Lead-free solder flip chip-on-laminate assembly and reliability

Author

Hou, Zhenwei ; Tian, Guoyun ; Hatcher, Casey ; Johnson, R. Wayne ; Yaeger, Erin K. ; Konarski, Mark M. ; Crane, Lawrence

Author_Institution

Lab. for Electron. Assembly & Packaging, Auburn Univ., AL, USA

Volume

24

Issue

4

fYear

2001

fDate

10/1/2001 12:00:00 AM

Firstpage

282

Lastpage

292

Abstract

This paper examines the assembly process for flip chip die with SnAgCu solder bumps and the results of liquid-to-liquid thermal shock testing. The SnAgCu alloy required a thicker dip layer of flux to achieve good wetting compared to the SnPb eutectic alloy. A liquid spray flux yielded more consistent solder wetting with the SnAgCu alloy. With both fluxes, a nitrogen reflow atmosphere was necessary with the SnAgCu alloy. A peak reflow temperature of 246°C was used for the assembly of the SnAgCu thermal shock test vehicles. A lower peak temperature of 235°C did not yield sufficient solder wetting. Liquid-to-liquid thermal shock testing was performed from -40°C to +125°C. The SnPb alloy performed slightly better than the SnAgCu and the dip flux was better that the spray flux. The degree of delamination with the SnAgCu alloy was significantly higher than with the SnPb alloy. Cracks in the underfill between adjacent solder balls were observed. The SnPb alloy extruded into these cracks more readily than the SnAgCu and created electrical shorts

Keywords

chip-on-board packaging; copper alloys; encapsulation; environmental factors; flip-chip devices; integrated circuit interconnections; integrated circuit packaging; integrated circuit reliability; integrated circuit testing; reflow soldering; silver alloys; temperature; thermal shock; tin alloys; wetting; -40 to 125 C; 235 C; 246 C; N₂; SnAgCu; SnAgCu alloy; SnAgCu solder bumps; SnAgCu thermal shock test vehicles; SnPb; SnPb alloy; SnPb alloy extrusion; assembly; assembly process; delamination; dip flux; dip layer flux; electrical shorts; flip chip die; lead-free solder flip chip-on-laminate assembly; lead-free solder flip chip-on-laminate reliability; liquid spray flux; liquid-to-liquid thermal shock testing; nitrogen reflow atmosphere; peak reflow temperature; solder balls; solder wetting; spray flux; underfill cracks; wetting; Assembly; Atmosphere; Electric shock; Environmentally friendly manufacturing techniques; Flip chip; Lead; Nitrogen; Spraying; Temperature; Testing;

fLanguage

English

Journal_Title

Electronics Packaging Manufacturing, IEEE Transactions on

Publisher

ieee

ISSN

1521-334X

Type

jour

DOI

10.1109/6104.980037

Filename

980037