DocumentCode :
2807473
Title :
Solder joint strengths and interfacial reactions in various Pb-free solder joints
Author :
Lin, Ching-Tsung ; Hsi, Chi-Shiung ; Chang, Tao-Chih ; Liang, Ming-Kann
Author_Institution :
Nat. United Univ., Miaoli
fYear :
2007
fDate :
1-3 Oct. 2007
Firstpage :
58
Lastpage :
61
Abstract :
Two kinds of Pb-free solders, Sn8Zn3Bi and Sn9ZnAl, were used to mount passive components onto OSP and ENIG PCB using a reflow soldering process. The component mounted boards were stored at 150degC for 200, 400, 600, 800, and 1100 h. The microstructures of the interfaces between the solders and pads of the aged assemblies were observed using scanning electron microscopy (SEM) and the chemical compositions of the intermetallic compounds (IMCs) formed at the interfaces were analyzed using energy dispersive spectrometry (EDS). After shear testing, both solders showed acceptable solderability on the OSP and ENIG layers, but the shear strengths of the Sn8Zn3Bi solder joints were better than those of the Sn9ZnAl solder joints. All of the solder joint strengths deteriorated during the aging process, but the degradation of the OSP solder joints was more evident than that of the ENIG solder joints. Scallop-shaped epsiv-Cu0.2Zn0.8 IMC and flat gamma-Cu5Zn8 IMC formed between the solders and Cu pad of the OSP board after reflowing with an increase of aging time, all of theepsiv-Cu0.2Zn0.8 layers transformed into gamma-Cu5Zn8 and the IMC layer became thicker. The Zn-depletion zone and Cu6Sn5 IMC were observed in the solders due to the interaction between the tin and zinc compounds. Both solder joints on the ENIG boards had similar interfacial microstructures; very thin gamma2-AuZn3 layers were formed at the interface of the solders and Ni-P layers. The gamma2-AuZn3 layer transformed into gamma2-AuZn8 IMC with a consistent thickness during aging. The Zn phase redeposited above the IMC layer and the size of the Zn phase grew with increasing aging time.
Keywords :
aluminium alloys; bismuth alloys; printed circuit testing; reflow soldering; reliability; scanning electron microscopy; shear strength; tin alloys; zinc alloys; EDS; SEM; SnZnAl; SnZnBi; energy dispersive spectrometry; interfacial microstructures; interfacial reactions; intermetallic compounds; passive components; reflow soldering process; scanning electron microscopy; shear strength; shear testing; solder joint strength; temperature 150 C; time 1100 h; time 200 h; time 400 h; time 600 h; time 800 h; Aging; Assembly; Chemical analysis; Chemical compounds; Intermetallic; Microstructure; Reflow soldering; Scanning electron microscopy; Tin; Zinc;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Microsystems, Packaging, Assembly and Circuits Technology, 2007. IMPACT 2007. International
Conference_Location :
Taipei
Print_ISBN :
978-1-4244-1636-3
Electronic_ISBN :
978-1-4244-1637-0
Type :
conf
DOI :
10.1109/IMPACT.2007.4433567
Filename :
4433567
Link To Document :
بازگشت