Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-10-15
2002-09-17
Paladini, Albert W. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S260000, C029S832000, C257S783000, C428S343000, C438S119000
Reexamination Certificate
active
06452111
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to anisotropic conductive adhesives used for electric connection between a semiconductor element and a flexible wiring board, for example.
PRIOR ART
Adhesives containing conductive particles have been used as means for connecting a semiconductor element and a flexible wiring board, for example.
Reference
130
in FIG.
8
(
a
) represents a semiconductor element comprising an element body
131
, a wiring film
135
provided on the top of element body
131
and a protective film
137
provided on wiring film
135
and having an opening
139
at a predetermined location.
Reference
110
in FIG.
8
(
a
) represents a flexible wiring board to be connected to semiconductor element
130
, and the flexible wiring board
110
comprises a base film
111
and a wiring film
115
formed on base film
111
.
Wiring films
115
,
135
of flexible wiring board
110
and semiconductor element
130
have connector parts
115
a,
135
a
serving for the connection described later and wiring parts
115
b,
135
b
running around in flexible wiring board
110
and semiconductor element
130
and connected at one end to connector parts
115
a,
135
a,
respectively.
Opening
139
in protective film
137
is located on connector part
135
a
of semiconductor element
130
. In the opening
139
is provided a bump
136
upright on connector part
135
a
with the top of bump
136
projecting from the surface of protective film
137
.
The flexible wiring board
110
and semiconductor element
130
are connected by first opposing the side of semiconductor element
130
having protective film
137
and the side of flexible wiring board
110
having wiring film
115
to each other and inserting an adhesive film
120
made of an adhesive containing conductive particles
125
between both, as shown in FIG.
8
(
a
).
Then, adhesive film
120
is sandwiched between semiconductor element
130
and flexible wiring board
110
while aligning bump
136
on semiconductor element
130
to face connector part
115
a
of wiring film
115
of flexible wiring board
110
, and the assembly is heated under pressure so that adhesive film
120
softens by heating so that the softened adhesive film
120
is displaced from the top of bump
136
of semiconductor
130
and the remaining adhesive film
120
is sandwiched between connector part
115
a
and bump
136
.
FIG.
8
(
b
) shows this state, in which conductive particles
125
in adhesive film
120
sandwiched between bump
136
and connector part
115
a
enter into the surface of the top of bump
136
and the surface of connector part
115
a
under pressure to connect wiring films
115
,
135
via the conductive particles
125
.
Reference
100
in FIG.
8
(
b
) represents an electric device obtained by heating, pressing and then cooling.
As adhesive film
120
hardens when it is cooled after heating, semiconductor element
130
and flexible wiring board
110
are not only electrically but also mechanically connected via conductive particles
125
in the electric device
100
.
A part of flexible wiring board
110
distant from connector part
115
to be connected to bump
136
is pressed against the surface of protective film
137
of semiconductor element
130
during heating under pressure because of its flexibility so that protective film
137
of semiconductor element
130
and wiring film
115
of flexible wiring board
110
come into close contact with each other.
As conductive particles
125
used in adhesive film
120
normally have an average particle diameter greater than the thickness of protective film
137
of semiconductor element
130
and made of a rigid metal, conductive particles
125
may break through protective film
137
under pressure when the surface of protective film
137
of semiconductor element
130
and the surface of flexible wiring board
110
come into close contact with each other.
The right half of FIG.
8
(
b
) is a schematic sectional view showing that conductive particles
125
have broken through protective film
137
, and the conductive particles
125
having broken through protective film
137
may come into contact with wiring parts
115
b,
135
b
to cause short circuit in wiring films
115
,
135
forming electric device
100
when wiring parts
115
b,
135
b
of wiring films
115
,
135
are faced to each other in the zone where flexible wiring board
110
and semiconductor element
130
are in close contact with each other.
With high densification of electronic components, the pattern of wiring film
135
of semiconductor
130
is becoming finer in recent years, so that when conductive particles
125
having broken through protective film
137
enter between wiring film members
135
, adjacent wiring film members
135
may be electrically connected via conductive particles
125
to cause short circuit between wiring film members
135
of semiconductor element
130
.
It is also possible to directly apply an adhesive on the surface of flexible wiring board
110
for connection to semiconductor element
130
without forming it into a film, but such an adhesive may readily cause connection failure because the conductive particles
125
are not homogeneously dispersed in the pasty adhesive and tend to precipitate.
The present invention was made to solve the problems of the prior art described above with the purpose of providing an adhesive film having high reliability of connection to fine-pitch circuits.
SUMMARY OF THE INVENTION
In order to solve the above problems, the present invention provides an adhesive comprising an insulating adhesive component and conductive particles dispersed in the insulating adhesive component wherein the conductive particles have an average diameter of from 10 nm or more to 90 nm or less.
The present invention provides the adhesive characterized in that the conductive particles contained in the adhesive have a specific surface area of from 5 m
2
/g or more to 80 m
2
/g or less.
The present invention provides the adhesive characterized in that the conductive particles contained in the adhesive represent a total volume of from more than 0.1% to less than 12% on the basis of the total volume of the insulating adhesive component and the conductive particles.
The present invention provides the adhesive characterized in that the conductive particles are based on at least one metal selected from the group consisting of nickel, palladium, copper, iron and silver.
The present invention provides the adhesive characterized in that the insulating adhesive component preferably contains an epoxy resin and an imidazole-based latent curing agent.
The present invention provides the adhesive characterized in that the adhesive has a viscosity of 1000 Pa.s or less at 25° C.
The present invention provides an adhesive film made of an adhesive in the form of a film comprising an insulating adhesive component and conductive particles dispersed in the insulating adhesive component wherein the conductive particles have an average diameter of from 10 nm or more to 90 nm or less.
The present invention provides an electric device comprising a semiconductor element and a wiring board, wherein the semiconductor element is adhesively bonded to the wiring board with the adhesive comprising an insulating adhesive component and conductive particles dispersed in the insulating adhesive component wherein the conductive particles have an average diameter of from 10 nm or more to 90 nm or less.
REFERENCES:
patent: 5620795 (1997-04-01), Haak et al.
patent: 5685939 (1997-11-01), Wolk et al.
patent: 6077382 (2000-06-01), Watanabe
patent: 6223429 (2001-05-01), Kaneda et al.
patent: 6340607 (2002-01-01), Yamada
“Plastics—Polymers/resins in the liquid state or as emulsions or dispersions-Determination of viscosity using a rotational viscometer with defined shear rate”, Japanese Industrial Standard, K 7117-2; 1999.
“Plastics—Polymers/resins in the liquid state or as emulsions or dispersions-Determination of viscosity using a rotational viscometer with defined shear rate”, International Standar
Oliff & Berridg,e PLC
Paladini Albert W.
Sony Chemicals Corp.
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