Homebrew PCBs

Imagine wiping the board with a window squeegee, but instead of one of
thouse use a pice of thin wood, it wont cool the solder, and it wont
stick or melt.

I often use a toothpick to clear out holes after desoldering a
component to change.






On 15/05/06, jzmuda2000 <hwhacker@...> wrote:
> I just now made up a simple single-sided circuit board with 12 mil
> tracks and 14mil spacing. Its all SMD.  (Except for the DB-9 and 10-
> pin header.)
>
> I used the Dyna-Art paper. (They are called Pulsar, now.) Needless to
> say, this stuff has been sitting around on my shelf un-noticed for too
> long.  But, I figured I should give TT a try for this small board
> (since I don't have any of the other method like EDM or CNC milling
> working - yet.)
>
> Anyway, the short of it is - the TT process went well.  I used an
> ancient HP-5L with a real HP C3906A toner cartridge.  I cleaned the
> board rather thoroughly  with Comet and steel wool.  I used moderate
> pressure on an iron for 5 minutes. (The Pulsar instructions say 3
> minutes - but that didn't work.)  All the toner ended up on the
> copper.
>
> I etched with Sodium Persulfate (it goes from clear to light blue,
> letting you easily monitor the process.) I used an aquarium bubbler in
> a shallow tank made from a small tupperware dish. I had the board
> horizontal the whole time.  Not a good idea. The etching process took
> over 1.5 hours.  Instead of the 0.5 indicated on the Sodium
> Persulfate. A couple of things might have worked against me.  I had
> started with a rather hot etchant bath (kitchen tap water warm) but
> with the large flat surface, it quickly cooled.  I was being stingy
> with the etchant...but it would be more effective I think to etch with
> the board held vertically in a thin tank, rather than horizontally in
> a shallow tank. Even with the bubbler, it was clear that the agitation
> was incomplete.  Since the copper nearest the bubbler etched much*
> faster that the copper elsewhere.  I ended up having to change the
> orientation of the board several times during the etching process.
> Disposable chopsticks made a good tool for doing this. :-)
>
> All-in-all, though, I was quite happy with the result.
>
> But, I wouldn't leave well enough alone.
>
> I decided I really wanted a tinned board.  So, I picked up some
> plumber solder paste at the local hardware store.
>
> Except they didn't have the lead-based "Solder-It" brand. Instead,
> they had some Silver-based stuff. It is called "Flo-Temp" Lead-free
> instant Plumbing solder***.  By Alpha Metals.
>
> Anyway, I spread on a thin layer using a chopstick. Well, not thin
> enough I think.  I then hit it with the hot air gun (part of my SMD
> soldering station.)  I watched it go through all the transitions that
> Stefan recounted.  It seemed to be doing pretty much what I wanted.
> (It was fun watching the image of the board re-emerge as the stuff
> heated, melted, and grabbed onto the copper leaving the etched areas
> free.)
>
> But I wasn't pleased with how it looked.  There was too much solder
> blobbed up on most of the board (some parts were OK...just at the
> edges...where I had probably accidently laid down less.) So I tried
> Stefan's suggested method for removing the excess. With a paper
> towel.  Except, it didn't really want to come off.  I used a slightly
> damp paper towel, btw.  I shot the board again with the hot air gun -
> just before applying the towel. I suspect the wet towel might have
> cooled the board, I mean the solder, off too quickly, so it froze in
> place, instead of wiping aside.
>
> Any hints as to what to do next?   On certain parts of the board, it
> looks tantilizingly like a professional job, with just the thinnest
> coating of silver barely hiding the copper.  But most of the board
> looks like hell.
>
> At least there aren't any (or many) shorts.  So, although its ugly, it
> should work.
>
> Should I try throwing it in the over to get even heat, and then a
> swipe with a dry paper towel?  It is a little hard getting the solder
> across the whole board to be shiny, at the same time, with the hot air
> gun. I have a little toaster oven which is destined someday to be a
> reflow oven...but right now it hasn't any temperature regulation other
> than what it came with.  Should I just set the oven to 450, wait for
> it to reflow, and then wipe off the excess?
>
> Or should I quit while I'm ahead...before I screw it up further...and
> over heat it so I pull up a trace?  Nah...full speed ahead.  Tomorrow
> I'll fire up that toaster oven.
>
> Jim
>
> *well, actually just a bit faster.  Obviously with a 1.5 hour etch
> time, this wasn't going anywhere fast.
>
> **Actually, I think there was one other thing working against me.  I
> am not certain that I cleaned the Pulsar papers "glue" off of the
> board completely enough before etching.   Their procedure is to wipe
> the board once with the "depleted" paper after making the transfer,
> and then rinse under running water. I am not sure, but I thought I saw
> some residue still on the board.  But, I figured it would come off in
> the bath.  Finally, perhaps the etchant is old?  I cannot remember how
> many years ago I purchased it. I am not clear on its shelf life.
>
> ***It says it melts at 430F.  Regular lead-tin solder melts at 370F.
>
>
>
>
>
>
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>
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-- 



Lez

- Looking for early starwars (episode 4, original starwars)
recordings, even pirate
-
- I dont need your originals just some information about running time
- and scene cut points
-
-
- also looking for a car, silver or white, 4 doors -
- diesel with a bosch pump, abs and pas  -
- aircon would be nice, and not a ford       -