Semiconductor module and manufacturing method thereof

Abstract

To provide a semiconductor module that can suppress dielectric breakdown due to generation of voids even when a gelatinous encapsulate is used, and a manufacturing method thereof.SOLUTION: A semiconductor module 1 includes an insulation substrate 2, a wiring layer 3 provided on an upper face side of the insulation substrate 2, a semiconductor chip 5 jointed to the wiring layer 3, a metal layer 4 provided on a lower face side of the insulation substrate 2, a base member 7 jointed to the metal layer 4, a case 9 bonded to the base member 7 and storing therein at least the semiconductor chip 5 and the insulation substrate 2, an upper-layer-side silicone gel 14, and a lower-layer-side silicone gel 13 filling in the case 9. The height of a boundary surface 15 between the upper-layer-side silicone gel 14 and the lower-layer-side silicone gel 13 is within a range lower than the upper face and higher than the lower face of the insulation substrate 2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor module and a manufacturing method thereof. [Background technology]

[0002] In general, a semiconductor module having a power semiconductor element is sealed with a sealing material such as silicone gel.

[0003] When a gel-type sealing material is used, voids (air bubbles) remain in gaps that cannot be completely filled with gel, and when the semiconductor module is in use and the temperature rises due to heat generation from the power semiconductor elements, the voids can grow and cause insulation breakdown.

[0004] A technique for suppressing the generation of air bubbles and improving insulation reliability is, for example, found in Patent Document 1. Figures 2, 4, and 14 of Patent Document 1 describe a semiconductor device in which silicone rubber is filled up to a height H2 (see Figure 14 of Patent Document 1) between the upper and lower surfaces of an electrode pattern on the upper surface of an insulating substrate, and silicone gel is filled on top of that. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2018 / 056287 Summary of the Invention [Problem to be solved by the invention]

[0006] In the semiconductor device of Patent Document 1, the lower layer side of the silicone gel is filled with silicone rubber in which air bubbles cannot be generated or grown during use of the semiconductor device, thereby improving insulation reliability.

[0007] However, as described in paragraph 0070 of Patent Document 1, silicone gel has the property of "adhering" to various components and re-adhering even after being peeled off from each component, whereas silicone rubber has the property of "bonding" to various components and not re-adhering once peeled off. Therefore, if silicone rubber is used as in Patent Document 1, there is a problem that it cannot be re-adhered if it is peeled off during a heat cycle test or during use, so it is desirable to avoid using silicone rubber as much as possible.

[0008] An object of the present invention is to provide a semiconductor module and a manufacturing method thereof that can suppress dielectric breakdown due to the growth of voids even when a gel-like sealing material is used. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the semiconductor module of the present invention comprises an insulating substrate, a wiring layer provided on the upper surface of the insulating substrate, a semiconductor chip bonded to the wiring layer, a metal layer provided on the lower surface of the insulating substrate, a base member bonded to the metal layer, a case adhered to the base member and accommodating at least the semiconductor chip and the insulating substrate therein, and an upper layer silicone gel and a lower layer silicone gel filled inside the case, and is characterized in that the height of the interface between the upper layer silicone gel and the lower layer silicone gel is within a range lower than the upper surface of the insulating substrate and higher than the lower surface.

[0010] Furthermore, a method for manufacturing a semiconductor module according to the present invention is a method for manufacturing the above-mentioned semiconductor module, characterized in that the upper layer silicone gel is filled in after the lower layer silicone gel has hardened. Effect of the Invention

[0011] According to the present invention, even when a gel sealant is used, it is possible to suppress dielectric breakdown due to the growth of voids. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a cross-sectional view of a semiconductor module according to an embodiment. [Diagram 2] 11A to 11C are cross-sectional views for explaining the effect of the semiconductor module according to the embodiment. [Diagram 3] 11 is a cross-sectional view illustrating a problem of a semiconductor module of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same or similar components are designated by the same reference numerals, and duplicated explanations will be omitted.

[0014] FIG. 1 is a cross-sectional view of a semiconductor module according to an embodiment.

[0015] The semiconductor module 1 of the embodiment includes an insulating substrate 2, a wiring layer 3, a metal layer 4, a semiconductor chip 5, a base member 7, and a case 9.

[0016] A wiring layer 3 is provided on the upper surface of the insulating substrate 2, and a metal layer 4 is provided on the lower surface of the insulating substrate 2. The insulating substrate 2, wiring layer 3, and metal layer 4 may be collectively referred to as a substrate.

[0017] The semiconductor chip 5 may be a power semiconductor element, such as a switching element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or a diode element. The semiconductor chip 5 is bonded to the wiring layer 3 via a bonding layer 6 under the chip such as solder. The wiring layer 3 forms a circuit pattern.

[0018] The base member 7 functions as a heat dissipation member. The base member 7 is bonded to the metal layer 4 via an under-substrate bonding layer 8 such as solder.

[0019] The case 9 is attached to the base member 7 via an adhesive 10. The case 9 accommodates at least the semiconductor chip 5 and the insulating substrate 2 inside.

[0020] The semiconductor module 1 of the embodiment also includes a terminal 11 and a wire 12 .

[0021] The terminals 11 are joined to the wiring layer 3. The terminals 11 are, for example, main terminals or auxiliary terminals, and are external connection terminals that are connected to the outside of the semiconductor module 1.

[0022] The wires 12 are bonding wires that connect between the semiconductor chips 5, between the semiconductor chip 5 and the wiring layer 3, or between the substrates. Note that, although the present embodiment has been described taking the case where there are a plurality of substrates as an example, the present invention is not limited to this.

[0023] Here, the semiconductor module 1 of the embodiment has an upper layer side silicone gel 14 and a lower layer side silicone gel 13 filled inside the case 9 as sealing materials. The height of an interface 15 between the upper layer side silicone gel 14 and the lower layer side silicone gel 13 is within a range lower than the upper surface of the insulating substrate 2 and higher than the lower surface. As a manufacturing method for the semiconductor module 1, for example, the lower layer side silicone gel 13 is filled, cured, and then the upper layer side silicone gel 14 is filled and cured, so that the interface 15 can be formed.

[0024] FIG. 2 is a cross-sectional view for explaining the effect of the semiconductor module according to the embodiment.

[0025] 2, even if voids 16 remain in gaps that cannot be filled with lower layer silicone gel 13 during heat cycle testing or use of semiconductor module 1, such as in depressions on the surface of under-substrate bonding layer 8 or in depressions on the surface of adhesive 10 for bonding case 9, and grow due to high temperatures caused by heat generation from semiconductor chip 5, the presence of interface 15 stops the growth of voids 16 at interface 15. Moreover, because the height of interface 15 is within a range lower than the top surface of insulating substrate 2 and higher than the bottom surface, the growth of voids 16 can be prevented from reaching wiring layer 3, thereby preventing dielectric breakdown.

[0026] FIG. 3 is a cross-sectional view illustrating a problem with the semiconductor module of the comparative example.

[0027] In the comparative example, the height of interface 15 is in a range lower than the upper surface and higher than the lower surface of wiring layer 3. Therefore, in the comparative example, there is a problem that voids 16 grow and reach wiring layer 3, which may cause dielectric breakdown.

[0028] Furthermore, although not shown, if the height of interface 15 is lower than the lower surface of insulating substrate 2, voids 16 are likely to occur in the gap between interface 15 and insulating substrate 2, and the voids 16 may grow inside upper silicone gel 14 and reach wiring layer 3, which may cause insulation breakdown.

[0029] As described above, according to the semiconductor module 1 of this embodiment, by setting the height of the interface 15 within the range lower than the upper surface of the insulating substrate 2 and higher than the lower surface, the growth of the voids 16 stops at the interface 15 and the growth of the voids 16 can be prevented from reaching the wiring layer 3, so that insulation breakdown due to the growth of the voids 16 can be prevented even when a gel-like sealing material is used.

[0030] It is desirable that the viscosity of the upper layer side silicone gel 14 before curing is lower than the viscosity of the lower layer side silicone gel 13 before curing. The lower the viscosity of the gel, the more easily it can fill narrow gaps, and therefore it is easier to suppress the occurrence of voids 16. In particular, since the upper layer side silicone gel 14 is filled in areas that tend to have narrow gaps, such as gaps in the wiring pattern of the wiring layer 3, the joints of the terminals 11, and the joints of the wires 12, it is desirable to use a silicone gel with a lower viscosity than that of a silicone gel that has been generally used in the past. On the other hand, if the viscosity of the lower layer side silicone gel 13 is too low, there is a possibility that it will leak from the interface between the adhesive 10 for adhering the case 9 and other members (the base member 7 or the case 9), so it is desirable to use a silicone gel with a viscosity similar to that of a silicone gel that has been generally used in the past. For example, it is desirable that the viscosity of the upper layer side silicone gel 14 before curing is 150 to 450 mPa, and the viscosity of the lower layer side silicone gel 13 before curing is 450 to 750 mPa.

[0031] It is also preferable that the upper silicone gel 14 has a penetration index of 45-80 after curing, and the lower silicone gel 13 has a penetration index of 45-80 after curing.

[0032] Although the embodiment of the present invention has been described above, the present invention is not limited to the configurations described in the embodiment, and various modifications are possible within the scope of the technical concept of the present invention. In addition, some or all of the configurations described in the embodiment may be combined and applied. [Explanation of symbols]

[0033] 1 Semiconductor module 2. Insulating substrate 3 wiring layer 4 metal layer 5. Semiconductor chips 6. Bonding layer under the chip 7 Base material 8 Bonding layer under substrate 9 Cases 10. Adhesive 11 Terminal 12 Wire 13 Lower layer silicone gel 14 Upper layer silicone gel 15 Interface 16. Void

Claims

1. An insulating substrate; A wiring layer provided on an upper surface side of the insulating substrate; a semiconductor chip bonded to the wiring layer; a metal layer provided on a lower surface side of the insulating substrate; a base member bonded to the metal layer; a case attached to the base member and housing at least the semiconductor chip and the insulating substrate therein; an upper layer side silicone gel and a lower layer side silicone gel filled inside the case, A semiconductor module, characterized in that the height of an interface between the upper silicone gel and the lower silicone gel is within a range lower than the top surface of the insulating substrate and higher than the bottom surface of the insulating substrate.

2. In claim 1, A semiconductor module, characterized in that the viscosity of the upper layer silicone gel before curing is lower than the viscosity of the lower layer silicone gel before curing.

3. In claim 2, The viscosity of the upper layer silicone gel before curing is 150 to 450 mPa, A semiconductor module, characterized in that the viscosity of the lower layer silicone gel before curing is 450 to 750 mPa.

4. In claim 1, the upper layer silicone gel has a penetration of 45 to 80 after curing; A semiconductor module, characterized in that the lower layer silicone gel has a penetration of 45 to 80 after hardening.

5. A method for manufacturing the semiconductor module according to claim 1, comprising the steps of:

2. A method for manufacturing a semiconductor module, comprising the steps of: filling said lower silicone gel with said upper silicone gel after said lower silicone gel has hardened;

6. In claim 5, 2. A method for manufacturing a semiconductor module, wherein the viscosity of the upper layer silicone gel before curing is lower than the viscosity of the lower layer silicone gel before curing.

7. In claim 6, The viscosity of the upper layer silicone gel before curing is 150 to 450 mPa, A method for manufacturing a semiconductor module, wherein the viscosity of the lower layer silicone gel before curing is 450 to 750 mPa.

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