Hi there,
I’ve been hand soldering LQFP-64 with no problems at all, and I decided to switch gears and use 100-LQFP chips.
However, After 2 trials, I have yet to succeed soldering one of these packages.
Getting the ship aligned on all the pins seems to be very difficult, I always end up with one side completely off…
Any tips on getting the chip properly aligned on the footprint?
Thanks!
I have soldered plenty of 0.3mm pitch 100 pin LQFPs.
I find the best way is to first coat a pad or two with solder on the PCB. Then carefully using tweezers, place the IC onto the footprint, trying to line up all the pads. While doing this, I use a soldering iron to melt the little glob of solder I put in one corner previously.
When you think it’s lined up, let the solder solidify. At this point you can check to ensure it’s lined up properly. If it’s not you can try again. If it is lined up, I tack down the opposite corner with a bit of solder on a pin or two, being careful not to bump the package and bend pins.
From here, I just use the glob-of-solder method to run across an entire side at a time, then wick away the excess with solder-wick.
I hope that helps a bit… With a bit of patience and practice, it’s not hard at all. 
Cheers
Roko:
I have soldered plenty of 0.3mm pitch 100 pin LQFPs.I find the best way is to first coat a pad or two with solder on the PCB. Then carefully using tweezers, place the IC onto the footprint, trying to line up all the pads. While doing this, I use a soldering iron to melt the little glob of solder I put in one corner previously.
When you think it’s lined up, let the solder solidify. At this point you can check to ensure it’s lined up properly. If it’s not you can try again. If it is lined up, I tack down the opposite corner with a bit of solder on a pin or two, being careful not to bump the package and bend pins.
From here, I just use the glob-of-solder method to run across an entire side at a time, then wick away the excess with solder-wick.
I hope that helps a bit… With a bit of patience and practice, it’s not hard at all.
Cheers
Thanks for the quick reply. I’ve used the same technique. What I believe is that it works great for 64LQFP packages, but slight alignment errors seem to be amplified with 100-LQFP…
How do you ensure the tracks are not going to come off when melting the solder around the pads, if the initial alignment is wrong?
Don’t use too much heat, or force the chip when the solder is not flowing readily.
If you have some tacky flux, you can use it as a very light glue to help hold the chip on the pads while you do the initial solder tacking.
I’ve always had the best success rate with flat finishes such as immersion silver or ENIG. HASL finishes are doable but a bit more frustrating.
Roko:
I have soldered plenty of 0.3mm pitch 100 pin LQFPs.
0.3MM, that’s crazy. Never even heard of those.
I don’t have much trouble with 0.5mm LQFP’s though it does take a few adjustments and some time to get the alignment straight. Same technique, just do one point and adjust it a bit when it’s hot to get everything in place, then tack the other corner. I had a fairly tough time with 0.4mm LQFP, I don’t know how well I would do with 0.3mm.
It’s easier on professional boards. On home etched boards the leads tend to fall between the pads and get stuck so they don’t slide back and forth so easily.
got a hot air station and some solder paste? itll make quick work of a 0.5mm pitch…
also drag soldering will work decent too but takes more practice than the hot air station.
i think a 150 investment for hot air is well worth it.