Chemistry: electrical current producing apparatus – product – and – With pressure equalizing means for liquid immersion operation
Reexamination Certificate
2000-01-10
2001-08-21
Bell, Bruce F. (Department: 1741)
Chemistry: electrical current producing apparatus, product, and
With pressure equalizing means for liquid immersion operation
C429S006000, C429S047000, C429S047000, C429S047000, C204S290030, C204S290050, C204S291000, C204S292000, C204S293000, C205S205000, C205S219000, C205S232000, C205S236000, C205S245000, C205S246000, C205S261000, C205S271000, C205S273000
Reexamination Certificate
active
06277510
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a porous electrode, and more particularly to a porous electrode used for conductive material-filled polymer composite.
2. Description of the Prior Art
Conductive material-filled polymer composites are well-known and include a polymer substrate and conductive particles that are filled in the polymer substrate. Since they have good electrical physical properties and a wide range of processability, conductive material-filled polymer composites are often used as conductive material for various resistors and positive temperatuve coefficient (PTC) passive devices. The conductive particles filled include carbon black, nickel powders, silver powders, and graphite. Due to limitations on conductivity, wear resistance, and soldering problems, a metal electrode should be bonded onto the surface of the conductive material-filled polymer composite; thus, it is more convenient to undergo the subsequent processing on the passive device.
FIG. 1
shows the bonding situation of two conventional metal electrode layers and a conductive material-filled polymer composite. The conductive material-filled polymer composite
10
is sandwiched between two metal electrode
11
layers. The surface
12
of the metal electrode
11
contacting the conductive material-filled polymer composite
10
is smooth.
When such a smooth metal electrode is bonded to the conductive material-filled polymer composite, the following problems arise. The difference of the thermal expansion coefficient between the metal electrode and the conductive material-filled polymer composite will induce poor adhesion between them. When the conductive material-filled polymer composite is utilized for various resistors and PTC passive devices, it encounters various cyclic or non-cyclic temperature changes; therefore, the adhesion requirements of the metal electrode will become even more critical. In addition, the interfacial resistance between the conductive material-filled polymer composite and the metal electrode is also a problem. Since the conductive material-filled polymer composite is composed of conductive particles and insulate polymer substrate, during the process of bonding the metal electrode to the conductive material-filled polymer composite, the insulate polymer substrate may flow and fill into the space between the metal electrode and the conductive particles. This will induce the increase of the interfacial resistance, thus affecting the electrical properties of the conductive material-filled polymer composite after the electrode is bonded.
To solve the problem that the adhesion strength between the conductive material-filled polymer composite and the metal electrode is poor, the concept of roughing the metal electrode surface is first disclosed in U.S. Pat. No. 4,689,475 (Raychem Corporation). Referring to
FIG. 2
, a conductive material-filled polymer composite
20
is sandwiched between two electrode layers
21
. The electrode layer
21
is contacted with the conductive material-filled polymer composite layer
20
by a rough surface
22
. On the rough surface
22
, there are a plurality of projections
23
with a height of 0.1 &mgr;m to 100 &mgr;m. In this manner, since the projections
23
on the rough surface
22
are inserted into the conductive material-filled polymer composite
20
, the adhesion strength between the electrode
21
and the conductive material-filled polymer composite
20
can be increased.
In U.S. Pat. No. 4,800,253 (Raychem Corporation), the concept of U.S. Pat. No. 4,689,475 is further improved by a structure shown in FIG.
3
. Referring to
FIG. 3
, a conductive material-filled polymer composite layer
30
is sandwiched between two electrode layers
31
. The electrode layer
31
is contacted with the conductive material-filled polymer composite layer
30
by a rough surface
32
. On the rough surface
32
, there are a plurality of macronodules
33
with a height of 0.1 &mgr;m to 100 &mgr;m. On the macronodule
33
, there are a plurality of micronodules
34
with a height of 0.5 &mgr;m to 2 &mgr;m. In this manner, since the macronodules
33
and the micronodules
34
on the rough surface
32
are inserted into the conductive material-filled polymer composite
30
, the adhesion strength between the electrode
31
and the conductive material-filled polymer composite
30
can be further increased.
In WO 9636057, the electrode used to be contacted with the conductive material-filled polymer composite has an open type cellular structure, which can improve the adhesion strength between the electrode and the conductive material-filled polymer composite.
In the above-mentioned two Raychem patents, the adhesion strength between the metal electrode and the conductive material-filled polymer composite is improved by making the electrode rough to cause physical insertion between them. However, during the process of bonding the metal electrode and the conductive material-filled polymer composite, the insulate polymer substrate will still flow and fill into the space between the metal electrode and the conductive particles, which increases the interfacial resistance. As to WO 9636057, the direct contact between the conductive particles of the conductive material-filled polymer composite and the electrode still needs further improvement.
SUMMARY OF THE INVENTION
The object of the present invention is to solve the above-mentioned problems and to provide a porous electrode with a novel structure which can be used for conductive material-filled polymer composites. When the porous electrode of the present invention is bonded to a conductive material-filled polymer composite, the polymer in the conductive material-filled polymer composite can flow into the pores of the porous electrode. This will cause a three dimensional insertion structure and improve the adhesion strength between them.
Another object of the present invention is to make the conductive particles of the conductive material-filled polymer composite have a better direct contact with the porous electrode, thus decreasing the interfacial resistance.
A further object of the present invention is to provide an electrical device containing the above-mentioned porous electrode, which includes the porous electrode of the present invention and a conductive material-filled polymer composite layer bonded thereon. The electrical device has good adhesion strength and lower interfacial resistance.
To achieve the above-mentioned object, the porous electrode of the present invention used for a conductive material-filled polymer composite has a structure described below. At least one surface of the porous electrode is an open type porous structure, the porous structure including a plurality of macropores and micropores which are randomly distributed and interconnected with each other. The conductive material-filled polymer composite includes a polymer substrate and conductive particles filled therein.
When the surface of the open type porous structure of the porous electrode is bonded with the conductive material-filled polymer composite, the conductive particles in the conductive material-filled polymer composite can be trapped in the macropores of the porous structure, and the insulate polymer substrate in the conductive material-filled polymer composite can be immersed into the micropores of the porous structure so as to enable a direct contact between the conductive particles and the porous electrode.
REFERENCES:
patent: 4689475 (1987-08-01), Kleiner et al.
patent: 4800253 (1989-01-01), Kleiner et al.
patent: WO 96/36057 (1996-11-01), None
Chang Kun-Huang
Chou Shu-Chin
Lin Chen-Ron
Yeh Wei-Wen
Bell Bruce F.
Industrial Technology Research Institute
Ladas & Parry
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