Hey, i want to remove some mosfets from a pcb board, but this boards backside is covered with aliminum (or other heat-sink material).
On the board my solder iron easily melts the solder of smd resistor and capacitors, but it cant melt the solder on mosfet connection points. I dont understand why ? I did everything to melt it but it didnt work. ( also 500 degrees hot air didnt work) Maybe solder is lead based solder or maybe heat transfer is so good that i cant melt it. (but iron is melting easily other components solders on the same board.)
I really have to replace these mofsets please help me...
Thank very much for explanations,
yes when i touch it with hot iron it doesnt liquify solder at all, it just looks like solder but i think it isnt, do you have any ideas what it might be and how can i remove it?
Yes, you are right. It is the efficiency of the heatsinks that is blocking you. Alot of the heat from your soldering iron / Air gun is being absorbed by the heatsinks. What you have to do is heat the heatsinks up as well. You will need an electric griddle. Some people heat the board and heatsinks in a toaster oven just prior to desoldering but the griddle gives you more time.
Basically, you just rest the heatsink(s) on the griddle and SLOWLY bring it up to temperature. Just be easy with it and it will then desolder just fine.
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