JPH06188331A - Low-expansion metal foil and laminated board for printed circuit - Google Patents

Abstract

PURPOSE:To reduce the coefficient of thermal expansion in a face direction of a circuit board as a whole by a method wherein a low-expansion metal foil in which an inorganic low-rate-of-expansion layer has been formed via an adhesive layer is used as a metal foil. CONSTITUTION:A foil in which an inorganic low-rate-of-expansion layer has been formed, via an adhesive layer, on the rough face of a metal foil which is used for a printed circuit and at least one face of which has been roughened is used as a low-expansion metal foil. At this time, a copper foil, an aluminum foil or the like is used for the metal foil. In addition, for the adhesive layer, a metal foil, provided with a mixture-type adhesive, which is used mainly in a paper-based phenol laminated board for civil products may be used as an intermediate raw material, or an adhesive layer which is used by a combination and which is the same as a prepreg matrix resin may be used. Thereby, the low-rate-of-expansion layer restrains the expansion of the part of an insulating layer, and the coefficient of thermal expansion in a face direction of a circuit board as a whole can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a package form of CL.
The present invention relates to a printed circuit laminate which is suitable for mounting a semiconductor device having a small coefficient of thermal expansion, such as CC and TSOP, and also has excellent through-hole reliability, and a low expansion metal foil used therein.

[0002]

2. Description of the Related Art Recent technological innovation has been remarkable, and downsizing of electronic devices has never stopped. It is based on the technology of high-density packaging, high integration of semiconductor, and miniaturization of semiconductor package. The package size is smaller than the semiconductor chip size.
Semiconductor devices such as SOPs are beginning to be widely used. However, a copper clad laminate that has been used as a laminate for a printed circuit of industrial equipment, that is, a base material such as glass cloth impregnated with a thermosetting resin and dried, and a copper foil are heated and pressed. The copper-clad laminate formed integrally is not necessarily suitable for mounting semiconductor devices such as CLCC and TSOP.

The CLCC has a package material of ceramic, has a coefficient of thermal expansion largely different from that of a glass-based epoxy laminate used for mounting, and has no lead for absorbing thermal stress. Further, TSOP has a small amount of epoxy encapsulant with respect to a silicon chip even if the package material is an epoxy encapsulant, and the overall coefficient of thermal expansion is much smaller than that of the conventional package, and the lead is Is also very short. Therefore, when both are mounted on a glass-based epoxy laminate, there is a drawback that defective solder cracks frequently occur due to mismatch of thermal expansion coefficients.

Therefore, an aramid-based epoxy laminate is sometimes used as a laminate having a small coefficient of thermal expansion in the plane direction (XY direction). However, the aramid cloth laminate is very difficult to machine, expensive and not suitable for practical use. Also,
Aramid paper cloth laminate has a coefficient of thermal expansion in the plane direction of 6-8p
pm / K is very low, but in the thickness direction (Z
Direction) has a very large coefficient of thermal expansion of 130-300ppm / K,
There was a problem with the through hole reliability of the board.

There is also a ceramic composite substrate. Known examples include those in which a ceramic layer is provided on a part of a glass / epoxy laminate, and those in which a glass / epoxy prepreg is arranged on the surface of a ceramic substrate. Although its characteristics are extremely excellent, the former is manufactured by spraying ceramics onto the surface of the substrate or copper foil by a thermal spraying method, which limits productivity due to problems with the thermal spraying method. The equipment is very expensive. The latter has the drawback that the size is limited because it is processed into a ceramic substrate itself, mass production is difficult, and low-cost supply is difficult.

Therefore, the present inventors have proposed a low-expansion copper foil in which an inorganic low-expansion layer is provided on a rough surface of a copper foil, and a low-cost printed circuit laminate using the same, which has a small coefficient of thermal expansion. did. However, there is a drawback that the adhesion between the copper foil and the inorganic low expansion coefficient layer is poor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has a small coefficient of thermal expansion, does not cause solder cracks in a mounted product, and has excellent adhesiveness and through-hole reliability. Moreover, the cost is low, CLCC, TSO
An object of the present invention is to provide a low expansion metal foil and a laminated board for a printed circuit suitable for mounting a semiconductor device such as P.

[0008]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have found that an inorganic low expansion coefficient layer is provided on a metal foil via an adhesive layer.
The inventors have found that the above objects can be achieved and completed the present invention.

That is, according to the present invention, in a laminated board for a printed circuit in which a metal foil is provided on at least one surface of an insulating layer, inorganic fine particles are provided on the rough surface of a metal foil having at least one surface roughened via an adhesive layer. A low-expansion metal foil having a low-expansion coefficient layer is used, and a low-expansion metal foil used for the same is used for a printed circuit laminate.

The present invention will be described in detail below.

As the insulating layer of the laminate for a printed circuit of the present invention, a prepreg obtained by impregnating a base material with a thermosetting resin and drying it is used as the insulating layer. As the base material used here, all those used for the thermosetting resin laminated plate such as glass cloth and glass paper can be used. In addition to these base materials, woven and non-woven fabrics made of synthetic fibers (aramid, fluororesin, polyimide resin) and the like, woven fabrics and mats made of metal fibers, etc. may be used alone or in combination. be able to.

The thermosetting resin used for impregnating the substrate in the present invention has a viscosity adjusted so that the substrate is easily impregnated with a solvent. As specific thermosetting resins, epoxy resins, polyimide resins and modified resins thereof are preferably used, but the thermosetting resins are not particularly limited thereto. A filler having a high thermal conductivity or a low dielectric constant can be blended with the solvent-added thermosetting resin varnish as long as the object of the present invention is not impaired.
Examples of the high thermal conductivity filler include aluminum hydroxide and silica, and examples of the low dielectric constant filler include fluororesin powder and hollow glass beads. If necessary, talc, calcium carbonate, etc. may be appropriately mixed. The varnish thus obtained is impregnated into the above-mentioned substrate and dried to form a prepreg, and the prepreg can be used as an insulating layer to produce a laminated board for a printed circuit.

The low-expansion metal foil of the present invention comprises a metal foil used for a printed circuit, at least one surface of which is roughened, and an inorganic low expansion coefficient layer provided on the rough surface of the metal foil via an adhesive layer. To use. Copper foil, aluminum foil, or the like is used as the metal foil here. As the adhesive layer used here, a metal foil with a mixed adhesive, which is mainly used for a paper-based phenol laminated plate for consumer use, may be used as an intermediate raw material, or the same as the matrix resin of the prepreg used in combination. Any one may be used, and it is not particularly limited and can be widely used. The method for forming the adhesive layer is not particularly limited, but industrially, the adhesive is continuously dropped onto the metal foil or coated by spraying, and the coating amount is provided by a squeegee or knife coater provided in front of it. A method of controlling the temperature and firing in a drying furnace is suitable.

The method of forming the low expansion coefficient layer is not particularly limited, but as a method suitable for industrial production, a mixture of inorganic fine particles and an inorganic or organic binder and a solvent is continuously added as an adhesive. A suitable method is to coat the layer by dripping or spraying, control the coating amount with a squeegee or knife coater provided in front of the layer, and fire in a drying furnace. However, the organic binder in the low expansion coefficient layer generally has a large expansion coefficient, and if the amount used is increased, the original purpose of low expansion is impaired, so care must be taken. Further, it is preferable that the low expansion coefficient layer is formed continuously with the step of providing the adhesive layer in the previous step and the drying step is performed at one time because the number of steps and the energy cost required for the drying furnace can be reduced.

The low-expansion metal foil thus produced can be combined with a prepreg and integrally molded under heating and pressure to produce a low-expansion printed circuit board laminate. This printed circuit laminated board can be suitably used for mounting a semiconductor device such as CLCC or TSOP.

[0016]

In the laminated board for a printed circuit according to the present invention, a low expansion metal foil having an inorganic low expansion coefficient layer provided on a metal foil via an adhesive layer is used. Can be suppressed, and the thermal expansion coefficient in the surface direction of the entire circuit board can be reduced. Also, the thermal expansion coefficient as a whole could be reduced by adding the portion of the low expansion coefficient layer even in the thickness direction. The low expansion due to the low expansion metal foil can exert a greater effect when manufacturing a multilayer board. As the number of layers increases, the ratio of the low expansion coefficient layer to the entire substrate increases, and lower expansion is achieved in both the plane direction and the thickness direction. Further, the adhesive layer is effective in improving the peeling strength of the conductor and ensuring high-density mounting of the substrate by forming a fine circuit.

The laminated board for a printed circuit according to the present invention comprises 25 to 12
Coefficient of thermal expansion in the plane direction of 13 to 15 ppm in the temperature range of 5 ° C
By adjusting / K and 50 to 60 ppm / K in the thickness direction, it was possible to match the coefficient of thermal expansion in the plane direction with the semiconductor devices such as CLCC and TSOP, and to improve the reliability of through holes.

[0018]

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1 On a rough surface of a 35 μm-thick electrolytic copper foil with a mixed adhesive for producing a consumer paper base phenol copper clad laminate, fused silica and titanium oxide were kneaded with water glass and alcohol to prepare an organic solution. A solution containing a small amount of an epoxy resin as a binder was applied and dried to provide an inorganic low expansion coefficient layer having a thickness of 0.1 mm to manufacture a low expansion coefficient copper foil. Heat-resistant epoxy resin varnish was impregnated and dried in 0.18 mm thick glass cloth, and the above-mentioned low expansion coefficient copper foil was placed on both sides of three prepregs obtained in a semi-cured state. A 0.8 mm thick low-expansion printed circuit board laminate was manufactured by molding.

Comparative Example 1 In Example 1, an electrolytic copper foil having a thickness of 35 μm for producing a glass epoxy copper clad laminate without an adhesive layer was used.
A low-expansion printed circuit laminate having a thickness of 0.8 mm was manufactured in the same manner as in.

Comparative Example 2 A laminated board (FR-4 grade) for a general-purpose glass substrate epoxy printed circuit having a thickness of 0.8 mm was prepared.

The printed circuit laminates manufactured in Example 1 and Comparative Examples 1 and 2 were tested for thermal expansion coefficient, TSOP connection stability, through-hole reliability, and peel strength. The results are shown in Table 1. It was shown to. The present invention is excellent in the balance of each characteristic, and the effect of the present invention was confirmed.

[0023]

[Table 1] * 1: coefficient of thermal expansion of the measurement range CTEα ₁ 25~125 ℃ * 2: TSOP connection stability, through-hole reliability of the test cycle conditions is a gas in a heat cycle of -40 ℃ · 1h~150 ℃ · 1h.

[0024]

As is clear from the above description and Table 1, the printed circuit laminate and the low-expansion metal foil of the present invention have a small coefficient of thermal expansion and do not cause solder cracks in the mounted product and thus the through holes. Excellent reliability, CLCC, TS
It is suitable for mounting OP and the like, and in particular, the adhesiveness of the copper foil is high and high-density mounting is possible.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H05K 3/00 R 6921-4E

Claims (2)

[Claims] 1. A low expansion coefficient of inorganic fine particles on a rough surface of a metal foil having a metal foil provided on at least one surface of an insulating layer, the metal foil being roughened on at least one surface via an adhesive layer. A laminated board for a printed circuit, characterized by using a low expansion metal foil provided with layers. 2. A low-expansion metal foil, characterized in that a low-expansion inorganic fine particle layer is provided on the rough surface of a metal foil having at least one surface roughened via an adhesive layer.