Semiconductor packaging has relied on Flip Chip (FC) solutions to mitigate the heat flux of powerful semiconductor chips.  A copper lid is the most popular choice for the thermal spreader as it has high thermal conductivity for connecting the chip to a heat sink.  HOWEVER, the coefficient of thermal expansions (CTE) is high at ~ 17ppm/°C, causing the solder joint become weak over numerous power cycles. 

Ravelin Materials offers a range of solutions for FC lids.  For those looking for a cost neutral substitution to copper, RAV20 can provide equivalent CTE and price but with much more stable pricing.  For those looking to improve the reliability over copper or are looking to reduce the price over other AlSiC providers, RAV30, RAV40, or RAV55 can fit the cost/performance curve you need for your application.