JP2017188518A - Metal base circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal base circuit board excellent in thermal conductivity, electric insulating property and adhesive property.SOLUTION: By containing an organic fiber having a thermal conductivity in a longitudinal direction of 25 W/mK or more and a fiber diameter of 3 μm or more and 50 μm or less by blending it to an insulating layer in the amount of 3 pts.mass or more and 40 pts.mass or less with respect to 100 pts.mass of resin, a metal base circuit board that is compatible with electrical insulation and high heat dissipation is obtained.SELECTED DRAWING: None

Description

The present invention relates to a metal base circuit board used when mounting a heat-generating component.

  In recent years, examples of high-density power transistors and hybrid ICs (Integrated Circuits) that are driven at high voltages have increased, and the problem of heat dissipation design has become important, so a metal base substrate with excellent heat dissipation has been used. It has come to be. In addition, the number of cases used outdoors is increasing, and not only the insulating layer but also the improvement in reliability such as moisture resistance and insulation of the resin (solder resist) to be coated on the surface is required. Resin is disclosed (refer patent document 1).

  However, many of such coating resins are a combination of epoxy resin and acrylic resin, are unsatisfactory in heat resistance and moisture resistance, and are feared to be inferior in insulation reliability.

On the other hand, Patent Document 2 discloses a metal base circuit board that achieves high heat dissipation and can withstand high humidity by highly filling an inorganic filler having a plurality of particle sizes.

  Insulating layers with improved heat dissipation due to high filling of inorganic fillers have a large difference in coefficient of linear expansion (CTE) from the metal used for the metal base and circuit foil, and in power transistors and hybrid ICs that are expected to be used There is a concern that disconnection or peeling due to this CTE difference may occur.

JP 2007-224169 A JP 2009-164540 A

  Accordingly, an object of the present invention is to construct an insulating layer capable of controlling CTE in the same manner as a metal base or circuit foil while maintaining thermal conductivity, and to provide a metal base circuit board with high reliability of high-temperature operation. .

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention.
That is, this invention consists of the following structures.
[1] In a metal base circuit board comprising at least a metal base, an insulating layer laminated on the metal base, and a circuit foil laminated on the insulating layer, the insulating layer has a thermal conductivity in the length direction of 50 W / A metal-based circuit board comprising 3 to 40 parts by mass of organic fibers having a diameter of mK or more and a fiber diameter of 3 to 50 μm with respect to 100 parts by mass of the resin.
[2] The resin constituting the insulating layer is at least one selected from silicone resins, acrylic resins, urethane resins, EPDM resins, and polycarbonate resins. Metal base circuit board.
[3] The organic fiber according to any one of [1] or [2], wherein the organic fiber is at least one selected from high-strength polyethylene fiber, polybenzazole fiber, and aromatic polyamide fiber. Metal base circuit board.

By including a specific organic fiber in the insulating layer portion, the metal base circuit board of the present invention can provide a metal base circuit board having higher reliability while maintaining the heat dissipation performance of the insulating layer.
A technique for controlling the CTE of an insulating layer by combining fibers with the insulating layer is widely used in printed wiring boards. However, since the glass fiber used for a general printed wiring board has a low elastic modulus, it is necessary to use a considerable amount in order to obtain a sufficient CTE control effect. On the other hand, the thermal conductivity of the glass fiber is low, and if a sufficient amount is used for CTE control, the thermal conductivity of the insulating layer is lowered.
However, since the specific organic fiber used in the present invention has a high elastic modulus, a sufficient amount of CTE can be obtained with a relatively small amount. Furthermore, the specific organic fiber of the present invention has a very high thermal conductivity in the fiber axis direction, and a thermal conductive filler blended in the insulating layer for the purpose of improving the thermal conductivity in the thickness direction separately from the organic fiber. By being in contact or in the vicinity, heat transfer in the insulating layer is made more efficient, the heat dissipation effect in the surface direction that is the main orientation direction of the fiber is promoted, and the heat conduction efficiency of the insulating layer is comprehensively improved Demonstrate.

  The resin used for the insulating layer of the present invention is preferably excellent in heat resistance and thermal stability, and these physical properties can be adjusted to a desired range by appropriately selecting the resin used. In view of adhesion, it is preferable to select a resin having excellent flexibility or a resin having adhesiveness. For example, examples of materials having excellent flexibility include silicone resins, acrylic resins, urethane resins, EPDM, and polycarbonate resins, and examples of materials having adhesive properties include semi-curing of thermoplastic resins and thermosetting resins. The thing of a state is mentioned. As a material excellent in flexibility, a silicone resin that is less susceptible to deterioration due to a change in physical properties due to heat cycle is particularly preferable. The material having adhesiveness is preferably a urethane-based resin having good shock absorption from the viewpoint of thermal shock resistance at the bonding interface with the heating element. It is also possible to impart flame retardancy by selecting a flame retardant material.

In order to improve thermal conductivity, an inorganic filler may be added to the insulating layer and used in combination with organic fibers.

As an inorganic filler for improving thermal conductivity, aluminum oxide, silicon nitride, magnesium oxide, aluminum nitride, silicon nitride, boron nitride, etc., as long as they are electrically insulating and have better thermal conductivity than resin, Can be used. In addition, the inorganic filler may be spherical, crushed, rod-shaped, or fibrous.
The average particle size of the inorganic filler of the present invention is preferably from 0.3 μm to 20 μm, more preferably from 0.5 μm to 12 μm, and preferably from 0.9 μm to 6 μm. Here, the average particle diameter is D50 determined by the light scattering method. The average particle diameter of the organic filler of the present invention is preferably in the range of the same size as the fiber diameter of the organic fiber to 1/10 of the fiber diameter. Heat transfer is particularly preferably performed when the ratio of the sizes falls within this range.

In a system containing such an inorganic filler, it is preferable to add a coupling agent such as a silane coupling agent to the resin. Since ionic impurities that deteriorate the electrical characteristics during moisture absorption are introduced in a large amount into the insulating layer by the inorganic filler, a significant improvement in characteristics can be achieved by using in combination with an ion-adsorbing inorganic substance. In addition, the deterioration of electrical characteristics during moisture absorption is greatly influenced by the interfacial adhesion between the inorganic filler and the resin, and the addition of a coupling agent that contributes to the interfacial adhesion is essential. Although the inorganic filler in an insulating layer is based on the objective to add, addition of 10 mass parts or more and 80 mass parts or less is preferable with respect to 100 mass parts of resin, and also addition of 20 mass parts or more and 50 mass parts is preferable.
The coupling agent is calculated from the coating area per unit weight of the coupling agent and the surface area of the inorganic filler as an addition amount to be covered with the monomolecular layer even if the surface area of the inorganic filler particles is small.

  As a method for producing the insulating layer of the present invention, it can be obtained by a known method. However, the following method can prevent bubbles from being caught in the insulating layer, and can stably form the metal base and the circuit foil. It is preferable because a cured resin body having excellent adhesiveness, electrical and electrical insulation, excellent thermal conductivity, and excellent high-temperature operation reliability can be obtained.

  The method for producing an insulating layer according to the present invention is characterized in that a urethane-based resin and a curing agent are mixed, and then organic fibers are blended and mixed before curing. About the mixer used here, it is sufficient to use a conventionally known mixer such as a universal mixing stirrer, a planetary stirring and defoaming device, a pressure kneader, and the coating conditions may be appropriately selected. There is no reason to set it.

  As for the coating method of the insulating layer of the present invention, a conventionally known coating process such as screen printing, tip coater, comma coater, die coater, etc. may be used, and the coating conditions may be appropriately selected. There is no reason to set it.

The organic fiber to be used has a fiber diameter of 3 μm or more and 50 μm or less. The fiber diameter of the organic fiber of the present invention is preferably 5 μm or more and 30 μm, and more preferably 7 μm or more and 30 μm or less. The fiber diameter may be measured on a scale by obtaining an enlarged image of the fiber with an electron microscope or the like.
The fiber diameter of the organic fiber is important for obtaining an interaction with the thermally conductive filler that is separately blended. When the fiber diameter exceeds a predetermined range, heat is transferred to and from the heat conductive filler quickly. Disappear. When the fiber diameter is below the specified range, the heat transfer effect is essentially increased, but the specific surface area of the fiber increases, so the amount of binder resin absorbed increases and the insulation layer is formed. Becomes difficult.

The thermal conductivity of the organic fiber of the present invention is essentially 25 W / mK or more, preferably 35 W / m, and more preferably 50 W / m. .
The fiber type is not particularly limited as long as it is electrically insulating and has a predetermined high thermal conductivity and fiber diameter, and examples thereof include high-strength polyethylene fiber, polybenzazole fiber, and aromatic polyamide fiber. Among them, polybenzazole fibers that have heat resistance and are easily available are particularly preferable. Polybenzoxazole fiber, polybenzothiazole fiber, and polybenzimidazole fiber can be used as the polybenzazole fiber. Among these, Zylon manufactured by Toyobo Co., Ltd., which is a kind of polybenzazole fiber, can be preferably used.

The organic fiber of the present invention is disposed mainly in the surface direction of the insulating layer. In the present invention, the organic fibers are preferably blended in a plain woven or non-woven form. In the present invention, it is particularly preferable to blend the organic fibers in the form of a pile weave. The pile woven fabric is a general term for a woven fabric obtained by weaving a pile on one side or both sides of a knitted fabric with plain weave or twill weave, and is also called garment weaving. Here, the pile is a fiber coming out of the base and is classified into two types according to the treatment after weaving. The one in which the pile is left in the loop is called a loop pile (Wana) or uncut pile, and the one in which the loop is cut is called a cut pile (cut hair).
The compounding quantity of the organic fiber of this invention is 3 to 40 mass parts with respect to 100 mass parts of resin components of an insulating layer. The blending amount of the organic fiber is more preferably 4 parts by mass or more and 24 parts by mass or less, and still more preferably 5 parts by mass or more and 12 parts by mass or less.

According to the present invention, the metal base circuit board of the present invention is manufactured by laminating an insulating layer on a metal base such as aluminum and then bonding the circuit foil such as copper foil by pressing or laminating.
The metal base preferably used in the present invention is not particularly limited as long as it is a metal plate material, but aluminum, aluminum alloy, copper, and copper alloy can be preferably used.
As the circuit foil in the present invention, copper foil, copper alloy stay, nickel foil, aluminum foil, silver foil, silver alloy foil can be preferably used.

  In the present invention, the circuit foil can be patterned by appropriately selecting a known processing method such as general etching processing or cutting processing with a high-power laser.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. In addition, the evaluation method of the physical property in the following examples is as follows.
1. Sheet linear expansion coefficient (CTE)
Stretch rate is measured under the following conditions for the insulating layer obtained by removing all metal base with Kanto Chemical Co., Ltd. aluminum etchant with cupric chloride etching solution on the circuit foil of the produced metal base circuit board, The stretch rate / temperature at intervals of 15 ° C. (30 to 45 ° C., 45 ° C. to 60 ° C.,...) Is measured, this measurement is performed up to 300 ° C., and the average value of all measured values is the linear expansion coefficient (CTE). Calculated as
Equipment used: “TMA4000S” manufactured by MAC Science
Sample length: 20mm
Sample width: 2 mm
Temperature rise start temperature: 25 ° C
Temperature rise end temperature: 400 ° C
Temperature increase rate: 5 ° C./min Atmosphere: Argon initial load: 34.5 g / mm 2
2. As a sample for measuring the withstand voltage of the metal base circuit board, the original plate of the metal base circuit board that was produced was etched, and the desired circuit was produced as a sample.
・ Initial ・ After migration test: after exposure under conditions of 85 ° C., humidity 85% RH, DC 1000V, 1000 hours (migration test) ・ After PCT test: conditions of 121 ° C., humidity 100% RH, 2 atm, 96 hours ( After exposure under PCT treatment)
In accordance with JIS C 2110, the dielectric breakdown voltage was measured when a parallel plate and DC were applied, and the dielectric breakdown strength was determined by dividing the dielectric breakdown voltage by the thickness of the insulating layer. As a measuring instrument, TOS-8700 manufactured by Kikusui Electronics Co., Ltd. was used.
3. A TO-220 type transistor was soldered on the heat resistance copper foil of the metal base circuit board, and fixed on the water-cooled heat radiation fin via heat radiation grease. Energize the transistor, heat the transistor, measure the temperature difference between the transistor surface and the back of the metal base, measure the thermal resistance value, and correct the thermal resistance value of the heat dissipation grease to measure the thermal resistance value of the test piece did.

〔Example〕
Specific examples will be described below.
Example 1
As an organic fiber, a pile woven fabric of ZylonHM (manufactured by Toyobo: fiber diameter 12 μm, thermal conductivity in the fiber axis direction is 60 W / mK, organic fiber A),
As resin solutions, Toyobo saturated copolymer polyester urethane resin UR3600 / 80.9 parts by weight, Toyobo saturated copolymer polyester urethane resin BX-10SS / 12.0 parts by weight, Toyobo epoxy resin AH-120 / 7.1 parts by weight Part and 200 parts by weight of methyl ethyl ketone were impregnated with a mixed solution (resin solution X).

A pile woven fabric impregnated with the above resin solution is layered on an aluminum metal base having a thickness of 1.5 mm, heated at 100 ° C. for 60 minutes to volatilize the solvent, and repeatedly repeated coating and drying of the solution as appropriate to form organic fibers. After increasing the thickness of the resin layer to the extent that it is almost buried and making it a semi-cured state, a copper foil with a thickness of 70 μm is stacked, pressurized with a vacuum press, and further cured by heating at 140 ° C. for 2 hours to form a metal base circuit A substrate original plate was produced.

  A metal base circuit board having a circuit pattern for mounting a power transistor and an electrode pattern for dielectric breakdown voltage evaluation by a conventional method using a dry film resist and cupric chloride etching solution on a copper foil of a metal base circuit board original plate Obtained.

  Each characteristic of the obtained metal base circuit board was examined as described above, and the results are shown in Table 1.

(Example 2)
The organic fiber is replaced with a plain woven fabric of Dyneema SK71 (Toyobo; fiber diameter 11 μm, thermal conductivity in the fiber axis direction is 50 W / mK, organic fiber B). A metal base circuit board original plate was produced in the same manner as in Example 1 except that the heating time was set to 80 ° C. and the heating time was set to 4 hours.
Hereinafter, patterns were similarly formed and evaluated. (Example 3)
Example 1 except that the organic fiber was changed to a pile woven fabric of Kevlar (manufactured by Toray DuPont, aramid fiber, fiber diameter 11 μm, thermal conductivity in the fiber axis direction is 60 W / mK, organic fiber C). A metal base circuit board was obtained. The results evaluated in the same manner are shown in Table 1.

Example 4
Resin solution (resin solution) mixed with liquid silicone rubber base TSE3431-A / 100 parts by mass of Momentive Performance Materials, and liquid silicone rubber curing agent TSE3431-C / 30 parts by mass of Momentive Performance Materials A metal base circuit board was obtained in the same manner as in Example 1 except for changing to Y). The results evaluated in the same manner are shown in Table 1. Shown in

(Example 5)
A metal base circuit board was obtained in the same manner as in Example 1 except that silicon dioxide (inorganic filler α) average particle size of 0.15 μm was added to the resin as an inorganic filler.
(Example 6)
A metal base circuit board was obtained in the same manner as in Example 1 except that aluminum oxide (inorganic filler β) average particle diameter of 3.6 μm was added as an inorganic filler to the resin.

(Comparative Example 1)
A metal base circuit board was obtained in the same manner as in Example 1 except that organic fibers were not used and coating and drying were performed so that the insulating layer had a thickness of 80 μm. The results evaluated in the same manner are shown in Table 1. Shown in

(Comparative Example 2)
A metal base circuit board was obtained in the same manner as in Example 5 except that the organic fiber was applied and dried so that the insulating layer had a thickness of 80 μm. The results evaluated in the same manner are shown in Table 1. Shown in

In the metal base circuit board according to the present invention, the CTE of the metal and the insulating layer is brought close to each other by laminating an insulating layer having an organic fiber between the metal base and the copper foil. It exhibits excellent characteristics with high withstand voltage, high humidity resistance, and high temperature operation reliability.

Claims (3)

In a metal base circuit board comprising at least a metal base, an insulating layer laminated on the metal base, and a circuit foil laminated on the insulating layer, the insulating layer has a thermal conductivity of 25 W / mK or more in the length direction. A metal-based circuit board comprising 3 to 40 parts by mass of an organic fiber having a fiber diameter of 3 to 50 μm with respect to 100 parts by mass of the resin.   The metal base circuit board according to claim 1, wherein the resin constituting the insulating layer is at least one selected from silicone resins, urethane resins, and epoxy resins.   The metal base circuit board according to claim 1, wherein the organic fiber is at least one selected from high-strength polyethylene fiber, polybenzazole fiber, and aromatic polyamide fiber.