Methods and apparatus for electroplating electrical contacts

• US 5,271,822 A
• Filed: 03/22/1993
• Issued: 12/21/1993
• Est. Priority Date: 12/11/1991
• Status: Expired due to Fees

• Current Assignee: Microelectronics and Computer Technology Corporation
• Original Assignee: Microelectronics and Computer Technology Corporation
• Inventors: Lin, Charles W. C., Nolan, Ernest R.
• Primary Examiner(s): Tufariello, T. M.
• Application Number:
  US08/034,027
• Time in Patent Office: 274 Days
• Field of Search: 205/122
• US Class Current: 205/122
• CPC Class Codes: C25D 17/004 Sealing devices
• CPC Class Codes: H05K 13/0465 by soldering H05K13/0469 takes precedence
• CPC Class Codes: H05K 3/241 characterised by the electroplating method; means therefor, e.g. baths or apparatus
• CPC Class Codes: H05K 3/3473 Plating of solder

Abstract

A method for selectively electroplating a metallic coating, such as solder, onto a plurality of small and closely spaced electrical contacts. The method includes sealingly enclosing the contacts in an electroplating cell having an anode, a cathode and a chamber, forming an electrical connection between the cathode and the contacts and electroplating the contacts.

Claims

1. A method of selectively electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing having an anode, a cathode and a chamber, said chamber having first and second fluid ports;

sealingly enclosing the contacts within the chamber;

forming an electrical connection between the cathode and the contacts;

before admitting an electroplating solution, admitting a fluid into the sealed chamber through one of the ports and expelling the fluid from the sealed chamber through the other of the ports;

admitting the electroplating solution into the sealed chamber through the one of the ports;

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution; and

expelling the electroplating solution from the sealed chamber through the other of the ports.

2. The method of claim 1 wherein the fluid is an etching solution, thereby etching the contacts prior to electroplating the contacts.

3. The method of claim 2 wherein etching solution removes gold from the contacts.

4. The method of claim 3 wherein the electroplated coating is one of tin or tin-lead.

5. A method of selectively electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing having an anode, a cathode and a chamber, said chamber having first and second fluid ports;

sealingly enclosing the contacts within the chamber;

forming an electrical connection between the cathode and the contacts;

admitting an electroplating solution into the sealed chamber through the one of the ports;

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution;

expelling the electroplating solution from the sealed chamber through the other of the ports; and

after expelling the electroplating solution, admitting a fluid into the sealed chamber through one of the ports and expelling the fluid from the sealed chamber through the other of the ports.

6. The method of claim 5 wherein the fluid is deionized water, thereby flushing out the chamber after electroplating the contacts.

7. A method of selectively electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing an anode, a cathode and a chamber, said chamber having first and second fluid ports;

sealingly enclosing the contacts within the chamber;

forming an electrical connection between the cathode and the contacts;

before admitting an electroplating solution, admitting an etching solution into the sealed chamber through one of the ports and expelling the etching solution from the sealed chamber through the other of the ports, thereby etching the contacts prior to electroplating the contacts;

admitting the electroplating solution into the sealed chamber through the one of said ports;

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution;

expelling the electroplating solution from the sealed chamber through the other of said ports; and

after expelling the electroplating solution, admitting deionized water into the sealed chamber through one of the ports and expelling the deionized water from the sealed chamber through the other of the ports, thereby flushing out the chamber after electroplating the contacts.

8. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode and resilient sealing means, said chamber having a side exposed to the outside of the housing and having inlet and outlet fluid ports, said anode located in the chamber, said cathode sized and shaped for directly contacting the contacts, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid ports in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting and expelling a first solution into and out of the sealed chamber through the fluid ports before admitting an electroplating solution;

admitting an electroplating solution through the inlet fluid port into the sealed chamber;

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts; and

expelling the electroplating solution from the chamber through the outlet fluid port.

9. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode and resilient sealing means, said chamber having a side exposed to the outside of the housing and having inlet and outlet fluid ports, said anode located in the chamber, said cathode sized and shaped for directly contacting the contacts, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid ports in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting an electroplating solution through the inlet fluid port into the sealed chamber;

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts;

expelling the electroplating solution from the chamber through the outlet port; and

admitting and expelling another solution into and out of the sealed chamber through the fluid ports after expelling the electroplating solution.

10. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode, resilient sealing means and a fluid port, said chamber having a side exposed to the outside of the housing, said anode located in the chamber, said cathode sized and shaped for directly contacting the contacts wherein the cathode is connected to the resilient sealing means, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid port in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting an electroplating solution through the fluid port into the sealed chamber; and

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts.

11. The method of claim 10 wherein the cathode is combined with the resilient seal means.

12. The method of claim 11 wherein the cathode and the resilient seal means include an elastomeric connection.

13. The method of claim 12 wherein the cathode and the resilient seal means are an elastomeric connection.

14. The method of claim 12 wherein the elastomeric connection is a carbon filled elastomeric material.

15. The method of claim 14 wherein the carbon filled elastomeric material includes carbon impregnated layers of silicone separated electrically by electrically non-conductive silicone layers.

16. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode, resilient sealing means and a fluid port, said chamber having a side exposed to the outside of the housing, said anode located in the chamber wherein the anode is a separate element from the housing, said cathode sized and shaped for directly contacting the contacts, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid port in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting an electroplating solution through the fluid port into the sealed chamber; and

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts.

17. The method of claim 16, further including

positioning the anode such that the anode is spaced over and extends across the contacts, thereby providing an even distribution of electroplating current to the contacts.

18. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode, resilient sealing means and a fluid port, said chamber having a side exposed to the outside of the housing, said anode located in the chamber, said cathode sized and shaped for directly contacting the contacts together in electrical parallel, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid port in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting an electroplating solution through the fluid port into the sealed chamber; and

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts.

19. The method of claim 18 wherein the cathode has high resistance, thereby overshadowing variations in contact resistance between the cathode and individual contacts.

20. The method of claim 19 wherein the contacts are electroplated to an even thickness.

21. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode, resilient sealing means and a fluid port, said chamber having a side exposed to the outside of the housing, said anode located in the chamber, said cathode sized and shaped for directly contacting the contacts, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid port in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting an electroplating solution through the fluid port into the sealed chamber; and

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts wherein the electroplated coating is at least 5 microns thick.

22. A method for electroplating a metallic coating onto a plurality of closely spaced outer lead fingers of a tape-automated-bonded tape, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode, resilient sealing means and a fluid port, said chamber having a side exposed to the outside of the housing, said anode located in the chamber, said cathode sized and shaped for directly contacting the fingers, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid port in fluid communication with the chamber;

sealingly enclosing portions of the fingers in the chamber wherein other portions of the fingers extend outside the chamber;

directly contacting and electrically connecting the cathode to the fingers wherein the cathode is positioned outside the chamber;

admitting an electroplating solution through the fluid port into the sealed chamber; and

electroplating a coating onto the fingers by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the fingers.

23. The method of claim 22 wherein the outer lead fingers extend outwardly from an integrated circuit.

24. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts wherein the contacts are disposed on the top surface of a substrate, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a cathode, resilient sealing means and a fluid port, said chamber having a side exposed to the outside of the housing, wherein the chamber encloses the contacts without enclosing the entire top surface of the substrate thereby protecting the unenclosed portion of the top surface from unwanted contact with the electroplating solution, said anode located in the chamber, said cathode sized and shaped for directly contacting the contacts, said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and said fluid port in fluid communication with the chamber;

sealingly enclosing the contacts in the chamber;

directly contacting and electrically connecting the cathode to the contacts;

admitting an electroplating solution through the fluid port into the sealed chamber; and

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution, thereby simultaneously electroplating the contacts.

25. The method of claim 24 wherein the unenclosed portion of the top surface of the substrate includes an area encompassed by the contacts.

26. The method of claim 24 wherein the unenclosed portion of the top surface of the substrate is partially populated with electronic components.

27. The method of claim 24 wherein the unenclosed portion of the top surface of the substrate contains surface plating other than solder.

28. A method for electroplating a metallic coating onto a plurality of closely spaced electrical contacts, comprising the steps of:

providing an electroplating cell housing which includes a chamber, an anode, a single cathode, resilient sealing means, and inlet and outlet fluid ports,

said chamber having a side exposed to the outside of the housing,

said anode a separate element from the housing and located in the chamber,

said cathode having high resistance, sized and shaped for directly contacting the contacts and connected to the resilient means,

said resilient sealing means connected to the housing and surrounding the exposed side of the chamber, and

said inlet and outlet fluid ports in fluid communication with the chamber;

sealably enclosing the contacts in the chamber using the resilient sealing means;

admitting an etchant solution into the sealed chamber through the inlet port and expelling the etchant solution from the sealed chamber through the outlet port, thereby etching the contacts;

positioning the anode such that the anode is spaced over and extends across the contacts;

directly contacting and electrically connecting the cathode to the contacts such that the contacts are connected together in electrical parallel and the high resistance of the cathode overshadows variations in contact resistance between the cathode and individual contacts;

admitting an electroplating solution into the sealed chamber through the inlet port after expelling the etchant solution;

electroplating a coating onto the contacts by a flow of electrical current between the anode and the cathode in the presence of the electroplating solution in the sealed chamber after positioning the anode and contacting the cathode to the contacts, thereby simultaneously electroplating the contacts using the single cathode;

expelling the electroplating solution from the chamber through the outlet port; and

admitting a fluid into the sealed chamber through the inlet port and expelling the fluid from the sealed chamber through the outlet port after expelling the electroplating solution, thereby flushing the electroplating solution out of the chamber.