Halogen-Free Mold Compound Development for Ultra-Thin Packages

Abstract

The growing concern of environmental issues is impacting the latest development trends for packaging materials in the semiconductor industry. Several types of brominated flame retardants are used in the electronics industry including PBB (Polybrominated biphenyl), poly brominated diphenyl ether (PBDE) and tetra bromo bisphenol-A (TBBPA). Although PBB and PBDE do not use in mold compound as flame retardant, but bromine-containing flame-retardants and antimony oxide flame retardant synergists are commonly used in molding compounds formulations and to be potentially unsafe if released into the environment. Therefore, the halogen free mold compound is further environmental issue that is cirtical thems for developing future packaging materials as that HP company to eliminate brominated flame retardants from all New HP brand products. LGA (Land grid array) package is a thinner and lighter assembly that design standard BGA without solder balls. It is suitable for applications to require high electrical performance. The halogen free mold compound is evaluated for ultra-thin LGA package in this study. Including choosing new resin structure, higher filler content, new flame retardant system to instead of the current antimony trioxide and brominated epoxy resin combination. In general, because IR reflow temperature is from 220degC to 260degC for lead free condition, it needs to consider the stress issue in package to pass lead free condition. Thus the glass transfer temperature (Tg) of new resin system will be reduced in advance halogen free mold compound technology. In this study, the halogen free mold compound is applied in ultra-thin LGA package; one key challenge for ultra-thin LGA package is the warpage and thermo mechanical stress that the CTE (Coefficient of thermal expansion) mismatch between the thinner mold compound and thinner organic substrate. However, the lower CTE of mold compound has warpage impact for ultra-thin LGA package with thinner substrate. Therefore, material property of halogen free mold compound is controlled to balance warpage performance in thinner package. On the other hand, the shrinkage of mold compound was found to affect the warpage of ultra-thin LGA package in our study. The mold shrinkage will be discussed in this paper. The reliability result such as moisture sensitivity level -JEDEC Level 3, 30degC/ 60%RH/ 192 hours at reflow temperature 260degC, TCT, PCT, HAST and HTSL are also shown in this paper.