Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating moving substrate
Reexamination Certificate
1999-04-16
2001-02-13
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating moving substrate
C205S152000, C204S206000, C204S207000, C204S227000, C204S211000, C204S241000
Reexamination Certificate
active
06187166
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of electroplating, and more particularly to continuous electroplating of metals used in the interconnection of electronic devices.
BRIEF DESCRIPTION OF PRIOR ART
A large variety of articles are made onto which high quality precious and non-precious metals are electroplated for protective coatings. Particularly well known are jewelry articles where metal coatings improve appearance. In many other applications, metal coatings are used for surface protection to prevent corrosion and/or serve as a diffusion barrier, as for example in the fabrication of electronic devices. In other applications of electrical or electronic devices, metal films are used as electrical contact surfaces. In many of these applications, metal films which have high purity, are free of defects, and have controlled thickness and hardness are required. These quality levels and the necessary manufacturing controls contribute to a significant increase in the cost of such articles.
Integrated circuit devices, having an integrated circuit chip and a lead frame which are sealed within a protective enclosure find wide use in products, among which are consumer electronics, computers, automobiles, telecommunications and military applications. A means to electrically interconnect an integrated circuit chip to circuitry external to the device frequently takes the form of a lead frame. The lead frame is formed from a highly electrically conductive material, such as copper or copper alloys, which are stamped or etched into a plurality of leads and a central area in which the integrated circuit chip is attached. The chip is electrically connected to the leads, usually by wire bonding and the device is encapsulated to provide mechanical and environmental protection. The surface finish of the lead frame plays and important role in the ability to attain a reproducible manufacturing process for connecting the chip. In turn, the required surface finish contributes to lead frames being the most costly piece part used in the assembly of plastic encapsulated integrated circuits.
In plating applications where it is feasible, there are cost advantages to plating a continuous part, as opposed to individual pieces. For relatively thin articles, use of a reel to reel handling mechanism allows continuous plating of long pieces with a minimum number of intervention and consequently fewer opportunities for contamination of the plating baths. In particular, this technique has been applied to the manufacture of thin metal coatings on lead frames for interconnecting integrated circuits.
While automation techniques, such as continuous plating of lead frames do help to reduce costs, expenses associated with plating also involves productivity of the plating lines, cost and maintenance of equipment, cost of plating chemicals and high purity water, and of increasing concern, the cost of waste treatment associated with plating chemicals. Methods to help decrease these costs is of ongoing interest to the industry.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a system for electroplating metal coatings onto a continuous metal article which reduces costs, and secondly, there is provided a process aiming at high productivity plating with a reduction in the number of process steps, process time, and chemical costs. This system and process is applicable to plating lines which have a series of plating cells containing the same or compatible chemical solutions.
It is an object of the invention to provide a cost effective plating system which conserves plating solution by minimizing the amount of said solution wasted as a result of the part to be plated being transported between tanks having different solutions.
Another object of the invention is to provide a process for electroplating which minimizes water consumption by using the plating solution itself for cooling the contacts.
Yet another object is to provide a process which reduces the need for waste treatment of cooling water contaminated with plating solution.
A further object of the invention is to provide a relatively short plating line which allows a linear space reduction.
A further object is to provide a system which avoids costs associated with additional equipment and plumbing required for cooling the electrode by exposure to a chemical solution different from the plating bath, such as cooling water.
A further object of the invention is to provide a system which minimizes damage to fragile parts caused by excess line tension.
A further object is to provide a system having a continuous electrical connection between the D.C. power supply and a rotating cathode contact.
Another object of the invention is to provide a process having a relatively high speed and throughput.
Other objects and advantages of the present invention will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.
A system for electroplating a metal coating onto a continuous article, which constitutes the cathode from a series of plating tanks having the same or compatible plating solutions, and in which said system comprises a continuous electrical connection between the D.C. power supply and the cathode via a rotating contact and wherein the contact cell wherein the rotating cathode contact is cooled by integrating the plating solution itself into the contact cell. The plating system with integrated plating solution cooling is applicable to, but not limited to continuous or reel to reel plating of metal coatings, such as nickel and copper onto a metal piece which constitutes the cathode. The cathode is a strip of metal, for example, copper or a copper alloy which is used for, but not limited to, the production of electronic parts, such as lead frames which provide electrical interconnection in integrated circuit packaging.
A system whereby continuous electrical connection between the D.C. power supply and the cathode is via a rotating contact which is maintained in continuous intimate contact by a non-rotating conductor secured with weights. Alternately, there is provided a system whereby continuous electrical connection between the D.C. power supply and cathode is via a rotating connector which is maintained in intimate contact by a mercury contact.
A process for electroplating a continuous part as it is transported through a series of tanks having the same or compatible chemical composition, wherein said process comprises passing a continuous current from the D.C. power supply to the cathode, and cooling the cathode contact by use of the plating bath solution itself.
The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. It is to be understood that in some instances various aspects of the invention may be shown exaggerated or enlarged to facilitate understanding of the invention.
REFERENCES:
patent: 3870618 (1975-03-01), Seyb, Jr. et al.
patent: 4662997 (1987-05-01), Hirt et al.
patent: 6007694 (1999-12-01), Walsh et al.
Drew David M.
Moehle Paul R.
Smith Stephen J.
Bell Bruce F.
Honeycutt Gary C.
Navarro Arthur I.
Telecky Fred
Texas Instruments Incorporated
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