I am having trouble accuratly modeling TO-247 packages in simulation. I was hoping to get some help on how best to set this up. My TO-247 package consists of three components, a copper case, a die(the transistor), and a plastic case. I modeled the die as silicon, the copper case as copper, and the plastic case as epoxy resin. For the insulator I used the manufactuer spec sheet to build a material (the spec sheet wasnt very good I had to leave a lot blank). I am still not getting accurate results. My prototype has far different values then simulation. I took a cross section of the temperature distribution and I found that the temp of my junction was the same temperature as my heat sink. I know this is not possible. Can anyone who has done this type of work before give me an accurate method for modeling this situtaion? I would much rather use the junction to case resistance, and insulator to heatsink resistance provided by the manufactuer then rely on material selection in simulation. I have upladed my heat sink model for extra clarification.