Modified Face-Down Bonding of Ridge-Waveguide Lasers Using Hard Solder

Author

Teo, J. W Ronnie ; Shi, X.Q. ; Yuan, S. ; Li, G.Y. ; Wan, Z.F.

Author_Institution

Nanyang Technol. Univ., Singapore

Volume

31

Issue

2

fYear

2008

fDate

4/1/2008 12:00:00 AM

Firstpage

159

Lastpage

167

Abstract

A modified face-down bonding technique of ridge-waveguide laser diodes (LDs) using 80Au20Sn solder has been performed. For ease of manufacturability, a bonding window with good bonding integrity and improved optical performance was determined. Metallographical investigation showed that the solder joint comprised of a layer of delta phase compound near the solder/heatsink interface, a layer of (Au,Ni)Sn intermetallic compound (IMC) at the solder/heatsink interface, and zeta´ phase Au/Sn compound at the center of the solder joint. The delta phase shifted to the interfaces after reflow was postulated by its lower surface tension than zeta´ phase Au/Sn compound. Good bonding integrity was observed with LD residues still adhering onto the bond pad after die shear testing. Scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) analyses of the fracture surface showed that the fracture occurred within the LD, at the GaAs/SiN interface. LDs bonded with this modified bonding process achieved an optical improvement of 2.5-3X compared to the unbonded LDs due to its good thermal management. These bonded LDs further exhibited good long-term reliability with no significant degradation in optical performance and no significant microstructure evolution in the solder joint after 500 thermal cycling test.

Keywords

III-V semiconductors; X-ray chemical analysis; bonding processes; fracture; gallium arsenide; gold alloys; heat sinks; laser reliability; optical fabrication; reflow soldering; ridge waveguides; scanning electron microscopy; semiconductor lasers; silicon compounds; solders; surface tension; tin alloys; waveguide lasers; AuSn; EDX; GaAs-SiN; SEM; bonding integrity; die shear testing; energy dispersive X-ray analysis; fracture surface; hard solder; intermetallic compound; long-term reliability; metallographical investigation; microstructure evolution; modified face-down bonding technique; optical performance; ridge-waveguide laser diodes; scanning electron microscopy; solder joint; solder-heatsink interface; surface tension; thermal cycling test; thermal management; Face-down bonding configuration; laser diode (LD); microassembly; optimal bonding window; reliability testing; solder preform;

fLanguage

English

Journal_Title

Electronics Packaging Manufacturing, IEEE Transactions on

Publisher

ieee

ISSN

1521-334X

Type

jour

DOI

10.1109/TEPM.2008.919329

Filename

4472224