Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making electrical device
Reexamination Certificate
2000-01-05
2001-09-25
Huff, Mark F. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making electrical device
C430S311000, C430S323000, C430S324000, C430S327000, C430S438000, C430S613000
Reexamination Certificate
active
06294316
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the field of flexible printed wiring boards, particularly to a technique for simply manufacturing a flexible printed wiring board having fine metal bumps.
PRIOR ART
Recently, great importance has been attached to flexible printed wiring boards on which a chip-like semiconductor device can be mounted as a demand for smaller semiconductor devices grows.
FIG.
8
(
a
) to (
d
) is a flow sheet of a process for manufacturing a flexible printed wiring board according to the prior art. In this process, a metal film of copper foil is initially applied on a polyimide film
113
, then patterned to form a copper wiring. Reference
111
in FIG.
8
(
a
) represents the copper wiring.
Then, the surface of the polyimide film
113
is irradiated with laser beam
114
(FIG.
8
(
b
)) to form an opening
115
having a predetermined diameter (FIG.
8
(
c
)). In this state, the surface of the copper wiring
111
is exposed at the bottom of the opening
115
. Then, copper plating is performed while the back face of the copper wiring
111
is protected with a resin film
117
, whereby copper grows at the portion of the copper wiring
111
exposed at the bottom of the opening
115
to form a metal bump
116
within and on the surface of the opening
115
. Reference
110
in FIG.
8
(
d
) represents a flexible printed wiring board having the metal bump portion
116
.
When a semiconductor chip is to be mounted on such a flexible printed wiring board
110
, the metal bump
116
and a bonding pad on the semiconductor chip are contacted and bonded together via an anisotropic conductive film. Only the bonding pad portion of the semiconductor chip is electrically connected with the flexible printed wiring board
110
, because the flexible printed wiring board is insulated with the polyimide film
113
except for the metal bump
116
.
Such a flexible printed wiring board
110
has recently been much used because it is thin, light and freely foldable to provide a high packaging flexibility.
However, residues of the polyimide film
113
remain on the surface of the metal wiring
111
exposed at the bottom face of the opening
115
when the opening
115
is formed with laser beam
114
as described above.
If copper plating is performed in the presence of residues, copper deposits at different speeds in a number of openings
115
to fail to form even metal bumps
116
.
Thus, the prior art used to remove residues at the bottom face of each opening
115
by immersing the whole of body in a chemical solution after the opening
115
has been formed.
However, the chemical solution becomes more difficult to enter the opening
115
as it becomes finer, with the result that residues become difficult to be totally removed.
Another problem is that fine openings
115
(about 40 &mgr;m to 50 &mgr;m) having an even opening diameter can not be formed by irradiating a rigid polyimide film
111
with laser beam
114
as described above, resulting in uneven metal bumps
116
with different diameters and heights to cause failure in contact with semiconductor chips.
Still another problem is that the opening
115
having a diameter smaller than 40 &mgr;m can not be formed because it is difficult to concentrate the spot diameter of high power laser beam
114
contrary to the recent demand for the opening
115
to be finer.
An object of the present invention is to provide a technique that can form fine metal bumps with high precision in order to overcome the above disadvantages of the prior art.
SUMMARY OF THE INVENTION
In order to solve the above problems, the invention relates to a process for manufacturing a flexible printed wiring board, comprising forming a resin coating at least on a metal bump on a metal film having said metal bump, pressing said resin coating on said metal bump, and then etching said resin coating to expose the surface of said metal bump.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein said resin coating is formed on said metal bump and on said metal film.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein said resin coating comprises a lower thermosetting resin coating and an upper thermoplastic resin coating formed on the surface of said lower resin coating.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein a pressure is applied on said metal bump after a resist film resistant to etching with a chemical for etching said resin coating is formed on said resin coating.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein a pressure is applied on said metal bump after a resist film resistant to etching with a chemical for etching said upper thermoplastic resin coating is formed on said upper thermoplastic resin coating.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein said metal bump is formed by forming a photosensitive mask film on the surface of said metal film, then patterning said mask film by exposure and development, and depositing a metal by plating on the surface of said metal film exposed at the opening of said mask film.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein said pressing of said metal bump comprises at least rotating a roller against said resin coating.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein said roller is heated during said pressing.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein a polyamic acid is used as a material for said resin coating.
The present invention relates to a process for manufacturing a flexible printed wiring board, wherein a polyamic acid is used as a material for said thermosetting resin coating and/or said thermoplastic resin coating.
The present invention relates to a flexible printed wiring board comprising a metal film, a resin coating on said metal film, and a metal bump located in an opening formed in said resin coating, connected at its bottom face to said metal film and having a height greater than the thickness of said resin coating, wherein said resin coating is removed by etching at least at the portion located at an end of said metal bump to expose the end of said metal bump from the surface of said resin coating.
The present invention relates to a flexible printed wiring board wherein said metal film is patterned in a predetermined form.
The present invention relates to a flexible printed wiring board wherein an electric device is mounted on said flexible printed wiring board and a bonding pad of said electric device is connected with the end of said metal bump.
The present invention as characterized above includes a metal bump formed on a metal film. A resin coating of polyimide or the like and a resist film are formed in this order on the surface of the metal film and on the surface of the metal bump, and a pressure is applied on the surface to depress the resist film on the metal bump. In this state, the resin coating is exposed at the depressed portion of the resist film, and the resin coating exposed at the top of the metal bump can be etched by spraying an etching solution or immersing the resin coating in an etching solution with the back face being protected. During then, the resist film serves as a mask so that the resin coating is protected against etching except for the portion on the metal bump.
The resin coating may be formed as a two-layer structure having a lower rigid resin coating and an upper flexible coating so that the flexible resin coating serves as an adhesive layer with which a semiconductor chip can be adhered.
If a pressure is applied on the resin coating in a softened state without forming a resist layer, the resin coating itself is depressed to reduce the thickness on the metal bump. If the resin coating is etched in this state, the thin portion of t
Hishinuma Hiroyuki
Kaneda Yutaka
Tsutsumi Akira
Barreca Nicole
Huff Mark F.
Oliff & Berridg,e PLC
Sony Chemicals Corp.
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