Another soldering station inquiry
I've been given a pcb that requires some SMD components. Boy, these things are small. I was thinking that maybe I should get a hot air soldering station to solder these minute components. Does anyone have any experience of using hot air soldering and have any thoughts on which hot air station to purchase?
I think a hot air station may also prove useful for desoldering and removing components. This aspect would currently be beyond my level of electronic experience, but maybe useful if I progress further in this electronics hobby.
I've done this, but I'm no expert by any means.
If you have a steady hand, good vision and a good pair of tweezers, you can solder some SMD devices using a soldering iron.
It can help to daub some flux onto the pads you'll be soldering beforehand, then melt a small slab of solder onto one pad, position the part with the tweezers holding the part's "pin" onto the solder while aligning the part so that all of the other "pin"s and pads line up properly and then touch the iron to the soldered pad and part side to melt the solder and attach that "pin". Then apply solder and iron to the other "pin"s and pads once the first pad has been attached. It's usually a good idea to check and re-solder the first pad after the rest of the "pin"s have been soldered.
I think that a hot air station would require you to use a custom solder paste and applicator to add the paste to the pads before applying the hot air gun. You might also need to hold the part down while applying the hot air.
I observed QFPs being soldered by hand in China. They were roughly 100 pin devices. The soldering iron had a flat tip with a dimple. The operator used wire solder to put a small ball of solder in the dimple. The solder ball was then pulled across one side of the QFP. It was only a couple of seconds per side to solder the part. If memory serves me they had brushed flux on prior to this. I recall writing a report long ago and mentioning this after visiting this factory. In general I was not impressed with their workmanship but found this very clever. The majority of the board was through hole components.
*** Changing gears to more convention soldering.
Solder paste can be applied to individual pads using a syringe. Most common is applying it with a stencil. Often parts are glued to the board.
If soldering with an iron the part needs to be held down so it doesn't leave with the iron. In hot air it may be blown off. Tweezers can be used in lieu of glue as can a vacuum pick-up device for holding the part down.
In general, I agree with Will's comments on the process.