Circuit board with terminal accommodating level differences

Details Circuit board with terminal accommodating level differences Circuit board with terminal accommodating level differences

1999-01-08

2001-03-06

Gaffin, Jeffrey (Department: 2841)

Electricity: conductors and insulators

Conduits, cables or conductors

Preformed panel circuit arrangement

C174S255000

Reexamination Certificate

active

06198052

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a circuit board with a conductor circuit formed on an insulating layer, a covering formed on the conductor circuit and a terminal connected to the conductor circuit penetrating through the covering.
2. Description of the Related Art
In recent years, with development of high speed and sophistication of electronic appliances, micromachining of several shapes is required on a circuit board on which an electronic component such as a semiconductor element or magnetic head is mounted. It is not too much to say that the reliability of the electronic appliance depends on the machining accuracy.
Generally, a terminal for connecting an electronic component is installed on the circuit board. The terminal surface is made of copper (Cu), nickel (Ni), gold (Au), etc. The terminal on a conventional circuit board was manufactured in such a manner that the surface of the conductor circuit is subjected to a prescribed electrolytic metal plating and a covering having a through-hole is formed on the surface. Specifically, the terminal portion, as shown in
FIG. 4
, has a structure in which the metal-plating surface exposed from a through-hole
33
of the covering
3
constitutes a terminal surface. In
FIG. 4
, the surface of the terminal
8
is made of an electrolytic-plating Au thin film
7
.
The terminal of an electronic component mounted on such a circuit board and that of the circuit board are generally connected to each other through a metallic ball.
However, at the terminal portion of a conventional circuit board as shown in
FIG. 4
, generally, there is a level difference
30
of 4 &mgr;m or more between the covering surface and the terminal surface (surface of the conductor circuit). The level difference corresponds to thickness of the covering. As shown in
FIG. 5
, presence of such a level difference may lead to poor connection between the terminal
32
of the electronic component
31
and the terminal
8
of the circuit board by the metallic ball
34
. Namely, in
FIG. 5
, the metallic ball
34
is brought into contact with the terminal
8
of the circuit plate but not with the terminal
32
of the electronic component.
SUMMARY OF THE INVENTION
The present invention has been accomplished in order to solve the above problem, and intends to provide a circuit board which can provide high reliability for the connection between the terminal of an electronic component mounted on the circuit board and that of the circuit board. A circuit board comprising: an insulating layer; a conductor circuit formed on the insulating layer; a covering formed on the conductor circuit; and a terminal connected to the conductor circuit penetrating through the covering, wherein a level difference between a surface of the covering and a surface of the terminal is 3 &mgr;m or less.


REFERENCES:
patent: 3726002 (1973-04-01), Greenstien et al.
patent: 4847136 (1989-07-01), Lo
patent: 4979074 (1990-12-01), Morley et al.
patent: 5305519 (1994-04-01), Yamamoto et al.
patent: 5329423 (1994-07-01), Scholz
patent: 5600103 (1997-02-01), Odaira et al.
patent: 5943212 (1999-08-01), Horiuchi et al.
patent: 6005777 (1999-12-01), Bloom et al.
patent: 5-206620 (1993-08-01), None
patent: 7-3663 (1995-01-01), None
English language abstract of JP5-206620.

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