JPH06244515A - Low-expansion laminate for printed circuit - Google Patents

Abstract

PURPOSE:To obtain a laminated plate, in which the coefficient of thermal expansion is small and no solder crack occurs in a mounted item and through-hole reliability is excellent, by using a prepreg composed of a base material containing 50% or more para-aromatic polyamide fiber in an insulating layer and also using a low-expansion metal foil provided with an inorganic low- expansion-coefficient layer on the roughened surface of the metal foil. CONSTITUTION:In addition to the use of a prepreg composed of a base material containing 50% or more para-aromatic polyamide fiber, a metal foil is provided with a low expansion-coefficient layer. The prepreg obtained by impregnating the base material with thermosetting resin and drying the material is used as insulating layer; and paper, nonwoven fabric and mats containing 50% or more para-aromatic polyamide fiber are cited as the base material to be used. Also, the roughened surface of the metal foil obtained by roughening one surface of the metal foil to be used for a printed circuit and then provided with the inorganic low-expansion-coefficient layer is used as a low-expansion metal foil. A copper foil, aluminum foil, etc., are used as the metal foil, and the low expansion-coefficient layer is obtained when the metal foil is thermally sprayed with inorganic particles and baked by a drying furnace.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a package form of CL.
CC (Ceramic Leaded Chip Carrier), TSOP (Th
The invention relates to a low expansion laminated board for a printed circuit, which is suitable for mounting a semiconductor device having a small coefficient of thermal expansion such as in a Small Outline Package) and has excellent through-hole reliability.

[0002]

2. Description of the Related Art Recent technological innovation has been remarkable, and downsizing of electronic devices has never stopped. This is due to the technology of high-density mounting technology, high integration of semiconductor, and miniaturization of semiconductor package, and CLC whose package size is smaller than semiconductor chip size.
Semiconductor devices such as C and TSOP are being 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 is impregnated with a thermosetting resin and dried, and a prepreg and a copper foil are integrated under heat and pressure. The copper-clad laminate obtained by molding is not necessarily suitable for mounting semiconductor devices such as CLCC and TSOP.

The packaging material of CLCC is ceramic, and its coefficient of thermal expansion is largely different from that of a glass-based epoxy laminated board used for mounting, and it has no lead for absorbing thermal stress. Even if the package material is epoxy encapsulant, TSOP has a small amount of epoxy encapsulant with respect to the silicon chip, the overall coefficient of thermal expansion is much smaller than the conventional package, and the lead 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. The thermal expansion coefficient of the aramid paper cloth laminate is 6 to 10 p in the surface direction.
Although it was kept very low at pm / K, the coefficient of thermal expansion in the thickness direction (Z direction) was extremely large at 100 to 300 ppm / K, and there was a problem in the through hole reliability of the substrate.

[0005]

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, is excellent in through-hole reliability, and is low in cost. In addition, it is an object of the present invention to provide a low expansion laminate for a printed circuit, which is most suitable for mounting a semiconductor device such as CLCC or TSOP.

[0006]

Means for Solving the Problems As a result of intensive studies aimed at achieving the above object, the present inventors have decided to use a prepreg made of a base material containing 50% or more of para aromatic polyamide fiber. In addition, the inventors have found that the above object can be achieved by providing a metal foil with a low expansion coefficient layer, and completed the present invention.

That is, according to the present invention, in a laminate for a printed circuit in which a metal foil is provided on at least one surface of an insulating layer, a thermosetting resin is added to a base material in which the insulating layer contains 50% or more of para aromatic polyamide fiber. A low expansion laminate for a printed circuit, comprising: an impregnated prepreg; and a low expansion metal foil in which an inorganic low expansion layer is provided on a rough surface of a metal foil having at least one surface roughened.

The present invention will be described in detail below.

As the insulating layer of the low expansion laminate for a printed circuit according to the present invention, a base material is impregnated with a thermosetting resin and dried to form a prepreg as an insulating layer. Examples of the substrate used here include papers, non-woven fabrics and mats containing 50% or more of para aromatic polyamide fibers, and these can be used alone or in combination. In addition to these base materials, woven cloths, non-woven cloths made of glass, cellulose, synthetic fibers and the like, woven cloths made of metal fibers and mats can be used in combination with the above-mentioned base materials.

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. The thermosetting resin varnish containing a solvent may be mixed with a colorant, a reinforcing agent, and a filler having a high thermal conductivity or a low dielectric constant, 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 base material and dried to form a prepreg, and this prepreg can be used as an insulating layer to manufacture a low expansion laminate for a printed circuit.

As the low-expansion metal foil of the present invention, a metal foil used for printed circuits, which has at least one surface thereof roughened, is provided with an inorganic 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, thermal spraying of inorganic fine particles onto a metal foil, or a mixture of inorganic fine particles and an inorganic or organic binder and a solvent is used. A method is suitable in which the metal foil is continuously applied by dripping or spraying, the coating amount is controlled by a squeegee or knife coater provided in front of the metal foil, and baking is performed in a drying furnace. The latter coating method is cheaper than the former thermal spraying method, and the productivity is excellent. However, it should be noted that the organic binder has a large expansion coefficient, and if the amount of the organic binder is increased, the original low expansion property is impaired. The low-expansion metal foil thus produced can be combined with the prepreg and integrally molded by heating and pressurization to produce a low-expansion low-expansion laminated plate for a printed circuit.

In the present invention, the inorganic fine particles used for forming the low expansion coefficient layer are not particularly limited. In particular, materials having a low expansion coefficient and suitable for this use include fused silica, cordierite, hexagonal boron nitride, and mullite, which can be used alone or in combination.

The low expansion laminated board for a printed circuit manufactured as described above can be suitably used as a circuit board for mounting a semiconductor device such as CLCC or TSOP having a small coefficient of thermal expansion in the surface direction.

[0014]

[Function] Para-aromatic polyamide fibers have a negative coefficient of thermal expansion in the spinning direction, but since the coefficient of thermal expansion in the radial direction of the fiber is positive, if the fiber orientation is deviated in the plane direction during papermaking, the coefficient of thermal expansion in the plane direction Is largely on the negative side, but a substrate having a large coefficient of thermal expansion in the thickness direction can be obtained. The laminate obtained by impregnating the base material with a resin and laminating the laminate has a small coefficient of thermal expansion in the plane direction, but has a larger coefficient of thermal expansion in the thickness direction. This is a result of the expansion stress of the matrix resin of the laminated plate in which the thermal expansion in the surface direction was suppressed in addition to the behavior of the base material, concentrated in the thickness direction.
In order to keep the thermal expansion coefficient of the para-aromatic polyamide fiber base material in the thickness direction small, the chemical structure of the resin and the spinning method should be changed. There are means such as suppressing, mixing with fibers other than the para-aromatic polyamide fibers, and changing the quality and amount of the papermaking binder. However, both
At the same time, it is a means of suppressing the advantage of negative thermal expansion in the plane direction, and impairs the low expansion coefficient in the plane direction.

Therefore, in the present invention, an inorganic low expansion coefficient layer is introduced in the thickness direction as a means for suppressing the thermal expansion coefficient in the thickness direction to be small while utilizing the low expansion coefficient in the plane direction of the para-aromatic polyamide fiber. Is. That is, the para-aromatic polyamide fiber base material is used to suppress the thermal expansion in the surface direction, and the expansion coefficient in the thickness direction is suppressed by introducing an inorganic low expansion coefficient layer. It was possible to produce a laminate for a printed circuit board having a coefficient of expansion.

The low expansion laminate for a printed circuit according to the present invention comprises:
The coefficient of thermal expansion in the temperature range of 25 to 125 ° C is 4 to
By adjusting 10 ppm / K and 40-80 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 through hole reliability. .

[0017]

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 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 epoxy resin as an organic binder was applied and dried,
An inorganic low expansion coefficient layer having a thickness of 0.10 mm was provided to produce a low expansion copper foil. Eight prepregs obtained by impregnating and drying a heat-resistant epoxy resin varnish on a Surmount (trade name, made by DuPont) of 0.07 mm thick fiber randomly oriented para-type aromatic polyamide paper base material, in a semi-cured state, both sides The above-mentioned low expansion copper foil was overlaid, sandwiched between stainless steel plates, and integrally molded by heating and pressuring to manufacture a 0.8 mm-thick low expansion laminate for a printed circuit.

Example 2 In Example 1, a fiber random orientation of 0.07 mm in thickness was used in place of Surmount (trade name of DuPont) of a para-aromatic polyamide paper substrate having a thickness of 0.07 mm, and a plane orientation of fibers was 0.1 mm in thickness. A 0.8 mm-thick low expansion laminate for a printed circuit was manufactured in the same manner as in Example 1 except that Para-Aromatic Polyamide Paper-based Technora (trade name, manufactured by Teijin Ltd.) was used. Comparative Example 1 11 prepregs used in Example 1, 18 μm thick on both sides
The electrolytic copper foil of No. 1 was placed between the stainless steel plates and laminated by hot pressing to produce a 0.8 mm-thick aramid paper epoxy printed circuit laminate.

Comparative Example 2 Eight prepregs used in Example 2, 18 μm thick on both sides
The electrolytic copper foil of No. 1 was placed between the stainless steel plates and laminated by hot pressing to produce a 0.8 mm-thick aramid paper epoxy printed circuit laminate.

Comparative Example 3 A glass cloth having a thickness of 0.18 mm was impregnated with an epoxy resin varnish and dried, and three low-expansion copper foils used in the above-mentioned examples were superposed on both surfaces of three prepregs obtained in a semi-cured state. It is sandwiched between the plates and integrally laminated by a heat press.
A 0.8mm thick low expansion laminate for glass epoxy printed circuit was manufactured.

Comparative Example 4 A 0.8 mm-thick general-purpose glass substrate epoxy printed circuit laminate (FR-4 grade) was prepared.

Regarding the printed circuit laminates produced in Examples 1-2 and Comparative Examples 1-4, the coefficient of thermal expansion, TSOP
The connection stability and the through hole reliability were tested, and the results are shown in Table 1. The present invention is excellent in the balance of each characteristic, and the effect of the present invention was confirmed.

[0024]

[Table 1] * 1: Thermal expansion coefficient measurement range CTE α1 25 to 125 ° C. * 2: Both TSOP connection stability and through-hole reliability test conditions are an air heat cycle of -40 ℃ ・ 1h to 150 ℃ ・ 1h.

[0025]

As is apparent from the above description and Table 1, the low expansion laminate for a printed circuit according to the present invention has a small coefficient of thermal expansion, does not cause solder cracks, is low in cost, and has high reliability of through holes. Also excellent, CLCC, TSOP
It is suitable for mounting semiconductor devices such as.

Claims (1)

[Claims] 1. A prepreg obtained by impregnating a thermosetting resin on a base material in which an insulating layer contains 50% or more of a para-aromatic polyamide fiber in a printed circuit laminate having a metal foil provided on at least one surface of the insulating layer. A low-expansion laminate for a printed circuit, comprising a low-expansion metal foil in which an inorganic low-expansion layer is provided on a rough surface of a metal foil having at least one surface roughened.