Methods of assembly for a semiconductor light emitting device package

• US 20060063287A1
• Filed: 08/18/2004
• Published: 03/23/2006
• Est. Priority Date: 08/18/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Andrews, Peter
• Granted Patent: US 7,405,093 B2
• Time in Patent Office: Days
• US Class Current: 438/22
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48227 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/81801 Soldering or alloying
• 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 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/01322 Eutectic Alloys, i.e. obtained by a liquid transforming into two solid phases
• CPC Class Codes: H01L 2924/12032 Schottky diode
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Methods of assembly for a semiconductor light emitting device package may include positioning a submount on a mounting substrate with a solder material and a flux therebetween. The semiconductor light emitting device is positioned on a top side of the submount with a solder material and a flux therebetween to provide an assembled stack that has not been reflowed. The assembled stack is reflowed to attach the submount to the mounting substrate and the light emitting device to the submount.

Claims

1. A method of assembly for a semiconductor light emitting device package, comprising:

positioning a submount on a mounting substrate with a solder material and a flux therebetween;

positioning the semiconductor light emitting device on a top side of the submount with a solder material and a flux therebetween to provide an assembled stack that has not been reflowed; and

reflowing the assembled stack to attach the submount to the mounting substrate and the light emitting device to the submount.

2. A method of claim 1 wherein:

positioning a submount on a mounting substrate with a solder material and a flux therebetween comprises positioning a submount on a mounting substrate with a solder paste therebetween; and

positioning the semiconductor light emitting device on a top side of the submount with a solder material and a flux therebetween includes forming a solder material layer on at least one of the semiconductor light emitting device and the top side of the submount.

3. The method of claim 2 further comprising:

disposing the solder paste on the mounting substrate; and

disposing the flux on the top side of the submount, displaced from the mounting substrate, wherein the flux contacts the solder material layer.

4. The method of claim 3 wherein reflowing the assembled stack comprises heating the assembled stack in an oven to a temperature and at a rate selected to provide a metal to metal bond between the mounting substrate and the submount and between the submount and the light emitting device.

5. The method of claim 4 wherein the metal to metal bonds comprise high temperature solder bonds.

6. The method of claim 5 wherein the solder paste comprises a gold-tin (AuSn) solder paste and wherein the solder material on the light emitting device comprises AuSn.

7. The method of claim 6 wherein the temperature is at least about 300°

C.

8. The method of claim 7 wherein the light emitting device comprises a light emitting diode (LED).

9. The method of claim 3 wherein reflowing the assembled stack is followed by soldering the reflowed assembled stack to a circuit board without reflowing attachment of the submount to the mounting substrate or of the light emitting device to the submount using a medium or low temperature solder.

10. The method of claim 3 wherein disposing a solder paste comprises disposing the solder paste on a contact pad on a top side of the mounting substrate.

11. The method of claim 3 wherein disposing a flux comprises placing a flux dot on a contact pad on the top side of the submount.

12. The method of claim 1 wherein reflowing the assembled stack comprises heating the assembled stack in an oven to a temperature and at a rate selected to provide a metal to metal bond between the mounting substrate and the submount and between the submount and the light emitting device.

13. The method of claim 12 wherein the metal to metal bonds comprise high temperature solder bonds.

14. The method of claim 13 wherein positioning a submount on a mounting substrate with a solder material and a flux therebetween comprises positioning a submount on a mounting substrate with a solder paste therebetween and wherein the solder paste comprises a gold-tin (AuSn) solder paste and wherein the solder material between the light emitting device and the submount comprises AuSn.

15. The method of claim 12 wherein the temperature is at least about 300°

C.

16. The method of claim 1 wherein the light emitting device comprises a light emitting diode (LED).

17. The method of claim 1 wherein reflowing the assembled stack is followed by soldering the reflowed assembled stack to a circuit board without reflowing attachment of the submount to the mounting substrate or of the light emitting device to the submount using a medium or low temperature solder.

18. A method of assembly for a semiconductor light emitting device package, comprising:

providing a mounting substrate, a high temperature solder backside terminated submount, a high temperature solder terminated semiconductor light emitting device, a high temperature solder paste and a solder flux to a pick and place assembly apparatus;

wherein the following operations are performed by the pick and place apparatus;

dispensing the high temperature solder paste on the mounting substrate;

placing the submount with a bottom face thereof on the mounting substrate with the dispensed solder paste therebetween;

dispensing the flux on a top face of the submount;

placing the light emitting device on the submount with the flux therebetween, the light emitting device having a high temperature solder material deposited on a face thereof contacting the dispensed flux to provide an unsoldered assembled stack; and

then

providing the assembled stack for heating in a reflow oven; and

wherein the following operation is performed by the reflow oven;

reflowing the assembled stack.

19. The method of claim 18 wherein reflowing the assembled stack is followed by flux cleaning the reflowed assembled stack.

20. The method of claim 18 wherein placing the light emitting device includes flipping the light emitting device before placing the light emitting device on the submount.

21. The method of claim 20 wherein the light emitting device is provided to the pick and place machine on a carrier tape.

22. The method of claim 21 wherein the light emitting device is positioned on the carrier tape with an epi-layer side thereof up and wherein placing the light emitting device includes punching the light emitting device off the carrier tape to a first chuck with a punch pin without contacting the epi-layer side of the light emitting device with the punch pin;

moving the light emitting device from the first chuck to a second chuck to flip the light emitting device; and

placing the light emitting device on the submount with the second chuck.

23. A method of placing a light emitting device on a mounting surface, comprising:

providing the light emitting device positioned on a carrier tape with an epi-layer side of the light emitting device up;

punching the light emitting device off the carrier tape to a first chuck with a punch pin without contacting the epi-layer side of the light emitting device with the punch pin;

moving the light emitting device from the first chuck to a second chuck to flip the light emitting device; and

placing the light emitting device on the mounting surface with the second chuck.