Journal of Welding and Joining

9: J Weld Join. 2015;33(3):19-24. Published online June 30, 2015.
DOI: https://doi.org/10.5781/JWJ.2015.33.3.19; A study of joint properties of Sn-Cu-(X)Al(Si) middle-temperature solder for automotive electronics modules; Dong-Yurl Yu^*, Yong-Ho Ko^*, Junghwan Bang^*, Chang-Woo Lee^*; Corresponding author: Chang-Woo Lee ,Email: cwlee@kitech.re.kr

Abstract: Joint properties of electric control unit (ECU) module using Sn-Cu-(X)Al(Si) lead-free solder alloy were investigated for automotive electronics module. In this study, Sn-0.5Cu-0.01Al(Si) and Sn-0.5Cu-0.03Al(Si) (wt.%) lead-free alloys were fabricated as bar type by doped various weight percentages (0.01 and 0.03 wt.%) of Al(Si) alloy to Sn-0.5Cu. After fabrications of lead-free alloys, the ball-type solder alloys with a diameter of 450 um were made by rolling and punching. The melting temperatures of 0.01Al(Si) and 0.03Al(Si) were 230.2 and 230.8℃, respectively. To evaluation of properties of solder joint, test printed circuit board (PCB) finished with organic solderability perseveration (OSP) on Cu pad. The ball-type solders were attached to test PCB with flux and reflowed for formation of solder joint. The maximum temperature of reflow was 260℃ for 50s above melting temperature. And then, we measured spreadability and shear strength of two Al(Si) solder materials compared to Sn-0.7Cu solder material used in industry. And also, microstructures in solder and intermetallic compounds (IMCs) were observed. Moreover, thickness and grain size of Cu₆Sn₅ IMC were measured and then compared with Sn-0.7Cu. With increasing the amounts of Al(Si), the Cu₆Sn₅ thickness was decreased. These results show the addition of Al(Si) could suppress IMC growth and improve the reliability of solder joint.

Keywords :Electric control unit (ECU), Lead-free solder, Al(Si), Intermetallic compound (IMC), Organic solderability perseveration (OSP)