METHODS OF ASSEMBLY FOR A SEMICONDUCTOR LIGHT EMITTING DEVICE PACKAGE

• US 20090315061A1
• Filed: 06/24/2008
• Published: 12/24/2009
• Est. Priority Date: 06/24/2008
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Andrews, Peter Scott
• Granted Patent: US 9,147,812 B2
• Time in Patent Office: Days
• US Class Current: 257/99
• CPC Class Codes: H01L 2224/83192 wherein the layer connectors are disposed only on another item or body to be connected to the semiconductor or solid-state body
• CPC Class Codes: H01L 33/48 characterised by the semiconductor body packages

Abstract

Methods of assembly for a semiconductor light emitting device package may include positioning a submount on a mounting substrate with a flux material therebetween and at least substantially free of solder material therebetween. The submount has a metal bonding layer facing the mounting substrate. A semiconductor light emitting device is positioned on a top side of the submount with a flux material therebetween to provide an assembled stack. The assembled stack is reflowed to attach the metal bonding layer of the submount to the mounting substrate and to attach the light emitting device to the submount.

Claims

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

positioning a submount on a mounting substrate with a flux material therebetween and at least substantially free of solder material therebetween, the submount having a metal bonding layer facing the mounting substrate;

positioning a semiconductor light emitting device on a top side of the submount opposite the mounting substrate with a flux material therebetween to provide an assembled stack; and

reflowing the assembled stack to attach the metal bonding layer of the submount to the mounting substrate and to attach the light emitting device to the submount.

2. The method of claim 1, wherein:

positioning the submount on the mounting substrate further comprises directly contacting at least a major portion of a lower surface of the metal bonding layer to the mounting substrate through a thin film of the flux material, with the flux material forming a blocking layer around a periphery of the interface between the metal bonding layer and the mounting substrate to inhibit and remove oxidation of the lower surface of the metal bonding layer during the reflowing of the assembled stack.

3. The method of claim 2, wherein, during reflowing of the assembled stack, the flux material between the lower surface of the metal bonding layer and the mounting substrate is at least substantially removed so that the lower surface of the metal bonding layer directly contacts and bonds to the mounting substrate.

4. The method of claim 2, further comprising placing a dot of the flux material on the mounting substrate before positioning the submount, wherein the dot of the flux material is placed on a metal bonding pad of the mounting substrate, and positioning the submount includes pressing the submount into the flux dot to directly contact the mounting substrate through the thin film of the flux material.

5. The method of claim 4, wherein:

positioning the submount on the mounting substrate further comprises directly contacting the lower surface of the metal bonding layer to the metal bonding pad of the mounting substrate through a thin film of the flux material; and

reflowing the assembled stack comprises heating the assembled stack in an oven to a temperature that provides a bond directly between the metal bonding layer of the submount and the metal bonding pad of the mounting substrate.

6. The method of claim 1, wherein:

positioning the submount on the mounting substrate further comprises directly contacting a lower surface of the metal bonding layer to the mounting substrate with the flux material forming a blocking layer around a periphery of the interface between the metal bonding layer and the mounting substrate to inhibit oxidation of the lower surface of the metal bonding layer during the reflowing of the assembled stack.

7. The method of claim 1, wherein reflowing the assembled stack comprises heating the assembled stack in an oven to a temperature that provides a bond directly between the metal bonding layer of the submount and metal in the mounting substrate and between metal in the mounting substrate and metal in the light emitting device.

8. The method of claim 7, wherein the metal bonding layer comprises AuSn and, during reflowing of the assembled stack, the assembled stack is heated to above 280°

C. for a sufficient length of time to form a metal-to-metal bond directly between the metal bonding layer and the mounting substrate and between the mounting substrate and the light emitting device.

9. The method of claim 1, further comprising forming the metal bonding layer of the submount to have a thickness that is controlled based on surface roughness of an upper surface of the mounting substrate that will be bonded to the metal bonding layer.

10. The method of claim 9, wherein the metal bonding layer is formed with a thickness of about 3 μ

m when the metal bonding layer is to be bonded to a metal layer on a surface of the ceramic mounting substrate that has been burnished after the ceramic mounting substrate has been diced from a ceramic rod.

11. The method of claim 9, further comprising measuring the surface roughness of the upper surface of the mounting substrate that will be bonded to the metal bonding layer, and using the measured surface roughness to define a thickness of the metal bonding layer formed on the submount.

12. The method of claim 9, further comprising metal plating the upper surface of the mounting substrate using a direct current electrodeless plating process to form a smooth upper surface on the mounting substrate to which the metal bonding layer of the submount is bonded during the reflowing of the assembled stack.

13. The method of claim 12, further comprising burnishing the plated metal on the upper surface of the mounting substrate to increase its smoothness before reflowing the assembled stack to attach the metal bonding layer of the submount to the burnished metal plated upper surface of the mounting substrate.

14. The method of claim 1, wherein the metal bonding layer comprises gold-tin (AuSn).

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

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

metal plating an upper surface of a mounting substrate using at least one of a sputter process, a electroless process, and a direct current and/or pulsed electroplating process;

patterning the plated metal on the mounting substrate to form a metal bonding pad;

forming a metal bonding layer on a submount with a thickness that is defined in response to a surface roughness of the metal bonding pad;

positioning the submount on the upper surface of the mounting substrate with a flux material therebetween and at least substantially free of solder material therebetween, and with the metal bonding layer of the submount facing the mounting substrate;

positioning a semiconductor light emitting device on a top side of the submount with a flux material therebetween to provide an assembled stack; and

reflowing the assembled stack to attach the metal bonding layer of the submount to the mounting substrate and to attach the light emitting device to the submount.

17-20. -20. (canceled)