The effect of wax on the properties of epoxy molding compound

Thermal stability and color change of carnauba wax, ester wax, OP wax, S wax, stearic acid, GMS and a few polyethylene wax types were investigated by heating them to a specific temperature 175C for about 50hours. Cluster analysis was adopted by analyzing the weight loss of the wax. Based on the weight loss data, these wax can be divided into three groups, the most stable group which includes carnauba wax and polyethylene wax; and the most unstable wax is stearic acid wax. Based on the observation of color changed analysis, the most stable is polyethylene wax without any functional group. The effects of these wax types on the properties of epoxy molding compound like water absorption, DMA modulus, Spiral flow and Tg. were studied by using basic epoxy molding compound (EMC) system. The EMC system consists of biphenyl and multifunction resin, with filler content of 86%. The results showed the EMC with GMS wax has the highest water absorption; stearic acid gives the most lubricating effect by showing the longest spiral flow; no significant effect was observed at room temperature but significant different at high temperature (260°C) with DMA modulus. Tg result showed wax has an effect on the cured crosslink density. The difference can be as high as 30°C. The compatibility between the wax and the EMC system was studied by observation on the surface flow mark of molded QFP package. It was found that the most incompatibility is carnauba wax, follow by E wax, oxidized polyethylene and GMS wax. S wax, stearic wax and polyethylene wax showed the best in terms of compatibility.