Nihon Superior’s Mr. Keith Sweatman to Present at the 2012 IPC APEX EXPO Technical Conference

The intermetallic layer plays a critical role in the reliability of solder joints and Mr. Sweatman will report the results of a study on the effect of cooling rate and isothermal ageing on the transformation of the Cu6Sn5 phase from the hexagonal to monoclinic form. This study was coupled with measurements of the expansion of the hexagonal and monoclinic forms of Cu6Sn5 as a function of temperature.

The change in volume associated with the phase transformation can create stresses sufficient to initiate cracking in the intermetallic layer. A significant conclusion of these studies is that by choosing the temperature at which the transformation occurs in the metastable hexagonal Cu6Sn5 created by rapid cooling, the volume change and hence the risk of cracking can be minimized.