On Tue, 13 Jan 2004 18:07:06 -0700, Robert Ussery <
uavscience@...>
wrote:
>
>
>> -----Original Message-----
>> From: Stefan Trethan
>
>> for this thers is some photoresist-like soldermask.
>> you spray it on, then expose it, and develop it.
>
> Cool... I'll have to look for this. Is this what the pros (boardhouses)
> use?
>
No board hoses use silk screen for that in 99% of the cases i think.
the screen can be rather coarse, the resolution requirement is not that
high.
on some boards you can make out the pattern of the mash if you look close
at the soldermask.
>> how do you plan to apply your homemade epoxy mask without covering
>> the pads?
>
> Just carefully brush it on around them. Time consuming, but better than
> solder bridges.
i assumed that.. a stencil, maybe cut with a vynyl cutter, may be a option
if you need more boards with the same pattern..
then it may be best to just apply it where really needed.
may even look better than if you try to paint the whole board..
try clear laquer, any should work. high-temperature may be best...
>
>> I always check if there is a short if i run more than one trace under a
>> 1206 smd part.
>> never found one, but i rarely use smaller parts so no experience there.
>
> Mostly I've been having probs with some of the really small, weird stuff
> like the ADXL202 accelerometer and ADXRS180 gyro. Standard dual-inline
> surface mount stuff probably isn't as bad, but the ball-grid package of
> the
> ADXRS180 is very short-prone, and the ADXL202's contacts run for some way
> under the part and sloppy soldering can lead to excess solder wicking
> underneath and causing bridges.
i see...
I suggest trying laquer on the dangerous spots, maybe you can even use a
laquer-pen.
you could also try to make a stencil for the "special" parts you mentioned.
take thin sheet metal, it can be etched like a pcb.
then just position the stencil exactly and spray on some laquer.
ST
>
> - Robert
>
>