Optical: systems and elements – Optical modulator
Reexamination Certificate
2000-06-01
2001-11-20
Dunn, Tom (Department: 1725)
Optical: systems and elements
Optical modulator
C359S242000, C359S245000, C359S254000, C359S295000
Reexamination Certificate
active
06320691
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART
The present invention relates to a method of connecting electrodes of two substrates to each other with a solder, specifically a method of connecting electrodes of a flexible film substrate loaded with a semiconductor chip to connection electrodes of a peripheral circuit board. Particularly, the present invention relates to a method of connecting input electrodes of a flexible circuit board loaded with a semiconductor chip for driving an optical modulation device, such as a liquid crystal device (or panel), to connection electrodes of a peripheral circuit board for supplying (inputting) a driving power and control signals to the semiconductor chip.
Hereinbelow, a method of connecting electrodes formed on two substrates to each other will be described while taking a packaging of a driver IC (integrated circuit) for an optical modulation device as an example.
In a packaging method of a driver IC for optical modulation apparatus, e.g., display apparatus including flat display devices having display electrodes arranged in the form of a matrix, such as EL display panels and liquid crystal display panels of the simple matrix-type and the active matrix-type, there has been generally practiced a method wherein transparent electrodes formed at the surface of a substrate of the display (optical modulation) panel are connected to connection electrodes formed at a periphery of the substrate; the connection electrodes are connected to output electrodes of a tape carrier package or tape carrier package structure (TCP) loaded with a driver semiconductor chip (e.g., driver IC) via an anisotropic conductive film (adhesive) by a thermocompression bonding method, such as a tape automated bonding (TAB) method; and input electrodes of the TCP are connected to connection electrodes of a print circuit board (PCB, herein after sometimes referred to a “PCB board”) as a peripheral circuit board for supplying a drive power and control signal to the driver IC by using solder.
FIG. 6
shows a schematic sectional view of an embodiment of a connection structure of a TCP and a PCB board. The TCP includes a flexible film substrate
100
, a plurality of input electrodes
101
and a plurality of output electrodes (not shown) respectively formed on the flexible film substrate
100
, and a semiconductor device (driver IC) (not shown) mounted on the substrate and connected to the input electrodes
101
and the output electrodes, respectively.
Referring to
FIG. 6
, the input electrodes
101
of the flexible film substrate
100
are connected via solder
104
to associated connection electrodes
103
of a PCB substrate
102
, respectively, at their lead portions
101
a
disposed in an exposed state at a spacing between the inner portion
100
of the substrate and an end portion
100
a
of the substrate. On the other hand, the output electrodes of the flexible film substrate
100
are bonded to a (glass) substrate (of the display panel) and fixed thereon at a prescribed position by, e.g., an anisotropic conductive film (not shown).
Soldering between the lead electrode portions
101
and the connection electrodes
103
may generally be performed in the following manner.
Referring to
FIG. 6
again, the connection electrodes
103
of the PCB board
102
disposed on a stage
105
and having thereon a solder resist
106
is pre-coated with a solder
104
at their exposed regions (not covered with the solder resist
106
) by, e.g., a plating method, a super-solder method or a super-jufit method. Then, the connection electrodes
103
are registered or positioned in alignment with the lead portions
101
a
of the input electrodes
101
, followed by thermocompression (heat-pressure bonding) with the solder
104
by using a thermocompression (heat-pressure bonding) head
107
having a width substantially equal to or larger than a length of the exposed (opening) region (where the solder
104
is pre-coated) of the solder resist
106
while pressing the lead portions
101
a
against the connection electrodes
103
at a position in the neighborhood of a boundary between the solder resist
106
and the solder
104
.
In this case, however, if the solder
104
is used excessively for pre-coating, an excessive solder
104
a
is concentrated or accumulated at one terminal region where the solder
104
can escape therefrom, of the lead portions
101
a
closer to the end portion
100
a
of the flexible film substrate
100
as shown in
FIG. 6
, thus resulting in a solder bridge between adjacent lead electrode portions at the terminal region. As a result, unnecessary electrical conduction between the adjacent lead electrode portions is liable to be caused to occur.
Further, as shown in
FIG. 7
, in case where an amount of the solder
104
for pre-coating is small, the lead electrode portions
101
a
of the flexible film substrate
100
are not made contact with the solder
104
since it is difficult to heat-press the lead electrode portions
101
a
against the associated connection electrodes
103
through such a small amount of the solder
104
having a height lower than the height (thickness) of the solder resist
106
(formed on the connection electrodes
103
), thus failing to effect an electrical connection between the lead electrodes
101
and the connection electrodes
103
.
For this reason, the pre-coating amount of the solder
104
is required to be controlled so that the resultant solder layer has a thickness (height) larger than the thickness of the solder resist
106
and the solder
104
does not cause a bridge between adjacent lead electrode portions
101
a
and/or between adjacent connection electrodes
103
.
However, in the case of the above-described heat-pressure bonding method as shown in
FIGS. 6 and 7
, it is technically difficult to appropriately control an amount of pre-coating solder. Further, the thickness of the solder resist layer
5
per se is not generally uniform.
SUMMARY OF THE INVENTION
An principal object of the present invention is to provide a method of connecting electrodes of one substrate to those of the other substrate through a solder, capable of effecting a good electrical connection irrespective of an amount of pre-coated solder placed on one of the substrate.
According to the present invention, there is provided a method of connecting first electrodes formed on a first substrate to second electrodes formed on a second substrate and partially coated with a resist pattern so as to substantially expose an opening thereof at a surface of the second electrodes, said method comprising the steps of:
(a) coating the second electrodes with a solder at the opening of the resist pattern,
(b) aligning the first electrodes with the second electrodes, and
(c) electrically connecting the first electrodes to the second electrodes through the solder by heat-pressing the first and second electrodes with a heat-pressure bonding head including a tip face (pressing or contacting face) having a width smaller than a width of the opening of the resist pattern so as to heat-press the first and second electrodes at an entire region of the tip face of the heat-pressure bonding head.
According to the present invention, there is also provided a method of connecting first electrodes formed on a first substrate to second electrodes formed on a second substrate, said method comprising the steps of:
(a) aligning the first electrodes with the second electrodes, and
(b) electrically connecting the first electrodes to the second electrodes by heat-pressing the first and second electrodes while supplying a cooling gas to at least one of the first and second substrates.
According to the present invention, there is further provided a method for producing an optical modulation apparatus which includes: an optical modulation panel, a tape carrier package structure comprising a flexible substrate, a semiconductor device for driving the panel mounted on the flexible substrate, and input electrodes and output electrodes for the semiconductor device; and a circuit board provided with connection ele
Ouchi Toshimichi
Saito Riichi
Takahashi Masanori
Canon Kabushiki Kaisha
Dunn Tom
Fitzpatrick ,Cella, Harper & Scinto
Stoner Kiley
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