Reliability Investigation and Interfacial Reaction of Ball-Grid-Array Packages Using the Lead-Free Sn-Cu Solder
Authors: Yoon, Jeong-Won; Kim, Sang-Won; Koo, Ja-Myeong; Kim, Dae-Gon; Jung, Seung-Boo
Source: Journal of Electronic Materials, Volume 33, Number 10, 1 October 2004 , pp. 1190-1199(10)
Abstract:The interfacial reactions between two Sn-Cu (Sn-0.7Cu and Sn-3Cu, wt.%) ball-grid-array (BGA) solders and the Au/Ni/Cu substrate by solid-state isothermal aging were examined at temperatures between 70°C and 170°C for 0 to 100 days. For the Sn-0.7Cu solder, a (Cu, Ni)6Sn5 layer was observed in the samples aged at 70-150°C. After isothermal aging at 170°C for 50 days, the solder/Ni interface exhibited a duplex structure of (Cu, Ni)6Sn5 and (Ni, Cu)3Sn4. For the Sn-3Cu solder, only the (Cu, Ni)6Sn5 layer was formed in all aged samples. Compared to these two Sn-Cu solders, the Cu content in the (Cu, Ni)6Sn5 layer formed at the interface increased with the Cu concentration in the Sn-xCu solders. And, the shear strength was measured to evaluate the effect of the interfacial reactions on the mechanical reliability as a function of aging conditions. The shear strength significantly decreased after aging for 1 day and then remained nearly unchanged by further prolonged aging. In all the samples, the fracture always occurred in the bulk solder. Also, we studied the electrical property of Cu/Sn-3Cu/Cu BGA packages with the number of reflows. The electrical resistivity increased with the number of reflows because of an increase of intermetallic compound (IMC) thickness.
Document Type: Research article
Publication date: 2004-10-01