TECHNIQUES FOR ARRANGING SOLDER BALLS AND FORMING BUMPS

• US 20090283575A1
• Filed: 05/15/2008
• Published: 11/19/2009
• Est. Priority Date: 05/15/2008
• Status: Active Grant

• Current Assignee: Ultratech Incorporated (Veeco Instruments Incorporated)
• Original Assignee: International Business Machines Corporation
• Inventors: Libsch, Frank R., Budd, Russell A., Nah, Jae-Woong
• Granted Patent: US 7,780,063 B2
• Time in Patent Office: Days
• US Class Current: 228/246
• CPC Class Codes: B23K 1/0016 Brazing of electronic components
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2101/42 Printed circuits
• CPC Class Codes: B23K 3/0623 for shaped solder piece feeding, e.g. preforms, bumps, balls, pellets, droplets
• CPC Class Codes: B23K 3/087 Soldering or brazing jigs, fixtures or clamping means
• 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 2224/05571 the external layer being disposed in a recess of the surface
• CPC Class Codes: H01L 2224/05573 Single external layer
• CPC Class Codes: H01L 2224/05599 Material
• CPC Class Codes: H01L 2224/06131 being uniform, i.e. having a uniform pitch across the array
• CPC Class Codes: H01L 2224/11003 for holding or transferring the bump preform
• CPC Class Codes: H01L 2224/11005 for aligning the bump connector, e.g. marks, spacers
• CPC Class Codes: H01L 2224/11334 using preformed bumps
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 2224/13111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 24/11 Manufacturing methods for bumps on insulating substrates H01L21/4853
• CPC Class Codes: H01L 24/13 of an individual bump connector
• 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 2924/0001 Technical content checked by a classifier
• 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 2924/01005 : Boron [B]
• CPC Class Codes: H01L 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01013 : Aluminum [Al]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/0103 : Zinc [Zn]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01051 : Antimony [Sb]
• CPC Class Codes: H01L 2924/01076 : Osmium [Os]
• CPC Class Codes: H01L 2924/01079 : Gold [Au]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/01327 : Intermediate phases, i.e. intermetallics compounds
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/14 : Integrated circuits
• CPC Class Codes: H01L 2924/181 : Encapsulation
• CPC Class Codes: H01L 2924/3025 : Electromagnetic shielding
• CPC Class Codes: H05K 2203/0113 : Female die used for patterning or transferring, e.g. temporary substrate having recessed pattern
• CPC Class Codes: H05K 2203/0292 : Using vibration, e.g. during soldering or screen printing
• 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 2203/041 : Solder preforms in the shape of solder balls soldering leadless components having an array of bottom contacts H05K3/3436
• CPC Class Codes: H05K 2203/0557 : Non-printed masks
• CPC Class Codes: H05K 2203/105 : Using an electrical field; Special methods of applying an electric potential electroplating H05K2203/0723
• CPC Class Codes: H05K 3/3478 : Applying solder preforms; Transferring prefabricated solder patterns

Abstract

A mask having a plurality of through holes and a mold having a plurality of cavities are provided, and the through holes and the cavities are aligned. Conductive balls ale dispensed into the aligned through holes and cavities Substantially one ball is dispensed into each aligned through hole and cavity, and the mask with the holes and the cavities in the mold ale configured and dimensioned such that the balls are substantially flush with, or recessed below, an outer surface of the mask. The mask is removed, the conductive balls are aligned with pads of a semiconductor device, and the conductive balls are transferred to the pads by fluxless reflow in a formic acid environment. Vibrational, electrostatic, and direct transfer aspects are also disclosed.

Claims

1. A method comprising the steps of:

providing a mask having a plurality of through holes and a mold having a plurality of cavities;

aligning said through holes and said cavities;

dispensing preformed conductive balls into said aligned through holes and cavities, substantially one preformed conductive ball to each aligned through hole and cavity, said mask with said holes and said cavities in said mold being configured and dimensioned such that;

said preformed conductive balls are one of substantially flush with, and recessed below, an outer surface of said mask under conditions of said alignment of said through holes and said cavities; and

upon removal of said mask from said mold, said preformed conductive balls extend beyond an outer surface of said mold;

removing said mask from said mold so that said preformed conductive balls extend beyond said outer surface of said mold;

aligning said preformed conductive balls with pads of a semiconductor device; and

transferring said preformed conductive balls to said pads by fluxless reflow in a formic acid environment.

2. The method of claim 1, wherein said preformed conductive balls comprise solder balls with a liquidus temperature of at least about 250 degrees Centigrade.

3. The method of claim 2, wherein said dispensing comprises at least use of a squeeze brush.

4. The method of claim 2, wherein said dispensing comprises at least vibration of said mask and mold.

5. The method of claim 2, wherein said dispensing comprises at least air flow from a location outward from said mask.

6. The method of claim 2, wherein said mask is formed from at least one of glass, ceramic, silicon, and polymer.

7. The method of claim 2, wherein said mold is formed from at least one of glass and silicon.

8. The method of claim 2, wherein said preformed conductive balls have a diameter and wherein said through holes have a diameter of about 100 percent to about 195 percent of said diameter of said balls.

9. The method of claim 8, wherein said mold cavities have a diameter of about 1 to about 2 times said diameter of said preformed conductive balls.

26. The method of claim 1, wherein:

said mold provided in said providing step comprises a glass mold;

said preformed conductive balls dispensed in said dispensing step have a diameter e; and

said cavities of said mold provided in said providing step comprise rounded cavities having a depth of from about thirty percent of e to about ninety five percent of e.

27. The method of claim 1, wherein:

said mold provided in said providing step comprises a silicon mold;

said preformed conductive balls dispensed in said dispensing step have a diameter e; and

said cavities of said mold provided in said providing step comprise pits having an opening diameter ranging from about e to about 2e and having tapered side walls with a tapered side wall angle controlled such that upon removal of said mask from said mold, said preformed conductive balls extend beyond said outer surface of said mold.

10. A method comprising the steps of:

providing a mold having a plurality of cavities;

dispensing conductive balls into said cavities, substantially one ball to each cavity, by tipping and vibrating said mold, said cavities in said mold being configured and dimensioned such that said balls are substantially secured therein during said tipping and vibrating;

aligning said conductive balls with pads of a semiconductor device; and

transferring said conductive balls to said pads by fluxless reflow in a formic acid environment.

11. The method of claim 10, wherein said cavities have substantially vertical side walls and a depth such that centers of said balls are substantially below an outer surface of said mold.

12. The method of claim 11, wherein said conductive balls comprise solder balls with a liquidus temperature of at least about 250 degrees Centigrade.

13. The method of claim 12, wherein said mold is formed from at least one of glass and silicon.

15. A method comprising the steps of:

providing an electrically resistive mold having a plurality of cavities;

dispensing conductive balls into said cavities, substantially one ball to each cavity, by charging said balls to a first polarity and said mold to a second polarity different than said first polarity;

aligning said conductive balls with pads of a semiconductor device; and

transferring said conductive balls to said pads by fluxless reflow in a formic acid environment.

16. The method of claim 15, wherein said conductive balls comprise solder balls with a liquidus temperature of at least about 250 degrees Centigrade.

17. The method of claim 16, wherein said mold is formed of one of silicon and glass.

18. The method of claim 17, wherein said mold further comprises an insulating oxide layer.

19. The method of claim 16, wherein said charging of said mold comprises rubbing with a cloth.

20. The method of claim 16, wherein said charging of said mold is carried out with an ion generator.

21. The method of claim 15, wherein said mold further comprises keep-out zones between said cavities, further comprising the additional step of charging said keep-out zones to repel said balls.

22. The method of claim 15, further comprising the additional step of keeping said mold substantially discharged and tied to one of a common potential and ground when not holding or attracting said solder balls.

23-25. -25. (canceled)