Power　devices　are　widely　used　in　household　appliances　and　industrial　products　even　in　the　space　industry.　Because　of　defects　in　the　package,　their　electrical　parameters　might　change.　Some　of　them　may　even　lead　to　irreparable　damage　on　devices.　This　paper　presents　a　new　method　for　evaluation　of　the　device　chips＇　welding　quality,　by　means　of　analyzing　thermal　resistance　and　structure　function　of　the　power　devices.　©　2011　IEEE.