How do you solder the surface mount FETs, and also prevent them from heating up?

I mounted the 4 FET surface mounts (Q3, Q4, Q7, Q7b) and they look awful.  I primed both surfaces with a little solder, and tried to be quick about it to prevent them from getting too hot.  But there's too much solder and they just look clumsy.

What do you guys do?  Use solder paste?

Joe

If you prime all surfaces you wont get it to sit flat.

I put a small dab of solder on one of the small pads. Then position the FET and put the iron on top off the FET leg to seat it into the dab.
This puts the FET flat on all pads.

Then you solder the others legs.

Shouldn't take more than a couple of seconds of heat per leg.

Saw your post about the FET’s.  I didn’t prime or tin any item, just used a little acid free flux.  I held the FET down with a screwdriver while briefly applying a ‘loaded’ soldering iron to each tail.  Oddly I got the FET’s in square but couldn’t get the larger Volt Reg in so tidy – just the way things are I suppose.

I put a couple of components in backwards so had to desolder them.  I could not get all the solder out of the holes so had to redrill with a 1mm bit, this had the side effect of damaging the plating that goes through the pcb to join the two sides up, I then had to be sure I soldered the item on both sides of the board.

  I can’t get the bike to start at the moment, just runs for about seconds then cuts out, may only be running on the prime fuel.  Have other bits of the bike apart so cannot take it out and warm it up on my OEM Ecu at present but hope to sort that soon.

Are you building the Optimiser?  After a couple of problems, notably missing the instruction about different versions of the display having differing pinouts, my optimiser now displays the TPS etc but not much else as engine not running.

I have a spare OEM crossover with an O2 sensor but unsure if it has a catalyser inside it and if so is it a good idea to use it as most people seem desperate to remove them.  I may cut it open to see if it can be modified, alternative is to drill the existing xover and weld in O2 bungs and try with the OEM O2 sensor or get an LC1 next time I get rich.

Admin, yes, with the pre-solder they aren't sitting flat.  That's not a problem, is it?  The connections seems fine.

Bobd, I'm not building the Optimiser.  I wish you luck with getting your bike running.  As for the catalytic converters, they are in the mufflers, not in the crossover.  Using the crossover made for the O2 sensor seems like a good idea.

Not sitting flat should not be a problem so long as your soldering is ok

For soldering big parts on well cooling surfaces I use a big 80W iron. Such an iron has enough capacity to heat up the whole stuff to get the tin running and this in max. 3 or 4 seconds.
Hubert