JP3006617B2 - Insulating adhesive composition for circuit board, hybrid integrated circuit board, and hybrid integrated circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an insulating adhesive composition for a circuit board, which can be filled with a specific inorganic filler at a high level, has a high thermal conductivity, and has a high adhesion to a metal substrate. And its uses.

(Prior art) Conventionally, an epoxy resin-based adhesive filled with an inorganic filler was applied to a metal substrate of aluminum, iron, iron-nickel alloy, or the like at a thickness of about 100 μm, and a metal foil was bonded thereon. Circuit boards are known (JP-A-56-62388).
JP-A-58-15290).

However, in these circuit boards, the thermal conductivity of the adhesive used as the insulating layer is low, so the original characteristics of a metal substrate with good heat conductivity cannot be used, and satisfactory heat dissipation can be obtained. There was a disadvantage that I could not do. As a countermeasure, attempts have been made to improve the thermal conductivity by reducing the thickness of this adhesive to several tens of μm, but conversely, when used as a substrate, the withstand voltage reliability of the insulating layer deteriorates. There were drawbacks.

For this reason, a method of further increasing the thermal conductivity of the adhesive by further filling the resin with an inorganic filler is generally used.However, when the filler is highly filled with an inorganic filler, the viscosity of the adhesive increases, and the coatability is poor. However, since air bubbles are involved, there is a problem that heat conductivity and insulation properties are reduced.

(Problems to be Solved by the Invention) The present invention solves such a drawback, and highly fills an inorganic filler having good thermal conductivity while maintaining a conventional adhesive force as an insulating adhesive composition for a circuit board. The developed adhesive composition has been used, and the use of the same has led to the completion of a hybrid integrated circuit substrate and a hybrid integrated circuit having high thermal conductivity.

(Means for Solving the Problems) That is, the present invention provides a heat-resistant resin of 10 to 40% by volume and a spherical coarse particle having a maximum particle diameter of 100 μm or less, having a particle diameter of 5 to 5%.
0 μm or more by weight and the average particle size is 5-5
0-μm inorganic filler 42-63% by volume and spherical fine particles having a particle diameter of 1.5 μm or less are 70% by weight or more and a particle diameter of 0.2 μm
m or more is 70% by weight or more, and the average particle diameter is 0.2 to 1.5.
The main component is 18 to 27% by volume of an inorganic filler of μm, and the thermal conductivity after curing is 6.4 to 20 × 10 ^-3 cal / cm.
The present invention is characterized by an insulating adhesive composition for circuit boards having a sec · deg, a high thermal conductive hybrid integrated circuit board and a high thermal conductive hybrid integrated circuit using the insulating adhesive composition.

As the heat-resistant resin used in the adhesive composition of the present invention, for example, epoxy resin, silicone resin, polyamide resin,
There are acrylic resins and the like. And the ratio of heat resistant resin is 10 ~
It is 40% by volume, and if it is less than 10% by volume, the viscosity of the adhesive composition increases and the workability decreases. If it exceeds 40% by volume, the thermal conductivity of the insulating layer is undesirably reduced.

Examples of the inorganic filler used in the adhesive composition of the present invention include oxide ceramics such as aluminum oxide (alumina), silicon oxide, and magnesium oxide; nitride ceramics such as aluminum nitride, silicon nitride, and boron nitride; and carbide ceramics. There is. The ratio of the inorganic filler is such that the inorganic filler contains 50% by weight or more of 5 to 50 μm in particle diameter as spherical coarse single particles having a maximum particle diameter of 100 μm or less, and has an average particle diameter of 5 to 50 μm.
Inorganic filler with 42 to 63% by volume and 70% by weight or more as a spherical fine particle having a particle diameter of 1.5 µm or less, 70% by weight or more with a particle diameter of 0.2 µm or more, and an average particle diameter of 0.2 to 1.5 µm
When the content is outside this range, the viscosity of the resin composition increases and the thermal conductivity decreases, which is not preferable. As the above-mentioned single spherical coarse particles, for example, alumina is preferably spherical corundum alumina particles having no cutting edge as described in JP-A-62-191420.

In addition, when the total amount of inorganic filler is 100, the ratio of spherical coarse particles and spherical fine particles having different particle diameters is 60 to 90% by volume in the ratio of spherical coarse particles. It is preferable as a compounding ratio. Outside this range, even if the filling is high, the thermal conductivity is poor. As a single spherical coarse particle, the maximum coarse particle is 100 μm or more, and the particle diameter of 5 to 50 μm is 50% by weight.
The content is above, and the average particle diameter is 5 to 50 μm. Outside this range, the thermal conductivity is unfavorably reduced. If the maximum particle diameter of the coarse particles exceeds 100 μm, the thickness of the insulating layer of the hybrid integrated circuit board using the metal substrate is generally around 100 μm, which results in poor withstand voltage and poor appearance of the substrate. In addition, spherical fine particles having a particle diameter of 1.5 μm or less
The content is 0% by weight or more, the particle size of 0.2 μm or more is 70% by weight or more, and the average particle size is 0.2 to 1.5 μm. In order to lower the viscosity of the adhesive composition, the sharper the particle size distribution of the spherical fine powder, the better.

Further, the adhesive composition of the present invention has a thermal conductivity after curing.
It is 6.4 to 20 × 10 ⁻³ cal / cm · sec · deg.

In the adhesive composition of the present invention, a silane-based coupling agent, a titanate-based coupling agent, a stabilizer, a curing accelerator, and the like can be used as necessary.

The present inventors have found that in the production of an inorganic filler high-filled adhesive using the specified inorganic filler according to the present invention, surprisingly, the skilled artisans conventionally used in the production of inorganic filler highly-filled adhesives are required. It has been found that kneading can be easily performed in a short time only with a commonly used kneading machine without the need for labor-intensive kneading of rolls under high shear.

In addition, since the hybrid integrated circuit board according to the present invention is filled with an inorganic filler more than before, there was a concern that the mold would be significantly worn when the circuit-formed board was divided by pressing, but it was formed into a spherical shape. Because of the inorganic filler, it was found that there was little mold abrasion and it could withstand practical use.

Next, FIG. 1 is a cross-sectional view of a hybrid integrated circuit substrate including a metal substrate 1 and a conductive metal foil layer 3 via an insulating adhesive composition 2 of the present invention. The metal substrate 1 is a clad material such as aluminum and its alloys, iron, silicon steel, stainless steel, copper / invar / copper clad material, and copper / molybdenum / copper. The conductive metal foil layer 3 is a copper foil, a copper-aluminum clad foil, a copper-nickel-aluminum clad foil, or the like. FIG. 2 is a cross-sectional view of a hybrid integrated circuit mounted using the circuit board. The circuit formed by etching the conductive metal foil layer 3 includes a power transistor 4 and a chip resistor. 5, a chip capacitor 6, and an external lead 7 are mounted by soldering.

(Examples) Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example 1) First, aluminum oxide (hereinafter referred to as alumina) spherical coarse single particles 70% by weight containing 50% by weight or more of 5 to 50 μm in a maximum particle diameter of 75 μm or less and having an average particle diameter of 17 μm;
An inorganic filler was prepared by mixing 90% by weight of 1.5 μm or less, 90% by weight of 0.2 μm or more and 30% by weight of alumina spherical fine particles having an average particle size of 0.7 μm. Next, the inorganic filler and the bisphenol A type liquid epoxy resin were added in the ratio shown in Table 1, 1 part by weight of a silane coupling agent (based on 100 parts by weight of the inorganic filler) was added and kneaded at a heating temperature of 50 ° C. The mixture was kneaded by a machine to prepare an insulating adhesive composition for a circuit board. During the kneading, the dispersed state of the inorganic filler was checked with time by a tube gauge method. As a result, the time required for the inorganic filler to have a particle size of 100 μm or less by the tub gauge method was 1.5 hours. Table 1 shows the thermal conductivity of each of the obtained insulating adhesive compositions.

(Example 2) The same spherical alumina coarse single particles as those of Example 1 were used.
% Alumina particles of 1.5 μm or less
An inorganic filler was prepared by mixing 70% by weight, 0.2% or more and 70% by weight and having an average particle diameter shown in Table 2 at 30% by weight. Next, a bisphenol A type liquid epoxy resin was mixed with the mixed inorganic filler by performing the same operation as in Example 1, and the ratio of the insulating adhesive composition capable of being filled to the maximum was examined. Table 2 shows the thermal conductivity of each insulating adhesive composition.

(Comparative Example) Bisphenol A type liquid epoxy resin, spherical coarse single particle of Example 1, alumina crushed powder having a maximum particle diameter of 75 μm or less and an average particle diameter of 12 μm, and an average particle diameter of a maximum particle diameter of 75 μm or less Is 22μm plate-like powder and maximum particle size is 75μm
An insulating adhesive composition was obtained in the same manner as in Example 1 except that the spherical granulated powder having an average particle diameter of 22 μm was changed to the ratio shown in Table 3 below. Table 3 shows the thermal conductivity of each insulating adhesive composition and the time required for dispersion.

(Example 3) 2 parts by weight of an amine-based curing agent was added to the insulating adhesive composition having a filling rate of 80% by volume of the mixed inorganic filler of Example 1, and the mixture was heated at 80 ° C.
After curing for 1 hour at + 150 ° C. for 2 hours, a cured product was obtained, and the thermal conductivity of the cured product was measured by a laser flash method. As a result, the thermal conductivity of the cured product was 14 × 10 ⁻³ cal / cm · sec · deg.

(Example 4) The insulating adhesive composition obtained with the same composition as in Example 3
It was applied on a 1.5 mm aluminum plate to a thickness of 100 μm and heated to a semi-cured state, and then a 35 μm-thick copper foil was adhered to this to produce a highly thermally conductive hybrid integrated circuit board. Table 4 shows the initial characteristics and long-term reliability test results of this substrate.

These results show that this substrate has sufficient heat resistance and moisture resistance as a hybrid integrated circuit substrate.

Example 5 The substrate obtained in Example 4 was cut into 3 × 4 cm and etched to form a copper foil pattern of 10 × 10 mm. On this copper foil
A TO-220 type transistor was soldered and fixed on a water-cooled heat dissipation fin via heat dissipation grease. Actually energize the transistor and generate heat to measure the thermal resistance value and correct the thermal resistance value of the heat radiation grease to 0.
A value of 24 ° C./W/cm ² was obtained.

Comparative Example A hybrid integrated circuit board was prepared in the same manner as in Example 4 except that an insulating adhesive containing 55% by volume of pulverized alumina was used.
Next, when the thermal resistance of this substrate was measured in the same manner as in Example 5, it was 0.50 ° C./W/cm ² .

(Effects of the Invention) As described above, the present invention can easily fill an inorganic filler with a high ratio by using two types of specified inorganic fillers at a specified ratio. Therefore, the insulating adhesive for a circuit board having a high thermal conductivity. Since the composition can be obtained and the heat dissipation property is good as the application, the composition has an effect that a hybrid integrated circuit board for high-density mounting and a hybrid integrated circuit not densely mounted can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of a high thermal conductive hybrid integrated circuit board of the present invention, and FIG. 2 is a side sectional view of the hybrid integrated circuit. Reference numeral 1: metal substrate, 5: chip resistance 2 ... adhesive composition, 6 ... chip capacitor 3 ... conductive metal foil layer, 7 ... external lead wire 4 ... power transistor, 8 ... solder layer

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-69661 (JP, A) JP-A-62-191420 (JP, A) JP-A-61-256921 (JP, A) JP-A-56-191 62388 (JP, A) JP 4634502 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 1/02 C09J 1/02 C04B 37/02 C04B 41/87

Claims (4)

(57) [Claims] 1. A heat-resistant resin having a maximum particle size of 10 to 40% by volume.
Spherical coarse particles having a particle diameter of 100 μm or less and containing 50% by weight or more of a particle diameter of 5 to 50 μm as a single particle, and having an average particle diameter of 5 to 50 μm, 42 to 63% by volume of an inorganic filler, and spherical particles having a particle diameter of 1.5 μm or less is 70% by weight or more, particle size
0.2 μm or more is 70% by weight or more, and the average particle diameter is 0.2
The main component is 18 to 27% by volume of an inorganic filler of 1.5 to 1.5 μm, and the thermal conductivity after curing is 6.4 to 20 × 10 ^-3 c
al / cm · sec · deg, an insulating adhesive composition for circuit boards. 2. The insulating adhesive composition for a circuit board according to claim 1, wherein the inorganic filler is aluminum oxide. 3. A hybrid integrated circuit board obtained by laminating a metal substrate and a metal foil layer via the adhesive composition according to claim (1). 4. A hybrid integrated circuit comprising an electronic component mounted on the hybrid integrated circuit board according to claim 3.