JPH06188531A - Low expansion metal foil and laminate for printed circuit - Google Patents

Abstract

PURPOSE:To provide a laminate for printed board having an insulation layer applied with a metal foil to at least one side thereof in which coefficient of thermal expansion is lowered by employing a low expansion metal foil obtained by applying a selica based layer having low expansion coefficient to the roughened surface of a metal foil. CONSTITUTION:Dissolution silica and titanium oxide are admixed with water glass and alcohol and added with a small quantity of epoxy resin, as a binder, to produce a solution which is applied to the roughened surface of an electrolytic copper foil and eventually dried to provide an inorganic layer having low expansion coefficient thus producing a copper foil having low expansion coefficient. On the other hand, a glass cloth is impregnated with a heat resistant epoxy resin varnish and dried to produce a semihardened prepreg. Copper foils having low expansion coefficient are then applied to the opposite sides each of three prepregs which are then sandwiched by stainless steel plates and hot pressed integrally thus producing a low expansion laminate for printed circuit. The layer having low expansion coefficient restraings expansion of the laminate thus lowerings overall coefficient of thermal expansion of the circuit board in the surface direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for mounting a semiconductor device in a package form having a small coefficient of thermal expansion such as CLCC and TSOP, and has excellent through-hole reliability, and a laminated board for a printed circuit and a low expansion metal foil used for the same. Regarding

[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 printed circuits in industrial equipment, that is, a substrate such as glass cloth is heated and impregnated with a thermosetting resin and dried to form a copper foil. The copper-clad laminate formed by press-fitting is not necessarily suitable for mounting semiconductor devices such as CLCC and TSOP.

The CLCC is made of ceramic as a package material, has a coefficient of thermal expansion greatly different from that of a glass-based epoxy laminate generally used for mounting, and has no lead for absorbing thermal stress in the package. Also, TSOP
Even if the package material is epoxy encapsulant, the amount of epoxy encapsulant on the silicon chip is small, the overall coefficient of thermal expansion is much smaller than the conventional package, and the leads are also very short. . Therefore, when both are mounted on a glass-based epoxy laminate, there is a drawback that solder crack defects 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, the thermal expansion coefficient of the aramid paper cloth laminate is 6 to 8 ppm in the surface direction.
However, the coefficient of thermal expansion in the thickness direction (Z direction) is extremely large at 130 to 300 ppm / K, and there is a problem in the through hole reliability of the substrate.

There are also known ceramic composite substrates, which are known such as 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. There is. 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, so there is a limit to productivity due to problems with the thermal spraying method. The equipment is very expensive.
Since the latter is processed into a ceramic substrate itself, its size is limited, mass production is difficult, and it is difficult to supply it at low cost.

[0006]

The present invention has been made in view of the above circumstances, and has a low coefficient of thermal expansion, does not cause solder cracks, is excellent in through-hole reliability, and is low-cost CLCC, An object of the present invention is to provide a low expansion metal foil and a laminate for a printed circuit, which are optimum for mounting a semiconductor device such as TSOP.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the inventors of the present invention can achieve the above object by providing a silica-based low expansion coefficient layer on a metal foil. The present invention has been completed and the present invention has been completed.

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, the silica foil has a low expansion coefficient on the rough surface of the metal foil having at least one surface roughened as the metal foil. A low-expansion metal foil having a low-expansion metal foil and a low-expansion metal foil used for the same are provided.

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 is used as the insulating layer. As the substrate 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, and the like may be used alone or in combination. You can

The thermosetting resin used for impregnating the substrate in the present invention is a thermosetting resin whose viscosity is adjusted so that the substrate is easily impregnated. 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 varnish is prepared by adding a solvent to the thermosetting resin, and a varnish can be blended with a filler having a high thermal conductivity or a low dielectric constant as long as the purpose of the present invention is not impaired. Examples of the filler having a high thermal conductivity include aluminum hydroxide and silica, and examples of the filler having a low dielectric constant 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 manufacture a laminated board for a printed circuit.

As the low-expansion metal foil of the present invention, a metal foil used for printed circuits in which at least one surface is roughened is provided with a silica-based low expansion coefficient layer on the rough surface.
Copper foil, aluminum foil, or the like is used as the metal foil here. The method of forming the low expansion coefficient layer is not particularly limited, but as a method suitable for industrial production, a mixture of silica fine particles and an inorganic or organic binder and a solvent is continuously dropped or sprayed on a metal foil. A method is suitable in which the coating amount is controlled by the above method, the coating amount is controlled by a squeegee or knife coater provided in front of the coating method, and baking is performed in a drying furnace. However, an organic binder 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. The low-expansion metal foil thus produced can be combined with a prepreg and integrally molded by heating and pressurization to produce a low-expansion printed circuit laminate.

The printed circuit board thus manufactured can be used as a circuit board having a small coefficient of thermal expansion in the plane direction, which is suitable for mounting a semiconductor device such as CLCC or TSOP.

[0014]

The laminated board for a printed circuit according to the present invention uses the low-expansion metal foil on the surface of the laminated board, and the low expansion coefficient layer suppresses the expansion of the laminated board portion, and the surface direction thermal expansion of the entire circuit board. The rate can be reduced. Further, the thermal expansion coefficient in the thickness direction as a whole could be reduced by adding the low expansion coefficient layer also 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. The printed circuit laminate of the present invention has a coefficient of thermal expansion of 13 to 15 ppm / K in the plane direction and 50 in the thickness direction in the temperature range of 25 to 125 ° C.
By adjusting to ~ 60 ppm / K, CLCC, TS
Through-hole reliability could be improved by matching the thermal expansion coefficient in the surface direction with the semiconductor device such as OP.

[0015]

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

EXAMPLE On a rough surface of an electrolytic copper foil having a thickness of 18 μm, fused silica and titanium oxide were kneaded with water glass and alcohol, and a solution containing a small amount of an epoxy resin as an organic binder was applied and dried to give a thickness of 0.1. An inorganic low expansion coefficient layer of mm was provided to manufacture a low expansion coefficient copper foil. A glass cloth with a thickness of 0.18 mm was impregnated with a heat-resistant epoxy resin varnish and dried, and the prepreg obtained as a semi-cured state was laminated with the low expansion coefficient copper foil on both sides, sandwiched between stainless steel plates, and integrated with heating and pressure A 0.8 mm thick low-expansion printed circuit board laminate was manufactured by molding.

Comparative Example 1 A prepreg was prepared by impregnating and drying a heat-resistant epoxy resin varnish, Technora (trade name, manufactured by Teijin Ltd.), a para-aromatic polyamide paper substrate having a fiber plane orientation of 0.1 mm. Eight layers are stacked, and the thickness is 18μm on both sides.
The electrolytic copper foil was placed, sandwiched between stainless steel plates, and integrally laminated by hot pressing to manufacture a 0.8 mm-thick aramid paper epoxy printed circuit laminate.

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

The printed circuit laminates manufactured in Examples and Comparative Examples 1 and 2 were tested for thermal expansion coefficient, TSOP connection stability, and through-hole reliability. The results are shown in Table 1. The present invention is excellent in all properties, and the effect of the present invention was confirmed.

[0020]

[Table 1] * 1: Thermal expansion coefficient measurement range CTEα ₁ 25 to 125 ° C, *
2: The test cycle condition for TSOP connection stability and through hole reliability is an air heat cycle of -40 ° C ・ 1h to 150 ° C ・ 1h.

[0021]

As is clear from the above description and Table 1, the laminated board for printed circuits and the low expansion metal foil of the present invention have a small coefficient of thermal expansion, no solder cracks, low cost, and through. Excellent in hole reliability, CL
It is suitable for mounting semiconductor devices such as CC and TSOP.

Claims (2)

[Claims] 1. A printed circuit laminated board having a metal foil provided on at least one surface of an insulating layer, wherein the metal foil is:
A laminated board for a printed circuit, comprising a low expansion metal foil having a silica-based low expansion coefficient layer provided on a rough surface of a metal foil having at least one surface roughened. 2. A low-expansion metal foil, characterized in that a silica-based low expansion coefficient layer is provided on a rough surface of a metal foil having at least one surface roughened.