Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Reexamination Certificate
1999-12-15
2001-09-04
Talbot, Brian K. (Department: 1762)
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
C427S350000, C427S385500, C427S294000
Reexamination Certificate
active
06284308
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method of a printed circuit board, particularly, relates to a manufacturing method of filling up appropriately a blind hole formed on a printed circuit board with insulative thermosetting resin
2. Description of the Related Art
Presently, a printed circuit board is required to have high packing density in accordance with development of minimizing electronic apparatuses and equipment. A multilayer printed circuit board having multilayers of wiring boards has been realized for the purpose of satisfying the demand therefor. Each wiring board of each layer is electrically and mechanically connected to each other by way of a through hole and a blind hole (or referred to a non-through hole). A blind hole is filled with insulative resin or conductive resin in accordance with usage of the blind hole, and the resin is hardened.
In a process of manufacturing a multilayer printed circuit board, it is required that the blind hole be filled efficiently and securely with resin.
Various kinds of examinations have been performed for the purpose of filling a blind hole with resin efficiently and securely. Japanese Patent Laid-open Publication No. 7-249866/1995, for example, discloses a method of filling a through hole or a blind hole provided on a substrate with hardening paste. According to the method, the filling process is completed by supplying vibration to the hardening paste, which has been temporarily filled up in a through hole or a blind hole provided on a substrate by printing process.
Japanese Patent Laid-open Publication No. 9232758/1997 discloses another filling method. According to this filling method, while manufacturing a wiring board having a blind hole by way of a process of filling up the blind hole with insulative resin in conjunction with coating the insulative resin on the surface of the wiring board, the blind hole is filled up with the insulative resin by coating the insulative resin after the inner circumference of the blind hole has been moistened with a solvent.
Each method mentioned above is an excellent method for filling up a blind hole with insulative resin However, these methods can not sufficiently remove a bubble possibly remaining in the resin filled up.
FIG. 4
typically shows a bubble
20
generating in a blind hole
6
of a printed circuit board. In
FIG. 4
, the blind hole
6
is formed in a resin layer
3
, which is coated on a substrate
1
and hardened. The bubble
20
may generate in a resin
7
by chance, while the resin
7
has been filled up in the blind hole
6
and hardened.
As mentioned above, if a bubble remains in an insulative resin after the insulative resin has been filled up in a blind hole and hardened by heating, the bubble expands and causes a problem in that the resin
7
easily swells when the printed circuit board is exposed to high temperatures such as occurs in a soldering process thereafter. The same problem occurs if the blind hole is not sufficiently filled up with the resin.
SUMMARY OF THE INVENTION
Accordingly, in consideration of the above-mentioned problems of the prior art, an object of the present invention is to provide a manufacturing method of a printed circuit board, which can effectively and securely fill up a blind hole with insulative thermosetting resin and suppress a bubble generating in the insulative thermosetting resin as well.
In order to achieve the above object, the present invention provides, according to an aspect thereof, a manufacturing method of a printed circuit board having a blind hole which comprising the steps of coating insulative thermosetting resin on a surface of a printed circuit board so as to form an insulative thermosetting layer and so as to fill up the blind hole with the insulative thermosetting resin in a normal pressure atmosphere, keeping the printed circuit board coated with the insulative thermosetting resin in a low pressure atmosphere of 1.3 to 666 hPa and hardening the insulative thermosetting resin.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.
REFERENCES:
patent: 5011793 (1991-04-01), Obinata
patent: 5153987 (1992-10-01), Takahashi et al.
patent: 5208068 (1993-05-01), Davis et al.
patent: 9-36544 (1997-02-01), None
patent: 9-232758 (1997-09-01), None
Seki Yasuaki
Shiratori Shigenori
Suzuki Kenji
Connolly Bove Lodge & Hutz
Talbot Brian K.
Victor Company of Japan Ltd.
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