Journal of SMT Article


Author: John J. Davignon
Company: Merix Corporation
Date Published: 10/1/2000   Volume: 13-4

Abstract: At the present time there is a major thrust to evaluate which of the many lead free solder alloys to use for assembling packages. Many of the newer alloys have higher eutectic temperatures and require higher reflow temperatures than the existing Sn/Pb reflow temperature. This paper evaluates the changes in PTH performance and laminate material properties for several epoxy-based laminate systems caused by the thermal reflow requirements of the NEMI higher temperature alloy. Although the epoxy systems evaluated will discolor at the higher temperatures, the glass transition temperatures (Tg) and the Z-axis coefficient of thermal expansion (CTE) are not greatly affected. Time to delamination (T-260) was lowered in 2 of the 3 systems but not to a level to cause concern. The PTH performance for the standard FR-4 epoxy and the high Tg epoxy was significantly degraded, while the PPO/epoxy blend did not significantly change.

Keywords: This paper will discuss the effects on the plated-through-hole (PTH) performance and epoxy-based laminate material properties caused by the higher temperature assembly reflow profiles required for the new NEMI 95.5Sn/3.8Ag/0.7Cu alloy. PTH performance was evaluated by the Interconnect Stress Test (IST) method.

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