Method for manufacturing module

Abstract

Provided is a method for manufacturing a module in which a member to be joined is joined via solder to a base material on which a protrusion is formed, the method comprising: a solution coating step in which a side surface that is continuous with the top surface of the protrusion is coated with a solution in which a soluble resin material is dissolved in a solvent; a solder material placement step in which a solder material is placed on a joint surface of the member to be joined; a base material placement step in which, after the solution coating step and the solder material coating step, the base material is placed on the member to be joined so that the top surface of the protrusion comes into contact with the solder material; and a heating step in which, after the base material placement step, a film composed of a resin material is formed on the side surface of the protrusion by drying the solution, and the top surface of the protrusion of the base material and the member to be joined are joined by melting the solder material.

Description

Module manufacturing method

[0001] The present invention relates to a method for manufacturing a module.

[0002] When mounting a semiconductor chip on a product, it is common to combine it with a heat dissipation member or the like in advance to form a module. Patent Document 1 discloses a method for manufacturing a semiconductor device, comprising: a first step of preparing an electrode block to be bonded to one surface of a semiconductor chip and two conductor members, at least one of which is bonded to the electrode block, and providing a bonding member adhesion prevention means on a side surface of at least one of the electrode block or the semiconductor chip; a second step of arranging the semiconductor chip and the electrode block so that they are interposed between the two conductor members via the bonding member, and bonding the two conductor members to the semiconductor chip and the electrode block with the bonding member; and a third step of sealing the space between the two conductor members with resin.

[0003] Japanese Patent Application Laid-Open No. 2003-188318

[0004] The invention described in Patent Document 1 leaves room for further consideration in terms of the manufacturing process.

[0005] A module manufacturing method according to a first aspect of the present invention is a module manufacturing method in which a member to be joined is joined via solder to a substrate having a convex portion formed thereon, and includes a solution application process of applying a solution in which a soluble resin material is dissolved in a solvent to a side surface continuing to the top surface of the convex portion; a solder material placement process of arranging a solder material on the joining surface of the member to be joined; a substrate placement process of, after the solution application process and the solder material application process, placing the substrate on the member to be joined so that the top surface of the convex portion is in contact with the solder material; and a heating process of, after the substrate placement process, drying the solution to form a coating made of the resin material on the side surface of the convex portion and melting the solder material to join the top surface of the convex portion of the substrate and the member to be joined.

[0006] According to the present invention, a module that prevents solder wetting can be manufactured with fewer steps.

[0007] Cross-sectional view of a semiconductor module. Diagram showing the manufacturing process of a semiconductor module. Diagram detailing the connection of a semiconductor chip and upper leads to a lead frame.

[0008] -Embodiment- Hereinafter, an embodiment of a method for manufacturing a module will be described with reference to FIGS.

[0009] FIG. 1 is a cross-sectional view of a semiconductor module 1. In the drawings of this embodiment, mutually orthogonal X, Y, and Z axes are depicted to clearly show the correlation between the drawings. The semiconductor module 1 includes a semiconductor chip 2, upper leads 4, a lead base 10, and a sealing material 6. An insulating sheet 5 is disposed to sandwich the upper leads 4 and the lead base 10 in the Z-axis direction, and copper foil 12 is disposed to sandwich the insulating sheet 5 in the Z-axis direction. Heat generated by the semiconductor chip 2 is dissipated in the positive direction of the Z-axis via the solder 3, upper leads 4, insulating sheet 5, and copper foil 12. Similarly, heat is dissipated in the negative direction of the Z-axis via the solder 3, lead base 10, insulating sheet 5, and copper foil 12.

[0010] The semiconductor chip 2 has an upper electrode 21 and a lower electrode 22. Hereinafter, the semiconductor chip 2 will also be referred to as the "joined member." The upper electrode 21 is an electrode provided on the surface of the semiconductor chip 2 on the positive side of the Z axis. The lower electrode 22 is an electrode provided on the surface of the semiconductor chip 2 on the negative side of the Z axis. The upper lead 4 has a protrusion 41 that protrudes in the negative direction of the Z axis, and is electrically connected to the semiconductor chip 2 via solder 3. Hereinafter, the upper lead 4 will also be referred to as the "substrate." The solder 3 holds the semiconductor chip 2, the upper lead 4, and the lead base 10. The solder 3 electrically connects the upper electrode 21 of the semiconductor chip 2 to the upper lead 4. The solder 3 electrically connects the lower electrode 22 of the semiconductor chip 2 to the lead base 10.

[0011] The upper electrode 21 of the semiconductor chip 2 is electrically connected to the upper lead 4 via the solder 3. The lower electrode 22 of the semiconductor chip 2 is electrically connected to the lead base 10 via the solder 3. The lead base 10 is electrically connected to the semiconductor chip 2 via the solder 3. Polyamideimide 8 is applied to the side walls of the convex portion 41 of the upper lead 4. The sealing material 6 electrically insulates the semiconductor chip 2 from the outside and prevents conductive foreign matter from adhering to the semiconductor chip 2. The insulating sheet 5 electrically insulates the lead base 10 and the upper lead 4 from the outside.

[0012] FIG. 2 shows the manufacturing process of the semiconductor module 1. The lead frame 10F shown in the upper left is made by processing a plate-shaped conductor. The lead frame 10F includes the lead base 10 described above and tie bars that will be cut in a later process. Therefore, if we focus on a portion of the lead frame 10F, it can also be called the lead base 10. The lead frame 10F extends in the XZ plane and has a thickness in the Y-axis direction. The lead frame 10F is the lead frame to which the collector side and cathode side of the semiconductor chip 2 are bonded. In the lead frame 10F shown in FIG. M1, the leads bonded to the semiconductor chip on the upper arm and the leads bonded to the semiconductor chip on the lower arm are integrally connected by tie bars.

[0013] Next, the semiconductor chip 2 and upper leads 4 are connected to this lead frame 10F via solder 3. This process will be described in detail later. Next, as shown in the lower left, insulating sheets 5 are arranged to sandwich the lead frame 10F from both sides of the Y axis. Note that an insulating substrate made of ceramic may be used instead of the insulating sheet 5. Next, an insulating sealing material 6 is formed by a transfer molding process. At this time, the insulating sheet 5 is sealed integrally so that it is exposed on the surface. Then, as shown in the lower right, the tie bars connecting the terminals on the lead frame 10F are cut, and the terminals are cut and shaped. However, cutting and shaping the terminals is not essential.

[0014] Fig. 3 is a diagram illustrating in detail the connection of the semiconductor chip 2 and the upper leads 4 to the lead frame 10F shown in the upper right of Fig. 2. Specifically, the first step, the solution application step, the second step, the placement step, and the third step, the heating step, will be described.

[0015] First, in the solution application process, a polyamideimide solution 81 is prepared in which polyamideimide 8 is dissolved in a predetermined solvent 82. This solvent 82 is preferably one that allows the solvent and resin material to mix evenly, and a polar solvent such as N-methyl-2-pyrrolidone is desirable. Also, if a stirring process is used, that is, if the materials are mixed physically without relying on the properties of the liquid, it is not necessary to use a polar solvent for the solvent 82. This polyamideimide solution 81 is applied to the side surfaces of the convex portions 41 formed on the upper lead 4. To improve application properties, the side surfaces of the convex portions 41 may be formed in a tapered shape.

[0016] The second step, the placement step, is strictly divided into a solder placement step and an upper lead placement step. In the solder placement step, a solder material 31 is placed on the bonding surface of the semiconductor chip 2. In the upper lead placement step, the upper lead 4 is placed on the semiconductor chip 2 so that the top surface of the convex portion 41 is in contact with the solder material 31. Because the solution application step is performed before the upper lead placement step, a polyamide-imide solution 81 is applied to the side surface of the upper lead 4 placed in the upper lead placement step. The solder material 31 has the same composition as the aforementioned solder 3, but its shape changes as it melts and solidifies, so it has a different name and symbol. The solder material 31 in this example is for reflow and does not contain flux. In the placement step, the solder material 31 is not melted, and the polyamide-imide solution 81 is in a state where the solvent 82 has not evaporated and remains.

[0017] In the third step, the heating step, the assembled semiconductor chip 2 and upper leads 4 are heated together in a heating furnace. The temperature at which the solvent 82 in the polyamideimide solution 81 evaporates is lower than the temperature at which the solder material 31 melts. Therefore, in the temperature-raising process for melting the solder material 31, the solvent 82 in the polyamideimide solution 81 evaporates before the solder material 31 dissolves, and polyamideimide 8 remains on the side surfaces of the protrusions 41 of the upper leads 4, forming a coating made of this polyamideimide 8 on the protrusions 41.

[0018] The temperature continues to rise, and when it reaches the melting point of solder material 31, solder material 31 begins to melt. The molten solder material 31 flows and tries to spread, but because the coating made of polyamideimide 8 is formed on the side surfaces of protrusions 41, it does not spread over the side surfaces of protrusions 41 and solder 3 is formed without overflowing from the top surfaces of protrusions 41.

[0019] This heating step is preferably carried out in a reducing atmosphere. Heating in a reducing atmosphere can suppress the formation of an unintended oxide film. Suppressing the formation of an unintended oxide film improves the wettability of the solder 3 in the area where the solder 3 is to be joined. In order to consistently carry out the solution application step, placement step, and heating step in a reducing atmosphere, it is preferable that these steps are all carried out in the same heating furnace.

[0020] The above-described embodiment provides the following advantageous effects. (1) A method for manufacturing a semiconductor module 1 in which a semiconductor chip 2 is solder-bonded to upper leads 4 having protrusions 41 includes a solution application step of applying a polyamideimide solution 81, in which a soluble resin material, polyamideimide 8, is dissolved in a solvent 82, to the side surfaces of the protrusions 41; a solder placement step of placing a solder material 31 on the bonding surface of the semiconductor chip 2; an upper lead placement step of, after the solution application step and the solder placement step, placing the upper leads 4 on the semiconductor chip 2 so that the top surfaces of the protrusions 41 contact the solder material 31; and a heating step of, after the upper lead placement step, drying the polyamideimide solution 81 to form a coating made of a resin material on the side surfaces of the protrusions 41 and melting the solder material 31 to bond the top surfaces of the protrusions 41 of the upper leads 4 to the semiconductor chip 2. This allows a module that prevents solder wetting to be manufactured with fewer processes. Specifically, the steps are as follows. The semiconductor module 1 has a coating of polyamideimide 8 on the side surfaces of the protrusions 41 to prevent the solder 3 from wetting up. The coating of polyamideimide 8 is not formed in an independent process, but in the same process as the joining with the solder 3, which reduces the number of processes. Furthermore, reducing the number of processes also leads to a reduction in the energy required for manufacturing and a reduction in CO2 emissions. In other words, the manufacturing method of the semiconductor module 1 in this embodiment also contributes to environmental conservation.

[0021] (2) The heating step is performed in a reducing atmosphere, which prevents the formation of an unintended oxide film and improves the wettability of the solder 3 in the area where the solder 3 is to be joined.

[0022] (3) The melting temperature of the solder material 31 is higher than the vaporization temperature of the solvent 82. Therefore, the solvent 82 volatilizes first, forming a coating of polyamideimide 8 on the side surface of the protrusion 41, and the solder 3 is prevented from penetrating into the side surface of the protrusion 41.

[0023] (4) The resin material used in this manufacturing method is polyamideimide.

[0024] (5) The solder material 31 does not contain flux.

[0025] (Modification 1) According to Modification 1, although polyamideimide is used as the material that dissolves in the solution in the above description, other soluble resin materials, such as polyamide or polyimide, may also be used.

[0026] (Variation 2) In the above-described embodiment, the solution applying step is performed before the placement step. However, the solution applying step may be performed before the upper lead placement step. In other words, the steps may be performed in the following order: solder placement step, solution applying step, and upper lead placement step.

[0027] The above-described embodiments and modifications may be combined with each other. Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention.

[0028] REFERENCE SIGNS LIST 1: Semiconductor module 2: Semiconductor chip 3: Solder 4: Upper lead 5: Insulating sheet 6: Sealing material 8: Polyamideimide 10: Lead base 10F: Lead frame 31: Solder material 41: Protrusion 81: Polyamideimide solution 82: Solvent

Claims

1. A method for manufacturing a module in which a member to be joined is joined via solder to a substrate having a convex portion formed thereon, the method comprising: a solution application step of applying a solution in which a soluble resin material is dissolved in a solvent to a side surface continuing to the top surface of the convex portion; a solder material placement step of arranging a solder material on the joining surface of the member to be joined; a substrate placement step of, after the solution application step and the solder material application step, placing the substrate on the member to be joined so that the top surface of the convex portion is in contact with the solder material; and a heating step of, after the substrate placement step, drying the solution to form a coating made of the resin material on the side surface of the convex portion and melting the solder material to join the top surface of the convex portion of the substrate to the member to be joined.

2. A method for manufacturing a module according to claim 1, wherein the heating step is carried out in a reducing atmosphere.

3. A method for manufacturing a module according to claim 1, wherein the melting temperature of the solder material is higher than the vaporization temperature of the solvent.

4. A method for manufacturing a module according to claim 1, wherein the resin material is polyamideimide.

5. A method for manufacturing a module according to claim 1, wherein the solder material does not contain flux.

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