Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-08-03
2003-07-22
Eley, Timothy V. (Department: 3723)
Metal working
Method of mechanical manufacture
Electrical device making
C029S847000, C029S851000, C029S852000
Reexamination Certificate
active
06594892
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the production of a resin composite ceramic printed wiring board having an electrical conductive portion (conductive plug) for conduction between both surfaces in a predetermined portion. The resin composite ceramic printed wiring board obtained according to the present invention may be used under vacuum and under a high temperature of more than 300° C., it substantially has no gas passing between both surfaces thereof and it has excellent dimensional accuracy under a high temperature so that it may be suitably used for materials and auxiliary materials used in steps of producing an electronic part for inspection.
PRIOR ART OF THE INVENTION
Ceramic has various excellent physical properties such as a low thermal expansion coefficient, high thermal dissipation properties and electric insulation properties. These excellent physical properties are utilized for producing printed wiring boards and other products for practical uses.
However, ceramic is generally poor in processability. There are required a special device and a highly developed processing technique for using ceramic as a desired part so that thus-obtained product is expensive. As a result, the use of ceramic is greatly limited.
For the above reasons, when a through hole conductive portion is made, there is taken a method comprising making a hole by drilling or punching at a green sheet stage, filling a conductive paste in the hole with a roller or squeegee and then calcining it.
Further, for overcoming a defect that processing after calcination is very difficult, a machinable ceramic having machinability is developed. However, a machinable ceramic is fragile so that its machinability has a limitation. Further, a machinable ceramic generally has a composite structure for imparting itself with machinability, so that it generally has pores. As a result, the machinable ceramic has a defect in that it shows great changes in physical properties due to moisture absorption.
The production process of a multilayer printed wring board includes a build-up process. This process comprises making a hole in, for example, a copper-clad glass epoxy laminate by drilling, forming a through hole, filling the through hole with a resin, curing the filled resin, polishing the filled resin two-dimensionally, carrying out etching to produce a printed wiring board, using the printed wiring board as a core material and carrying out a build-up multilayer formation.
The build-up multilayer formation is performed by bonding sheets of a B-stage film material and copper foils for a multilayer formation to both surfaces of a core material under heat, curing the sheets of a B-stage film material, making a hole with a properly selected device, e.g. a laser, filling the hole by pulse plating or the like to form an electrically conductive portion connecting to wiring on a lower layer, forming printed wiring networks on both surfaces by etching and repeating these steps.
Here, a core material is subjected to several heatings in accordance with the number of build-ups so that the core material needs to endure the above heatings sufficiently. For this reason, for example, a general copper-clad glass epoxy laminate has a limitation on the number of build-ups, and a high heat-resistant polyimide film having a low thermal expansion coefficient can not be used as a material for a multilayer formation. Further, it is also difficult to employ a thin film method which can form a fine printed wiring network when a printed wiring network is formed at a build-up time.
Previously, the present inventors completed a process for the production of a substrate having a high thickness accuracy, which is obtained by slicing a novel resin-impregnated cured ceramic that overcomes a defect of water absorption properties, is improved in machinability and is imparted with impact resistance (JP-A-5-291706, etc.). The present inventors made furthermore studies and completed a metal-foil-clad resin composite ceramic board (JP-A-8-244163, etc.) obtained by bonding metal foils to a resin-impregnated cured ceramic layer.
The present inventors have made diligent studies for application of the above production processes and have reached to the present invention.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for the production of a composite ceramic printed wiring board which has excellent properties such as high airproof properties, a low thermal expansion coefficient, high thermal dissipation properties and etc.
According to the present invention, there is provided a process for the production of a composite ceramic printed wiring board, comprising
(1) making a penetration hole having a diameter of 0.1 to 0.8 mm in a ceramic board having an open porosity of at least 5% and a thickness of 0.1 to 10 mm,
(2) fixing metal (M) to the penetration hole such that the metal (M) penetrates through the penetration hole,
(3) impregnating a heat-resistant resin precursor (R) under vacuum, polymerizing the heat-resistant resin precursor (R) and polishing both surfaces of the resultant board to produce a resin composite ceramic substrate (MRA) having a conductive portion for conduction between both surfaces in a predetermined portion, and
(4) forming printed wiring networks on one or both surfaces of the resin composite ceramic substrate (MRA).
DETAILED DESCRIPTION OF THE INVENTION
In the process for the production of a composite ceramic printed wiring board, provided by present invention, open pores of the ceramic board (A) are impregnated with an organic substance which is solid or may be converted to a solid at room temperatures, and the formation of the hole in the above 1) is performed in the organic substance-impregnated ceramic board. After the formation of a hole, the above organic substance is removed before the impregnation of the thermosetting resin (R) in the above 3). The metal (M) is selected from gold, silver, copper, tin, nickel, and alloys of these metals, a conductive paste containing a powdery material of the metal (M) and an inorganic binder as essential components is used to fill the hole, the binder is dried and cured at a low temperature of 90 to 250° C. and an organic compound is decomposed and removed at a maximum temperature of 1,100° C. or less as required. Otherwise, the metal (M) is a wire or a cross-section multiform wire made of a metal or alloy selected from gold, silver, copper, tin, nickel, and alloys of these metals, or a wire of a low thermal-expansion-coefficient metal, such as Kovar (Fernico) or tungsten, of which the surface is plated with gold, copper, nickel or the like, the wire is inserted through the hole and the inserted wire is fixed through the hole.
The constitution of the present invention will be explained hereinafter.
The ceramic board (A) of the present invention is selected from ceramic boards having an opening porosity of at least 5% by volume, preferably 5 to 35% by volume, an average pore diameter of 0.1 to 10 &mgr;m and a thickness of 0.1 to 10 mm.
Specifically, it includes composite materials having a boron nitride (h-BN) content of 8 to 40% by weight, such as aluminum nitride-boron nitride (AlN-h-BN), aluminum oxide-boron nitride (Al
2
O
3
-h-BN), silicon nitride-boron nitride (Si
3
N
4
-h-BN), zirconium oxide-aluminum nitride-boron nitride (ZrO
2
-AlN-h-BN) and aluminum oxide-zirconium oxide-boron nitride (Al
2
O
3
-ZrO
2
-h-BN) and an inorganic continuously porous body (A) such as &bgr;-silicone carbide porous body (&bgr;-SiC), silicone oxide-aluminum oxide-zirconium oxide (SiO
2
-Al
2
O
3
-ZrO
2
), &bgr;-wollastonite (&bgr;-CaSiO
3
), spodumene (LiAlSi
2
O
6
), magnesium titanate (MgTiO
3
), barium titanate (BaTiO
3
) and mica.
Of these, preferred are those which contains aluminum nitride (AlN) or zirconium oxide (ZrO
2
) as a main component.
In the present invention, the metal (M) to be fixed in the penetration hole is formed by a method using a conductive paste. Otherwise, there is employed method in which a wire of metal or its
Nobukuni Takeshi
Ohya Kazuyuki
Sayama Norio
Eley Timothy V.
Grant Alvin J
Mitsubishi Gas Chemical Co. Inc.
Wenderoth , Lind & Ponack, L.L.P.
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