Supplying a cover gas for wire ball bonding

• US 6,234,376 B1
• Filed: 11/08/1999
• Issued: 05/22/2001
• Est. Priority Date: 07/13/1999
• Status: Expired due to Term

• Current Assignee: Kulicke and Soffa Industries Incorporated
• Original Assignee: Kulicke & Soffa Investments, Inc.
• Inventors: Wicen, Rudolph M.
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): EDMONDSON, LYNNE RENEE
• Application Number:
  US09/435,796
• Time in Patent Office: 561 Days
• Field of Search: 228/180.5, 228/4.5, 228/904, 219/56.1, 219/56.22, 438/617
• US Class Current: 228/180.5
• CPC Class Codes: B23K 20/007 Ball bonding
• CPC Class Codes: H01L 2224/45015 being circular
• CPC Class Codes: H01L 2224/45124 Aluminium (Al) as principal constituent
• CPC Class Codes: H01L 2224/45144 Gold (Au) as principal constituent
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/48 of an individual wire connector
• CPC Class Codes: H01L 2224/78268 Discharge electrode
• CPC Class Codes: H01L 2224/78301 Capillary
• CPC Class Codes: H01L 2224/85045 using a corona discharge, e.g. electronic flame off [EFO]
• CPC Class Codes: H01L 2224/85075 being inert
• CPC Class Codes: H01L 2224/85203 Thermocompression bonding
• CPC Class Codes: H01L 2224/85205 Ultrasonic bonding
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 24/78 Apparatus for connecting with wire connectors
• CPC Class Codes: H01L 24/85 using a wire connector wire bonding in general B23K20/004
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/00015 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed as prior art
• CPC Class Codes: H01L 2924/01005 Boron [B]
• CPC Class Codes: H01L 2924/01007 Nitrogen [N]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01018 : Argon [Ar]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01046 : Palladium [Pd]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding

Abstract

Method and apparatus for supplying a protective cover gas during ball formation on a wire bonding machine to permit the use of wire formed from metals which may react with air, such as copper or aluminum.

Claims

1. A wire ball-bonding apparatus comprising a capillary head having a tip through which a metal bonding wire can be fed, a gas-containment tube having first and second in-line transverse orifices through which the tip of the capillary head can pass, and an electric flame-off device having an electrode which is positioned to be able to form an arc discharge in the tube with the end of the bonding wire, wherein said gas-containment tube and said electric flame-off device are stationary during ball bonding.

2. The apparatus of claim 1 wherein the electrode is positioned inside the gas-containment tube and does not pass through the side of the tube.

3. The apparatus of claim 1 wherein the electrode is embedded within the wall of the gas-containment tube.

4. The apparatus of claim 1 wherein the electrode extends through a third orifice in the side of the gas-containment tube.

5. The apparatus of claim 1 further comprising an end cap at one end of the gas-containment tube.

6. The apparatus of claim 1 wherein the gas-containment tube is round in cross section.

7. The apparatus of claim 1 wherein the gas-containment tube is rectangular in cross section.

8. The apparatus of claim 1 wherein the gas-containment tube is made from a ceramic material.

9. The apparatus of claim 1 wherein the gas-containment tube is made from a glass material.

10. The apparatus of claim 9 wherein the gas-containment tube is made from quartz glass.

11. The apparatus of claim 1 further comprising a source of gas coupled to supply gas to said gas-containment tube.

12. The apparatus of claim 1 wherein said first and second orifices are of size, shape and position so that said capillary head can be positioned in a first position such that said tip extends within said tube through said first orifice such that said tip is adjacent said electrode and in a second position such that said tip extends through said first and second orifices without said tube.

13. A method for forming a wire ball bond using a wire ball-bonding apparatus comprising a capillary head having a tip through which a metal bonding wire can be fed, a gas-containment tube having first and second in-line transverse orifices through which the tip of the capillary head can pass, and an electric flame-off device having an electrode, said method comprising the steps of:

charging a cover gas to the gas-containment tube;

positioning the tip of the capillary head through the first transverse orifice in the gas-containment tube;

feeding the bonding wire through the tip of the capillary head;

energizing the electric flame-off device to form an arc discharge between the electrode and the end of the bonding wire thereby forming a molten ball at the end of the bonding wire;

de-energizing the electric flame-off device, advancing the tip of the capillary head through the second transverse orifice of the gas-containment tube; and

forming a bond between the ball and a substrate outside the gas-containment tube;

wherein said gas-containment tube and said electric flame-off device are stationary during said steps.

14. The method of claim 13 wherein the cover gas is inert to the metal of the molten wire ball.

15. The method of claim 13 wherein the wire comprises copper or aluminum.

16. The method of claim 15 wherein the cover gas is inert to the metal of the molten wire ball.

17. The method of claim 16 wherein the cover gas is argon.

18. The method of claim 13 further comprising permitting the ball to at least partially solidify before advancing the tip of the capillary head through the second orifice.

19. A method for forming a wire ball bond using a wire-bonding machine comprising a capillary head having a tip through which a wire to be bonded may extend, said method comprising the steps of:

positioning said capillary head so that said tip extends through a first orifice into a gas-containment tube;

charging said gas-containment tube with a cover gas;

feeding bonding wire through said tip of said capillary head such that an end of said wire is within said tube;

melting said end of said wire within said tube;

advancing said tip of said capillary head through a second orifice in said tube without moving said tube such that said tip and said melted portion of said wire are without said tube; and

forming a bond between the ball and a substrate outside the gas-containment tube.

20. A method as set forth in claim 19 wherein said melting step comprises:

creating an arc between said end of said wire and an electrode positioned within said tube.