JPH069290B2 - Metal board for printed circuit - Google Patents

Description

The present invention relates to a metal substrate for a printed circuit, which has extremely high Invar characteristics by interposing a specific metal in order to increase the adhesive strength between the Invar plate and the insulating layer. Regarding

(Prior Art) Conventionally, metal substrates for printed circuits, which are based on aluminum, iron, and copper, have rapidly spread due to their good thermal conductivity and excellent punching workability. It is used for a hybrid IC of a type having a ceramic chip resistor, a chip capacitor, a ceramic chip carrier, etc., a power hybrid IC for directly bonding a semiconductor to a metal except a part of an insulating layer, an LED printer, and the like.

However, with conventional aluminum, iron, and copper-based metal substrates, the occurrence of solder cracks at the time of heat shock becomes a problem due to the difference in the thermal expansion coefficient between the component and the substrate, and LED elements are mounted in contact with each other like LED printers. In this case, when the semiconductor elements are mutually compressed during cooling and cracking occurs, there is a problem.

In order to solve the above problems, a metal substrate based on a copper clad Invar plate, for example, 64% iron and 36% nickel.
An alloy Invar material and a base metal in which copper is clad with an insulating layer and a wiring circuit are developed and known (for example, (1) "Printed Circuit Journal" (Sho 60.
5.5), printed circuit journal, P10,
(2) "Furukawa Electronics Material Guide", (Sho 51.
9), Furukawa Electric Co., Ltd., Catalog, (3) Susumu Honda, Kazuo Mizuno "Hybrid IC Technology" (Sho 59.6.1)
Industrial Research Institute Co., Ltd., P13, (4) Shinichi Enomoto "Precision Machinery", (Sho 60.5.9), Japan Society of Seiki, VOL51, P5
8).

(Problems to be Solved by the Invention) However, in the copper clad invar base metal substrate, the adhesive strength between the insulating material and the copper surface is low, and it is sufficient to perform feathering treatment, blackening treatment, chelating treatment, or the like. You can't get good adhesion.

The present invention has solved these drawbacks, and has achieved the completion of a metal substrate for a printed circuit having a low thermal expansion coefficient and a high thermal conductivity by clad an insulating material and a metal capable of obtaining a strong adhesive strength on the surface of the Invar material. Ivy.

(Means for Solving Problems) That is, according to the present invention, at least one surface of an Invar plate is provided with one layer selected from aluminum, iron, zinc, and alloys containing these as a main component, and an insulating layer is formed thereon. A metal substrate for a printed circuit, characterized in that a wiring circuit is provided through the metal substrate.

The present invention will be described in detail below with reference to the drawings.

FIG. 1 (a) is a cross-sectional view of a substrate of the present invention. The structure of the substrate is such that a metal layer 3 for improving the adhesive strength is adhered to both sides of an Invar material 1 and an insulating layer 4 is provided on one side of the metal layer 3. The circuit 5 is formed through the above. Further, a metal layer 3 for improving the adhesive strength is joined to one surface of the invar material 1 in FIG. 1 (b), and an insulating layer 4 and a circuit 5 are formed on the metal layer 3. Invar material 1 is
For example, a material with a composition ratio of iron and nickel adjusted, and the same as the ceramic element mounted together with the adhesive layer metal
The linear thermal expansion coefficient is preferably in the range of 10 × 10 ⁻⁶ cm / ° C., and the plate thickness is preferably 0.1 to 10.0 mm. The adhesive strength improving metal layer 3 may be on both surfaces of the Invar material 1 or on one surface on which the insulating layer 4 is laminated. The adhesive strength improving metal layer 3 is made of aluminum,
Iron, zinc and alloys based on these metals are preferred. The invar material 1 and the metal layer 3 for improving the adhesive strength, such as aluminum, iron, zinc and alloys containing these as the main components, are usually joined by rolling, and the method is, for example, electrolysis, melting, vapor deposition, electrodeposition, thermal spraying, etc. It does not matter if you use the above method. Since all of these metals have an affinity with the organic insulating agent and have a strong adhesive force, the effect is recognized in any of these metals and alloys containing these as the main components.

The layer thickness of the metal layer 3 for improving the adhesive strength of aluminum, iron, zinc or the like to the Invar material 1 may be sufficient to improve the adhesiveness, and is usually used in a thickness of about 1 μm to 500 μm. Any number may be used as long as the thermal expansion coefficient of the Invar material 1 is not significantly impaired. Next, the insulating layer 4 used here is an organic insulating agent such as phenol, epoxy, glass / epoxy, polyimide, or silicone resin, and those filled with a high thermal conductive filler or the like.

For forming the circuit 5, a metal foil such as a copper foil which is usually used is etched, a metal such as copper is plated by an additive method, a conductor paste such as copper or silver is used.

In this way, in order to have a coefficient of thermal expansion similar to that of the ceramic element, aluminum with a low thermal expansion Invar material alloy plate,
By metallizing a metal layer selected from metals such as iron and zinc and alloys thereof, the metal having the Invar property and the insulating layer can be sufficiently bonded.

This metal-based substrate can be manufactured by using conventional equipment because it may be a method usually used for manufacturing a conventional aluminum substrate or iron substrate, for example, a method of degreasing with alkali or polishing of a cloth.

Example 1 An alloy Invar plate of 64% iron and 36% nickel having a thickness of 1.0 mm was coated with 100 μm aluminum on both sides by a rolling method. After degreasing this in 5% caustic soda,
An epoxy resin containing alumina powder was applied to one surface of the aluminum foil to a thickness of 100 μm to form an insulating layer. Next, a 35 μm electrolytic copper foil was attached to the insulating layer to prepare a circuit metal (FIG. 1 (a)). As a result of the drop impact test, the holding power was 10 times or more.

Example 2 A carbon steel (JIS standard spcc iron plate) plate of 1.0 mm on one side of the Invar plate used in Example 1 was clad by rolling. This was washed with 1,1,1, -trichloroethane, and the surface was ground by polishing with a cloth. Polyimide film is adhered to the carbon steel surface side with butyral and 35
A μm electrolytic copper foil was attached. This was heat-treated and then etched to produce a circuit metal substrate (FIG. 1 (b)). As a result of the drop impact test, the holding power was 10 times or more.

Example 3 An invar plate made of an alloy of 58% iron and 42% nickel having a thickness of 1.0 mm was rolled with 100 μm aluminum.
This was washed with 1,1,1-trichloroethane and subjected to surface treatment by polishing the cloth, and a prepreg of 100 μm glass cloth impregnated with epoxy resin as an insulating layer was attached to the aluminum surface side of the surface. A 35 μm electrolytic copper foil was adhered on the top to prepare a circuit metal substrate (FIG. 1b). As a result of a drop impact test, it had a holding power of 10 times or more.

Example 4 Both sides of the Invar plate used in Example 1 were electrolyzed to 30
μm zinc was applied. This was washed with 1,1,1-trichloroethane, and then the surface was ground by polishing with a cloth. 80 μm of a phenol resin was applied to this surface as an insulating layer, 35 μm of electrolytic copper foil was further adhered thereto, heat-treated, and etched to prepare a circuit metal substrate (FIG. 1 (a)). As a result of the drop impact test, the holding power was 10 times or more.

Example 5 Zinc was plated to a thickness of 20 μm on both surfaces of the Invar plate used in Example 1 by a melting method. This was washed with 1,1,1-trichloroethane and then the surface was ground by polishing with a cloth. Silicon resin was applied to this surface as an insulating layer in a thickness of 80 μm, a 35 μm electric field copper foil was further adhered thereto, heat-treated, and etched to prepare a metal substrate for a circuit (FIG. 1 (a)). As a result of the drop impact test, the holding power was 10 times or more.

Comparative Example 1 A 1.0 mm thick copper clad invar plate having a copper foil layer of 200 μm on both sides was subjected to blackening treatment, and an epoxy resin containing alumina powder was coated on the treated surface to a thickness of 100 μm to form an insulating layer. A 35 μm electrolytic copper foil was attached to the layer to prepare a metal substrate for a circuit (FIG. 2). Result of drop impact test 1
The insulating layer and the copper clad invar plate were peeled off at the time.

Comparative Example 2 A metal substrate for a circuit was prepared in the same manner as in Comparative Example 1 except that the surface was ground by rag cloth polishing after washing with 1,1,1-trichloroethane instead of the blackening treatment. (Fig. 2). As a result of a drop impact test, the insulating layer and the copper clad invar plate were separated at one time.

Drop impact test measurement method The test method was as follows. Solder a copper block of 13 mm x 13 mm x 2 mmt on the 44 mm x 68 mm board obtained in the example and the comparative example.
Each piece was dropped on a flat plate of oak wood having a thickness of 30 mm from a height of 75 cm, with the flat surface facing down, and evaluation was made by peeling of the copper block.

(Effects of the invention) As described above, the present invention is to control the alloy composition of iron and nickel of the Invar material, and by providing a specific metal on at least one surface of the Invar material, a thermal expansion coefficient similar to that of the ceramic element. It has the effect of becoming a metallic material having heat conductivity and having good adhesion between the Invar material and the organic insulating layer.

[Brief description of drawings]

1 (a) and 1 (b) are sectional views of the substrate of the present invention, and FIG. 2 is a sectional view of a comparative example. 3 (a) and 3 (b) are a sectional view and a plan view of the impact test sample. Reference numeral 1 ... Invar material, 2 ... Copper foil, 3 ... Adhesive strength improving metal layer, 4 ... Insulating layer, 5 ... Circuit, 6 ... Copper block, 7 ...
substrate.

Claims (1)

[Claims] 1. An invar plate is provided with at least one surface of one layer selected from aluminum, iron, zinc, and alloys containing these as a main component, and a wiring circuit is provided thereon with an insulating layer interposed therebetween. A printed circuit metal board characterized by.