JPH11168161A - Power module and its attaching method to heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with a work for an user applying silicon grease on a heat radiating surface of a power module, when the power module is attached to a heat sink. SOLUTION: Silicone grease 7 is applied on a heat radiating surface 2a of a metal base plate 2, the silicone grease 7 is (prior to shipping from the factory) covered by a protective sheet 8 beforehand and a protective sheet 8 is made to peel during the work of attachment to the heat sink. An user need not do applying work of the silicone grease 7, and a method of the power module 5 for attaching to the heat sink through which a work duration can be shortened is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an operation for attaching a power module to a heat sink.

[0002]

2. Description of the Related Art FIG. 5 is a cross-sectional view of a package in a conventional power module. In the figure, 1 is a power module case, 2 is a metal base plate, 3 is a power semiconductor chip, 4 is an electrode (terminal), Reference numeral 5 denotes a power module including the case 1 to the electrode 4. Reference numeral 6 denotes a heat sink provided in an application device (not shown) such as an inverter device, and reference numeral 7 denotes silicon grease as a non-drying heat conductive agent applied to a contact surface between the metal base plate 2 and the heat sink 6.

The power module 5 includes a case 1 in which an insulating plate with a thick metal foil (not shown) is joined to a metal base plate 2 and a semiconductor chip 3 is soldered on the thick metal foil.
The semiconductor chip 3 and the electrode 4 are electrically connected to each other, and are sealed with a resin lid. To attach the manufactured power module 5 to an application device (not shown), the heat radiating surface 2a of the metal base plate 2 is brought into surface contact with the heat sink 6 for heat radiation of the power module 5, and is screwed (not shown). The screws are fixed.

In general, a relatively high-density large current is applied to the semiconductor chip 3 to generate significant heat, and if the temperature exceeds the allowable temperature, the semiconductor chip 3 is destroyed. Therefore, cooling by heat radiation is required. Heat is transferred to the heat sink 6 via the insulating plate with a thick metal foil (not shown) and the metal base plate 2 to be radiated.

Usually, in order to improve the heat radiation effect of the power module 5, in order to eliminate an air layer between the contact surfaces of the metal base plate 2 and the heat sink 6, silicon grease 7 as a non-drying heat conductive agent is substantially applied to the contact surfaces. The silicon grease 7 is applied to the heat sink 6 after being applied uniformly, but the user normally applies the silicon grease 7 at an installation site.

[0006]

When the conventional power module 5 is mounted on an application device (not shown), it is usually
At the installation work site, since the silicon grease 7 as the non-drying heat conductive agent was applied to the contact surface with the heat sink 6 before the installation, the work was troublesome and the work time was lengthened. Solid dust or the like may be mixed into the silicon grease 7 during the coating operation, which may cause unevenness.
There have been problems such as the possibility of lowering the heat radiation characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has been improved so that the work of applying a non-drying heat conductive agent at a work site for attaching a power module to a heat sink can be omitted. It is intended to provide a power module.

[0008]

According to a first aspect of the present invention, there is provided a power module in which a heat radiating surface attachable to a heat sink by surface contact is formed, and the heat radiating surface is coated with a non-drying heat conductive agent. A heat conductive agent protection sheet covering the non-drying heat conductive agent is detachably provided in a state where the heat conductive agent protective sheet is not yet attached to the heat sink.

A power module according to a second aspect of the present invention is the power module according to the first aspect, wherein the thermal conductive agent protective sheet has at least a part of a peripheral portion thereof provided with a heat radiating surface or a heat radiating surface via a non-drying thermal conductive agent. It has been roughened so that it can be adhered to its peripheral edge.

[0010] The power module according to a third aspect of the present invention is the power module according to the first aspect, wherein the heat conductive agent protective sheet is adhered to at least a part of the peripheral portion so as to be adhered to the heat radiation surface or the peripheral portion. The agent has been applied.

A power module according to a fourth aspect of the present invention is the power module according to the first aspect of the present invention, wherein a heat conductive agent protection sheet is provided on at least a part of the heat dissipation surface coated with the non-drying heat conductive agent or at the periphery thereof. It is one coated with an adhesive so that it can be adhered.

A power module according to a fifth aspect of the present invention is the power module according to any one of the first to fourth aspects, wherein the heat conductive agent protective sheet is provided on at least a part of a peripheral portion thereof with a non-drying heat-resistant sheet. A portion where the conductive agent is not covered or where the adhesive is not applied is provided.

A power module according to a sixth aspect of the present invention is the power module according to any one of the first to fourth aspects, wherein the heat conductive agent protective sheet is provided on at least a part of a peripheral portion thereof with a non-drying heat-resistant sheet. A part where a release agent is applied is provided so that the conductive agent or the adhesive does not stick.

A power module according to a seventh aspect of the present invention is the power module in which a heat radiating surface that can be attached to a heat sink by surface contact is formed, and the heat radiating surface is coated with a non-drying heat conductive agent. Are melted by heat.

According to an eighth aspect of the present invention, there is provided a method of attaching a power module to a heat sink, wherein a non-drying heat conducting agent is provided on the heat radiation surface of the power module having a heat radiation surface attachable to the heat sink by surface contact before shipping. Applying the heat conductive agent with a heat conductive agent protective sheet, and attaching the power module to the heat sink, applying the heat conductive agent protective sheet to the non-drying heat conductive agent. Peeling off from the surface.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 First Embodiment A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side view of the power module, and FIG. 2 is a plan view of a protective sheet covering silicon grease applied to the power module shown in FIG. In the figure, those denoted by the same reference numerals as those of the conventional example indicate the same or equivalent parts as those of the conventional example.

In FIG. 1, reference numeral 8 denotes a thermal conductive agent protection sheet for covering a silicon grease 7 as a non-drying thermal conductive agent applied to a heat radiating surface 2a of a metal base plate 2 as a mounting surface of the power module 5. It is described as a protection sheet. The central portion 8a of the protective sheet 8 has a smooth surface on which the silicon grease 7 does not stick or hardly sticks, and the peripheral portion 8b has the heat radiating surface 2a of the metal base plate 2 through the silicon grease 7.
Is formed on the peripheral edge of the protective sheet 8 so as to be adhered, that is, the silicon grease 7 is easily adhered physically, and a projection 8c is formed so that the protective sheet 8 can be easily peeled off.

Power Module 5 as First Embodiment
In a factory, a silicon grease 7 is applied to the heat radiating surface 2a of the metal base plate 2 of the power module 5, while a protective sheet 8 having a roughened peripheral portion 8b is prepared. The protective sheet 8 is peeled off from the coated surface of the silicon grease 7 when the power module 5 is mounted on the heat sink 6, and is mounted on a heat sink (not shown) provided in the application apparatus.

As described above, the heat release surface 2a of the metal base plate 2 in the power module 5 has the silicon grease 7
Is applied in advance, and the silicon grease 7 is covered with a protective sheet 8. The central portion 8a does not adhere or hardly adheres to the silicon grease 7, but the peripheral portion 8b adheres to the silicon grease 7 and the protective sheet 8 forms the heat radiating surface 2a.
The surface is protected while being held by the silicon grease 7 applied to the surface.

When the protective sheet 8 is peeled off, a part of the silicon grease 7 adheres to the peripheral portion 8b and is carried away. However, the central portion 8a does not adhere or hardly adheres to the silicon grease 7. Almost the whole amount remains in a state of being attached to the heat radiation surface 2a. Since the protection sheet 8 is easily peeled off when the protrusion 8c is pulled, it is only necessary to peel off the protection sheet when attaching a heat sink (not shown) in the application apparatus.

Embodiment 2 FIG. Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a plan view of another protective sheet covering the silicon grease in the power module shown in FIG. In the figure, reference numeral 81 denotes a protective sheet that covers the silicon grease 7 applied to the heat radiation surface 2a of the metal base plate 2 of the power module 5. The difference from the protective sheet 8 shown in FIG. Is formed, and the entire surface is a smooth surface on which the silicon grease 7 does not stick or hardly sticks. The peripheral portion 81b can be adhered to the peripheral portion of the heat radiating surface 2a of the metal base plate 2, and is incompatible with the silicon grease 7. Adhesive 9 is applied,
This prevents peeling of the protective sheet 81 during transportation. Incidentally, 81
Reference numeral c denotes a protrusion provided so that the protective sheet can be easily peeled off.

In the above example, the peripheral portion 81 of the protective sheet 81 is used.
Although the adhesive 9 was applied to the base b, the silicone grease 7 may be applied to the center of the heat radiation surface 2a of the metal base plate 2, and then the adhesive (not shown) may be applied to the peripheral edge thereof. .

Power Module 5 as Second Embodiment
In a factory, silicon grease 7 is applied to the heat radiation surface 2a of the metal base plate 2 of the power module 5, and the peripheral portion thereof or a separately prepared protective sheet 81
The adhesive 9 is applied to the peripheral portion 81b of the protective sheet 81.
The coated surface of the silicon grease 7 is covered with
The power module 5 covered with 1 is packed and shipped, and when the power module 5 is mounted on the heat sink 6 at the mounting work site, the protection sheet 81 is peeled off from the surface to which the silicon grease 7 is applied, and is transferred to a heat sink (not shown). Can be attached.

As described above, the silicon grease 7 previously applied to the heat radiating surface 2a is covered with the protective sheet 81.
a, and the peripheral portion 81b is not applied. The protective sheet 81 is held by the adhesive 9 applied to the peripheral portion 81b, and protects the surface of the applied silicon grease 7.

When the protective sheet 81 is peeled off, most of the adhesive 9 on the peripheral portion 81b adheres to the protective sheet 81 and hardly adheres to the heat radiating surface 2a. Almost all of them remain in a state of being attached to the heat radiation surface 2a. When the protrusion 81c of the protection sheet 81 is pulled, the protection sheet 81 is easily peeled off. Therefore, when attaching a heat sink (not shown) in the application apparatus, it is only necessary to peel off the protection sheet.

The adhesive 9 does not necessarily need to be applied to the periphery of the heat radiating surface 2a of the metal base plate 2 or the entire periphery of the periphery 81b of the protection sheet 81. The adhesive 9 may be applied only in the horizontal or vertical direction.

Embodiment 3 Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a plan view of another protective sheet covering the silicon grease in the power module shown in FIG. In the figure, reference numeral 82 denotes a protective sheet, which is provided with a portion where the silicone grease 7 or the adhesive 9 is not applied near a corner 82c of a peripheral edge portion 82b, from which the protective sheet 82 is peeled off. The protection sheet 82 does not have the protrusion 8c of the protection sheet 8 shown in FIG. 2 and can be made smaller accordingly, so that the same effects as those of the first to third embodiments can be obtained and more economical. Is obtained.

If a release agent is applied to the vicinity 82c of the corner of the protective sheet 82 shown in FIG. 4, even if the silicone grease 7 or the adhesive 9 is applied to the portion of this 82c, the adhesive may adhere. Without this, the protective sheet can be peeled off from here, and further, a convenient one can be obtained.

Embodiment 4 Embodiment 4 of the present invention will be described. The protective sheet (not shown) according to the fourth embodiment has the same shape as protective sheet 82 shown in FIG. 4, has an affinity for silicon grease as the non-drying heat conductive agent, and A material that is melted and integrated by the heat generated by the power module 5, for example, a material that is thinned in the same system as the grease and has an adhesive property with silicon grease, and is attached to a heat sink. It does not need to be peeled off sometimes. In addition, the protective sheet has a predetermined thickness, and one surface is a heat radiation surface 2.
If a material having adhesiveness to a is selected, the application of the silicone grease can be omitted.

As described above, in the power module 5 according to the first to fourth embodiments, the silicon grease 7 is applied to the heat radiation surface 2a of the metal base plate 2 in advance in the manufacturing stage, and the protective sheets 8, 81 Or 82, it is not necessary to apply the silicon grease 7 by simply peeling off the protective sheet 8, 81 or 82 when attaching to the device at the installation work site. One can be omitted, the time can be reduced, and the work efficiency can be greatly improved.

In the first to third embodiments, the protective sheet 8, 81 or 82 to which the silicon grease 7 does not stick is used.
For example, there is a fluororesin-based sheet as a material, but this fluororesin-based sheet is generally expensive, and a relatively inexpensive sheet material such as polyethylene, polypropylene or the like is used, and a silicon resin-based sheet is formed in the central portion 8a. Similar effects can be obtained by using a material coated with a release agent, or a paper material impregnated with the release agent.

Further, in the first to fourth embodiments, as the non-drying heat conductive agent, the silicon grease 7 which has relatively little deterioration at a high temperature and can maintain a stable performance as a grease is exemplified, but is limited to the silicon grease. Not something
The same effect can be obtained by using grease or adhesive other than silicon-based materials as long as they have similar performance.

[0033]

According to the first and eighth aspects of the present invention, a non-drying heat conductive agent is applied to the heat radiating surface of the heat radiating base plate, and the non-drying heat conductive agent is preliminarily applied to the heat conductive agent protecting sheet (from the factory). Before), the heat conductive agent protection sheet is peeled off during the mounting work on the heat sink, so that the work of applying the non-drying heat conductive agent at the mounting work site is unnecessary, the working time can be reduced, and the working efficiency is excellent. The power module and the method of attaching the power module to the heat sink can be obtained.

According to the second aspect of the present invention, at least a part of the periphery of the thermal conductive agent protective sheet is processed into a rough surface.
According to the third aspect of the present invention, it is possible to adhere to the heat radiating surface of the power module or the peripheral portion thereof through the non-drying heat conductive agent.
At least a part of the peripheral portion of the thermal conductive agent protective sheet,
According to the fourth aspect, since the adhesive is applied to at least a part of the heat radiating surface of the power module or the peripheral portion thereof, the heat conductive agent protective sheet can be adhered to the heat radiating surface of the power module or the peripheral portion thereof, There is an effect that a material that can more reliably protect the non-drying heat conductive agent can be obtained.

According to the fifth aspect of the present invention, at least a portion of the peripheral portion of the thermal conductive agent protective sheet that is not covered with the non-drying thermal conductive agent or to which the adhesive is not applied is provided. According to the sixth aspect of the invention, since the place where the release agent is applied is provided so that the non-drying heat conductive agent or the adhesive does not stick, the peeling operation of the heat conductive agent protective sheet becomes easy, and further, the work efficiency is improved. There is an effect that a power module excellent in the above can be obtained.

According to the seventh aspect of the present invention, since the heat conductive agent protective sheet has an affinity for the non-drying heat conductive agent and is melted by the heat generated by the power module, the heat conductive agent protective sheet can be attached to the heat sink at the time of mounting work. There is no need to peel off the thermal conductive agent protective sheet, and furthermore, there is an effect that a power module with excellent work efficiency can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a power module as a first embodiment of the first, second, and eighth inventions.

FIG. 2 is a plan view of a protective sheet in the power module shown in FIG.

FIG. 3 is a plan view of a protection sheet in a power module as a second embodiment of the first, third, fourth, and eighth inventions.

FIG. 4 is a plan view of a protection sheet in a power module according to a third embodiment of the fifth and sixth inventions.

FIG. 5 is a diagram showing a cross section of a conventional power module.

[Explanation of symbols]

1 case, 2 metal base plate, 3 power semiconductor chip, 4 electrodes (terminals), 5 power module, 6 heat sink, 7 silicon grease, 8 protection sheet,
9 Adhesive, 81, 82 Protective sheet

Claims (8)

[Claims] 1. A power module having a heat sink formed with a heat-dissipating surface that can be attached to a heat sink by surface contact, and the heat-dissipating surface coated with a non-drying heat-conducting agent. A power module, wherein a thermal conductive agent protective sheet covering the agent is detachably disposed. 2. The power module according to claim 1, wherein the thermal conductive agent protective sheet has at least a part of its peripheral portion roughened so as to be adhered to a heat radiating surface or its peripheral portion via a non-drying thermal conductive agent. A power module characterized by being processed into a surface. 3. The power module according to claim 1, wherein the heat conductive agent protective sheet has at least a part of a peripheral edge thereof coated with an adhesive so as to be able to adhere to a heat radiation surface or the peripheral edge. Power module characterized by the following. 4. The power module according to claim 1, wherein an adhesive is applied to at least a part of the heat radiating surface to which the non-drying heat conductive agent is applied or a peripheral portion thereof so as to be able to adhere to the heat conductive agent protection sheet. A power module, characterized in that: 5. The power module according to claim 1, wherein the thermal conductive agent protective sheet is
A power module, wherein at least a part of a peripheral portion of the power module is not covered with a non-drying heat conductive agent or coated with an adhesive. 6. The power module according to any one of claims 1 to 4, wherein the heat conductive agent protection sheet comprises:
A power module characterized in that at least a part of a peripheral portion thereof is provided with a portion to which a release agent is applied so that a non-drying heat conductive agent or an adhesive does not adhere. 7. A power module in which a heat radiating surface that can be attached to a heat sink by surface contact is formed, and the heat radiating surface is coated with a non-drying heat conductive agent, wherein the heat conductive agent protective sheet is melted by heat. Power module. 8. A step of applying a non-drying heat conductive agent to the heat radiating surface of a power module having a heat radiating surface attachable to a heat sink by surface contact at a pre-shipment stage, and applying the non-drying heat conductive agent. Covering the surface with a thermal conductive agent protective sheet, and, in the step of attaching the power module to the heat sink, peeling the thermal conductive agent protective sheet from the application surface of the non-drying thermal conductive agent. How to attach the power module to the heat sink.