Patterned array of metal balls and methods of making

• US 6,000,603 A
• Filed: 05/23/1997
• Issued: 12/14/1999
• Est. Priority Date: 05/23/1997
• Status: Expired due to Fees

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: McCollam, Robert P., Koskenmaki, David C., Schueller, Randolph D.
• Primary Examiner(s): Ryan, Patrick
• Assistant Examiner(s): STONER, KILEY SHAWN
• Application Number:
  US08/862,804
• Time in Patent Office: 935 Days
• Field of Search: 228/254, 228/160, 228/164, 228/170, 228/174, 228/180.22, 228/246, 228/252, 438/613
• US Class Current: 228/246
• CPC Class Codes: H01L 21/4814 Conductive parts
• CPC Class Codes: H01L 21/4853 Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps
• CPC Class Codes: H01L 21/6835 using temporarily an auxiliary support
• CPC Class Codes: H01L 2224/11003 for holding or transferring the bump preform
• CPC Class Codes: H01L 2224/1111 Shaping
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01025 Manganese [Mn]
• CPC Class Codes: H01L 2924/01057 Lanthanum [La]
• CPC Class Codes: H01L 2924/01078 Platinum [Pt]
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01087 Francium [Fr]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H05K 2201/10734 Ball grid array [BGA]; Bump grid array
• CPC Class Codes: H05K 2203/0113 Female die used for patterning or transferring, e.g. temporary substrate having recessed pattern
• CPC Class Codes: H05K 2203/0156 Temporary polymeric carrier or foil, e.g. for processing or transferring
• CPC Class Codes: H05K 2203/033 Punching metal foil, e.g. solder foil affixing a prefabricated self-supporting metal foil pattern H05K3/202
• CPC Class Codes: H05K 2203/0338 Transferring metal or conductive material other than a circuit pattern, e.g. bump, solder, printed component affixing a prefabricated conductor pattern H05K3/20
• CPC Class Codes: H05K 2203/0405 Solder foil, tape or wire
• CPC Class Codes: H05K 2203/043 Reflowing of solder coated conductors, not during connection of components, e.g. reflowing solder paste
• CPC Class Codes: H05K 3/041 : by using a die for cutting the conductive material
• CPC Class Codes: H05K 3/3478 : Applying solder preforms; Transferring prefabricated solder patterns

Abstract

The present invention relates to a method for making an array of metal balls. The method includes the step of generating a first pattern on a metal foil which includes a plurality of foil projections. The method also includes the step of generating a second pattern on a carrier substrate. The second pattern includes a plurality of carrier recesses that are arranged and configured to correspond with the foil projections of the first pattern. The method further includes the steps of placing the metal foil and the carrier substrate together such that the foil projections of the metal foil fit within the carrier recesses of the carrier substrate, and melting the metal foil such that the foil projections form metal balls positioned within the carrier recesses of the carrier substrate. The invention also relates to metal ball arrays constructed via the above method.

Claims

1. A method for making an array of metal balls comprising the steps of:

generating a first pattern on a continuous sheet of metal foil, the first pattern including a plurality of metal foil projections on the continuous sheet of metal foil;

generating a second pattern on a carrier substrate, the second pattern including a plurality of carrier recesses arranged and configured to correspond with the foil projections of the first pattern;

placing the continuous sheet of metal foil and the carrier substrate together such that the foil projections of the metal foil fit within the carrier recesses of the carrier substrate such that the opposing surfaces of the metal foil and carrier substrate are in intimate contact with one another prior to melting the metal foil; and

melting the metal foil such that the foil projections form metal balls positioned within the carrier recesses of the carrier substrate.

2. The method of claim 1, further comprising the step of coating the metal foil with a fluxing agent after the metal foil and the carrier substrate are placed together.

3. The method of claim 1, wherein the opposing surfaces are bonded together by means of an adhesive prior to melting the metal foil.

4. The method of claim 1, wherein the exposed side of the metal foil includes a plurality of ridges, and the ridges comprise portions of the metal foil that are removed or displaced to partition the projections into discrete sections prior to complete melting of the metal foil to form balls.

5. The method of claim 4, wherein the portions of metal foil are displaced by compressing the metal ridges with a die.

6. The method of claim 4, wherein the portions of metal foil are removed via abrasion.

7. The method of claim 4, wherein the portions of the metal are displaced via melting.

8. The method of claim 7, wherein the melting occurs in a temperature gradient applied so that the metal at the ridges of the exposed side of the foil are the hottest and the metal in the recesses against the carrier substrate are the coolest.

10. The method of claim 1, wherein the first pattern is generated on the metal foil by:

pre-generating the second pattern on the carrier substrate; and

depositing a metal foil on the patterned surface of the carrier substrate.

11. The method of claim 1, wherein the second pattern is generated on the carrier substrate by:

pre-generating the first pattern on the metal foil;

placing a flowable backing material over the patterned metal foil such that the foil projections of the first pattern are substantially covered by the backing material; and

hardening the backing material on the metal foil such that the hardened backing material forms the carrier substrate, wherein first pattern on the metal foil generates the second pattern on the carrier substrate.

12. The method of claim 1, wherein the metal foil comprises solder.

13. The method of claim 1, wherein the carrier substrate comprises a carrier tape.

9. A method for making an array of metal balls comprising the steps of:

generating a first pattern on a metal foil, the first pattern including a plurality of metal foil projections;

generating a second pattern on a carrier substrate, the second pattern including a plurality of carrier recesses arranged and configured to correspond with the foil projections of the first pattern;

placing the metal foil and the carrier substrate together such that the foil projections of the metal foil fit within the carrier recesses of the carrier substrate; and

melting the metal foil such that the foil projections form metal balls positioned within the carrier recesses of the carrier substrate,

wherein the first and second patterns are generated by concurrently embossing both the carrier substrate and the metal foil with an embossing tool.