Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

hi, some ideas and experiences that may come in hand if you are doing smd
work:


First, the good news:
I have a manual vacuum pic tool now for placing.
After wondering for hours where i will get the required solenoid valves
to make it work i had a really simple idea:
drill a hole in the pick handle, which bleeds the vacuum.
if yo want to hold a part close the hole with your finger.

The small residual flow through the thin nozzle did still hold parts,
so i put a piece of cloth in the way of the tip to slow it.
i also drilled a second hole which is smaller than the main bleed hole.
it is never closed and ensures the vacuum doesn't build up when holding
a part for a long time.

for a tip i used a 0,8mm inner dia. syringe needle (cut and grind flat).
For me it is more convenient to have a tip bent at about 60 degrees.

oh yes, for a handle i used a old ball point pen of course...


really cheap tool and GREAT help.


Second, other good news:

smd reflow works perfectly well with the hot air gun on low volume setting.
hold it relatively high away from the board and the parts are not blown
off.
works much better than oven reflow for me. (and i do not have to add
another big
item to my overcrouded workspace)


Third, the bad and important stuff:

I tried to thin solder paste with denatured alcohol to make it more tacky
and easier to use (it is old). Was much easier to dispense and stick parts
to it.
But when i tried to reflow the really worst thing hapened: the components
were catapulted
right off the board as soon as a certain temperature was reached.
i tried to dry it for a hour, and then tried to dry the alcohol out at
lower temp.
but it didn't help much. ended up with holding the parts down and
soldering with iron.
MAN this small things can jump, i was really surprised.

Well, don't try this at home ;-).

Have you any ideas which solvent can be used on solder paste?


thanks

ST