RoHS-compliant molding compound evaluation and manufacturability for FBGA packages

The European Union through its waste electrical and electronic equipment (WEEE) and the restriction of the use of certain hazardous substances in electrical and electronic equipment (RoHS) requires lead and certain brominated flame-retardants to be phased out of electronic products by July 1,2006. Bromine-containing flame-retardants and antimony oxide flame retardant synergists are commonly used in molding compounds formulations and are thought to be potentially unsafe if released into the environment. Phosphorus-containing compounds have been proposed as flame-retardants. Although phosphorus is less hazardous, it has been shown to have a negative effect on package reliability. New molding compounds have been developed that are substantially free of bromine, antimony and phosphorous and are able to pass UL94V-0 flammability rating. Our company has evaluated and qualified new molding compounds for FBGA (fine pitch ball grid array), which are free of bromine, antimony flame-retardants, and phosphorous and can pass precondition reliability test at 30°C70%RH for 216 hours and 3× reflow at 260°C temperature. In this evaluation, six (6) alternative molding compound formulations were studied. These molding compound formulations contain different flame retardant additives, which enable the compound to pass UL94V-0 flammability rating. Four (4) molding compounds use biphenyl resin base with different flame retardant additives, while two (2) other molding compounds use aromatic resin without flame retardant additive. The evaluation used a FBGA1 package with die size 51 mm² as a test vehicle. Optimized molding process parameters were determined for each compound and the six compounds were compared to each other on the basis of molded quality, wire sweep, die top surface delamination on and package warpage. Based on moldability and manufacturability results, the two (2) best molding compounds were selected for reliability test with 2 FBGA packages as - FBGA1 and FBGA2 at different package and die size. The results of both the manufacturability and package reliability evaluations have indicated that new molding compound with biphenyl resin without flame retardant has the best performance in term of quality and reliability.