Interface Growth and Void Formation in Sn/Cu and Sn0.7Cu/Cu Systems

In this work, the effects of electroplated Cu (EP Cu) and Cu addition (0.7%) in Sn solder on the intermetallic compounds (IMCs) growth and void formation were clarified by comparison with solder joints comprising of high purity Cu (HP Cu) substrate and pure Sn solder. After aging processes, a new IMC, Cu3Sn, was formed at the interface, in addition to Cu6Sn5 formed in the as-soldered joints. The EP Cu and Cu addition (0.7%) both had limited effects on the total IMCs thickness. However, the effects varied on the growth behaviors of different IMCs. Comparing to the void-free interface between Sn and HP Cu, a large number of voids were observed at the Cu3Sn/Cu interface in Sn/EP Cu joints. The formation of these voids may be induced by the impurities and fine grain, which were introduced during the electroplating process. The addition of Cu suppressed the inter-diffusion of Cu and Sn at the interface. Consequently, the growth of the Cu3Sn layer and formation of voids were suppressed.

Effect of Aging Temperature on the Intermetallic Compound (IMC) Formation of Sn-0.7Cu/Si3N4 Composite Solder

Nowadays, excessive growth intermetallic formation becomes the major issue in electronic packaging industry. The investigation on the effect of aging temperature to the intermetallic compound (IMCs) growth formation for Sn-0.7Cu/1.0-Si3N4 was studied. Isothermal aging process was carried out for 24 hours, with 5 difference aging temperature from 50°C up to 150°C. It is found that the Cu-Sn IMCs which appear after reflowed process, has grew rapidly when aging temperature was increased up to 125°C and started to reduced after 150°C aging temperature.