on the surface of the heat radiating member 3. On the other hand, the surface of the heat radiating member 3 may be flat, and a heat radiating plate joining region having the same structure may be provided on the surface of the metal heat radiating plate 7. Furthermore, similarly to the second embodiment, both the heat radiating member bonding region and the heat radiating plate bonding region may be provided, and these may be fitted.

  Examples of the present invention (including comparative examples that are conventional techniques) will be described below.

  Silicon nitride ceramics was used as the ceramic substrate. The thickness after the sintering was 0.32 mmt, and the ceramic substrate was processed into a desired shape by laser processing from a size of about 300 mm. Here, four circuit boards having a size of 50 × 50 mm were produced by using a single circuit board.

Next, the substrate surface was cleaned and smoothed by wet blasting with a lubricating material such as h-BN that had been applied to the sheet surface before degreasing and sintering. The characteristics of this silicon nitride ceramic substrate were a three-point bending strength of 700 MPa or more, a thermal conductivity of 90 W / m / K or more, and a fracture toughness value of 5 MPa · m ^1/2 or more. By the way, this silicon nitride ceramic substrate can be produced in accordance with the use from a thermal conductivity of 120 W / m / K to 60 W / m / K depending on sintering conditions, amount of auxiliary agent and components. .

  The material of the metal circuit board and the metal heat sink was oxygen-free copper (yield stress after brazing heat treatment was about 20 MPa). The thickness of both the metal circuit board and the metal heat sink was 1.5 mmt. A silicon nitride ceramic substrate having a thickness of 0.32 mmt was used. As the heat radiating member, a copper plate (80 × 60 mm size) having a thickness of 3 mmt and larger than the circuit board was used.

  In the step of joining the metal circuit board, the metal heat sink and the ceramic substrate, a silver (Ag) -copper (Cu) -titanium (Ti) based active metal brazing material is printed on the surface of the ceramic substrate or the metal plate, These were joined at 700 ° C. or higher. The metal circuit board and the metal heat sink were processed by wet etching to form individual circuit boards. In addition, in this etching process, a photosensitive resist is pasted on the metal plate of the joined body of the brazed metal plate and the ceramic substrate by lamination, and after the exposure / development processing, the front and back metal plate surfaces are adhered. A desired resist pattern was formed. Thereafter, unnecessary portions of the metal plate were removed by wet etching using an iron chloride solution or the like, and a desired metal circuit pattern (metal circuit plate and metal heat dissipation plate) was simultaneously formed. Next, the resist was removed, and cleaning and drying were performed. Moreover, the division | segmentation into the piece of a circuit board was performed after that.

  As a material of the solder joint layer for joining the semiconductor chip, a sheet of Sn-3Ag-1.5Pb and 0.2 mmt was used. A solder sheet (thickness of 0.1 to 0.2 mmt) having a composition of 40 Pb-Sn is used for the solder joint layer for joining the metal heat radiating plate and the heat radiating member, and each is separately used at 355 ° C. and 235 ° C. using a reflow furnace. Joined. Here, a nickel (Ni) ball having a size of 50 μm is added in advance to the sheet used for the latter solder layer. The joining by the solder layer was performed in the order of the former solder joining layer and the latter solder joining layer. Moreover, the load was applied to the circuit board or the semiconductor element as necessary, and the thickness of the solder joint layer was adjusted. Note that a solder resist was formed around the molten solder so that the molten solder would not flow out to other than the joint.

  As a circuit pattern of the metal circuit board, a pattern obtained by dividing a flat plate into three parts was adopted, and one semiconductor element was mounted on only two of the patterns. Further, the PPS resin case and this semiconductor module were bonded. The bonding wire for electrically connecting the terminal of the case, the semiconductor element, and the metal circuit pattern was ultrasonically bonded using an aluminum wire having a diameter of 0.3 mm. A semiconductor module was produced as described above. Then, the gel sealing which protects a semiconductor chip and a wire was performed.

  The semiconductor module thus fabricated has an ambient temperature of 25 ° C. (holding time 5 minutes) → −40 ° C. (holding time 15 minutes) → 25 ° C. (holding time 5 minutes) → 125 ° C. (holding time 15 minutes) → 25 It was put into a cooling cycle (cooling thermal shock test) test apparatus with a cycle of 1 ° C., and an increase in the void ratio corresponding to the crack growth of the solder layer after a predetermined cycle was evaluated using an ultrasonic microscope. Warpage measurement was evaluated from a three-dimensional laser measuring device or cross-sectional observation. The thickness of the solder layer was evaluated by cross-sectional observation after cutting the module. Also, the thermal resistance from the semiconductor chip side to the back surface of the heat radiating member is the voltage / temperature measured in advance from the forward voltage change of the PN junction of the semiconductor chip before and after applying the predetermined power for a predetermined time. The temperature was converted from the calibration curve and measured using a thermal resistance evaluation apparatus (manufactured by Cats Electronics) that obtains a thermal resistance value (temperature increase / applied power: unit ° C / W), particularly a saturation value of thermal resistance. As for the thermal resistance, the initial value and the value after application of a predetermined number of cycles were measured, and the increase rate was examined.

  In addition, the surface of the heat radiating member or the metal heat radiating plate in each example is uneven, but the metal heat radiating plate is formed by machining, the heat radiating member is pressed, and the depth of the concavo-convex is 0.5 mm. Semiconductor modules were produced in which the width of the part and the width of the recess (see FIG. 2 and the like) were changed. Moreover, the thickness of the solder layer was 0.5 mm in terms of a conversion value when the solder layer was flat. As another method of forming the unevenness of the metal heat sink, the wet etching method described above or a metal plate that has been previously formed with unevenness by using a press or the like is used as the metal heat sink, and the surface without unevenness can be joined to ceramics. Good.

  Examples 1-5 changed the width | variety of the convex part and the recessed part of the heat radiating member in the structure of 1st Embodiment (FIG. 1, FIG. 2) (convex part: 0.5-3.0 mm, recessed part) : 0.8 to 3.3 mm) semiconductor module. Examples 6-10 changed the width | variety of the convex part of the metal heat sink and the heat radiating member in the structure of 2nd Embodiment (FIG. 3), and the width | variety of a recessed part (convex part: 0.5-3.0 mm, (Recess: 0.8 to 3.3 mm) is a semiconductor module. Examples 11-15 changed the width | variety of the convex part and the recessed part of the heat radiating member in 4th Embodiment (FIG. 5) (convex part: 0.5-3.0 mm, recessed part: 0.8-). 3.3 mm) semiconductor module. In Examples 16 to 20, in the fourth embodiment, both the heat radiating member bonding region and the heat radiating plate bonding region are provided, and the widths of the convex portions and the concave portions when these are fitted are changed (the convex portions). : 0.5-3.0 mm, recess: 0.8-3.3 mm). The comparative example is a semiconductor module in which the thickness of the solder layer is 0.04 to 0.19 mm in a conventional structure in which neither the heat radiating member nor the metal heat radiating plate is provided with unevenness.

  Table 1 shows the results of measuring the initial (before thermal cycle application) thermal resistance value and the void increase rate in the solder layer of the above samples.

  In the comparative example, when the solder layer is thinned to 0.04 mm (Comparative Example 1), the thermal resistance value is lowered, but the durability (void increase rate) is deteriorated to 47.6%. On the other hand, when the thickness of the solder layer is increased to 0.19 mm, the void increase rate is 38.2%, but the thermal resistance increases to 0.263 ° C / W, and the thermal resistance and durability (void increase rate) Became a trade-off relationship. On the other hand, in all the examples, the void increase rate is decreased while the thermal resistance value is equal to or less than or equal to that of the comparative example. Therefore, it was confirmed that all the examples had a low thermal resistance value and a high durability. In particular, it was confirmed that better durability (low void increase rate) can be obtained when the interval between the concave and convex portions is smaller.

It is an assembly perspective view showing the composition of the semiconductor module concerning a 1st embodiment. It is sectional drawing of the joining interface of the metal heat sink and heat radiating member in the semiconductor module which concerns on 1st Embodiment. It is sectional drawing of the joining interface of the metal heat sink and heat radiating member in the semiconductor module which concerns on 2nd Embodiment. It is sectional drawing of the joining interface of the metal heat sink and heat radiating member in the semiconductor module which concerns on 3rd Embodiment. It is an assembly perspective view which shows the structure of the semiconductor module which concerns on 4th Embodiment. It is sectional drawing which shows the structure of the conventional semiconductor module.

Explanation of symbols

1, 2, 51 Semiconductor module 2, 52 Circuit board 3, 58 Heat dissipation member 4, 59 Solder layer 59 Second solder layer 54 First solder layer 5, 55 Ceramic substrate 6, 56 Metal circuit board 7, 57 Metal heat dissipation Plate 8, 53 Semiconductor chip (element)
11, 31 Heat dissipation member bonding area 12 Heat dissipation plate bonding area

Claims (13)

A semiconductor module in which a semiconductor chip is mounted on a circuit board in which a metal circuit board and a metal heat sink are respectively formed on both surfaces of a ceramic substrate, and the metal heat sink is bonded to a heat dissipation member via a solder layer,
A heat dissipating member bonding region in which a plurality of irregularities are formed on the surface of the heat dissipating member that is in contact with the metal heat dissipating plate is provided,
The semiconductor module according to claim 1, wherein the heat radiating member is joined to the metal heat radiating plate via a solder layer in the heat radiating member joining region.   2. The semiconductor module according to claim 1, wherein linear concavo-convex patterns formed in parallel to each other are formed in the heat radiating member bonding region.   The semiconductor module according to claim 1, wherein a plurality of arranged convex patterns or concave patterns are formed in the heat dissipation member bonding region. On the surface of the metal heat radiating plate in contact with the heat radiating member, there is provided a heat radiating plate bonding region in which irregularities are formed that fit into the heat radiating member bonding region,
4. The semiconductor module according to claim 1, wherein the heat radiating plate bonding region and the heat radiating member bonding region are bonded via a solder layer. 5. A semiconductor module in which a semiconductor chip is mounted on a circuit board in which a metal circuit board and a metal heat sink are respectively formed on both surfaces of a ceramic substrate, and the metal heat sink is bonded to a heat dissipation member via a solder layer,
A heat sink joint region in which a plurality of irregularities are formed on the surface of the metal heat sink in contact with the heat dissipation member is provided,
The semiconductor module, wherein the metal heat sink is bonded to the heat dissipation member via a solder layer in the heat sink bonding region.   The semiconductor module according to claim 5, wherein linear concavo-convex patterns formed in parallel to each other are formed in the heat sink joint region.   The semiconductor module according to claim 5, wherein a plurality of arranged convex patterns or concave patterns are formed in the heat sink joint region. A circuit board in which a metal circuit board and a metal heat sink are respectively formed on both sides of a ceramic substrate,
A circuit board comprising: a heat sink joining region having a plurality of irregularities formed on a surface of the metal heat sink opposite to a surface in contact with the ceramic substrate.   The circuit board according to claim 8, wherein linear uneven patterns formed in parallel to each other are formed in the heat sink joint region.   The circuit board according to claim 8, wherein a plurality of arranged convex patterns or concave patterns are formed in the heat sink joint region. A method of manufacturing a semiconductor module in which a circuit board having a metal circuit board and a metal heat sink formed on both sides of a ceramic substrate is joined to a heat dissipation member,
Forming a heat sink joining region having a plurality of irregularities on the surface of the metal heat sink in contact with the heat dissipation member;
A method for manufacturing a semiconductor module, wherein the heat radiating plate joining region of the metal heat radiating plate and the heat radiating member are joined via a solder layer. On the surface of the heat radiating member that is in contact with the metal heat radiating plate, a heat radiating member bonding region having irregularities that are shaped to fit with the heat radiating plate bonding region is formed.
The method of manufacturing a semiconductor module according to claim 11, wherein the heat radiating plate bonding region and the heat radiating member bonding region are bonded via a solder layer. A method of manufacturing a semiconductor module in which a circuit board having a metal circuit board and a metal heat sink formed on both sides of a ceramic substrate is joined to a heat dissipation member,
Forming a heat radiating member joining region having a plurality of irregularities on the surface of the heat radiating member in contact with the metal heat radiating plate;
A method of manufacturing a semiconductor module, comprising joining the heat radiating member joining region of the heat radiating member and the metal heat radiating plate via a solder layer.

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