Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-08-24
2001-12-11
Dawson, Robert (Department: 1712)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C029S831000, C029S832000, C156S292000, C523S458000
Reexamination Certificate
active
06328844
ABSTRACT:
TECHNICAL FIELD
This invention relates to a filmy adhesive for connecting circuits which is used to connect circuit substrates together or to connect electronic parts such as IC chips to a wiring substrate, and also relates to a circuit board.
BACKGROUND ART
To make an electrical interconnection between circuit substrates themselves or between electronic parts such as IC chips and a circuit substrate, an adhesive or an anisotropic conductive adhesive with conductive particles dispersed therein is used. More specifically, the electrical interconnection can be made by providing any of these adhesives between electrodes facing each other, connecting the electrodes by heating and pressing and thereafter imparting a conductivity in the direction of pressing. For example, Japanese Patent Application Laid-open No. 3-16147 discloses an adhesive for connecting circuits which is basically comprised of epoxy resin.
However, conventional adhesives making use of epoxy resin as base resin have a problem that, when reliability tests such as a thermal shock test, a PCT test and a solder bath immersion test are made, the connection resistance may become great or the adhesive may come apart at the joints because of internal stress ascribable to a difference in coefficient of thermal expansion of the connecting substrates.
Especially when chips are directly mounted on a substrate through an adhesive, the chips and substrate tend to warp because of internal stress ascribable to a difference in coefficient of thermal expansion between them when a printed substrate making use of an FR-4 base material or a flexible wiring board comprised of a polyimide or polyester base material is used as the connecting substrate.
SUMMARY OF THE INVENTION
The filmy adhesive for connecting circuits according to the present invention comprises a heat-activated adhesive for electrically connecting electrodes in the pressing direction by heating and pressing circuit electrodes facing each other, wherein the adhesive has a modulus of elasticity of from 100 to 2,000 MPa at 40° C. after adhesion.
This adhesive may contain at least an epoxy resin, an acrylic rubber and a latent curing agent, and the acrylic rubber may have a glycidyl ether group in the molecule. Such an adhesive may preferably be used.
The filmy adhesive for connecting circuits according to the present invention is also characterized in that, in a heat-activated adhesive for electrically connecting electrodes in the pressing direction by heating and pressing circuit electrodes facing each other, the adhesive contains at least an epoxy resin, an acrylic rubber having a glycidyl ether group in the molecule, and a latent curing agent.
In the above filmy adhesive for connecting circuits according to the present invention, the area of the adhesive after connection may preferably be from 2.0 to 5.0 times the area before connection.
The circuit board of the present invention comprises;
a first circuit member having a first connecting terminal; and
a second circuit member having a second connecting terminal;
the first connecting terminal and the second connecting terminal being so provided as to face each other; and
the first connecting terminal and the second connecting terminal being electrically connected by heating and pressing them through an adhesive put between the first connecting terminal and the second connecting terminal which face each other;
the adhesive having a modulus of elasticity of from 100 to 2,000 MPa at 40° C. after adhesion.
The circuit board of the present invention also comprises;
a first circuit member having a first connecting terminal; and
a second circuit member having a second connecting terminal;
the first connecting terminal and the second connecting terminal being so provided as to face each other;
the first connecting terminal and the second connecting terminal being electrically connected by heating and pressing them through an adhesive put between the first connecting terminal and the second connecting terminal which face to each other; and
the adhesive containing at least an epoxy resin, an acrylic rubber having a glycidyl ether group in the molecule, and a latent curing agent.
In the circuit board of the present invention, it is preferable that the first circuit member having a first connecting terminal is a semiconductor chip; and the second circuit member having a second connecting terminal is an organic insulating substrate having a second connecting terminal.
As the first circuit member having a first connecting terminal, a semiconductor chip may preferably be used; and
as the second circuit member having a second connecting terminal, a multi-layer wiring board which has a surface insulating layer on which the second connecting terminal is formed, the given number of insulating layers, a given number of wiring layers provided through the insulating layers, and conductive holes which provide electrical interconnection between given electrodes and given wiring layers; a given number of the insulating layers being formed of a resin reinforced with a glass substrate, and, when the modulus of elasticity of the surface insulating layer as measured by the DVE method is represented by E
2
, E
1
, and the modulus of elasticity of the insulating layer formed of a resin reinforced with a glass substrate as measured by the DVE method is represented by
E
1
=0.01E
2
to 0.5E
2
;
or a wiring substrate comprising an insulating substrate in the surface portion of which the second connecting terminal is embedded.
In the above adhesive, from 0.2 to 15% by volume of conductive particles may be dispersed.
REFERENCES:
patent: 4680226 (1987-07-01), Takeda
patent: 4735847 (1988-04-01), Fujiwara et al.
patent: 4999136 (1991-03-01), Su et al.
patent: 03-016147 (1991-01-01), None
patent: 05-160200 (1993-06-01), None
patent: 06-203627 (1994-07-01), None
patent: 06-260533 (1994-09-01), None
Kojima Kazuyoshi
Nagai Akira
Shiozawa Naoyuki
Takemura Kenzo
Tanaka Toshiaki
Aylward D.
Dawson Robert
Griffin & Szipl, P.C.
Hitachi Chemical Company Ltd.
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