JP2014150204A - Power module and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which maintains the insulation capability from outer air thereby inhibiting the deterioration of the quality and continuously uses the current outer shape and the basic structure to enable easy implementation in a power module.SOLUTION: A power module includes: a case 2; a base plate 7 disposed at a lower end part of the case 2; a chip 6 which is disposed on the base plate 7 and serves as a power element; a silicone gel 8 which seals the chip 6; and a thin sheet member 9 which covers a surface 8a of the silicone gel 8 and has a thickness such that the sheet member 9 bends so as to match the movement of the silicone gel 8; and a lid member 1 disposed at an upper end part of the case 2.

Description

  The present invention relates to an improvement in sealing power of a power module, which is a power semiconductor device component.

  In a general industrial power module, a base plate is disposed at the lower end of the case, and a power element disposed on the base plate via a substrate is sealed with silicone gel and epoxy resin (see, for example, Patent Document 1). A sealing structure in which a lid member is disposed on the upper end of the case in a state where the case is filled with silicone gel has been the mainstream. Among these, from the viewpoint of productivity and quality assurance, a sealing structure using a silicone gel and a lid member tends to be employed.

  In the conventional sealing structure with silicone gel and lid member, there is an air layer between the silicone gel and lid member, but the lid member can not be sealed structure even if mainly screwing or snap fit is adopted. The outside air contacts the surface of the silicone gel.

  In addition, since the silicone gel is a material that is relatively easy to permeate humidity and gas among the sealing materials, the external environment is in a high humidity state, or there is a gas component that adversely affects the power module, There is a possibility that the silicone gel may be adversely affected such as deterioration of insulating properties.

Japanese Patent Laid-Open No. 2005-57875

  In a power module having a sealing structure of a conventional silicone gel and a lid member, the inside cannot be sealed so as not to be exposed to the outside air. In addition, since the silicone gel has a large amount of expansion and contraction due to temperature, the silicone gel thermally expands when the power module is energized, pushing out the air existing between the silicone gel and the lid member, but the silicone gel contracts when not in operation. Then inhale the outside air. If the outside air contains a large amount of moisture and sulfide, for example, the silicone gel is highly permeable. Therefore, there is an adverse effect such as corrosion of the power element disposed inside the silicone gel and deterioration of insulation. As a result, there is a problem that the quality of the power module may be deteriorated.

  In addition, for example, in the structure described in Patent Document 1, a diffusion prevention resin layer is formed between the silicone gel and the epoxy resin, that is, on the upper surface of the silicone gel in order to maintain the insulation property of the silicone gel. Since the diffusion preventing resin layer is formed by potting or dispensing, it is necessary to cure the diffusion preventing resin layer.

  As described above, since it is necessary to change the structure to take measures to improve the sealability of products currently in mass production, there is a problem of cost and time required for material development, changes to molds and drawings, etc. There is also.

  Therefore, the present invention is a technology that can suppress deterioration in quality by maintaining insulation performance from outside air in a power module, and can be easily implemented by following the current external shape and basic structure. The purpose is to provide.

  The power module according to the present invention includes a case, a base member disposed at a lower end of the case, a power element disposed on the base member, a silicone gel for sealing the power element, and the silicone gel. A sheet member that is thin enough to be flexible in accordance with the movement of the silicone gel, and a lid member that is disposed at the upper end of the case.

  The method for manufacturing a power module according to the present invention includes a step of placing the sheet member on the surface of the cured silicone gel.

  Moreover, the manufacturing method of another power module which concerns on this invention is equipped with the process of mounting the said sheet | seat member on the surface of the said silicone gel before hardening.

  According to the present invention, since the power module includes a sheet member that covers the surface of the silicone gel and is flexible enough to move according to the movement of the silicone gel, the sheet can be used even when the silicone gel is thermally expanded and contracted. The member adheres to the silicone gel and follows the movement of the silicone gel. As a result, it is possible to maintain high insulation performance against the outside air regardless of whether the temperature is high or low, so that intruders from the external environment that cause insulation failure and corrosion can be reduced. Can be suppressed.

  In addition, since the sheet member is arranged on the surface of the silicone gel, there is no need to harden the sheet member when arranging the sheet member, and it is possible to follow the outer shape and basic structure of the current power module. Can be implemented.

  Further, according to the method for manufacturing a power module of the present invention, since the sheet member is placed on the surface of the cured silicone gel, there is no need to cure the sheet member when the sheet member is arranged, and the current power module It can follow the external shape and basic structure of this, and can be implemented easily.

  Further, according to another method of manufacturing a power module of the present invention, in order to place the sheet member on the surface of the silicone gel before being cured, it is only necessary to cure only the silicone gel after placing the sheet member, The external shape and basic structure of the current power module can be followed and can be easily implemented.

2 is a cross-sectional view of the power module according to Embodiment 1. FIG. It is a figure which shows the manufacturing method of a power module. It is a figure which shows the state which the sheet | seat member followed the movement of the silicone gel. 6 is a cross-sectional view of a power module according to Embodiment 2. FIG. It is sectional drawing of the power module which concerns on a premise technique.

<Embodiment 1>
Embodiment 1 of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view of a power module according to Embodiment 1. FIG. As shown in FIG. 1, the power module includes a case 2, a base plate 7 (base member), a chip 6 that is a power element, a silicone gel 8, a sheet member 9, and a lid member 1. .

  The base plate 7 is disposed at the lower end of the case 2, and the chip 6 is soldered and fixed via an insulating substrate 5 soldered to the upper surface of the base plate 7. The silicone gel 8 is filled in the case 2 and seals the chip 6, the wire 4 bonded to the chip 6, the insulating substrate 5, and the like.

  The sheet member 9 is disposed on the surface 8 a of the silicone gel 8 and covers the surface 8 a of the silicone gel 8. The sheet member 9 is formed of, for example, a polyphenylene sulfide (PPS) resin having high heat resistance and gas high insulation, and also moves the silicone gel 8 (more specifically, thermal expansion / contraction of the silicone gel 8). It is formed into a thin sheet so as to be flexible. The lid member 1 is disposed at the upper end of the case 2 and is screwed to the case 2, for example, and covers the surfaces of the sheet member 9 and the silicone gel 8.

  Next, a method for manufacturing the power module according to Embodiment 1 will be briefly described. FIG. 2 is a diagram illustrating a method for manufacturing a power module. The insulating substrate 5 is fixed to the base plate 7 by soldering, and the chip 6 is fixed on the insulating substrate 5 by soldering. After the wires 4 are joined and the chip 6 is mounted, the base plate 7 and the case 2 are fixed. Next, the silicone gel 8 is filled to a height at which the chip 6 and the wire 4 are buried in the case 2 to cure the silicone gel 8. As shown in FIG. 2, after the silicone gel 8 is cured, the sheet member 9 is placed on the surface 8 a of the cured silicone gel 8, and the lid member 1 is attached to the upper end portion of the case 2.

  Next, the operation and effect of the power module according to Embodiment 1 will be described in comparison with the base technology. FIG. 3 is a view showing a state in which the sheet member 9 follows the movement of the silicone gel 8. FIG. 5 is a cross-sectional view of the power module according to the base technology and is a view showing the movement of the silicone gel 8. 3 and 5, the state in which the silicone gel 8 has moved up and down is indicated by a two-dot chain line.

  First, the power module according to the base technology will be described. As shown in FIG. 5, the power module according to the base technology has a configuration in which the sheet member 9 is not provided with respect to the power module according to the first embodiment. Since there is a gap between the lid member 1 and the case 2, the outside air cannot be blocked.

  For this reason, when the silicone gel 8 moves up and down due to thermal expansion and contraction of the silicone gel 8, outside air is taken in from the gap between the lid member 1 and the case 2, and the outside air contacts the entire surface 8a of the silicone gel 8. . If the outside air contains a large amount of moisture and sulfide, for example, the silicone gel 8 is highly permeable, and therefore adverse effects such as corrosion of the chip 6 and the like disposed inside the silicone gel 8 and deterioration of insulation properties. As a result, the quality of the power module may be degraded.

  In contrast, as shown in FIG. 3, in the power module according to the first embodiment, since the sheet member 9 is disposed so as to cover the surface of the silicone gel 8, the outside air is the surface 8 a of the silicone gel 8. There is almost no contact except for the outer peripheral portion. Further, the sheet member 9 follows the vertical movement of the silicone gel 8 in a state where the sheet member 9 is stuck to the surface 8a of the silicone gel 8 having a high thermal expansion / shrinkage rate. Thereby, even if the outside air that has entered the power module contains high humidity and sulfide, the influence on the chip 6 and the like disposed inside the silicone gel 8 can be minimized.

  Further, when the power module according to the first embodiment is manufactured, it is only necessary to place the sheet member 9 on the surface of the cured silicone gel 8 with respect to the current structure which is a prerequisite technology. There is no need to change, change the mold, or change the drawing, and the work can be done in a short time and easily.

  As described above, in the power module according to Embodiment 1, the power module includes the sheet member 9 that covers the surface 8a of the silicone gel 8 and is thin enough to be flexible in accordance with the movement of the silicone gel 8. Even when the silicone gel 8 is thermally expanded and contracted, the sheet member 9 adheres to the silicone gel 8 and follows the movement of the silicone gel 8. As a result, it is possible to maintain high insulation performance against the outside air regardless of whether the temperature is high or low, so that intruders from the external environment that cause insulation failure and corrosion can be reduced. Can be suppressed. Moreover, since the insulation defect and corrosion can be suppressed by reducing the intruding substance from the external environment, the power module can be used for a long time.

  In addition, since the sheet member 9 is disposed on the surface 8a of the silicone gel 8, more specifically, the sheet member 9 is disposed on the surface 8a of the cured silicone gel 8, At this time, it is not necessary to harden the sheet member 9, and the outer shape and basic structure of the current power module can be followed, which can be easily implemented.

  Moreover, since the sheet member 9 is formed of a polyphenylene sulfide resin having high heat resistance and high gas insulation properties, it is possible to further improve the insulation performance from the outside air in the power module.

  The sheet member 9 may be formed of a resin including a synthetic resin other than polyphenylene sulfide resin and rubber, a metal including a nonferrous metal, a ceramic material, or a glass material. In this case, the same effect as described above can be obtained. The sheet member 9 may be formed of a material obtained by mixing a plurality of types from resin, metal, ceramic material, and glass material. In this case, the same effect as described above can be obtained.

  Furthermore, the sheet member 9 may be formed of a resin (for example, silicone rubber) including a synthetic resin and rubber having high hygroscopicity and high gas absorption. In this case, the insulation performance from the outside air in the power module can be further enhanced.

<Embodiment 2>
Next, a power module according to Embodiment 2 will be described. FIG. 4 is a cross-sectional view of the power module according to the second embodiment. In the second embodiment, the same components as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the second embodiment, the sheet member 9 is placed on the surface 8a of the silicone gel 8 before being cured, and then the silicone gel 8 is cured. As shown in FIG. 4, the sheet member 9 is placed on the surface 8 a of the silicone gel 8 when the silicone gel 8 is cured. That is, the portion on which the sheet member 9 is placed in the silicone gel 8 is formed with a dent corresponding to the thickness of the sheet member 9, so that the surface of the sheet member 9 and the outer peripheral portion of the silicone gel 8 (more specifically, The surface of the portion where the sheet member 9 is not placed has substantially the same height.

  As described above, in the power module according to the second embodiment, since the sheet member 9 is placed on the surface 8a of the silicone gel 8 before being cured, the silicone gel 8 is disposed after the sheet member 9 is disposed. It is sufficient to cure only the outer shape and the basic structure of the current power module, which can be easily implemented.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  1 Lid member, 2 Case, 6 Chip, 7 Base plate, 8 Silicone gel, 8a Surface of silicone gel, 9 Sheet member.

Claims (7)

Case and
A base member disposed at the lower end of the case;
A power element disposed on the base member;
A silicone gel for sealing the power element;
A sheet member that covers the surface of the silicone gel and is thin enough to be flexible in accordance with the movement of the silicone gel;
A lid member disposed at the upper end of the case;
Power module with   The power module according to claim 1, wherein the sheet member is formed of a resin, a metal, a ceramic material, or a glass material.   The power module according to claim 1, wherein the sheet member is formed of a material obtained by mixing a plurality of types of resin, metal, ceramic material, and glass material.   The power module according to claim 1, wherein the sheet member is made of a resin having high heat resistance and high gas insulation properties.   The power module according to claim 1, wherein the sheet member is made of a highly hygroscopic and gas-absorbent resin. It is a manufacturing method of the power module of Claim 1, Comprising:
A method for manufacturing a power module, comprising a step of placing the sheet member on the surface of the cured silicone gel. It is a manufacturing method of the power module of Claim 1, Comprising:
A method for producing a power module, comprising a step of placing the sheet member on the surface of the silicone gel before curing.

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