Re: Not all solder pastes are created equal

Joe Street
 

My two cents is use a chisel tip iron with a solder well in the tip and heed Alison's advice to clean it and freshen the well before each use, not after.  After experimentation with hand application of paste, initially thinking it was great and then being alarmed by the number of parts flipping on end (the term is "tombstoning") on me I realized that the paste process is really that, a process, which was developed in conjunction with the use of stencils and a squeegee which makes for a uniform application of the paste, and there's no point going to all that trouble for onesies and twosies.  Yes you can learn to get fairly consistent with a given batch of paste and develop a somewhat consistent dispense technique but my guess is that the inconsistency there is the cause of the tombstoning I witnessed.  Having a screen printer and an RTC belt furnace in my lab at work I am not just talking out of my hat here.  Anyways, for hobby projects I realized it is actually faster and less rework to solder SMD's with an iron.  I built an mchf with over 500 SMD's in about a week of evenings a few hours per night and it worked off the bat. Yeah it's pretty cool to place a board on a hotplate and watch the paste do its thing when all goes right, but for me at least, I'm leaving the paste for the kind of equipment it was designed for.  Your mileage may vary.

On Sun, Feb 17, 2019 at 11:36 AM ajparent1/kb1gmx <kb1gmx@...> wrote:
I have liquid rosin.  Its pour-able but still has a bit of tack to it.  A small paint
brush puts down a film rather than a puddle.  I don't use it all that much.

Generally I use my Kester 44 rosin 63/37 and the SMT parts I find my larger (1/4")
tip Weller easier but there is a lot of technique and experience.  Been doing SMT
for a few decades.  I do hate the 0402 parts though, I wear a dust mask so I
don't accidentally blow them away breathing.

Biggest thing I see keep the iron tip clean, do not clean it before replacing it in
the stand, clean when you go to use it, and put it back dirty.  Putting it in the stand
clean allows it to sit there and oxidize, it will be harder to clean then.  I've told people
that and then videoed them doing exactly the opposite.

Allison

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