JP2000022289A - Resin composition for circuit board and circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metal base circuit board for assuring practical pressure resistance and high productivity with a specific value or more of thermal conductivity and a specific value or less of a relative permittivity, by constituting a resin composition for a circuit board of a boron nitride aggregate particles obtained by bonding a baron nitride with a resin (A) and a resin (B). SOLUTION: High thermal conductivity is performed by adopting a structure in which boron nitride aggregate particles containing a small amount of a resin (A) exist in an island-like state in a resin (B) and using the particles as a heat transfer passage without disturbing flowability of the resin. As a result, a metal base circuit board having characteristics of low relative permittivity, high thermal conductivity so that the permittivity of 4.5 or less which has not been heretofore obtained and the conductivity is 8.0×103 cal/ cm.sec. deg.C or more, and a practical withstand voltage, can be obtained with good productivity. Since the circuit board uses the resin composition, excellent reliability for a long period is provided for advantageous in an industry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board having excellent heat dissipation and electrical insulation properties and high electrical reliability, in particular, a metal-based circuit board used for electronic equipment, communication equipment, automobiles, and the like, and used therefor. The present invention relates to an insulating composition.

[0002]

2. Description of the Related Art Circuit boards on which semiconductor elements and the like are mounted have been used for various purposes. However, metal base circuit boards have been used for various power supply applications because of their excellent heat dissipation. In this application field, high power elements such as IGBT elements are mounted, and there is a strong demand for a metal-based circuit board having both high withstand voltage and high thermal conductivity.

[0003] Generally, a metal-based circuit board is made of copper, aluminum, or the like on a main surface of a metal plate made of copper, aluminum, steel, or a composite metal thereof via an insulating layer made of a resin containing an inorganic filler. It has a configuration in which a circuit made of a highly conductive material such as is provided, and various electric components such as a semiconductor element are mounted on the circuit or the insulating layer, and the circuit is connected to form a module, which is put into practical use. Is done.

In order for a module to operate with high reliability, heat radiated from various electric components or the circuit itself is quickly dissipated in a use environment and the electric components are prevented from rising by preventing the temperature of the electric components from rising. It must be operated with high efficiency, and high withstand voltage for a long time is required. Further, the metal base circuit board is liable to generate noise due to the leakage current in the metal plate due to the above configuration, but the relative dielectric constant of the insulating layer is set to, for example, 6 or less, preferably 4.5 or less. By lowering it, this can be prevented to a practically acceptable level.

In order to ensure high reliability over a long period of time, an insulating layer having a high withstand voltage and a high heat dissipation and a low relative dielectric constant is desired for a metal-based circuit board. Is an important technical issue in industry.

In conventional metal-based circuit boards,
Edge layer is highly filled with inorganic filler such as aluminum oxide
It has a thermal conductivity of 8.0 ×
10 ^-3cal / cm · sec · ° C or less
The electric conductivity was 7.0 to 8.0. As an example of this,
JP-A-2-286768 discloses an inorganic filler having a specific particle size.
By using, the inorganic filler can be highly filled.
High thermal conductivity, resulting in an insulating adhesive composition for circuit boards.
And the metal substrate and the conductive foil are laminated via the adhesive composition.
A layered circuit board is disclosed.

Further, Japanese Patent Application Laid-Open No. Hei 7-320538 discloses that
For the purpose of obtaining a circuit board having a low relative dielectric constant, a metal-based circuit board in which boron nitride having a low relative dielectric constant is added to a resin such as an epoxy resin as it is or together with a surface treatment agent or the like is disclosed.

[0008] When the surface treatment agent is not added, the viscosity of the boron nitride-containing resin composition sharply increases when the filling ratio of boron nitride is about 30% by volume or more. In addition, it is difficult to apply the resin composition to the coating layer, and the flake-like particles of boron nitride are planarly oriented in the coating layer, so that only a circuit board having low thermal conductivity can be obtained. Had occurred. Therefore, the relative dielectric constant is 4.5 or less, but the thermal conductivity is 3.0 × 10 ⁻³ cal.
Only an insulating material composition having a characteristic of about / cm · sec · ° C. has been obtained.

On the other hand, by adding a surface treatment agent, the above problem can be solved, and an insulating material composition having a low relative dielectric constant and a high thermal conductivity can be obtained. However, these materials contain boron nitride in a resin. It is not easy to mix and disperse well,
It takes a lot of time to obtain a homogeneous resin composition, and as a result, there is a problem that productivity is not sufficient.

[0010] The relative dielectric constant is 4.5 or less, and the thermal conductivity is 8.
A metal-based circuit that satisfies both characteristics of a low dielectric constant of 0 × 10 ⁻³ cal / cm · sec · ° C. or more and a high thermal conductivity, has excellent withstand voltage, has high productivity of a circuit board, and can be provided practically. There is a demand for a resin composition for a substrate and an insulating material used for the substrate.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned state of the art, and is an insulating composition for a circuit board having excellent withstand voltage and heat radiation and a low relative dielectric constant. It is an object of the present invention to provide a metal-based circuit board having high reliability over a long period of time with high productivity. More specifically, the thermal conductivity is 8.0 ×
An insulating material for a circuit board that satisfies both characteristics of 10 ⁻³ cal / cm · sec · ° C. or more and a relative dielectric constant of 4.5 or less and that can secure practical voltage resistance and high productivity. An object of the present invention is to provide a metal-based circuit board using the same.

[0012]

SUMMARY OF THE INVENTION The present invention is a resin composition for a circuit board, comprising boron nitride aggregated particles in which boron nitride is bound by a resin (A) and a resin (B). Preferably, there is provided a resin composition for a circuit board, wherein boron nitride is dispersed in the resin (B).

Further, according to the present invention, at least one of boron nitride forming the boron nitride aggregated particles bonded by the resin (A) and boron nitride dispersed in the resin (B) has an average particle diameter of 0.1 μm. The resin composition for a circuit board according to claim 1, wherein the resin composition is boron nitride having a thickness of about 20 μm, wherein the resin (A) is made of an epoxy resin and the resin (B) is made of an epoxy resin.

Further, in a preferred embodiment of the present invention,
The content of boron nitride is 30 to 75 with respect to the total amount of the resin composition.
% By volume.

In addition, the present invention is a circuit board characterized by using the above resin composition.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has been made in consideration of the above-mentioned prior art. According to the study of the present inventor, boron nitride is generally composed of particles of several to several hundred μm, and the particles are scaly due to the crystal structure of boron nitride being hexagonal. Since it has a (or plate-like) shape, the filling property into the resin does not increase, and the particles are likely to be oriented in a later step. But,
The present inventors have added a small amount of resin to flaky boron nitride and mixed well to form individual particles of boron nitride into agglomerated particles having no orientation. When mixing and dispersing in the resin, it becomes easy to mix boron nitride in the resin without using a special additive such as a surface treatment agent, and the boron nitride particles can be hardly oriented, and as a result, The inventors have found that a circuit board having high thermal conductivity can be easily obtained, and have reached the present invention.

That is, the present invention relates to a resin composition for a circuit board, comprising boron nitride aggregated particles in which boron nitride is bonded with a resin (A) and a resin (B). When employed, the dielectric constant is low and the thermal conductivity is high, specifically, the dielectric constant is 4.5 or less, and the thermal conductivity is 8.0 × 10 ⁻³ cal / cm · sec · ° C
There is an effect that the above-mentioned metal-based circuit board can be easily and stably obtained, and thus can be obtained with high productivity.

In the present invention, the agglomerated boron nitride particles are composed of scaly (or plate-like) boron nitride particles bonded by the resin (A) without being oriented, and the boron nitride agglomerated particles are formed of the resin (B). The fact that it is dispersed inside is essential. The boron nitride agglomerated particles form discrete or adjacent island-like regions in the matrix of the resin (B) when, for example, observing the resin composition in an arbitrary cross section with a scanning electron microscope. ing. Then, the resin (A) is present therein.

The orientation of the boron nitride particles in the boron nitride aggregated particles can be determined qualitatively and easily by merely observing the cross section of the boron nitride aggregated particles using a scanning microscope. Quantitatively, for example, about 50% of individual particles of boron nitride in the boron nitride agglomerated particles of the observation photograph are taken.
The orientation direction (the direction parallel to the scale or the flat plate) of at least the number of particles is examined, and the ratio (X) of the number of particles (X) in the direction with the largest number and the number of particles (Y) oriented perpendicular to the direction is determined / Y). In the present invention, the ratio may be 3 or less.

The boron nitride used in the present invention comprises flaky or plate-like particles as described above, and preferably has an average particle diameter of 0.1 μm to 20 μm. In boron nitride having an average particle diameter of less than 0.1 μm, most of the particles constituting the powder are small, and the particle shape is scaly or flat to granular, and there is no need to apply the present invention. When the average particle size exceeds 20 μm, it becomes difficult to obtain boron nitride aggregated particles having a small orientation. 0.
2 μm to 15 μm is preferable, and 0.5 μm to 10 μm is a more preferable range.

Regarding the crystallinity of the boron nitride of the present invention, those having high crystallinity, particularly those having a graphitization index of 3.5 or less are preferable because a metal-based circuit board having more excellent thermal conductivity can be easily obtained. . Here, the graphitization index is calculated from the diffraction intensity (peak area) of the (100), (101), and (102) planes by X-ray diffraction using the following equation.
The smaller the graphitization index, the higher the crystallinity of boron nitride. Graphitization index = ((100) area + (101) area) /
((102) area)

The resin (A) used in the present invention includes:
An epoxy resin, a silicone resin, a BT resin, a polyimide resin, or the like is used, and is preferably cured or gelled before being added to the resin (B). In addition, among the above resins, epoxy resins are preferable in terms of adhesion to boron nitride and physical characteristics, and among them, bisphenol A type epoxy resin and bisphenol F type epoxy resin have low viscosity, and are highly filled with boron nitride particles. It is preferable because the obtained boron nitride aggregated particles can be obtained. As the resin (B), an epoxy resin, a silicone resin, a BT resin, a polyimide resin, or the like is used. For the purpose of achieving high thermal conductivity, a resin having a strong bonding force with the resin (A) is preferable. (A)
The same is more preferable.

In the present invention, in the resin composition, an inorganic filler such as boron nitride, alumina, silica, silicon nitride, and aluminum nitride may be dispersed in the resin (B). By adopting the above configuration, a higher thermal conductivity can be achieved. Many of the inorganic fillers may be treated with a surface treatment agent such as a silicone coupling agent, a titanate coupling agent, or a silylating agent for the purpose of enhancing the filling property of the resin (B). In addition, it is preferable to disperse boron nitride in the inorganic filler in order to achieve both low dielectric constant and high thermal conductivity. As for the boron nitride dispersed in the resin (B), the same boron nitride as the boron nitride agglomerated particles can be used, provided that the individual boron nitride particles are dispersed in the resin (B). Because it is good, it is not necessarily limited to this.

In the resin composition of the present invention, by adopting a structure in which boron nitride aggregated particles containing a small amount of the resin (A) are present in the resin (B) in an island shape, the flow of the resin is improved. The high thermal conductivity is achieved by using the boron nitride aggregated particles as a heat transfer path without impairing the properties. Although the respective compounding ratios will be described in detail later, the content of boron nitride with respect to the entire resin composition is preferably 30 to 75% by volume. If the content is less than 30% by volume, contact between the aggregated boron nitride particles in the resin composition may be insufficient, and the thermal conductivity may not be increased. 7
If the content exceeds 5% by volume, the boron nitride aggregated particles may be broken when mixed with the resin (B), resulting in a significant increase in viscosity and inability to achieve high thermal conductivity. A preferred range is 50 to 75% by volume.

With respect to the boron nitride aggregated particles, the resin (A)
Is filled with boron nitride to fill only the gaps between the boron nitride particles.
It is preferable to make the residual resin (A) at 5 to 95% by volume because the form of the boron nitride aggregated particles is easily maintained when mixed with the resin (B) in a later step. On the other hand, the amount of the inorganic filler in the resin (B) is preferably 50% by volume or less, particularly when boron nitride is used.

The method for obtaining the resin composition of the present invention includes:
A boron nitride powder is prepared, a predetermined amount of the resin (A) is added thereto, and the mixture is granulated using a conventionally known granulator to form boron nitride agglomerated particles. A mixer such as a Henschel mixer can also be used. If necessary, the boron nitride aggregated particles are subjected to an appropriate treatment such as heating to cure or gel the resin (A) so that the particles are not destroyed by mixing with the resin (B) in a later step. Next, a predetermined amount of the boron nitride aggregated particles obtained by the above operation and the resin (B) are blended and mixed using, for example, a universal mixer, so that it can be applied to ordinary use.

The present invention is a metal-based circuit board using the above resin composition, and has excellent reliability over a long period of time due to the characteristics of the resin composition having a low dielectric constant and a high thermal conductivity. Moreover, it is a metal-based circuit board excellent in productivity. The insulating layer of the metal base circuit board is made of the above resin composition, and the thickness thereof is usually used in the range of 20 to 500 μm.

The metal base circuit board of the present invention has a structure in which one or more insulating layers and conductor circuits are repeatedly laminated on one or both sides of a metal plate, and the metal plate has good heat conductivity. 2. Generally, the thickness is 0.5-3.
0 mm aluminum, aluminum alloy, copper,
Iron, stainless steel, invar, or a composite metal thereof is used.

The conductive circuit formed on the insulating layer of the metal-based circuit board is made of a copper foil, a composite foil, an alloy containing two or more kinds of metals such as copper, aluminum, nickel and the like, and a clad foil using each metal. , Its thickness is 5
μm to 1 mm is common. In addition, nickel plating, nickel-
Gold plating may be applied on the surface of the conductor circuit.
Further, these conductor circuits are etched before or after mounting the metal foil on the insulating layer, and the circuits are formed into a desired shape. A ceramic chip component such as a resistor and a capacitor and / or a semiconductor element and a terminal such as a diode, a thyristor, and a transistor may be mounted on the circuit.

[0030]

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

Example 1 Boron nitride (GPS-2, manufactured by Denki Kagaku Kogyo Co., Ltd.) and bisphenol F type epoxy resin (Epicoat 807, manufactured by Yuka Shell Co., Ltd.) were mixed at a volume ratio of 95: 5. The resulting mixture was granulated using a Henschel mixer to obtain powder of aggregated boron nitride particles having an average diameter of 40 μm.

The agglomerated boron nitride particles were dispersed in a bisphenol F type epoxy resin (manufactured by Yuka Shell Co., Ltd .; Epicoat 807), and the volume fraction of the boron nitride powder after adding an amine-based curing agent was determined. Adjust it to be 55%
A resin composition was obtained.

The above resin composition is 510 mm × 510 mm
Coating to a thickness of 100 μm on an aluminum plate of × 1.5 mm, copper foil with a thickness of 35 μm is laminated by a laminating method, heated and cured, and etched to form a desired circuit. A substrate was prepared. The withstand voltage, relative dielectric constant, and productivity of this metal-based circuit board were measured by the following methods. Moreover, about the thermal conductivity, a test piece was separately prepared from the resin composition, and the test piece was measured. The results are shown in Table 1.

[0034]

[Table 1]

<Method of Measuring Thermal Conductivity of Resin Layer> 2 m thick
ATT was measured by a laser flash method thermal conductivity measuring device (“LF / TCM-FA-8510B” manufactured by Rigaku Denki Kogyo Co., Ltd.) using a disk-shaped test piece of mx 10 mm in diameter.
Range: 20μV, sampling rate: 1000μ
Seconds, filter; measured at 100 Hz.

<Measurement Method of Withstanding Voltage> A circular electrode having a diameter of 20 mm was formed on a metal base circuit board by an etching method, and a circular electrode at the center and another circular electrode were formed by a step-up method specified in JIS C 2110. The withstand voltage between the electrodes was measured.

<Measurement Method of Relative Dielectric Constant> JIS C648
1, measurement frequency 100 kHz, measurement temperature 25 ° C
I went in.

<Productivity Evaluation Method> Evaluation was made based on the time required to produce 10,000 substrates of business card size (90 mm × 50 mm) in each production method.

Example 2 The same procedure as in Example 1 was performed except that a silicone resin (manufactured by Toray Dow Corning Silicone Co., Ltd .; SEI880) was used to obtain the boron nitride aggregated particle powder. The withstand voltage, relative dielectric constant, and productivity, and the thermal conductivity of the cured resin body were measured for the metal-based circuit board by the following methods. The results are shown in Table 1.

[Example 3] A polyimide resin (manufactured by Mitsui Toatsu Co., Ltd .; LARC-T) was used to obtain boron nitride aggregated particles.
With respect to the metal-based circuit board obtained by performing the same operation as in Example 1 except that PISEI 880) was used, the withstand voltage, the relative dielectric constant, and the productivity, and the thermal conductivity of the cured resin body were as follows. It was measured by the method shown. The results are shown in Table 1.

Example 4 The same procedure as in Example 1 was carried out except that the volume fraction of the boron nitride powder after adding the amine-based curing agent was adjusted to be 75%. The withstand voltage, relative dielectric constant, and productivity of the metal-based circuit board, and the thermal conductivity of the cured resin were measured by the following methods. The results are shown in Table 1.

Example 5 A metal obtained by performing the same operation as in Example 1 except that a silicone resin (manufactured by Toray Dow Corning Silicone Co., Ltd .; SEI880) was used to obtain the boron nitride aggregated particle powder. Withstand voltage, relative dielectric constant, and productivity of the base circuit board were measured for the thermal conductivity of the cured resin by the following method. The results are shown in Table 1.

Example 6 Boron nitride agglomerated particle powder was prepared by dispersing 31 vol% of boron nitride powder in advance in bisphenol F type epoxy resin (manufactured by Yuka Shell Co., Ltd .; Epicoat 8).
07), the withstand voltage, relative dielectric constant, and productivity of the metal-based circuit board obtained by performing the same operation as in Example 1 except that the resin was dispersed in The measurement was performed by the method shown in FIG. The results are shown in Table 1.

Comparative Example 1 Boron nitride (GPS-2, manufactured by Denki Kagaku Kogyo Co., Ltd.) was dispersed in a bisphenol F-type epoxy resin (Epicoat 807, manufactured by Yuka Shell Co., Ltd.), and amine-based curing was performed. The volume fraction of the boron nitride powder after adding the agent was adjusted to be 55%. This one is 51
It is applied on a 0 mm × 510 mm × 1.5 mm aluminum plate so as to have a thickness of 100 μm.
A 5 μm copper foil was laminated by a laminating method and cured by heating to produce a metal-based circuit board. Withstand voltage, relative permittivity, and productivity of this metal-based circuit board,
The thermal conductivity of the cured resin was measured by the method described below. As a result, the viscosity at the time of coating was extremely high, and the withstand voltage and productivity were poor.

[0045]

According to the resin composition of the present invention, the boron nitride aggregated particles containing a small amount of the resin (A) are mixed with the resin (B).
By adopting a structure in which it exists in an island shape, it does not hinder the fluidity of the resin, and achieves high thermal conductivity by using the boron nitride aggregated particles as a heat transfer path. As a result, it has a low relative dielectric constant and a high thermal conductivity, and has a relative dielectric constant not obtained conventionally of 4.
5 or less, and the thermal conductivity is 8.0 × 10 ⁻³ ca
It has a characteristic of l / cm · sec · ° C. or higher, and has an effect that a metal-based circuit board having practical withstand voltage can be provided with high productivity.

Further, since the metal-based circuit board of the present invention uses the above resin composition, it has excellent long-term reliability,
Industrially useful.

Claims (7)

[Claims] 1. A resin composition for a circuit board, comprising a resin (B) and boron nitride aggregated particles in which boron nitride is bonded by a resin (A). 2. The resin composition for a circuit board according to claim 1, wherein boron nitride is dispersed in the resin (B). 3. An average particle diameter of at least one of boron nitride constituting the aggregated boron nitride particles bonded with the resin (A) or boron nitride dispersed in the resin (B) is 0.1 μm.
The resin composition for a circuit board according to claim 1, wherein the composition is boron nitride having a thickness of m to 20 μm. 4. The resin composition for a circuit board according to claim 1, wherein the resin (A) comprises an epoxy resin. 5. The resin composition for a circuit board according to claim 1, wherein the resin (B) comprises an epoxy resin. 6. The resin composition according to claim 1, wherein the content of boron nitride is from 30 to 75% by volume based on the total amount of the resin composition. Resin composition for circuit boards. 7. A circuit board comprising the resin composition according to claim 1, 2, 3, 4, 5, or 6.