You can even have success with 0603 and TQFP32 chips with a bit of care!After years of delaying attempts to try SMD soldering and then a couple of really bad attempts using traditional solder wire, now using solder paste I have confidently started soldering 0603 and TQFP32 SMD parts.
After several successes, today I wanted to solder six 0603 SMD parts, and rather then getting the solder paste out of the fridge and warming it up, I thought I would just use traditional solder wire.
Well first try was one out of six and second try none out of five, so I switched back to solder paste and finished the task easily.
So why is using traditional solder wire harder, especially with SMD sizes 0603 and below?
Because now you need three hands and even tools to hold the SMD part … but even these are not that good, as the part just seem to keep moving about
Because the PCB needs larger sized pads, especially longer to allow enough space to hand solder. With paste it just runs UNDER the ends of the SMD part!
With solder paste and hand soldering, you still need to hold the SMD part, but this easier as the SMD is partly held in place by the paste, instead of slipping all over the place, and now only “pushing against it” with the soldering iron, not with solder AND iron!
Hand soldering 0603 with solder paste is not too difficult, but without paste, 0603 are quite a challenge!
TIP – Double check positioning of parts, especially fine pitch ones with more than 3 pins!
TIP – Pin count > 3? Then solder ONE pin check alignment REALLY carefully under STRONG magnification, solder a 2nd pin oppiste corner/side and check again really carefully, then once OK, solder remaining pins.
TIP – Use correct amount of paste, not too much or little. For smallish pads that are just larger than the SMD part contact, then just fill the area with a roundish blob a couple of millimentrs tall, if the pad is larger, don’t fill it up!
TIP – Do thorough visual inspection after soldering to find any streaks, runs, blobs of left over paste, check how well the solder has filleted (run from PCB to part), for any parts that are twisted or standing up, or not soldered.
TIP – Do not get over confident (I’m looking in the mirror) – always follow best practice tips and advice!
TIP – Use larger SMD pads for hand soldering with traditional solder wire than those used for SMD paste. Kicad has many hand soldering footprints in recent versions.
TIP – Don’t have syringe or good size tips? Then just use a toothpick to apply the paste!
TIP – Have a spare syringe, any size, so tips can be cleaned with water then air dried, instead of throwing them out.
So find cheap source of solder paste, don’t worry that it has not been in fridge, have plenty of really cheap disposable needle tips, ones that do not have a large interior volume, as the paste dries out in the tips, and get stuck in!