Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-12-23
2002-04-23
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S323000, C428S343000, C428S344000, C428S3550RA, C428S213000, C428S901000, C174S259000
Reexamination Certificate
active
06376050
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and an apparatus for electrically connecting an electrical connecting portion of a first object to an electrical connecting portion of a second object.
2. Description of the Related Art
The circuitry used in electronic parts has continued to increase in density and complexity in order to keep up with trends in size and thickness reduction of these parts. For interconnecting such electronic parts to a small-sized electrode, adhesives or film-like products, referred to below as connecting members, exhibiting superior anisotropy and electrical conductivity in order to cope with the finer pitch, are used prevalently.
The connecting members are comprised of an adhesive containing a pre-set quantity of an electrically conductive material, such as electrically conductive particles. These connecting members are provided between projecting electrodes of electronic parts and electrically conductive patterns of a printed circuit board, and are pressurized with or without heating to electrically connect the electrodes of the two components. At the same time, electrically insulating properties are afforded to the neighboring electrodes as the projecting electrode of the electronic part is secured to an electrically conductive pattern of the printed circuit board.
The basic concept for dealing with the connecting member in order to cope with the fine pitch is: 1) to select the particle size of the electrically conductive particles to be smaller than the size of the insulating portion between the neighboring electrodes to maintain insulation between the neighboring electrodes, 2) to set the content of the electrically conductive particles such as to prevent contact of the particles with one another, and 3) to cause the electrically conductive particles to be present positively on the electrodes to realize electrical conductivity in the connecting portion.
However, if, with the above-described conventional method, the electrically conductive particles are reduced in diameter, the electrically conductive particles are increased appreciably in surface area and hence undergo secondary agglomeration so that the particles cohere together. This prevents electrical insulating properties between neighboring electrodes from being maintained.
Conversely, if the content of the electrically conductive particles is decreased, the number of the electrically conductive particles on the electrodes to be interconnected is reduced so that the number of contact points is decreased. This prevents electrical conduction across the connection electrodes and renders it difficult for the connecting members to cope with the fine pitch in order to maintain long-term connection reliability.
As the electrode area or the spacing between neighboring electrodes becomes smaller with the marked tendency to fine pitch, the electrically conductive particles on the electrodes flow along with the adhesive to a gap between the neighboring electrodes under the effect of pressurization or the pressurization/heating at the time of connection to obstruct the connecting member coping with the fine pitch.
In order to solve this problem, proposals have been made for a connecting member in which an insulating coating is applied to electrically conductive particles to increase the number of the electrically conductive particles in the connecting member, and for a connecting member including an adhesive layer containing electrically conductive particles and a layer not containing the electrically conductive particles.
These conventional connecting members are shown in
FIGS. 1 and 2
.
Referring to
FIGS. 1A-D
, if an object is a glass substrate
200
, having planarity in a mounting area of an integrated circuit (IC)
201
on the order of a fraction of a micrometer, and if a projecting electrode
202
of the IC
201
permits slight height variations of the projecting electrodes (on the order of a fraction of a micrometer) as in case of a gold plating bump, a wiring pattern
203
on the glass pattern
200
is electrically connected to the projecting electrode
202
of the IC
201
via electrically conductive particles
205
contained in the connecting member
204
.
The reason may be summarized as follows: The parts, such as IC
201
, exhibit planarity, so that, if the thickness of the connecting member
204
is on the order of the height of the projecting electrode
202
plus 5 &mgr;m, the connecting member
204
is positively charged onto the lower surface of the IC
201
, so that it is unnecessary to increase the thickness of the connecting member
204
to an extent more than is necessary. It is noted that the height of the projecting electrode
202
s usually 15 to 25 &mgr;m, with an ITO pattern applied to the glass being a few Angstroms thick.
The ITO (indium tin oxide electrode) film is a transparent electrically conductive film affording electrical conductivity to the glass surface for operating as an electrode of a liquid crystal display plate. In an initial state of provisional pressure bonding (pressurization), the electrically conductive particles
205
can be sandwiched between the wiring pattern
203
on the glass substrate
200
and the projecting electrode
202
of the IC
201
. If the binder of the connecting member flows out at the time of ultimate pressure bonding (pressurization with heating), the sandwiched electrically conductive particles
205
are not fluidized to establish positive electrical connection across the wiring pattern
203
on the glass substrate
200
and the projecting electrode
202
on the IC
201
via the electrically conductive particles
205
.
FIG. 1A
shows the state in which the connecting member
204
, such as an anisotropic electrically conductive film (ACF), has been bonded to the glass substrate
200
. The anisotropic electrically conductive film is usually bonded to the glass substrate by thermal pressure bonding (with pressurization under a pressure of
100
N/cm
2
and with heating to a temperature of the order of 70 to 100° C.). In this state, the wiring pattern
203
on the glass substrate
200
is aligned with the projecting electrode
202
on the IC
201
.
FIG. 1B
shows the state in which the IC
201
is provisionally pressure bonded to the glass substrate
200
. The pressure bonding of the IC
201
is by pressurization only or by pressurization and heating, with the heating temperature being 70 to 100° C.
FIG. 1C
shows the state of ultimate pressurization of the IC
201
on the glass substrate
200
. The IC
201
is ultimately pressure bonded under pressurization and heating. Since the heating temperature at this time is higher than the melting temperature of the anisotropic electrically conductive film, the binder is fluidized. At this time, the electrically conductive particles
205
, sandwiched between the projecting electrode
202
of the IC
201
and the wiring pattern
203
of the glass substrate
200
, is not fluidized, however, the other electrically conductive particles
205
are fluidized.
FIG. 1D
shows the cured state of the anisotropic electrically conductive film. If pressurization and heating is performed at the time of ultimate pressure bonding, the resin is first fluidized and subsequently cured. The aforementioned sequence of operations represents the connection process.
However, if, when an object is not a glass substrate, but is a printed circuit board (
FIGS. 2A-D
)
300
, the wiring pattern
303
undergoes variations in height on the order of a few &mgr;m, or the projecting electrode
202
of the IC
201
undergoes variations in height on the order of a few &mgr;m, as in the case of a gold wire bump, as shown in
FIGS. 2A-D
. In such case, the thickness of the connecting member
204
needs to be equal to the height of the wiring pattern
303
of the printed circuit board
300
(of the order of 20 &mgr;m) plus the height of the projecting electrode
202
of the IC
201
(of the order of 20 &mgr;m) plus 10 to 20 &mgr;m for a safety margin.
In this case, since the connecting mem
Honda Noriyuki
Miyachi Seiichi
Suga Yasuhiro
Terasaki Tohru
Jones Deborah
Sonnenschein Nath & Rosenthal
Sony Corporation
Stein Stephen
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