Packaging Structure and Method

• US 20090227072A1
• Filed: 05/26/2009
• Published: 09/10/2009
• Est. Priority Date: 03/10/2000
• Status: Active Grant

• Current Assignee: Stats Chippac Pte. Ltd. (JCET Group Co., Ltd.)
• Original Assignee: Stats Chippac Limited
• Inventors: Kweon, Young-Do, Kim, Kyung-Moon, Ahmad, Nazir, Tam, Samuel, Pendse, Rajendra D.
• Granted Patent: US 8,119,450 B2
• Time in Patent Office: Days
• US Class Current: 438/118
• CPC Class Codes: H01L 21/563 Encapsulation of active face of flip-chip device, e.g. underfilling or underencapsulation of flip-chip, encapsulation preform on chip or mounting substrate
• CPC Class Codes: H01L 2224/10135 Alignment aids
• CPC Class Codes: H01L 2224/1134 Stud bumping, i.e. using a wire-bonding apparatus
• CPC Class Codes: H01L 2224/13144 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/13147 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/16145 the bodies being stacked
• CPC Class Codes: H01L 2224/16225 the item being non-metallic, e.g. insulating substrate with or without metallisation
• CPC Class Codes: H01L 2224/29111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/29144 Gold [Au] as principal constituent
• CPC Class Codes: H01L 2224/2919 with a principal constituent of the material being a polymer, e.g. polyester, phenolic based polymer, epoxy
• CPC Class Codes: H01L 2224/73203 Bump and layer connectors
• CPC Class Codes: H01L 2224/81139 Guiding structures on the body
• CPC Class Codes: H01L 2224/81203 Thermocompression bonding, e.g. diffusion bonding, pressure joining, thermocompression welding or solid-state welding
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• CPC Class Codes: H01L 2224/83102 using surface energy, e.g. capillary forces
• CPC Class Codes: H01L 2224/83191 wherein the layer connectors are disposed only on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/83194 Lateral distribution of the layer connectors
• CPC Class Codes: H01L 2224/92125 the second connecting process involving a layer connector
• CPC Class Codes: H01L 24/29 of an individual layer connector
• CPC Class Codes: H01L 24/81 using a 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 2924/00012 : Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• 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 2924/01006 : Carbon [C]
• CPC Class Codes: H01L 2924/01028 : Nickel [Ni]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/0105 : Tin [Sn]
• CPC Class Codes: H01L 2924/01058 : Cerium [Ce]
• 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 2924/0132 : Binary Alloys
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/07802 : not being an ohmic electrical conductor
• CPC Class Codes: H01L 2924/181 : Encapsulation

Abstract

A method for forming metallurgical interconnections and polymer adhesion of a flip chip to a substrate includes providing a chip having a set of bumps formed on a bump side thereof and a substrate having a set of interconnect points on a metallization thereon, providing a measured quantity of a polymer adhesive in a middle region of the chip on the bump side, aligning the chip with the substrate so that the set of bumps aligns with the set of interconnect points, pressing the chip and the substrate toward one another so that a portion of the polymer adhesive contacts the substrate and the bumps contact the interconnect points, and heating the bumps to a temperature sufficiently high to form a metallurgical connection between the bumps and the interconnect points. Also, a flip chip package is made by the method. In some embodiments the metallurgical connection includes an alloy of gold and tin at the interface between the bumps and the interconnect points.

Claims

1. A method of interconnecting a chip to a substrate, the method comprising:

forming a plurality of bumps with a first metal that is devoid of any other metals, the plurality of bumps being formed on a first surface of the chip;

forming a plurality of spots with a second metal that is devoid of any other metals, the plurality of spots being formed on a first surface of the substrate;

contacting each of the plurality of bumps with each of the plurality of spots to form a plurality of bonding interfaces;

heating each bonding interface to a melting point of the second metal to melt a portion of the second metal from each of the plurality of spots;

metallurgically reacting the first and second metals at the melting point to increase the temperature at each bonding interface above the melting point; and

creating a bonding phase at each bonding interface in response to the increased temperature.

2. The method of claim 1, wherein forming a plurality of bumps on the chip with a first metal that is devoid of any other metals comprises forming the plurality of bumps with pure gold.

3. The method of claim 1, wherein forming a plurality of spots on the substrate with a second metal that is devoid of any other metals comprises forming the plurality of spots with pure tin.

4. The method of claim 1, wherein contacting each of the plurality of bumps with each of the plurality of spots to form a plurality of bonding interfaces comprises:

applying adhesive to the first surface of the chip; and

adhering the first surface of the chip to the first surface of the substrate with the adhesive.

5. The method of claim 4, wherein adhering the first surface of the chip to the first surface of the substrate with the adhesive comprises preventing the adhesive from spreading to the bumps or to the spots.

6. The method of claim 1, wherein heating each bonding interface to a melting point of the second metal comprises heating each bonding interface to a temperature of 232 degrees C. for a duration of 1 or 2 seconds.

7. The method of claim 1, wherein metallurgically reacting the first and second metals at the melting point to increase the temperature at each bonding interface above the melting point comprises dissolving a portion of the first metal from each of the plurality of bumps.

8. The method of claim 7, wherein creating a bonding phase at each bonding interface in response to the increased temperature comprises mixing a portion of the dissolved first metal with a portion of the molten second metal.

9. The method of claim 8, wherein mixing a portion of the dissolved first metal with a portion of the molten second metal comprises mixing the first metal with the second metal in the bonding interface to create a 4:

1 alloy composition.

10. The method of claim 9, wherein the 4:

1 alloy composition comprises 80% of the first metal and 20% of the second metal.

11. A method of forming a metallurgical connection between first and second interconnects, the method comprising:

forming a first interconnect with pure gold;

forming a second interconnect with pure tin;

contacting the first and second interconnects to form a bonding interface;

heating the bonding interface to a melting point of tin to melt a portion of the tin from the second interconnect;

metallurgically reacting the gold and tin at the melting point to increase the temperature at the bonding interface above the melting point; and

creating a bonding phase at the bonding interface in response to the increased temperature.

12. The method of claim 11, wherein heating the bonding interface to a melting point of tin comprises heating the bonding interface to a temperature of 232 degrees C. for a duration of 1 or 2 seconds.

13. The method of claim 12, wherein metallurgically reacting the gold and tin at the melting point to increase the temperature at the bonding interface above the melting point comprises dissolving a portion of the gold from the first interconnect.

14. The method of claim 13, wherein creating a bonding phase at the bonding interface in response to the increased temperature comprises mixing a portion of the dissolved gold with a portion of the molten tin.

15. The method of claim 14, wherein mixing a portion of the dissolved gold with a portion of the molten tin comprises mixing the gold with the tin in the bonding interface to create a gold-tin alloy with four parts gold to one part tin.

16. A method of interconnecting a chip to a substrate to form a package, the method comprising:

forming a plurality of bumps with a first metal that is devoid of any other metals, the plurality of bumps being formed on a first surface of the chip;

forming a plurality of spots with a second metal that is devoid of any other metals, the plurality of spots being formed on a first surface of the substrate;

contacting each of the plurality of bumps to each of the plurality of spots to form a plurality of bonding interfaces, wherein the chip and the substrate are held together with a spot adhesive applied to the first surface of the chip;

heating each bonding interface to a melting point of the second metal to melt a portion of the second metal from each of the plurality of spots;

metallurgically reacting the first and second metals at the melting point to increase the temperature at each bonding interface above the melting point;

creating a bonding phase at each bonding interface in response to the increased temperature to bond the chip to the substrate; and

underfilling and overmolding the bonded chip and substrate with adhesive polymer to form the package.

17. The method of claim 16, wherein forming a plurality of bumps on the chip with a first metal that is devoid of any other metals comprises forming the plurality of bumps with pure gold.

18. The method of claim 16, wherein forming a plurality of spots on the substrate with a second metal that is devoid of any other metals comprises forming the plurality of spots with pure tin.

19. The method of claim 16, wherein heating each bonding interface to a melting point of the second metal comprises heating each bonding interface to a temperature of 232 degrees C. for a duration of 1 or 2 seconds.

20. The method of claim 16, wherein metallurgically reacting the first and second metals at the melting point to increase the temperature at each bonding interface above the melting point comprises dissolving a portion of the first metal from each of the plurality of bumps.

21. The method of claim 20, wherein creating a bonding phase at each bonding interface in response to the increased temperature comprises mixing a portion of the dissolved first metal with a portion of the molten second metal.

22. The method of claim 21, wherein creating the bonding phase at each bonding interface in response to the increased temperature further comprises mixing the first metal with the second metal in the bonding interface to create a 4:

1 alloy composition.

23. The method of claim 22, wherein the 4:

1 alloy composition comprises 80% of the first metal and 20% of the second metal.