JPH05198711A - Heat-dissipating insulating spacer for high-frequency circuit - Google Patents

Abstract

PURPOSE:To provide a heat-dissipating insulating spacer for high-frequency circuit, which can remarkably reduce noise generation by suppressing the mounting capacity of electronic circuit components for handling the high-frequency of a drive circuit for high-quality television to the minimum when the spacer is used at the time of mounting the electronic circuit parts. CONSTITUTION:A heat-dissipating insulating spacer for high-frequency circuit is composed of sheet molded product, of which the dielectric constant in the high-frequency range of 30MHz-1GHz is 4 or less and the thermal conductivity is 1.5-5W/m.K.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipation insulating spacer for a high frequency circuit, which is used by being sandwiched between an element such as a transistor and a radiator when an electronic circuit handling a high frequency is mounted.

[0002]

2. Description of the Related Art In designing a drive circuit for a high-definition CRT monitor or a high-definition television (HDTV), a high-frequency transistor or module is used because the frequency to be handled is high, and noise is minimized with low power consumption. It is important to keep it to the limit. For that purpose, it is necessary to reduce the circuit current by using a transistor having a collector capacitance as small as possible to increase the load resistance. Furthermore, in order to efficiently dissipate the generated heat to the radiator, it is necessary to minimize the mounting capacity of the spacer during mounting.

Since the collector of the transistor is connected to the case and the case needs to be attached to the radiator via an insulating material, an insulating material having a high thermal conductivity and a good frequency characteristic is used as the heat radiating spacer. It
However, as the frequency becomes higher, the capacity of a commonly used mica plate becomes too large, so that an expensive boron nitride plate or the like is used.

[0004]

However, since the relative permittivity of the boron nitride plate exceeds 4 in the high frequency region of 30 MHZ or more, there is a limit in reducing the mounting capacitance. Moreover, since boron nitride is difficult to sinter, high-purity products are expensive.

As a result of various studies to solve the above problems, the inventor of the present invention uses a flexible resin having a small relative dielectric constant as a matrix, in which a powder having a high thermal conductivity and a small relative dielectric constant is formed. The filled compact is 1GHZ
The relative permittivity can be suppressed to a low level even in a high frequency range, and if it is used as a heat dissipation insulating spacer when mounting elements such as electronic circuits that handle high frequencies, the mounting capacitance is reduced and noise is reduced. The inventors have completed the present invention by finding that they can be significantly reduced.

[Means for Solving the Problems]

[0006] That is, the present invention, 30MHZ ~ 1GH
A heat dissipation insulating spacer for a high frequency circuit, characterized in that it has a relative dielectric constant of 4 or less in a high frequency region of Z and is made of a sheet-shaped molded product having a thermal conductivity of 1.5 to 5 W / mK.

The present invention will be described in more detail below. The heat dissipation insulating spacer for a high frequency circuit according to the present invention comprises:
Basically, it is composed of a sheet-shaped molded product of a heat resistant resin and a high thermal conductive low dielectric powder.

The heat resistant resin used in the present invention is
Not only has a low dielectric constant, but also has excellent heat resistance required for electronic circuit components and long-term reliability under high temperature and high humidity.
Moreover, silicone rubber is the most suitable from the viewpoint of excellent adhesion to elements such as transistors and a radiator and obtaining high heat radiation characteristics, but resins such as polybutadiene, polyimide, and polyphenyl sulfide may be used.

On the other hand, the high-thermal-conductivity low-dielectric powder used in the present invention is preferably boron nitride powder because of its high thermal conductivity and stable low relative permittivity up to a high frequency band. However, depending on the price and required properties, silicon dioxide powder or fluororesin powder may be used in combination or alone.

The heat-resistant resin and the high-thermal-conductivity low-dielectric powder are compounded in proportions of 20 to 40% by weight for the former and 80 to 6 for the latter.
0% by weight is preferred. If the heat-resistant resin is less than 20% by weight, the mixability of the resin mixture and the sheet formability deteriorate. on the other hand,
If it exceeds 40% by weight, the thermal conductivity becomes too high and the function as a heat dissipation insulating spacer becomes small.

In order to improve the heat dissipation characteristics, it is necessary to increase the compounding ratio of the high thermal conductive low dielectric powder.
In that case, it is desirable to compound and reinforce the glass cloth. Since the glass cloth is a substance having a high relative dielectric constant, it is desirable to use the glass cloth as little as possible. The glass cloth has a thickness of 0.03 mm and a mass of 20 g / m ² (J
From ISR3414 product number EP03A) to thickness 0.1
0 mm, mass 100 g / m ² (JISR3414 part number EP10
It is preferable to use those in the range of A). Thickness 0.
If the thickness is less than 03 mm and the weight is less than 20 g / m ² , the reinforcing effect is poor. On the other hand, if the thickness is more than 0.10 mm and the weight is more than 100 g / m ² , the relative permittivity of the heat dissipation insulating spacer is high and the thermal conductivity is small. ..

Since flame retardancy is required for mounting electronic circuits, it is desirable to add 0.2 to 1 part by weight of flame retardant such as platinum complex to 100 parts by weight of heat resistant resin.

In order to produce the heat dissipation insulating spacer for a high frequency circuit of the present invention, the above-mentioned heat resistant resin, high thermal conductive low dielectric powder, flame retardant and cross-linking agent are mixed, then the doctor blade method and the calendar roll method are used. Etc. to form a sheet, and sandwich it with a glass cloth to form a laminated body, at a temperature of 140 to 17
Heating / pressing is performed under the conditions of 0 ° C., pressure of 50 to 100 kg / cm ² , and time of 10 to 50 minutes. Since the obtained molded body is a sheet-shaped molded body having a resin matrix, it is cut or punched with a Thomson blade to be processed into a mounting component shape, and the high-frequency circuit heat radiation insulation spacer of the present invention is used. To do. The thickness of the molded body is 0.2 to 0.8
mm is preferred.

[0014]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Examples 1 to 3 Comparative Examples 1 to 4 Commercially available silicone rubber (trade name "DY32-2009u" manufactured by Toray Dow Corning Silicone) and commercially available boron nitride (BN) powder (produced by Denki Kagaku Kogyo Co., Ltd.) Product name "GP") is mixed in a ratio shown in Table 1, and a commercially available platinum-based flame retardant (Toray Dow Corning Silicone product name "SRX-212" is added to 100 parts by weight of silicone rubber.
cat. )) 0.3 part by weight, a cross-linking agent (2,5 dimethyl 2,5 (tertiarybutylperoxy) hexane).
8 parts by weight were added and mixed, and the mixture was formed into a sheet by a doctor blade method, and a commercially available glass cloth (trade name “K.
S1090 "(thickness 0.05 mm, mass 47g / m ² ··· J
ISR3414 product number EP05B equivalent product) was sandwiched in the center and laminated by heating and pressure at a temperature of 140 ° C. and a pressure of 80 kg / cm ² to produce a sheet having a thickness of 0.45 mm.

Comparative Example 1 is a commercially available raw mica (made by Bival, India, thickness: 0.25 mm), Comparative Example 2 is a commercially available boron nitride plate (trade name "HC", manufactured by Denki Kagaku Kogyo Co., thickness 1.17).
Comparative Example 3 is a 0.45 mm thick silicone rubber sheet obtained by vulcanizing a commercially available silicone rubber (trade name “SH35u” manufactured by Toray Dow Corning Silicone Co., Ltd.) with 2,4 dichlorobenzol peroxide. Example 4 is a commercially available alumina plate (trade name “SSA-S” manufactured by Nikkato,
The thickness is 0.64 mm).

The relative permittivity and thermal conductivity of the obtained sheet were measured as follows. The results are shown in Table 1. Relative permittivity: JISK6911 Thermal conductivity: Sample is sandwiched between a heater with a heat transfer area of 6 cm ² and a radiating fin made of aluminum, and 5 kg with two M3 screws.
The temperature difference between the top and bottom of the sample when the heater was heated at 15 W with a torque of fcm was measured and calculated by the following formula. Thermal conductivity (W / m · K) = W · t / S (T ₁ −T ₂ ) W (W); Heat value of heater (15 W) t (m); Sample thickness S (m ² ); Heat transfer area (6 cm ² ) T ₁ (K); Temperature of sample upper part (heater side) T ₂ (K); Temperature of sample lower part (heat radiation fin side)

[0018]

[Table 1]

Examples 4 to 5 Sheet molding was performed with the compounding composition of Example 2, and three types of glass cloths (1) to (3) below were laminated as a reinforcing material with the glass cloth sandwiched in the center. Heat and pressure crosslinking was performed under the same conditions to produce a sheet having a thickness of 0.45 mm. Table 2 shows the measurement results of the relative permittivity and thermal conductivity of the obtained sheet. (1) “KS1061”: trade name (thickness 0.0
3 mm, mass 21 g / m ² ... JISR3414 part number EP0
(3A equivalent product) (2) "KS1090": Kanebo's trade name (thickness 0.0
5 mm, mass 47 g / m ² ... JISR3414 part number EP0
5B equivalent product) (3) "KS1220": Kanebo brand name (thickness 0.1
0mm, mass 108g / m ²・ ・ ・ JISR3414 Part number EP
10A equivalent product)

[0020]

[Table 2]

The heat-dissipating insulating spacers of Examples 1 to 5 and Comparative Examples 1 to 4 were connected to the cascade ground of a high-definition CRT monitor +
It is mounted on a transistor for voltage amplification by grounding the base of the video output circuit of the emitter follower system, and 30 MHZ ~ 3
When operated at a frequency of 00 MHZ or higher, Example 1
When the heat-dissipating insulation spacers of ~ 5 were used, a stable image with a horizontal resolution of 1000 pixels or more was obtained, whereas when the heat-dissipating insulation spacers of Comparative Examples 1 to 4 were used, the horizontal resolution was lowered. However, a good image was not obtained. Moreover, in Comparative Examples 1 and 3, the heat dissipation characteristics were poor, and the mounted transistor was damaged by overheating.

[0022]

By using the heat dissipation insulating spacer for a high frequency circuit of the present invention at the time of mounting an electronic circuit component handling a high frequency of 30 MHZ or higher such as a driving circuit for a high definition television, its mounting capacity can be minimized. It can be suppressed, and the noise generation can be significantly reduced. The heat dissipation insulating spacer for a high frequency circuit of the present invention is used not only when mounting a drive circuit for a high-definition television or a high-definition CRT monitor, but also for mounting an electronic circuit that handles a high frequency in a mobile telephone or satellite broadcasting. It can also be applied to.

Claims (1)

[Claims] 1. A dielectric constant in a high frequency range of 30 MHZ to 1 GHZ is 4 or less, and a thermal conductivity is 1.5 to 5 W /.
A heat radiation insulation spacer for high frequency circuits, characterized by being formed from a sheet of m · K.