JP2000294698A - Thermal conductive spacer - Google Patents

Abstract

(57) [Summary] To provide a spacer for an electronic component having high flexibility and high thermal conductivity. A thermally conductive spacer comprising a resin containing a thermally conductive filler, wherein the thermally conductive filler comprises magnesium and / or calcium borate powder coated with hexagonal boron nitride as a heat conductive filler. volume%,
A thermally conductive spacer comprising a resin containing BN powder having a flatness of 10 or more and 5 to 25% by volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a computer,
ICs in information processing equipment such as word processors,
The present invention relates to a heat conductive spacer useful for efficiently releasing heat generated from a semiconductor element such as an LSI, a CPU, and an MPU.

[0002]

2. Description of the Related Art In recent years, portable information processing apparatuses such as computers and word processors have become thinner. Along with this, semiconductor elements have been increased in density and reduced in size, and the heat generated therefrom has steadily increased, and it has become an important issue to efficiently remove it.

Conventionally, removal of heat generated from a semiconductor element has been performed by attaching the semiconductor element to a radiating fin or a metal plate via a heat conductive sheet. However, as information processing devices have become smaller and thinner, there are many cases where there is no space for mounting a radiation fin or the like. In such a case, a method of directly transferring heat to a case or the like of the information processing device and dissipating heat is adopted.

In such a method, a soft heat conductive spacer filled with a heat conductive filler in a cured resin such as silicone having a thickness to fill the space is used between a semiconductor element and a case. Therefore, a material having a higher thermal conductivity is required.

[0005] In order to achieve high thermal conductivity of a thermally conductive spacer (hereinafter, also simply referred to as a "spacer"), a thermally conductive filler existing in the spacer may be continuously contacted. Although it has been performed to increase the amount of the heat conductive filler, in this method,
This method has limitations, for example, the softness of the spacer is reduced, the contact with the case of the information processing equipment is deteriorated, and the thermal conductivity is significantly reduced.

[0006] Hexagonal boron nitride (hBN) powder is often used as the heat conductive filler. However, when hBN powder is subjected to shear stress during mixing, kneading and molding to form a spacer, the particles are in a horizontally oriented state. In this state, the surface direction of the hBN particles (a-axis direction)
Despite having a thermal conductivity of 110 W / m · K, only a thermal conductivity of 2 W / m · K in the thickness direction of the particles (c-axis direction) can be used, and a sufficiently satisfactory heat radiation characteristic is obtained. It was difficult to obtain a spacer having the same.

For example, as disclosed in Japanese Patent Publication No. 6-12643, the thermal conductivity is considerably increased by randomly arranging boron nitride particles, but it is still insufficient and has room for improvement.

[0008]

The inventors of the present invention have conducted various studies with the aim of further increasing the thermal conductivity and flexibility of the spacer, and as a result, have found that magnesium and / or magnesium coated with hexagonal boron nitride can be used. Calcium borate powder (hereinafter referred to as “BN-coated borate powder”);
When hBN powder having a flatness of 10 or more (hereinafter referred to as “flat BN powder”) is used in combination, a part of the flat BN particles becomes B
Between the N-coated borate particles, we found that the number of contact points or surfaces of the particles increased, the thermal conductivity of the spacer was considerably improved, and the BN loading was reduced to increase the flexibility of the spacer. They have also found that they exhibit extremely high thermal conductivity, and have completed the present invention.

[0009]

That is, according to the present invention, there is provided a heat conductive spacer comprising a resin containing a heat conductive filler, wherein the heat conductive filler is BN-coated borate powder in an amount of 25 to 50% by volume. , Flat BN powder 5-25
It is a heat conductive spacer characterized in that a volume% is contained in a resin.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

As the resin used as the matrix of the high thermal conductive spacer of the present invention, epoxy resin, phenol resin, silicone resin, polyimide resin, bismaleimide triazine, etc. can be used without any problem. Is preferably a silicone resin.

The BN-coated borate powder used in the present invention comprises a core of magnesium or calcium borate particles and a scale-like hB covering all or a part of the surface thereof.
And a shell portion made of N. Confirmation of magnesium or calcium borate and hBN can be performed using an energy dispersive X-ray fluorescence spectrometer. The ratio of the core portion is preferably 10 to 80% in terms of the area occupation ratio of the particle cross section, and the thickness of the shell portion is several to several tens of μm.
m is preferable.

The BN-coated borate powder can be produced, for example, as follows. That is, a ternary composition diagram of the molar percentage of at least one inorganic compound selected from melamine, boric acid, and hydroxides and carbonates of magnesium and calcium (melamine, boric acid, inorganic compound)
At points A (35, 60, 5), B (25, 70,
5) The mixture within the range surrounded by the line connecting C (5, 80, 15) and D (5, 5, 90) is used as it is or 300 kgf / cm ² or less, preferably 100 kgf.
/ Cm ^{2 at} a pressure of not more than 1 / cm ² at a temperature of 1700-2200 ° C. in a non-oxidizing atmosphere such as nitrogen or ammonia.
When calcined for 5 to 24 hours, preferably 2 to 10 hours, B
Since it is possible to produce a mixed powder containing N-coated borate particles and hBN, this mixed powder is ultrasonically dispersed in a solvent such as water, and the residue on the sieve is screened by a 24 μm JIS sieve. , A mixed powder having an increased proportion of BN-coated borate particles can be produced. (Japanese Patent Application No. 10
-352519).

The flatness of the flat BN powder is determined by dividing the average particle diameter (Da) of one particle [(long axis + minor axis) / 2] by the maximum particle thickness (Dc) of the particle. The value is an average of 200 values. In the present invention, the flatness needs to be 10 or more. If the flatness is less than 10, the contact with the BN-coated borate particles is not sufficient, and the improvement in heat conduction is small.

As the heat conductive filler constituting the spacer of the present invention, BN-coated borate powder and flat BN powder are essential components. When the ratio is shown by the mixing ratio to the resin, the BN-coated borate powder has a volume of 25 to 50% by volume,
N powder is 5 to 25% by volume. When the BN-coated borate powder exceeds 50% by volume, the thermal conductivity is improved, but the flexibility is remarkably reduced. Conversely, if it is less than 25% by volume, the thermal conductivity does not improve. On the other hand, when the flat BN powder exceeds 25% by volume, the BN which is directed sideways increases and the thermal conductivity decreases, and when it is less than 5% by volume, the contact with the BN-coated borate powder becomes insufficient. Thermal conductivity decreases.

The average particle size is not limited for both the BN-coated borate powder and the flat BN powder,
5 to 25 μm for BN-coated borate powder, flat B
It is desirable for the N powder to be in the range of 5 to 15 μm.

The planar shape of the spacer of the present invention is not limited as long as it is a shape capable of burying the heating element, and examples thereof include a polygon such as a triangle, a quadrangle and a pentagon, a circle and an ellipse. Further, irregularities may be provided so that the heating element is easily buried. The thickness of the spacer is 0.05 to 5 mm, particularly 0.2 to 2 mm
Is common.

In manufacturing the spacer of the present invention, the flat BN powder and the silicone resin, and the BN-coated borate powder and the silicone resin are mixed in advance, respectively.
A method of mixing each mixture again at a predetermined ratio,
It is optimal in that a spacer having the best thermal conductivity and flexibility can be obtained.

For the mixing, a known mixer such as a roll mill, a kneader or a Banbury mixer can be used.
The extrusion is preferably performed by an extrusion molding method. In the pressing method, flat BN powder having a high degree of flatness is easily oriented horizontally.
In addition, in the doctor blade method, an organic solvent must be added until the viscosity becomes usable, and a step of removing the organic solvent after molding is required, resulting in poor productivity.

[0020] The vulcanization temperature is desirably in the range of 80 to 200 ° C. If the temperature is lower than 80 ° C., the sheet is not sufficiently vulcanized, and if it exceeds 200 ° C., a part of the spacer deteriorates. For vulcanization, a general hot air dryer, far-infrared dryer, microwave dryer, or the like can be used.

[0021]

The present invention will be described below more specifically with reference to examples and comparative examples.

Examples 1 to 5 Comparative Examples 1 to 3 An addition reaction type silicone resin (trade name "SE1885" manufactured by Toshiba Silicone Co., Ltd.) and a BN-coated borate powder shown in Table 1 were used. A commercially available hBN powder which is a flat BN powder (trade name “DENCABORON NITRIDE GP Grade” manufactured by Denki Kagaku Kogyo Co., Ltd.)
After being individually mixed, they were blended so as to have a predetermined ratio shown in Table 1, and further mixed.

[0023] The obtained mixture was applied to a thickness of 1 with a vacuum extruder.
After extrusion molding to a thickness of 0.1 mm, the mixture was allowed to stand in a dryer at 140 ° C. for 15 hours for vulcanization and curing to produce a spacer. The thermal conductivity and the compressibility of the obtained spacer were measured as follows. Table 1 shows the results.

As reference values, Table 1 shows the physical properties of spacers made of flat BN powder alone.

(1) Thermal conductivity: A spacer is sandwiched between a TO-3 type copper heater case and a copper plate, and 10% of the spacer thickness is compressed.
W was held for 4 minutes, the temperature difference between the copper heater case and the copper plate was measured, and the thermal conductivity (W / m · K) = {power (W) × thickness (m)} /｝ temperature difference (K) × measurement area (m
² ) The thermal conductivity was calculated in ①. (2) Compression ratio: After punching a spacer into 1 cm ² square, measure the amount of compressive deformation when a 1 kgf load is applied in the thickness direction by a precision universal testing machine (trade name “Autograph” manufactured by Shimadzu Corporation). Then, the compression ratio was calculated by the following equation: compression ratio (%) = {compression deformation (mm) × 100} / original thickness (mm). (3) Flatness of flat BN powder: The spacer is cut in a state of cooling with liquid nitrogen to expose a fractured surface, and the fractured surface is observed by SEM to observe the average particle diameter (D) of the flattened BN powder.
a) and the maximum particle thickness (Dc) were measured to determine the flatness.

[0026]

[Table 1]

Example 6 A spacer was produced in the same manner as in Example 1 except that BN-coated magnesium borate was used instead of BN-coated calcium borate as the BN-coated borate powder. Almost the same good results were obtained.

[0028]

The spacer of the present invention has excellent heat radiation characteristics and flexibility.

Claims (1)

[Claims] 1. A heat conductive spacer comprising a resin containing a heat conductive filler, wherein the heat conductive filler comprises magnesium and / or calcium borate powder coated with hexagonal boron nitride in an amount of 25 to 50%. A thermally conductive spacer comprising 50 to 25% by volume of BN powder having a flatness of 10 or more and a resin content of 5 to 25% by volume.