Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Reexamination Certificate
1999-05-28
2001-04-03
Nguyen, Tuan H. (Department: 2813)
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
C174S251000
Reexamination Certificate
active
06210746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for fabricating a solder mask. More particularly, the present invention relates to a method for fabricating a solder mask by performing two printing steps.
2. Description of the Related Art
In the conventional method for fabricating a solder mask, a solder resist layer is formed on a printed circuit board. Then, a portion of the solder resist layer covering a region of bonding pads is totally removed; thus, no solder mask is formed between the bonding pads. This may cause a short between the bonding pads. Furthermore, an electroplating layer is usually formed on the bonding pads for coupling with other devices, and the shorts easily occur due to an absence of solder mask formation between the bonding pads. When the pitch is narrower than 8 mil or 0.2 mm, the short thus more easily occurs. As a result, the reliability and the yield of the printed circuit board are both reduced.
SUMMARY OF THE INVENTION
The present invention provides a method for fabricating a solder mask. By the method, the solder mask is formed by performing two printing steps; thus, unwanted electrical connection is avoided. Furthermore, the reliability and the yield of the substrate are both increased.
The invention provides a method for fabricating a solder mask. A substrate having wires with bonding pads for coupling with other devices is provided. A first solder resist layer is formed over the substrate to cover the wires and the substrate. A precure process is performed. A portion of the first solder resist layer is removed to expose the wires, and then the residual first solder resist layer is cured. A second solder resist layer is formed to cover the residual first solder resist layer and the wires. After precuring, a portion of the second solder resist layer is removed to expose the bonding pads.
In the invention, the solder mask is formed by performing two printing steps. By the solder mask, the unwanted electrical connection is avoided. As a result, the reliability and the yield of the printed circuit board are both increased. Additionally, it is easy to form the electroplating layer for coupling with other devices because only the bonding pads are exposed.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4289575 (1981-09-01), Matsumoto et al.
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patent: 4994349 (1991-02-01), Blumenstock et al.
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patent: 5400948 (1995-03-01), Sajja et al.
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patent: 5843621 (1998-12-01), Scafer
patent: 196 19 292 A1 (1997-11-01), None
patent: 63-001544 (1988-01-01), None
Huang Jiawei
J C Patents
Nguyen Tuan H.
Pert Evan
Unimicron Taiwan Corp.
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