JPH09183953A - Heat-conductive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-conductive adhesive sheet satisfactory in heat dissipation properties and adhesiveness by forming a specified layer on at least either surface of a heat-conductive base to constitute a sheet body and forming a specified structure on the base. SOLUTION: A pressure-sensitive adhesive (e.g. natural rubber adhesive) layers 2A or 2B is formed on at least either surface of a heat-conductive base (e.g. flexible aluminum foil) to constitute a sheet body 3, and many heat- conductive parts 4 are formed on the base 1 in the direction (x) of the thickness of the pressure-sensitive adhesive layers 2A or 2B. Desirably, a pressure-sensitive adhesive layer 5 for adhesion reinforcement is formed on at least either surface of the sheet body 3. If required, heat-conductive particles (e.g. silica particles) are added to pressure-sensitive adhesive layers 2A or 2B constituting the sheet body 3 and/or the pressure-sensitive adhesive layer 5 for adhesion reinforcement.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a heat conductive adhesive sheet.
Regarding sheets (formed in the form of sheets, tapes, etc.), a heat conductive adhesive sheet for electronic devices that mainly bonds electronic components such as IC chips to heat sinks and radiators.
Regarding the kind.

[0002]

2. Description of the Related Art When bonding various electronic components including hybrid packages, multi-chip modules, plastics and metal-sealed integrated circuits to heat sinks and radiators There is a need for thermally conductive adhesive sheets that can release the heat generated to a heat sink or other heat dissipation device. In particular, with the high integration of IC chips, etc., the amount of heat generated from IC chips, etc., has increased to an extent comparable to that of conventional ones, and how efficiently this generated heat is transferred through adhesive sheets. How to dissipate heat becomes an important issue.

US Pat. No. 4,722,960 describes powdered aluminum fillers such as aluminum metal elements and anhydrous aluminum oxide, at least one polymerizable acrylate ester monomer, free radical initiation. Agent and optionally metal chelator (chelat
or)) has been reported as a material for attaching a heat sink of an electric component.

This heat conductive adhesive composition is of a type which is cured by a specific means, and a lot of labor is spent at the time of using the adhesive, and parts are temporarily fixed until the adhesive composition is cured. You need to do it. In order to avoid such inconvenience, the use of a heat-conductive filler-filled pressure-sensitive adhesive containing a heat-conductive filler such as a powdery aluminum filler and exhibiting pressure-sensitive adhesiveness has been studied. ing.

[0005]

However, this heat-conductive filler-filling type pressure-sensitive adhesive contains a large amount of heat-conductive filler in order to improve the heat dissipation, and thus the adhesive properties, especially There is a problem that the retention property at high temperature is deteriorated.
Recently, the main body and substrate of a personal computer to which an IC chip or the like is attached are often placed vertically, and along with this, holding of electronic parts such as the IC chip at high temperature with respect to a heat dissipation device. Since the characteristics have become very important, it is strongly desired to solve the above problems.

In view of the above-mentioned conventional circumstances, the present invention is mainly used as a heat conductive adhesive sheet for electronic devices, and is excellent in heat dissipation and is excellent in adhesive property, especially retention property at high temperature. The purpose is to provide things.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a sheet having a pressure-sensitive adhesive layer provided on one or both surfaces of a heat conductive substrate. While constructing the main body, by adding specific heat radiation improving means to this sheet main body, it is possible to add no heat conductive filler to the pressure sensitive adhesive layer at all, or to add it only slightly. Then, it was found that good heat dissipation was obtained, and by doing so, both heat dissipation and adhesive properties were successfully achieved, and the present invention was completed.

That is, according to the present invention, mainly for electronic devices such as IC chips, the sheet main body is formed by providing a pressure sensitive adhesive layer on at least one surface of a heat conductive base material, and the pressure sensitive material described above is used. The present invention relates to a heat conductive adhesive sheet in which a large number of heat conductive portions that penetrate the adhesive layer in the thickness direction are provided on the base material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing an example of a heat conductive adhesive sheet according to the present invention, and FIG. 2 is a sectional view taken along line II-II in FIG.

In both figures, the heat conductive base material 1 and pressure sensitive adhesive layers 2A and 2B provided on both surfaces of the base material 1 are shown.
The sheet body 3 is constituted by Further, in this sheet main body 3, a large number of heat conduction parts 4 penetrating the pressure sensitive adhesive layers 2A and 2B in the thickness direction x are provided on the base material 1.

The heat conductive base material 1 may be any material having heat conductivity, and examples thereof include metal foils such as aluminum foil, copper foil, stainless steel and beryllium copper, alumina sintered sheets, and epoxy. In addition to sheets with heat conductive particles added to resin, heat conductive silicone rubber, etc., polyimide film, polyester film, polytetrafluoroethylene film, polyethylene ketone film,
It is also possible to use heat-resistant films such as polyethylene sulfone film, polymethylpentene film and polyethylene 2,6-naphthalate film.

The pressure sensitive adhesive layers 2A and 2B include
Any pressure-sensitive adhesive such as natural rubber-based or acrylic-based can be used, and a heat-resistant pressure-sensitive adhesive such as a UV-curable type is preferable in order to improve the holding property at high temperature. It is not particularly necessary to add the heat conductive particles as a filler to the layers 2A and 2B, but a small amount of the heat conductive particles can be added if a better heat dissipation property is desired.

The heat conductive particles are particles having a spherical shape, a needle shape, a flake shape or the like, and have a particle size of 0.5 to 25.
Those having a size of about 0 micron, for example, silica, aluminum oxide, aluminum nitride, titanium dioxide, boron nitride, silicon nitride, titanium boride and the like are used. The addition amount is 1 with respect to 100 parts by weight of the solid content of the pressure sensitive adhesive.
The amount is preferably 20 parts by weight or less, preferably 20 to 100 parts by weight, and if too much is added, the adhesive properties are adversely affected, which is not preferable.

The heat conducting portions 4 are arranged at desired intervals in the longitudinal direction and the width direction of the sheet body 3, for example, as shown in FIG.
The distance a in the longitudinal direction and the distance b in the width direction are each 1 to
A large number are formed on the entire surface of the base material 1 so as to be in the range of 20 mm, preferably 3 to 10 mm. Further, each hole diameter c of the heat conducting portion 4 is 0.1 to 5 mm, preferably 0.3 to
1 mm. If the intervals a and b are too small,
If the pore size c becomes too large, the adhesive properties will be impaired.

The heat conducting portion 4 is punched out from the pressure sensitive adhesive layer 2A side of the base material 1 by using a drawing die and a press to form a through hole through the sheet body 3. A part of the base material 1 is cylindrically formed on the pressure-sensitive adhesive layer 2B side, and its tip is press-formed in a horizontally bent shape. At that time, if a method of punching from the pressure-sensitive adhesive layer 2B side of the base material 1 is used together, as shown in FIG. 3, a part of the base material 1 is squeezed into a cylindrical shape also on the pressure-sensitive adhesive layer 2A side. It can be molded and the tip thereof can be bent horizontally, whereby heat dissipation can be further enhanced.

The heat conducting portion 4 is formed as a through hole as described above, and a part of the base material 1 is simply bent to the surface side of the pressure sensitive adhesive layer 2A and / or 2B in a protruding shape. It may be formed by adding or other heat conductive material. In addition, the pressure-sensitive adhesive layer 2 on the substrate 1
Only one of A and 2B may be provided.

In the heat conductive adhesive sheet thus constructed, the thickness of the entire sheet (here, the thickness of the sheet main body 3) can be appropriately set according to the purpose of use. , Usually 30 to 500 μm, preferably 130 to 30
It is preferably 0 μm. Among them, the thickness of the base material 1 is usually 10 to 125 μm, preferably 25 to 100 μm, and the thickness of the pressure-sensitive adhesive layers 2A and 2B is usually 10 to 200 μm, preferably 30 to 130 μm.

As described above, the pressure sensitive adhesive layer 2A (2B) is provided on at least one surface of the heat conductive substrate 1 to form the sheet body 3, while the layer 2A (2B) is formed in the thickness direction. When a large number of heat conducting portions 4 are provided so as to penetrate therethrough, the heat generated in the electronic component is successfully conducted to the heat dissipation device such as a heat sink through the heat conducting portions 4 described above, and as a result, the layer 2A is formed.
Good heat dissipation can be obtained even if (2B) does not contain the heat conductive particles or only contains a small amount, and in this case, the original adhesive property based on the layer 2A (2B), especially at high temperature, is obtained. The retention characteristic of is exhibited well.

FIG. 4 shows another example of the heat conductive adhesive sheet according to the present invention, in which pressure sensitive adhesive layers 2A and 2B are provided on both surfaces of the heat conductive base material 1 to form a sheet. The main body 3
Further, the structure of providing a large number of heat conducting portions 4 penetrating the layers 2A and 2B in the thickness direction is the same as the above, but here, one side of the sheet body 3 for adhesive reinforcement is further provided. The pressure sensitive adhesive layer 5 is provided.

The pressure-sensitive adhesive layer 5 for reinforcing the adhesion may be the same pressure-sensitive adhesive as the pressure-sensitive adhesive layers 2A and 2B forming the sheet body 3 or different pressure-sensitive adhesives. May be The sheet is not limited to the one shown in the figure, and may be provided on both sides of the sheet body 3. The pressure-sensitive adhesive layer 5 has a thickness of usually 10 to 100 μm, preferably 20.
.About.80 .mu.m, which is thinner than the pressure-sensitive adhesive layers 2A and 2B constituting the sheet body 3, and the total thickness of the sheet body 3 is 30 to 500 .mu.m, preferably 130 to 300 .mu.m. It should be so.

When such a pressure sensitive adhesive layer 5 is provided,
Further favorable results are obtained with respect to the adhesive properties, especially the holding properties at high temperatures. In particular, when the occupied area of the heat conducting portion 4 in the sheet body 3 becomes large, for example, when the distances a and b shown in FIG. 1 are 1.0 mm or less, the strength of the sheet decreases and the sheet is held at high temperature. Although the characteristics may be deteriorated, when the layer 5 is provided, the holding property can be improved without significantly affecting the heat dissipation property, and the heat dissipation property and the adhesive property can be easily compatible with each other.

[0022]

Next, an embodiment of the present invention will be described in more detail. In the following, “parts” means “parts by weight”.

Example 1 As a heat conductive base material, JIS H 4160 IN30
The soft aluminum foil with a thickness of 30 μm specified in 1. is used, and an adhesive layer made of a natural rubber pressure-sensitive adhesive with a thickness of 40 μm is applied to both sides of this base material to form a sheet body. Configured. Then, the distance a and b in Fig. 1 is 5 mm.
The outer diameter of the punch is 0.425 mm and the inner diameter of the die is 0.5 mm.
A heat conductive adhesive tape having a heat conductive portion having a shape shown in FIG. 2 was produced by punching using a drawing die and a press.

Comparative Example 1 A heat-conductive adhesive tape was produced in the same manner as in Example 1 except that the heat-conducting portion was not formed by omitting punching by a drawing die and a press.

Example 2 90 parts of 2-ethylhexyl acrylate, 1 acrylic acid
0 parts, 210 parts of ethyl acetate, 0.4 parts of 2,2'-azobisisobutyronitrile were charged into a flask, and after the system was sufficiently replaced with nitrogen gas, the solution was heated and stirred at 60 to 80 ° C to prepare a solution. Polymerization is carried out, the viscosity is 120 poise and the polymerization rate is 9
A polymer solution having a solid content of 9.2% by weight and a solid content of 31.4% by weight was obtained. To 100 parts of this polymer solution, 2 parts of a polyfunctional isocyanate compound as a crosslinking agent was added and mixed to prepare a pressure-sensitive adhesive solution.

This pressure-sensitive adhesive solution was coated on a polyester film having a thickness of 25 μm which had been subjected to a peeling treatment, dried in a hot air dryer at 40 ° C. for 5 minutes, and then dried.
After drying for 5 minutes at ℃, the thickness of the adhesive layer after drying is 5
An adhesive sheet having a thickness of 0 μm was obtained. This adhesive sheet was transferred to both sides of the heat conductive base material made of soft aluminum foil having a thickness of 30 μm used in Example 1 to form a sheet main body. Then, by punching and molding in the same manner as in Example 1, a heat conductive adhesive tape having a heat conductive portion having a shape shown in FIG. 2 was produced.

Example 3 In punching using a drawing die and a press in Example 2, the punching direction is appropriately changed and combined to produce a heat conductive adhesive tape having a heat conducting portion having a shape shown in FIG. did.

Example 4 The pressure-sensitive adhesive solution prepared in Example 2 was further coated on one side of the heat conductive adhesive tape prepared in Example 2, and the same method as in Example 2 was carried out. After drying, the thickness is 3
A pressure-sensitive adhesive layer for adhesion reinforcement having a thickness of 0 μm was formed, and a heat conductive adhesive tape having a heat conductive portion having a shape shown in FIG. 4 was produced.

Comparative Example 2 A heat conductive adhesive tape was produced in the same manner as in Example 2 except that the heat conducting portion was not formed by omitting punching by a drawing die and a press.

Example 5 60 parts of isononyl acrylate, butyl acrylate 2
8 parts, acrylic acid 12 parts, 2,2 as a photopolymerization initiator
A premix was prepared using 0.1 part of'-dimethoxy-2-phenylacetophenone (trade name "Irgagiyua 651" manufactured by Ciba-Geigy). The premix was partially polymerized by exposing it to ultraviolet light in a nitrogen atmosphere to give a coatable syrup having a viscosity of about 4,500 centipoise.

100 parts of this partially polymerized syrup was added to tetrabismethylene-3- as a radical chain inhibitor.
4 parts of (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate methane and 0.2 part of trimethylolpropane triacrylate as a cross-linking agent were added and mixed. , This composition was coated on a polyester film that had been subjected to a release treatment, and under a nitrogen gas atmosphere,
900 mj / cm with a high-pressure mercury lamp with a light intensity of 5 mw / cm ^2.
By irradiating the ultraviolet ray ² and photopolymerizing, a layer of a photopolymerized material having a thickness of 85 μm was formed, and it was used as a pressure-sensitive adhesive layer.

The pressure-sensitive adhesive layer thus formed was transferred to both sides of the heat conductive base material made of soft aluminum foil having a thickness of 30 μm used in Example 1 to form a sheet main body. . Then, by punching and molding in the same manner as in Example 1, a heat conductive adhesive tape having a heat conductive portion having a shape shown in FIG. 2 was produced.

Example 6 Instead of the soft aluminum foil as the heat conductive base material, J
In the same manner as in Example 5 except that a tough Pitch copper foil having a thickness of 35 μm specified in ISH 2101, was used.
A heat conductive adhesive tape having a heat conductive portion having a shape shown in FIG. 2 was obtained.

Example 7 In addition to the radical chain inhibitor and the cross-linking agent, the partially polymerized syrup obtained in Example 5 was supplemented with 50 parts of silica, which is a thermally conductive particle, and an additional photopolymerization initiation. In the same manner as in Example 5 except that 0.1 part of 2,2′-dimethoxy-2-phenylacetophenone was added as an agent,
A heat conductive adhesive tape was obtained.

Comparative Example 3 A heat conductive adhesive tape was produced in the same manner as in Example 5 except that the heat conduction part was not formed by omitting punching by a drawing die and a press.

Comparative Example 4 The partially polymerized syrup obtained in Example 5 was added to the radical chain inhibitor and the cross-linking agent, as an additional component, 150 parts of silica, which is a thermally conductive particle, and an additional photopolymerization initiator. As a result, 0.1 part of 2,2'-dimethoxy-2-phenylacetophenone was added and mixed, and this composition was coated on a polyester film which had been subjected to a peeling treatment, and the light intensity was 5 mw in a nitrogen gas atmosphere. 9 / cm ² high-pressure mercury lamp
By irradiating with ultraviolet rays of 00 mj / cm ^{2 to} carry out photopolymerization, a layer of a photopolymerized material having a thickness of 200 μm was formed to obtain a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer thus formed was transferred to both sides of the heat-conductive base material made of soft aluminum foil having a thickness of 30 μm used in Example 1 to prepare a heat-conductive adhesive tape. .

With respect to the heat conductive adhesive tapes of Examples 1 to 7 and Comparative Examples 1 to 4, the adhesive force, the holding force and the thermal resistance were examined by the following methods. These results
The results are shown in Table 1 below.

<Adhesive strength> According to JIS Z-1522,
The measurement was performed using a stainless steel plate as the adherend. The adhesive strength is shown in g / 20 mm width.

<Holding power> As a holding property at high temperature, the adhesive area is 20 mm × 10 mm at one end of the aluminum plate (125 mm × 25 mm × 0.4 mm) in the longitudinal direction.
Adhesive tapes (width 10 mm) were stuck together, left at 80 ° C. for 30 minutes, then a load of 200 g was applied at 80 ° C., and the deviation distance after 2 hours was measured.

<Thermal Resistance> As a measure of thermal conductivity, the thermal resistance was measured by the following test method. First, the transistor in the TO-220 package was adhesively bonded (without tightening or mechanical fixing) to an aluminum heat sink by an adhesive tape. Next, a constant amount of output was supplied to the transistor, and the difference in temperature between the transistor and the heat sink was measured. The temperature of the transistor is
It was measured with a T-type thermocouple having a 0.13 mm diameter wire spot-welded to a metal base of J. When the transistor was adhesively bonded to the heat sink, the thermocouple of the heat sink was positioned below the center of the transistor package.

The thermal resistance (unit: ° C-cm ² / watt) was determined by the following formula. All values of thermal resistance are 10 watts of apparent power dissipation.
Ion) is displayed. Thermal resistance _{= (T 2 -T 1) A} / P , however, T _2: the temperature of the transistor T _1: heat - the temperature of the heat sink A: heat transfer area P: output which is supplied to the transistor

[0042]

As is apparent from Table 1 above, Comparative Example 1
As shown in ~ 3, when the heat conduction part is not formed in the sheet body, the thermal resistance is as large as 6.3 to 6.5 ° C-cm ² / w,
Although a problem occurs in heat dissipation, in order to solve this problem, as in Comparative Example 4, a large amount of thermally conductive particles are contained in the pressure-sensitive adhesive layer to obtain 3.3 ° C.-cm ² / w. It can be seen that when the heat resistance is made small, the adhesive force and the holding property at high temperature are significantly lowered, and it is difficult to satisfy both the heat dissipation property and the adhesive property.

On the other hand, when the heat conducting portion is formed in the sheet body as in Examples 1 to 7 of the present invention, the adhesive strength and the high temperature are higher than those of Comparative Examples 1 to 3 corresponding thereto. The thermal resistance is 5.1 ℃ -cm without causing the deterioration of the holding property.
^It can be reduced to ² / w or less. In particular, by selecting the mode of forming the heat conducting portion (Example 3), or by including a small amount of heat conductive particles in the pressure-sensitive adhesive layer (Example 7). , The above thermal resistance is 2.0 ° C-cm ² / w or 3.0 ° C-cm ²
/ W, on the other hand, by forming a pressure-sensitive adhesive layer for adhesion reinforcement on one surface of the sheet body (Example 4), it is possible to suppress the deterioration of the adhesive properties as much as possible. It is clear that it is easier to achieve both heat dissipation and adhesive properties as compared with

[0045]

As described above, according to the present invention, it is possible to provide a heat conductive adhesive sheet for an electronic device such as an IC chip which satisfies both heat dissipation and adhesive properties.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a heat conductive adhesive sheet of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a cross-sectional view showing another mode of forming the heat conducting portion.

FIG. 4 is a cross-sectional view showing another example of the heat conductive adhesive sheet of the present invention.

[Explanation of Codes] 1 heat conductive base material 2A, 2B pressure sensitive adhesive layer 3 sheet body 4 heat conduction part 5 pressure sensitive adhesive layer for adhesion reinforcement x thickness direction

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takao Yoshikawa 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation

Claims (4)

[Claims] 1. A heat-conductive base material having a pressure-sensitive adhesive layer provided on at least one surface thereof to form a sheet body, and a plurality of heat-conductive parts penetrating the pressure-sensitive adhesive layer in the thickness direction. A heat conductive adhesive sheet having the above-mentioned base material provided on the base material. 2. The heat conductive adhesive sheet according to claim 1, wherein a pressure-sensitive adhesive layer for adhesive reinforcement is further provided on at least one surface of the sheet main body. 3. The heat-conductive material according to claim 1, wherein the pressure-sensitive adhesive layer and / or the pressure-sensitive adhesive layer for reinforcing the adhesive constituting the sheet body contains heat conductive particles. Adhesive sheets. 4. The heat conductive adhesive sheet according to claim 1, which is for an electronic device such as an IC chip.