Creep measurements on SnAgCu solder joints in different compositions and after mechanical and thermal treatment

Solder joints are still the main conductor element between electronic components and carrier substrates. The visco-plastic behaviour of the particle strengthened SnAgCu solder alloys depends strongly on its composition. Additionally, the mechanical behaviour is influenced by solder condition after the soldering reflow process. Further influencing factors are dissolution of metal from the connection pad area, cooling rate, volume, thermal or mechanical load. An in-house developed creep measurement unit allows the observation of real package solder joints in sizes Oslash = 200_hellip400 mum within a temperature range of T = 20_hellip125degC. The resulting creep measurements were fitted by mathematical description, either by sinh- or by power-law. Finite-Element-Method calculations were used to determinate the right material coefficients (activation energy, stress exponent, etc.) and complete data sets are provided related to solder alloys under certain micro-structural conditions. The paper presents creep measurement results of SnAgCu-Alloys to determine effects on solder behaviour influenced by: different silver content m_Ag = 0_hellip3,5 %, different pad metallization (Cu, Sn, Ni, Ag), supply of solder (paste, ball, preform) and time above liquidus- temperature during reflow soldering (t_L = 45 s/ 180 s). Further, the paper describes measurement results of isotherm mechanically and thermally aged solder joints. Thermal aging causes changes in the microstructure of solder joints. The measurements show the effect of thermal aging over time ranges of t= 168 h/500 h at temperatures T = 150degC. Mechanical load leads to changes in the microstructure. In situ observations of material behaviour were done by creep measurements over isothermal creep cycles up to 100 (epsiv_piast = max. 1,5 %).