Method of producing a wiring substrate

Details Method of producing a wiring substrate Method of producing a wiring substrate

1997-07-21

2001-12-11

Le, N. (Department: 2861)

Incremental printing of symbolic information

Ink jet

Ejector mechanism

C439S886000

Reexamination Certificate

active

06328427

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flexible printed circuit board, and more particularly to a flexible printed circuit board for electrical connection by wire bonding and an ink jet recording head using the same.
2. Related Background Art
As the size of an electronic equipment is reduced, a flexible printed circuit board (FPC) is widely used in view of the freedom of packaging form and the space saving. In connecting the FPC and other wiring material or an electronic part mounted on the FPC, a wire bonding (WB) is frequently used when a high density packaging is required or a packaging space is limited.
An ink jet recording head is explained as an example of using the WB for the connection of the FPC.
FIG. 8
shows a sectional view of a packaging unit of an ink jet recording head previously proposed by the inventors of the present invention, as an example of the use of the WB for the connection of the FPC.
FIGS. 4A and 4B
show perspective views of the ink jet recording head of FIG.
8
.
An overall construction of the ink jet recording head is explained with reference to
FIGS. 4A
,
4
B and FIG.
8
.
On an upper surface of a support plate
5
made of aluminum, a heater board
4
having an Si substrate on which a heater for applying a thermal energy to ink is formed and one end of an FPC
1
for transmitting an electrical signal sent from a main unit of a recording apparatus to the heater board
4
are electrically connected by a wire bonding
12
. The FPC
1
is bent toward a rear surface (lower surface) of the support plate
5
and the other end of the FPC
1
is connected to the support plate
5
. Contact pads
111
which are electrically connected to a contact pad of the main unit of the recording apparatus are formed on the FPC
1
. The ink jet recording head is supplied with the electrical signal from the main unit of the recording apparatus through the contact pads
111
on the FPC
1
. The support plate
5
is covered with a packaging cover
9
and ink is supplied from the main unit of the recording apparatus to a grooved top plate
8
having a common liquid chamber and discharge ports
10
forming nozzles through an ink supply member
11
provided in the packaging cover
9
, and it is heated by the heater on the heater board
4
and discharged from the discharge ports
10
. Sealing agent
10
such as silicone rubber is applied to the connecting area of the wires
12
to protect the bonding part from an external force.
A layer structure of the WB connecting part of the FPC
1
is now explained with reference to FIG.
7
.
The layer structure in the connecting part of the FPC
1
usually comprises, starting from a bottom layer, reinforcing plate
101
made of glass epoxy and provided only on the support member, a bonding layer
108
made of a acryl resin, a base film
103
made of polymide, a bonding layer
104
made of epoxy resin, a conductive layer
105
(10-35 &mgr;m) made of a copper foil, a nickel plating layer
109
(2-3 &mgr;m), a gold plating layer
107
(1 &mgr;m) serving as a contact member, in this order. Since the nickel plating layer is provided to enhance the contact of the copper of the conductive layer and the gold of the contact member, a thickness of 2-3 &mgr;m is sufficient.
The FPC
1
is bonded to the substrate
5
by the bonding material
2
a
applied to the reinforcement plate
101
. Other printed circuit board
7
is also bonded to the substrate
5
by the bonding material
2
b.
The gold plating layer
107
of the FPC
1
and the WB pad
701
of the other printed circuit board
7
are electrically connected by a gold wire
12
. The gold wire, the gold plating layer
107
and the WB pad
701
are ball-bonded.
In such an FPC, where a number of wires are required as it is in an ink jet recording head, aluminum wires may be used for the WB because the gold wires are expensive.
However, when the aluminum wires are used for the WB in the prior art FPC, defects in the connection are frequently found and a yield is very low.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an FPC which permits highly reliable WB packaging by an aluminum wire with a stable condition.
It is another object of the present invention to provide a highly reliable and inexpensive ink jet recording apparatus which uses the FPC.


REFERENCES:
patent: 3927841 (1975-12-01), Iacobucci
patent: 4032929 (1977-06-01), Fischbeck et al.
patent: 4327247 (1982-04-01), Mituhashi
patent: 4503131 (1985-03-01), Baudrand
patent: 4635080 (1987-01-01), Watanabe
patent: 4801067 (1989-01-01), Kondo
patent: 4881318 (1989-11-01), Komuro et al.
patent: 5182580 (1993-01-01), Ikeda et al.
patent: 4-402811 (1990-12-01), None
patent: 60-107845 (1985-06-01), None
patent: 60-255995 (1985-12-01), None
patent: 1-86525 (1989-03-01), None
patent: 4-51582 (1992-02-01), None
patent: 4-116837 (1992-04-01), None
English Version JP64-86525 (IDS), Mar. 1989, Japan.

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