its not a free software.I don't have knowledge of any thermal software that is freeware.Anyway you can download its demo copy and simulate upto 10 pcb component design.
I know many thermal analysis software, what cad/cam application you are using? I am using a solid works + cosmos floworks, to analysis the device as a assembly. Also flotherm from Flomerics Company is a very good product. I have may other demos but for me cosmos product is enough.
h**p://eldevice.net/upload/COSMOSFlo/
there is a some screen shots