JP3255814B2 - Metal-based circuit board and module using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-based circuit board having excellent heat dissipation and high electrical reliability and a module using the same.

[0002]

2. Description of the Related Art In recent years, electronic equipment has been reduced in size and weight, and it is important to determine how to radiate heat from high heat-generating components such as ICs, LSIs, and power transistors, and to mount them at high density. It has become. Against this background, metal-based circuit boards have been used, especially in the high power field.

[0003] In order to exhibit high thermal conductivity, a metal-based circuit board is coated with a resin highly filled with an inorganic substance, such as aluminum oxide, and is cured on a metal plate to form an insulating layer.
It has a structure in which an electric circuit made of metal foil or the like is mounted via this insulating layer.

[0004] Further, the metal-based circuit board has a history of mounting only a power element as an alternative to a ceramic substrate, and uses aluminum oxide having a high relative dielectric constant as an inorganic filler for the purpose of improving thermal conductivity. (JP-A-64-69
No. 661).

However, the IPM (Interigent Po
As control elements and power elements have been integrated and mounted, metal-based circuit boards that use aluminum oxide as an inorganic filler have developed modules using them due to noise generated from power elements. There is a problem that causes a malfunction. That is, although the conventional metal-based circuit board has a thermal conductivity of 0.6 ° C./W or less, the capacitance is larger than 50 pF / cm ² , so that there is a problem that noise from the power element cannot be absorbed.

With respect to the metal-based circuit board, the capacitance increases when the thickness of the insulating layer is reduced in consideration of the thermal resistance, so that the thickness of the insulating layer is reduced in order to reduce the capacitance. Since there is a restriction that the thermal resistance increases when the thickness is increased, it is not possible to obtain a circuit board having high thermal conductivity, low capacitance, excellent noise resistance, and as a result, high electrical reliability. Not easy.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a metal-based circuit board and a module having a small thermal resistance and a small capacitance, excellent noise resistance, and high electrical reliability.

[0008]

SUMMARY OF THE INVENTION The present invention is a metal-based circuit board having a metal foil provided on at least one main surface of a metal plate via an insulating adhesive layer made of epoxy resin, and having a thermal resistance of 0. 0.6 ° C./W or less and the capacitance is 50
A metal-based circuit board having a pF / cm ² or less.

[0009] The present invention is characterized in that the insulating adhesive layer is obtained by mixing and curing an inorganic compound containing aluminum oxide in an amount of 1 to 80% by volume with an epoxy resin in an amount of 50 to 80% by volume. Is a metal-based circuit board.

According to the present invention, there is provided an inorganic compound in which the insulating adhesive layer contains aluminum oxide in an amount of 1% by volume to 80% by volume and the balance is at least one selected from the group consisting of silicon oxide, boron nitride and aluminum nitride. A metal-based circuit board characterized by being mixed with an epoxy resin of 50% by volume or more and 80% by volume or less and cured.

The present invention, the insulating adhesive layer, the remainder containing boron nitride 30 volume or 80% by volume or more inorganic compounds are silicon oxide, Epo 50 volume% to 80 volume% or less
A metal-based circuit board characterized by being mixed with a xy resin and cured. Further, the present invention is a module using the above metal-based circuit board.

Hereinafter, the present invention will be described in detail.

The term "capacitance" as used in the present invention refers to a capacitance per 1 cm ² . The metal-based circuit board of the present invention has a capacitance of 50 pF / cm ² or less and a thermal resistance of 0.6 ° C./W or less in order to obtain a module having high electrical reliability for a long time. Required. Capacitance is 50
If it exceeds pF / cm ² , the noise resistance of the module using this substrate will deteriorate rapidly, and if the thermal resistance exceeds 0.6 ° C / W, the electronic components mounted on the metal-based circuit board Is not sufficient for long-term reliability due to insufficient heat radiation.

Specific means for achieving the present invention include:
Hereinafter, description will be made with reference to the drawings.

FIG. 1 is a schematic diagram showing an example of the metal-based circuit board of the present invention. It has a structure in which a metal foil 3 is laminated on a metal plate 1 via an insulating adhesive layer 2. The lamination of the insulating adhesive layer 2 and the metal foil 3 is not limited to one side, but may be on both sides. The adhesive layer 2 and the metal foil 3
May be provided on the entire surface of the metal plate 1 or only on a part thereof.

Here, the metal plate 1 is made of aluminum, aluminum alloy, copper, iron, stainless alloy, invar-based multi-layer metal or the like having a thickness of about 0.5 to 3.0 mm.

The insulating adhesive layer 2 is prepared by mixing a mixture of various inorganic substances in addition to aluminum oxide into an epoxy resin, applying the mixture to a metal plate, further applying a metal foil to form a layer, and then curing. Are common, but in particular,
There is no need to limit the manufacturing method.

The inorganic material forming the insulating adhesive layer 2 is made of conventional aluminum oxide (relative permittivity 9.0, thermal conductivity 0.
(07-0.09 cal / cm · sec · ° C), a substance having a low relative dielectric constant and a high thermal conductivity is selected. Such materials include boron nitride, silicon oxide, diamond, beryllium oxide,
Aluminum nitride and the like can be mentioned, but silicon oxide, boron nitride, and aluminum nitride are industrially preferable in consideration of economy and safety.

In the following, examples of the case where these inorganic substances are obtained by mixing will be described. However, the present invention is not limited to this, and the mixture may be formed into a sintered body in advance and ground. Regarding the particle size, 15
It is sufficient that the particles have a size of about μm or less, and the shape of the particles is preferably close to a sphere in order to highly fill the resin. Further, it is preferable that the silicon oxide is a crystalline silicon oxide having excellent thermal conductivity, and the boron nitride is also a crystal having a developed crystallinity.

The resin referred to in the present invention is an epoxy resin ,
Among them, bisphenol A type epoxy resin and bisphenol F type epoxy resin have a low viscosity, are suitable for high filling of inorganic substances, and are preferable.

In order to achieve the object of the present invention, the present inventors mixed aluminum oxide with one or more of the above-mentioned inorganic substances, and selected two or more inorganic substances from the above-mentioned inorganic substances.
Experimentally studying the mixing of more than one kind of inorganic substance,
This has led to the present invention.

First, when an inorganic substance is mixed with aluminum oxide, and when aluminum oxide exceeds 80% by volume of the mixture of aluminum oxide and inorganic substance, the characteristics of the obtained metal base circuit board are the same as those of conventional aluminum oxide. Since there is no significant difference from the characteristics of the metal base circuit board used alone, if it is less than 1% by volume, it is the same as a known metal base circuit board to which aluminum oxide is not substantially added, and the low heat obtained in the case of aluminum oxide is obtained. Resistance becomes difficult to exert. As the inorganic substance, silicon oxide, boron nitride, and aluminum nitride are preferable for the reasons described above.

Next, when two or more inorganic materials are selected and blended, boron nitride and silicon oxide are combined, and boron nitride is used in an amount of 30% by volume or more and 80% by volume. %, It has been experimentally found that a metal-based circuit board having desired characteristics can be obtained, and the present invention has been achieved.

It is not clear why the combination of boron nitride and silicon oxide obtained a good result, but if the compounding ratio of boron nitride is less than 30% by volume, the relative permittivity of the obtained metal-based circuit board is not as high as desired. You get something, but the thermal resistance is
Nothing less than 0.6 ° C / W can be obtained. If the boron nitride content is more than 80% by volume, the boron nitride particles may be flattened, or sometimes only a metal-based circuit board with low withstand voltage characteristics may be obtained, which is not practical. .

The above-mentioned aluminum oxide and an inorganic substance or a mixture of inorganic substances are added to the above-mentioned epoxy resin by 50%.
It is blended in an amount of at least 80% by volume. The mixing ratio of less than 50 volume%, do not metal base circuit board having a desired thermal resistance without thermal conductivity of the epoxy resin is improved is obtained when more than 80 volume percent, epoxy resin in mixing <br / > Since the viscosity of the fat increases and bubbles are easily entrained, only a metal-based circuit board having deteriorated electric properties such as dielectric breakdown can be obtained.

At the time of compounding, a surface treatment agent such as a silicone coupling agent, a titanate coupling agent, or a silylating agent may be added in order to enhance the adhesiveness at the interface between the epoxy resin and aluminum oxide or an inorganic substance. Alternatively, the surface of aluminum oxide or an inorganic substance can be treated prior to mixing for the purpose described above.

The thickness of the insulating adhesive layer 2 is 20 μm or more and 2
00 μm or less is preferable. When the thickness of the insulating adhesive layer is less than 20 μm, the capacitance of the obtained metal-based circuit board increases, and when it exceeds 200 μm, the thermal resistance increases. The substrate cannot be obtained. Practically, in particular, 80 μm or more and 200 μm
The following ranges are preferred.

The metal foil 3 used in the present invention may be a copper foil for a conductor circuit, a composite foil, or a metal such as copper, aluminum, nickel or the like.
A general-purpose material such as an alloy containing two or more kinds or a clad foil using the metal is used. Its thickness ranges from 5 μm to 1
mm. Nickel plating and nickel-gold plating are applied to the metal foil 3 to impart wire bonding characteristics.
It may be applied on top.

[0029]

EXAMPLES Examples will be specifically described below. (Example 1) Aluminum oxide (AS3, manufactured by Showa Denko KK)
0) 25 vol% of crystalline silicon oxide (Tatsumori Co., Ltd., Crystallite) was blended with 75 vol%, and this mixture was blended with bisphenol F type epoxy resin at 80 vol% and mixed to obtain an insulating adhesive. Next, the size is 640mm x 640mm and the thickness is
On a 1.5 mm aluminum plate, apply the above insulating adhesive so that the thickness after curing becomes 145 μm, and then bond a copper foil with a thickness of 35 μm and cure to produce a metal-based circuit board. did. Using this metal-based circuit board, measure the thermal resistance, measure the capacitance per 1 cm ² , create a module with a transistor mounted, measure the Vt characteristics, and measure the average destruction by the methods shown below. The time and the presence or absence of a malfunction of the transistor during that time were examined. As a result, Table 1
The thermal resistance is 0.43 ° C / W and the capacitance is 49.
It was 0 pF / cm ² , the average lifetime when the transistor was mounted exceeded 10,000 hours, no malfunction of the transistor was observed, and the noise resistance was improved.

<Measurement of Thermal Resistance> A 30 mm × 30 mm portion is cut out from a metal base circuit board, and a metal foil located at the center is etched to form a pad portion having a size of 10 mm × 15 mm. Then, a transistor (TO220, manufactured by Toshiba Corporation) is soldered to this pad portion.
While cooling the surface of the metal plate on which the transistor is not mounted, 100 W is supplied to the transistor, and the temperature of the transistor is measured. At this time, the thermal resistance is calculated from the difference between the transistor temperature and the temperature of the cooling section metal plate, and the additional power to the transistor.

<Measurement of capacitance> Based on JIS C6481,
Measurement frequency 100kHz, performed at a measurement temperature of 25 ° C., the results, 1 cm ²
Convert to per hit.

<Measurement of Vt Characteristics> Size 640 mm × 640 m
With respect to the metal base circuit board of m, a circular electrode pattern having a diameter of 20 mm was formed by etching at a total of five locations, one at the center and one at each of the four corners, excluding the metal foil. Next, a voltage of 2 kV AC half-wave is applied to the metal plate and the circular electrode pattern portion, and the time until dielectric breakdown is measured. The measurement was performed at a temperature of 125 ° C. for acceleration. From the obtained five data points, the average life is calculated by the Weibull plot method.

(Examples 2 to 15 and Comparative Examples 1 to 5) The types of inorganic substances and their mixing ratios, the mixing ratio of the inorganic substances to the epoxy resin, and the thickness of the insulating adhesive layer were varied. Except for the change, various metal-based circuit boards and modules using the same were prepared in the same manner as in Example 1, and their characteristics were evaluated as in Example 1. Table 1 shows the results of the examples, and Table 2 shows the results of the comparative examples.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

According to the comparison between Table 1 and Table 2, the product of the present invention is:
It is evident that it is electrically reliable and has a long life, so that it can be applied to smaller and lighter electronic devices.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating an example of a metal-based circuit board according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal plate 2 Insulating adhesive layer 3 Metal foil 4 Solder 5 Ceramic chip component 6 Semiconductor element 7 Terminal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 1/05 B32B 7/02 104 B32B 7/12 B32B 15/08

Claims (5)

(57) [Claims] 1. A metal-based circuit board having a metal foil provided on at least one main surface of a metal plate via an insulating adhesive layer made of epoxy resin, and having a thermal resistance of 0.6 ° C./W or less. And the capacitance at 100 kHz is 50 pF / cm ²
A metal-based circuit board, characterized in that: 2. The method according to claim 1, wherein the insulating adhesive layer contains 50% by volume of an inorganic substance containing 1% by volume to 80% by volume of aluminum oxide.
2. The metal-based circuit board according to claim 1, wherein the metal-based circuit board is mixed with an epoxy resin in an amount of at least 80% by volume and cured. 3. An inorganic material comprising 1 to 80% by volume of aluminum oxide and the balance consisting of at least one selected from the group consisting of silicon oxide, boron nitride and aluminum nitride, wherein the insulating adhesive layer contains 50% by volume of an inorganic material. 3. The metal-based circuit board according to claim 2, wherein the metal-based circuit board is blended with an epoxy resin in an amount of at least 80% by volume and cured. 4. The insulating adhesive layer contains 30% by volume of boron nitride.
2. The metal-based circuit board according to claim 1, wherein an inorganic substance containing at least 80% by volume and the balance being silicon oxide is mixed with an epoxy resin at at least 50% by volume and at most 80% by volume and cured. 5. A module using the metal-based circuit board according to claim 1.