Electricity: conductors and insulators – Conduits – cables or conductors
Reexamination Certificate
1999-09-21
2001-11-20
Patel, Rajnikant D. (Department: 2838)
Electricity: conductors and insulators
Conduits, cables or conductors
C205S109000
Reexamination Certificate
active
06320129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention generally relates to a method for making a conductive electrode for a composite polymer material, and more particularly, relates to a method for making a metallic electrode on which a microrough surface is formed by a composite plating process.
2. Related Art
For the demands of electrical conductivity, abrasion resistance and wiring with other metal elements, a conductive polymer composite is generally coated with a metallic film so as to be made into a reactive element, such as a capacitor or a resistor.
Due to the different coefficients of expansion for the metallic electrode and the conductive polymer, poor contact between the two generally occur. A first problem is that when the polymer composites are applied to resistors or components of positive temperature coefficient, the poor contact between the metallic electrode and the conductive polymer becomes more critical since they encounter cyclic or non-cyclic temperature variances. The second problem concerns with the resistance of interface between the metallic electrode and the conductive polymer. Since the conductive polymer is made from conductive grains and insulating polymer material, during the adhering process of the metallic electrode to the conductive polymer, the insulating polymer material may flow into the interface of the conductive grains and the metallic electrode, causes higher resistance and decreases the performance of the finished polymer composite.
FIGS. 1
a
to
1
c
are sectional views showing the interface of the conductive polymer
10
and the metallic electrode
12
in three stages of enlargement. The views clearly show that the contact surfaces of the polymer
10
and the metallic electrode
12
are smooth.
To solve the problems of poor contact and higher interface resistance, U.S. Pat. Nos. 4,689,475 and 4,800,253 disclose compositions of metallic electrode and conductive polymer element in which the metallic electrode has a microrough surface, for example, having irregularities which protrude from the surface with a height of 0.1 to 100 microns, to improve its adhesion to the conductive polymer. As shown in
FIGS. 2
a
to
2
c,
the three stage enlarged sectional views of the interface of the conductive polymer
10
and the metallic electrode
14
, the microrough surface of the metallic electrode
14
will improve the adhesive strength of the electrode
14
to the polymer
10
, and enhance the conductivity of the electrode
14
and the conductive polymer
10
by the larger contact area of the microrough surface. But, the processes for forming the microrough surfaces are not disclosed in the two patents, and the roughness of the electrode
14
is not enough. In the U.S. Pat. No. 4,689,475, the metallic electrode
14
and the polymer
10
contact only by impacting. The U.S. Pat. No. 4,800,253, which is a continuation-in-part of U.S. Pat. No. 4,689,475, makes the electrode in direct physical contact with the conductive polymer element and having two-stage protrusions which may enhance the connection of the electrode and the polymer. But, during impacting, there is no excess cavity for the polymer composite to flow, as a result, the insulating polymer material flowing into the interface of the conductive grains and the metallic electrode still decreases the conductivity of the electrode and the polymer.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a conductive film, having microrough surface made by a composite plating method, to be applicable as an electrode of a polymer composite, so that the conductive polymer composite performs higher adhesive strength between the electrode and the polymer, and lower interface resistance therebetween.
In order to achieve the foregoing objective, the present invention provides a method for making a conductive polymer composite. The method includes the following steps: providing a conductive polymer base material; utilizing a composite plating method to form an electrode having microrough surface of layer, measured 0.1 to 100 microns, on a surface of a base material; and finally pressing the electrode onto the conductive polymer base material. The microrough electrode made by composite plating method enhances the adhering strength of the electrode to the polymer composite, and provides suitable cavities for the flow of polymer so as to prevent the insulating polymer from filling into the clearance between the electrode and the conductive grains, and ensures the lower interface resistance.
Another objective of the present invention is to provide a process for fabricating composite plating films which have microrough surfaces. The process includes the following steps: preparing a plating tank containing a metal plating solution and insoluble particles dispersed in the metal plating solution; placing a polymer base material on the cathode while placing a metal on the anode of a power supply for plating and forming a microrough surface of 0.1 to 100 microns roughness on the base material.
A further objective of the present invention is to provide an electronic element including a conductive polymer base material and a conductive electrode having microrough surface of 0.1 to 100 microns in roughness. The microrough surface of the electrode can firmly adhere to the composite polymer.
REFERENCES:
patent: 3591468 (1971-07-01), Nishio et al.
patent: 3676308 (1972-07-01), Brown
patent: 3945893 (1976-03-01), Ishimori et al.
patent: 4689475 (1987-08-01), Kleiner et al.
patent: 4904545 (1990-02-01), Sagiyama et al.
patent: 5865976 (1999-02-01), Takeuchi et al.
patent: 5928547 (1999-07-01), Shea et al.
Chang Kun-Huang
Chou Shu-Chin
Lin Chen-Ron
Industrial Technology Research Institute
Patel Rajnikant D.
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