Homebrew PCBs

> If you have never DONE that for hours in a
> "professional assembly house", you 
> are asking for PAIN and damage!  
Having been there done that, if care is taken, I don't
see the problem. But, one must not be sloppy about it,
as molten solder is not something to play with.
 
> This process is done by "wave soldering" where a
> WAVE or "linear bump" of 
> solder is pumped up with the rig, in the middle of a
> tank of molten solder, so 
> that the crest of the wave just-touches the bottom
> of the PCB as it moves along 
> on a speed-controlled track. 
> 
It can be done, and is done with small benchtop units
as well. They do create a liner bump, which can be
smooth or turbulent depending on your process, and a
motor controlled track or positioner. Solder pots are
useful for tinning, and in some cases soldering small
areas. I think with practice on small boards, one can
do it successfully.

> Go trying to "dip-solder" an entire board will WARP
> the boards, NOT solder 
> every point, cause a general mess with lots of
> "solder-bridges" that will have 
> to be cleaned off manually, which will take even
> LONGER than simply soldering 
> the entire PCB with a good clean iron of the correct
> size/tip!
I disagree to a point, a small board with low density
should work ok.... But to take even a 4"X4" board
would result in much havoc without some type of motion
control, as well as a wave.

> Solder-alloy (tin/lead) costs a FORTUNE, these days,
> and if OSHA ever gets 
> wind of your hopes of doing this, they will come
> knocking at your door, asking 
> for the assay of your solder, to insure there is
> less than 0.003% lead in it 
> (or whatever bureacratically-chosen number), and
> that all the equipment you are 
> using is approved by the FDA, FEC, surely several
> federally sanctioned 
> labor-unions, etc.
OSHA is not concerned with the home hobbyist, as long
as employess are not involved. The FDA does not
regulate production equipment. Not even food
processing equipment (they do however approve some
materials). The FEC has zero interest. However, the
vapors and or flux may fall into community right to
know, and or EPA regs which are a pita. As far as the
lead issue goes, the European no lead requirements may
force the issue through market demand, as less and
less 63/37 will be available and the prices will go
up. There are however regulatory issues to be dealt
with concerning lead exposure and periodic testing.
This is critical if you have employees.

  Next, DOING a few boards,
> assuming you manage to get it working 
> as you want, will result in contamination of the
> solder-pot, requiring some 
> metal-purification proceedures I don't even KNOW
> where/what/ how-much!  Not to 
> mention the effects dissolved COPPER has on the
> solder (same story).
With proper temperature control, flux chemistry, and
testing, its not a big deal. We ran solder pots as
well as wave soldering machines for years with little
tweaking. Sure if its a govt contract, or a customer
requirement, thats different. But for most, its not an
issue, just follow the vendors recommendations.

> COOKING UTENSILS are not DESIGNED for melting 20 kG
> of solder, and even if 
> you DO manage to find something that will make a
> giant solder-pot that will melt 
> 60-40, it probably won't remain mechanically intact
> long enough for you to 
> shut it down, after the first trial, and you will
> become an involuntary 
> track-star, running from the giant hungry puddle of
> molten solder chasing you across 
> the floor and out into the street!
I agree 100%, do not use cooking utensils for a large
vat. I also question 20KG. Thats a fairly large pool
for home use, and if something goes wrong, you have
problems. Many years ago, one of our waves lost a
board, and it jammed itself right where the wave
ended. As such, solder went everywhere. The operator
got it shut down in 30 seconds or so... but it took 2
guys almost 3 days to clean it up and fix it. And yes,
molten solder was flowing onto the floor.

What you may find is that benchtop waves are going to
become super cheap in the next year or two. The
residual lead contamination, coupled with the
reduction in wave soldering should allow one to pick
them up for a song. That way, you have the solder
pump, motion control, and everything you need.

Ron, who has been there, done similiar things, and see
it as less of a problem if you are careful.

__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com