How do you solder a MOSFET?

Soldering a MOSFET is about the same as soldering any other semiconductor. Get your static protection on and park yourself at your workstation. Clean the mounting area for the device. Apply heat sink compound if required and/or a mica or other insulator. Heat sink compound is lightly applied, and is put on both sides of an insulator, if one is used. Pick up the device (having bent or cut the leads as required), and put in on the board. Make the mechanical connection using appropriate hardware. Snug things up. Heat up the iron or station if it isn't on. Have your damp sponge and solder handy. Pick up your solder and the iron. Give the tip a quick wipe and tin it. Work on the side appropriate to the application. On double sided or just through-hole applications, you'll be on the bottom of the board away from the component. On surface-mount applications, you're on the component side. Apply the tip to the place where the lead of the MOSFET meets the copper land on the board. (You'll be heating the lead of the device and the land where the solder is going to bond.) Apply the end of the solder to the place where the tip of the iron meets both the component and the board. Watch for melting to occur. Some people "trap" the solder under the tip of the iron and gently press the solder into the component lead and board, but this has a tendency to create solder balls. As the solder melts, continue to apply it to build up a fillet appropriate to the application, and then remove the solder and the iron tip. Clean the tip with a quick wipe, re-tin it and repeat. Clean and tin the iron, and rack it in the holder. Inspect your work. (For SMD applications, you won't have to turn the board over.) Look for a clean, shiny fillet that is not too concave and not convex. Clean the extra flux off the board and the leads as required or as desired. Inspect a final time and you're done. Shut down your iron.