<stefan_trethan@g...> wrote:
> Nice to hear someone was done work on it too. sadly i have to disagree on
> almost all points.
> On Mon, 16 May 2005 14:02:02 -0500, <milwiron@t...> wrote:
> > 2. Use two layers of masking tape at the outside edges of the paper to
> > hold the squeegee .008" off the paper.
> > I'm using a 2" bar of acrylic as a squeegee.....
> I disagree on this one. I use a steel squeegee and wipe it off as thin as
> i can, no spacers.
> I found it works better than a thick layer. I hold the squeegee almost
> vertical and apply a lot of force, basically scrape off as much as you
> can....
Hi Stefan,
I'm not sure how you can say a method is "wrong" if it works for me.
What I posted works very well with the equipment and materials I have on hand.
I use a bar of acrylic because it's rigid, glass smooth and is easy to clean since any cured silicone just peels off. Using the acrylic bar and the masking tape spacers gives me perfect coatings of uniform thickness every time, it's one less variable to deal with.
> > 3. Let it cure -completely- for 4 to 7 days. Longer doesn't hurt.
> Don't see the need, even a thick layer (mm) is cured in half an hour, i
> have used a coated paper after 30 minutes with no adverse effects.
I get better results letting the silicone go through its full post cure period.
For years I worked with dozens upon dozens of different types of single and two part silicones in industrial applications, very few silicones are fully cured in a couple of hours.
Most of the silicones you'll ever run in to are compounded to be 100% solids after full cure, full cures can take days or even weeks. Less than a full cure and it's not 100% solid.
In my experiments I found that with anything less than a full cure I had the silicone sticking to the copper board and the toner not releasing entirely... the longer I let it sit the better it worked for transfers. And with a full cure there's no risk of gluing the silicone paper to a fuser roller or leaving behind any prepolymers to contaminate the printer.
Letting the silicone paper sit for a week isn't a big deal for me if I plan ahead. (No, planning ahead doesn't always happen)
> > 4. I'm printing with a HP2100 laser printer, factory cartridges only.
> > Off brands of toner don't always work.
> > The first time I use a piece of silicone paper I run the whole sheet,
> > tape and all through the printer.
> > 5. Lightly sand and clean PCB stock with lacquer thinner, not acetone.
> > I've gotten very poor results using acetone, I don't know why. Trim the
> > printed silicone paper to fit.
> I always use acetone, and have very good results. i do not like the
> possible adverse effects to health of laquer thinner.
One thing I learned in my Polymeric Chemistry courses is that all hydrocarbon and chlorinated solvents are hard on living tissue. If you think acetone is somehow better for you than lacquer thinner you're not looking at the whole picture.
Any solvent that can dissolve thermoplastics like polystyrene or acrylic will make a mess out of your liver, lungs and nervous system. The above also goes for "natural" solvents, orange oil based solvents are a tad scary. It's natural, yeah and it removes dried paint. Asbestos and uranium are natural too.
Cancer is bad no doubt, so is permanent damage your nervous system and have you tried to get a new liver lately? ;-)
The bottom line is, I've known people who died from cancer and others from liver failure and both together also. It's a tossup which one I'd choose.
Two over simplified but good to remember rules are:
1. If you can see it don't breath it.
2. If you smell it, it's too late.
Acetone has an affinity to water/moisture/humidity, something I've learned to try and avoid during copper cleaning before transfer.
To clean a board after etching and drilling I use a small sandblast cabinet with glass beads to clean off 99% of the toner in maybe 2 seconds. Then I use lacquer thinner for any minute traces of toner left behind.
I found if I used acetone at this point the copper traces and pads, if left uncoated, started to turn green at the edges after a day or two. This doesn't happen with lacquer thinner.
Again, these are my observations based on what I've run in to. Other people may get varied results.
About less potent stuff:
In my limited years of making toner transfer prototypes I've never had any success with soaps or detergents for cleaning the copper, even with distilled water rinses. Hopefully somebody has had better luck out there.
> > 6. Run it 5 to 6 times through GBC Laminator.
> Run one time through old copier fuser converted to slow speed with chicken
> grill motor.
GBC laminator, this is what works best for me.
I found 5 times quickly through a GBC laminator gives a more even heat and transfer than once through a slow fuser, I have both and it doesn't take any longer time-wise since the GBC is running 5 or 6 times faster.
> > 7. Let cool and peel.
> peel when still hot. (thicker coating can be peeled cold, but thin coating
> is better peeled hot)
> > The results are 99.99% perfect, there's very little touch up.
> the results are 100% perfect, if you have done nothing wrong (e.g. bad
> cleaning, pits in silicone, creases..)
I found peeling the paper when the board is hot can damage the transfer since the toner is still soft.
I prototyped a 3 x 6 inch board, every other board had a couple of 15 to 20 thousandths diameter pits of missing toner to fix. From your previous posts I didn't get the impression you were doing any better than that, I may be very wrong.
> > To reuse the silicone paper, clean it with lacquer thinner and stick the
> > leading edge to a carrier piece of paper with a glue stick.
> I just print the sheet again. why do you stick it to another paper?
I trim the silicone covered paper away from the uncoated paper for better registration on the board.
To get it to go through the printer after the first printing and trimming it needs a carrier sheet with my HP2100.
Once again, what I posted is what I found worked for me, I hope I made that clear in my first post. I was simply trying to share that information. If I somehow twisted your panties in a knot by posting, I humbly apologize.
Just a quick addition: I've found using commercially available .010 inch thick silicone sheeting attached to a carrier sheet of paper works extremely well and the preparation time is next to nothing. Best of all you don't have a dozen sheets of paper hanging around and laying on every horizontal surface in your shop.
I do greatly appreciate you sharing your original concept and experiments with silicone paper.
Denny