JP3596899B2 - Low expansion metal foil and laminate for printed circuit - Google Patents

Description

【００２３】
【発明の効果】
以上の説明および表１から明らかなように、本発明のプリント回路用積層板および低膨張率金属箔は、熱膨張率が小さく、半田クラックの発生がなく低コストで、スルーホール信頼性にも優れたもので、ＣＬＣＣ、ＴＳＯＰ等の半導体装置の実装に最適なものである。[0001]
[Industrial applications]
INDUSTRIAL APPLICABILITY The present invention is suitable for mounting a semiconductor device having a small coefficient of thermal expansion such as a package of a ceramic led chip carrier (CLCC) or a thin small outline package (TSOP), and a printed circuit excellent in through-hole reliability. And a low-expansion metal foil used therefor.
[0002]
[Prior art]
Technological innovation in recent years has been remarkable, and downsizing of electronic devices has never stopped. This is due to the technology of high-density mounting, high integration of semiconductors, and miniaturization of semiconductor packages. Semiconductor devices such as CLCC and TSOP, which have smaller package sizes than semiconductor chip sizes, have begun to be used frequently. However, conventionally, copper-clad laminates that have been used as printed circuit boards for industrial equipment, that is, prepregs and copper foils in which a base material such as glass cloth is impregnated with a thermosetting resin such as an epoxy resin and dried. Is not necessarily suitable for mounting semiconductor devices such as CLCC and TSOP.
[0003]
CLCC has a package material of ceramic, has a significantly different coefficient of thermal expansion from a glass-based epoxy laminate used for mounting, and does not have a lead for absorbing thermal stress. Even if the package material is epoxy encapsulant, TSOP has a small amount of epoxy encapsulant for the silicon chip, the overall coefficient of thermal expansion is very small compared to the conventional package, and the leads are very short. . Therefore, when both are mounted on a glass-based epoxy laminated board, there is a defect that solder cracking failure frequently occurs due to thermal expansion coefficient mismatch.
[0004]
Therefore, an aramid-based epoxy laminate may be used as a laminate having a small coefficient of thermal expansion in the plane direction (XY directions). However, aramid fabric laminates are very difficult to machine and expensive and unsuitable for practical use. Aramid paper cloth laminates have a very low coefficient of thermal expansion in the plane direction of 6 to 8 ppm / K, but have a very large coefficient of thermal expansion in the thickness direction (Z direction) of 130 to 300 ppm / K. There was a problem with the reliability of the through hole of the substrate.
[0005]
There is a so-called ceramic composite substrate. There are known a glass-epoxy laminate having a ceramic layer provided on a part thereof, and a ceramic substrate having a glass-epoxy prepreg disposed on a surface thereof. Although its properties are very good, the former has a limited productivity due to problems in the thermal spraying method because it is manufactured by spraying ceramics onto the surface of the substrate or copper foil by thermal spraying. The equipment is very expensive. The latter is disadvantageous in that it is processed into the ceramic substrate itself, so that its size is limited, mass production is difficult, and supply at low cost is difficult.
[0006]
The present invention has been made in view of the above circumstances, has a low coefficient of thermal expansion, has no occurrence of solder cracks in a mounted product, has excellent through-hole reliability, and is low-cost, and can be used for semiconductors such as CLCC and TSOP. An object of the present invention is to provide a low-expansion metal foil and a laminate for a printed circuit, which are most suitable for mounting the device.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, it has been found that the above object can be achieved by providing a metal foil with a low expansion coefficient layer in which an inorganic filler is mixed with a specific polyimide binder. The present invention has been completed.
[0008]
That is, the present invention
In a printed circuit laminate in which a metal foil is provided on at least one surface of an insulating layer, as the metal foil, a condensed cyclized polyimide-based polyimide film is formed on the roughened surface of the metal foil whose surface in contact with the insulating layer is roughened. A laminated board for a printed circuit and a low-expansion metal foil used therefor, characterized by using a low-expansion metal foil provided with a low-expansion coefficient layer formed by mixing an inorganic filler into a binder.
[0009]
Hereinafter, the present invention will be described in detail.
[0010]
As the insulating layer of the laminate for a printed circuit according to the present invention, a prepreg is used as an insulating layer by impregnating and drying a base material with a thermosetting resin. As the base material used here, all materials used for thermosetting resin laminates such as glass cloth and glass paper can be used. In addition to these substrates, woven fabrics and nonwoven fabrics made of synthetic fibers (aramid, fluororesin, polyimide resin) and the like, woven fabrics and mats made of metal fibers, and the like can be used alone or in combination. Can be.
[0011]
The thermosetting resin used for impregnating the base material in the present invention is a resin whose viscosity has been adjusted so that the base material can be easily impregnated by adding a solvent. As specific thermosetting resins, epoxy resins, polyimide resins, modified resins thereof and the like are preferably used, but are not particularly limited to these. The thermosetting resin varnish to which the solvent has been added may contain 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 adversely affected. 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 a fluororesin powder and hollow glass beads. In addition, talc, calcium carbonate, and the like can be appropriately added as needed. The varnish thus obtained is impregnated into the above-described substrate and dried to form a prepreg, and the prepreg can be used as an insulating layer to produce a printed circuit laminate.
[0012]
The low expansion metal foil of the present invention has a low expansion coefficient layer in which an inorganic filler is mixed with a condensed cyclized type polyimide binder on a rough surface of a metal foil having at least one surface roughened, which is used for a printed circuit. It is provided. Here, a copper foil, an aluminum foil or the like is used as the metal foil. Further, as the condensed cyclized polyimide binder used here, a polyimide obtained by subjecting an acid anhydride of an acid component and a diamine of a diamine component to a condensation reaction can be widely used. Usually, treatment is performed in the state of a polyamic acid resin which is a precursor thereof, and cyclization is performed by heating or the like. An inorganic filler is mixed with the polyamic acid resin. The inorganic filler used here has a low expansion coefficient , and is not particularly limited. For example, silica, alumina and the like are preferable, and these can be used alone or as a mixture.
[0013]
The method of forming the low expansion coefficient layer is not particularly limited, but as a method suitable for industrial production, a polyamic acid resin solution mixed with an inorganic filler dissolved in a solvent is continuously dropped or sprayed on a metal foil. In this method, the amount of coating is controlled by a squeegee or a knife coater provided in advance, and the imidization is performed by firing in a drying furnace.
[0014]
The low-expansion metal foil thus manufactured can be combined with a prepreg and integrally molded by heating and pressing to produce a low-expansion printed circuit laminate. This printed circuit board can be suitably used as a circuit board for mounting a semiconductor device having a small coefficient of thermal expansion in the plane direction such as CLCC and TSOP.
[0015]
[Action]
The laminated board for a printed circuit of the present invention uses a low-expansion metal foil in which an inorganic filler is mixed with a condensed cyclized polyimide binder on the surface of the laminated board, so that the low-expansion layer suppresses expansion of the insulating layer portion. Thus, the coefficient of thermal expansion in the surface direction of the entire circuit board can be reduced. Further, the addition of the low expansion coefficient layer also in the thickness direction could reduce the thermal expansion coefficient as a whole. Reducing the expansion with the low expansion metal foil can exert a greater effect when manufacturing a multilayer board. That is, as the number of layers increases, the ratio of the low expansion coefficient layer to the entire substrate increases, and lower expansion can be achieved in both the surface direction and the thickness direction.
[0016]
The printed circuit laminate of the present invention has a coefficient of thermal expansion in the temperature range of 25 to 125 ° C. of 15 to 20 ppm / K in the plane direction and 30 to 40 ppm / K in the thickness direction, so that CLCC and TSOP can be obtained. The thermal expansion coefficient in the plane direction is matched with that of the semiconductor device, and the reliability of the through hole can be improved.
[0017]
【Example】
EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
[0018]
EXAMPLE A solution obtained by mixing silica powder with an N-methyl-2-pyrrolidone solution of a polyamic acid derived from biphenyltetracarboxylic anhydride and paraphenylenediamine was applied to the roughened surface of an electrolytic copper foil having a thickness of 18 μm and dried. Then, a low expansion coefficient layer having a thickness of 0.10 mm was provided to produce a low expansion copper foil. 0.18mm thick glass cloth impregnated with heat-resistant epoxy resin varnish, dried, three prepregs obtained in a semi-cured state, the above low expansion copper foil laminated on both sides, sandwiched between stainless steel plates, heat and pressure integrated To produce a 0.8 mm thick low expansion laminate for printed circuits.
[0019]
Comparative Example 1
A prepreg is prepared by impregnating and drying a heat-resistant epoxy resin varnish on a 0.1 mm thick para-aromatic polyamide paper base Technora (trade name, manufactured by Teijin Limited) with a fiber plane orientation, and stacking eight prepregs. An 18 μm-thick electrolytic copper foil was placed on both sides, sandwiched between stainless steel plates, and integrally laminated and formed by a heat press to produce a 0.8-mm-thick aramid paper epoxy printed circuit laminate.
[0020]
Comparative Example 2
A laminated board (FR-4 grade) for a 0.8 mm thick general-purpose glass substrate epoxy printed circuit was prepared.
[0021]
The thermal expansion coefficient, TSOP connection stability, and through-hole reliability of the printed circuit laminates manufactured in Examples and Comparative Examples 1 and 2 were tested. The results are shown in Table 1. The present invention was excellent in the balance of each property, and the effect of the present invention was confirmed.
[0022]
[Table 1]

[0023]
【The invention's effect】
As apparent from the above description and Table 1, the printed circuit board and the low expansion coefficient metal foil of the present invention have a low coefficient of thermal expansion, no solder cracks, low cost, and high through-hole reliability. It is excellent and is most suitable for mounting semiconductor devices such as CLCC and TSOP.

Claims (2)

In a printed circuit laminate in which a metal foil is provided on at least one side of a prepreg obtained by impregnating and drying a thermosetting resin on a fiber base material, a surface of a side in contact with the insulating layer is roughened as the metal foil. A laminated board for a printed circuit, comprising: a low-expansion metal foil having a low-expansion coefficient layer formed by mixing a condensed-cyclized polyimide binder with an inorganic filler on a rough surface of the metal foil thus obtained. In the low-expansion metal foil used for integrated molding of the printed circuit laminate in combination with the prepreg, at least one surface of the roughened metal foil is mixed with an inorganic filler in a condensed cyclized polyimide binder. A low-expansion metal foil provided with a low-expansion coefficient layer.