Solder reflow with microwave energy

• US 20030121958A1
• Filed: 12/28/2001
• Published: 07/03/2003
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Gonzalez, Carlos, Wang, Lejun, Ratificar, Glenn
• Granted Patent: US 6,644,536 B2
• Time in Patent Office: Days
• US Class Current: 228/246
• CPC Class Codes: B23K 1/008 Soldering within a furnace B23K1/012 takes precedence
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05022 the internal layer being at least partially embedded in the surface
• CPC Class Codes: H01L 2224/05027 the internal layer extending out of an opening
• CPC Class Codes: H01L 2224/0508 being stacked
• CPC Class Codes: H01L 2224/05572 the external layer extending out of an opening
• CPC Class Codes: H01L 2224/1134 Stud bumping, i.e. using a wire-bonding apparatus
• CPC Class Codes: H01L 2224/81805 involving forming a eutectic alloy at the bonding interface
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/11 Manufacturing methods for bumps on insulating substrates H01L21/4853
• 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 2924/00011 Not 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 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 2924/14 Integrated circuits
• CPC Class Codes: H05K 3/3436 having an array of bottom contacts, e.g. pad grid array or ball grid array components
• CPC Class Codes: H05K 3/3494 Heating methods for reflowing of solder using integral heating means H05K1/0212

Abstract

The present invention includes a mechanical joint between a die and a substrate that is reflowed by microwave energy and a method of forming such a mechanical joint by printing a solder over a substrate, placing the solder in contact with a bump over a die, reflowing the solder with microwave energy, and forming a mechanical joint from the solder and the bump.

Claims

1. A method comprising:

forming a solder over a substrate;

placing said solder in contact with an input/output connection of a die;

heating said substrate and said die with microwave energy to reflow said solder; and

forming a mechanical joint between said substrate and said die.

2. The method of claim 1 wherein frequency of said microwave energy is swept very rapidly.

3. The method of claim 1 further comprising mixing said microwave energy by moving said substrate and said die during said heating.

4. The method of claim 1 further comprising mixing said microwave energy by stirring with a reflective material.

5. The method of claim 1 further comprising activating flux prior to said reflowing of said solder.

6. The method of claim 1 wherein said input/output connection is a bump.

7. The method of claim 6 wherein said solder comprises an eutectic solder and said bump comprises a high Lead solder.

8. The method of claim 6 wherein said solder comprises a no-Lead solder and said bump comprises Alternate Ball Metallurgy (ABM).

9. A method comprising:

forming a final passivation layer over a die;

removing said final passivation layer over a bond pad of said die;

forming an Under Bump Metallurgy (UBM) over said bond pad and said passivation layer;

forming a photoresist over said UBM;

uncovering a first portion of said UBM by selectively removing said photoresist, said first portion disposed over said bond pad;

covering said first portion of said UBM by selectively forming a first solder;

removing rest of said photoresist;

removing a second portion of said UBM, said second portion not covered by said first solder;

reflowing said first solder into a bump;

placing said bump in contact with a second solder on a substrate; and

reflowing said second solder with microwave energy.

10. The method of claim 9 wherein said microwave energy has variable frequency.

11. The method of claim 9 wherein said reflowing of said first solder into said bump is with microwave energy.

12. The method of claim 11 wherein said microwave energy has variable frequency.

13. The method of claim 9 wherein said reflowing of said second solder is at a temperature that is about 50 degrees Centigrade lower than said reflowing of said first solder.

14. A mechanical joint comprising:

a bump on a die; and

a solder on a substrate wherein said solder was reflowed by microwave energy.

15. The mechanical joint of claim 14 wherein said microwave energy has variable frequency.

16. The mechanical joint of claim 14 wherein said bump was reflowed by microwave energy.

17. The mechanical joint of claim 16 wherein said microwave energy has variable frequency.