Organic, Non-woven Aramid Reinforced Substrates With Controlled In-Plane CTE Means More Reliable Solder Joint Reliability

摘要

More functions, higher reliability and lower cost made it necessary to reduce the dimensions of the component packages. New component packages like Chip Size Package ( CSP) or Ceramic Ball Grid Arrays (BGAs) are needed to meet these requirements of the OEMs. This resulted in PWBs with finer circuit lines, higher packaging density and smaller holes. However, these new components don't have long leads for solder connection to the PWBs. As a consequence, a higher sensitivity to the thermal mismatch between the PWBs and the packages has been shown. In addition, lead free solder, which contains Tin, Silver and Copper is not as elastic compared to the standards eutectic solder (SnPb) used today. Also 15 to 30℃ higher soldering temperature is needed for this alloy. Using standard laminate or new materials with a high CTE, the components and solder joints to the PWB are more stressed during the solder process. This may result in a shorter functionality life expectation of the electronic equipment. This paper will discuss advanced material and technology that should meet these OEM needs. Discussions will be centered on the ability of aramid-reinforced laminate and prepregs like DuPont THERMOUNT~(~R) to meet strict dimensionally stability of substrates that are needed for increasingly demanding service. The paper will review the converging requirements of PWB and IC substrates, electrical (Dk, Df) and mechanical (CTE, dimensionally stability, moisture re-sistance, migration) performance of reinforced aramid substrates, and selected application in mobile phones, avionics, and that proves reliability and manufacturability of reinforced aramid substrates.