Researchers at IMEC have found that quartz-filled compounds used in place of halogen flame retardants in plastic packages lowered the CTE, and the subsequent mismatch in thermal expansion between the package and board is causing solder joint fatigue cracking, researchers found. The investigators are calling this failure mode “Cu lead fatigue fracture.”

Here’s the link: http://circuitsassembly.com/cms/news/12195-paper-halogen-free-packages-reveal-new-failure-mode