25 Jan
2002
25 Jan
'02
4:29 p.m.
--- "Clint Wolff (VAX collector)" <vaxman(a)earthlink.net> wrote:
DON'T TIN THE PADS!
You'll end up with major problems getting the QFP to sit down,
leading to unsoldered pins!
Agreed... it doesn't take more than a few microns of solder humping
up to skew the chip, or at least a few pins.
If you have a microscope, use it!!!
I wish I had one of the stero microscopes we had at the repair shop
at Lucent - hey... maybe when they close the plant here, someday,
I'll be able to pick one up. Very nice... includes a 2-axis sliding
table you clamp your board to with edge clips. It's what we used
when a friend of mine and I replaced the 68EC030 with a full 68030
from my Amiga 4000. I eventually got a real 68040 CPU
board (A3640?)
and sidelined my upgraded '030 board, but for a few months, I
could
develop software with Enforcer and Mungwall - a big help.
If you screw up, DONT try to remove the part.
Let me add that if you have a heat-gun-type soldering/unsoldering
tool, with the QFP tip (to spread the air over all the pins at one),
you can probably remove it. I'd tend to agree that the PCB is more
important than most chips and to cut it loose to save the board.
PS If I was you, I'd try and find someone that
does
electronic assembly for a living, and give them
twenty bucks to solder the parts on. For twenty
bucks, they'd probably be willing to build the
entire board for you, but you might enjoy that part
of the work...
No doubt. The right tools, though, make all the difference in the
world. I worked an SMT bench for a few weeks in 1998 (assembly-line
rework prior to initial electrical inspection) and *wished* I had
half the equipment in front of me at my house... foot-operated pneumatic
solder paste dispenser, adjustable hot-air soldering tool, stereo
microscope, electric torque driver (for handle screws), RF soldering iron
with a dozen quick-change tips... about the only thing on the list that
I'm ever likely to get is the RF soldering iron. They can be had for under
$500 with one or two handles running from one RF/Power source.
-ethan
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