A　model　of　heat　source　is　presented　for　tunnel　regeneration　laser　diodes.　Three　dimension　temperature　distribution　of　the　tunnel　regeneration　semiconductor　laser　with　two　active　regions　is　simulated　by　using　the　finite　element　method,　and　the　influence　of　solder　voids　on　temperature　distribution　is　discussed.　Simulated　result　shows　that　thermal　accumulating　of　the　active　region　close　to　the　substrate　is　higher　than　that　of　the　active　region　close　to　the　heat　sink　when　there　is　no　solder　voids　between　the　diode　and　the　sink.　Whereas　localized　temperature　of　the　active　region　close　to　the　heat　sink　rise　more　rapidly　with　localized　hot　spot　caused　by　solder　voids,　which　lead　to　positive　feedback　resulting　in　catastrophic　optical　damage　(COD).　The　experimental　phenomena　are　well　coincident　with　the　simulations.