Homebrew PCBs

I finally got a chance to experiment some with the dry film resist. I
just did a quick test where I applied the resist and put pennys on the
surface. Here is what I have learned so far.

1. There is a coating on each side of the resist. A plastic and a
mylar side. Make sure you remove the plastic side before laminating.
How do you tell which side is which? I am not sure yet. I just got lucky.

2. Lamination with my stock GBC H200 laminator works great. I ran it
through three times and it stuck just fine. It was easier than when I
 do toner transfer.

3. Be careful of the resist overlapping the board. After laminating I
found my pcb stuck to my carrier. No real problem. I just cut it out
with the knife.

4. Leave the mylar film on until you finish exposing. I did not do
that. When I went to develop all my resist washed away! Fortunately, I
accidentally did not remove all the mylar. The areas where the mylar
was present during exposure stayed stuck when soaked in the developer.
 
5. Make sure you remove all the mylar. Despite the fortunate case in 
4,  you really want to make sure all the mylar is removed before
developing.

6. I used Arm and Hammer washing soda for developer and it worked just
fine.

7. Exposure time under a fluorescent lamp was about 30 minutes. Good
enough for a quick test and maybe for one board I am working on that
is does not have fine pitched components. I will need a better light
source for my more complex board.

--- In Homebrew_PCBs@yahoogroups.com, "javaguy11111"
<javaguy11111@...> wrote:
>
> I finally got a chance to experiment some with the dry film resist. I
> just did a quick test where I applied the resist and put pennys on the
> surface. Here is what I have learned so far.
> 
> 1. There is a coating on each side of the resist. A plastic and a
> mylar side. Make sure you remove the plastic side before laminating.
> How do you tell which side is which? I am not sure yet. I just got
lucky.
> 
The mylar cover is crinkly, the plastic film is very soft.

> 2. Lamination with my stock GBC H200 laminator works great. I ran it
> through three times and it stuck just fine. It was easier than when I
>  do toner transfer.
> 
> 3. Be careful of the resist overlapping the board. After laminating I
> found my pcb stuck to my carrier. No real problem. I just cut it out
> with the knife.
>
A component of the resist is cyano-acrylate!  IE. super-glue.
When fresh, it is extremely sticky.
 
> 4. Leave the mylar film on until you finish exposing. I did not do
> that. When I went to develop all my resist washed away! 
You are supposed to leave the mylar on for 15 minutes AFTER
exposure, it traps gases that are part of the polymerization process.
If you peel it too soon, it doesn't fully polymerize.

> 
> 7. Exposure time under a fluorescent lamp was about 30 minutes. Good
> enough for a quick test and maybe for one board I am working on that
> is does not have fine pitched components. I will need a better light
> source for my more complex board.
>
Although it is expensive, get a Stauffer transmission test scale,
(ST-7 or ST-21) at a professional photography store (hard to find
these days).  You put it on a blank part off the edge of the film and
it shows you how strong your exposure is.

Jon

Congratulations to your first experiments.

You got some answers already, but the answers also depend a bit on the 
KIND of resist. I don't know what product you use, but I will add my 2\ufffd 
anyways if you dont mind :-). So here we go:

1) The side that was on the inner side of the roll goes off easiest. I 
was once told by the supplier that with the resist I use it would not 
matter which side to use first so I never cared too much about this. I 
use two "tesa" stripes that I attach on both sides on a corner of the 
resist and then pull them apart. I then use the side that comes of first...

2) The number of times you have to pass it through the laminator may 
vary and depends on the kind of laminator and also the temperature 
setting. Actually with professional setup one time is enough, and I do 
have one laminator (regular office thingy) where one time is enough 
also. Another laminator I use also takes three passes. You must probably 
"burn" some laminate to get an overall feeling of the process, cause the 
surrounding parameters varry so much among hobbyist users. After all a 
configuration where you have to pass it multiple times, but you end up 
with less scrambled instances is prefereable. Stripping it off and 
relaminate is not the end of the world, but overall a source for loosing 
time.

3) Yep, cut off excess laminate after laminating every side. I use one 
of these sheet cutting machines to cut the resist into a size where 
there is only ~2 mm in excess. Cutting it out somewhat precisely helps 
in arrangeing it nicely and this helps in keeping the instances where 
laminating fails low in count. The laminate must kind of "flow" or 
"hover" above the base material when you feed it into the laminator. 
Some people press the first few millimeters onto the material but hold 
the reminder in the air then feed the laminate by hand as the laminator 
sucks it in. That way they avoid that the laminate gets scrambled.

4) I figure this happened because you exposed it too long. I do both 
things. Usually I try to leave the protection foil on the laminate, but 
sometimes (i.e. if the positioning shafts were not precisely enough 
punched out) I have to hand alling and then peeling the foil off helps 
in that the film is then automatically attached to the laminate due to 
it glueing somewhat.

5) I don't know what you mean with mylar. If you refer to the protective 
foil, then this one comes usually easily off and in one piece.

6) washing soda is the prefect developper. Use caustic soda to later on 
stripp of the resist (after etching)

7) Fluorescent lamp :-) Well, I figure you then also could have leave it 
on your shelf just "as is" to get to a similar result :-). With UV 
tubes, the exposure time is somewhere between 7 - 10 seconds only... You 
will see that some kind of exposure setup will help a great deal here.

Markus

javaguy11111 schrieb:

>
> I finally got a chance to experiment some with the dry film resist. I
> just did a quick test where I applied the resist and put pennys on the
> surface. Here is what I have learned so far.
>
> 1. There is a coating on each side of the resist. A plastic and a
> mylar side. Make sure you remove the plastic side before laminating.
> How do you tell which side is which? I am not sure yet. I just got lucky.
>
> 2. Lamination with my stock GBC H200 laminator works great. I ran it
> through three times and it stuck just fine. It was easier than when I
> do toner transfer.
>
> 3. Be careful of the resist overlapping the board. After laminating I
> found my pcb stuck to my carrier. No real problem. I just cut it out
> with the knife.
>
> 4. Leave the mylar film on until you finish exposing. I did not do
> that. When I went to develop all my resist washed away! Fortunately, I
> accidentally did not remove all the mylar. The areas where the mylar
> was present during exposure stayed stuck when soaked in the developer.
>
> 5. Make sure you remove all the mylar. Despite the fortunate case in
> 4, you really want to make sure all the mylar is removed before
> developing.
>
> 6. I used Arm and Hammer washing soda for developer and it worked just
> fine.
>
> 7. Exposure time under a fluorescent lamp was about 30 minutes. Good
> enough for a quick test and maybe for one board I am working on that
> is does not have fine pitched components. I will need a better light
> source for my more complex board.
>
>

thinktink.com has a wealth of information, if you can find your way to it.

>1. There is a coating on each side of the resist. A plastic and a
>mylar side. Make sure you remove the plastic side before laminating.
>How do you tell which side is which? I am not sure yet. I just got lucky.

     Use two pieces of tape on a corner of the cut film, one on each side 
(I like slightly used masking tape for this). The side that comes off 
easier is the one that's supposed to come off. Only pull the leading inch 
(2cm) or so, so you can peel it as it feeds into the laminator.

>2. Lamination with my stock GBC H200 laminator works great. I ran it
>through three times and it stuck just fine. It was easier than when I
> do toner transfer.

     I've used a cheap desktop laminator - and I mean $25 cheap - and it 
was fine for thin brass sheet with several passes. I recently tried pcb 
material and it ended up requiring a couple of "tacking" passes, a short 
stay in the oven, and then a few more passes. That came out great, the 
laminator-only attempt had the resist lifting off the board.

>3. Be careful of the resist overlapping the board. After laminating I
>found my pcb stuck to my carrier. No real problem. I just cut it out
>with the knife.

     I tape the leading edge of the resist to a sheet of paper, position 
the substrate, and then pass it into the laminator. I only strip that 
protective sheet a little way so I can pull it as it feeds into the 
laminating rollers. This helps eliminate bubbles, overlaps, etc. I also 
cut the resist oversize, but I have a lot to play with.

>4. Leave the mylar film on until you finish exposing.

     Um, yeah. That's there to protect the resist, and keeps it from 
sticking to the hot laminator rollers. I had no idea that it had anything 
to do with the resist hardening (?)

>5. Make sure you remove all the mylar.

     Yours didn't all come off in a single piece?

>6. I used Arm and Hammer washing soda for developer and it worked just
>fine.

     Perfecto, cheap sodium carbonate. Wish I could find the washing soda 
around here, seems nobody's heard of it. I've been using my photographic 
stuff.

>7. Exposure time under a fluorescent lamp was about 30 minutes.

     Cool, it worked. However, go to the hardware store and spend $10 - 
$20 on a 500 watt halogen work light, if you don't already own one. 
Assemble it and leave out the screw that secures the front cover. Use it 
with the cover open (glass out of the way), try 4 - 5 minutes at 18" 
distance as a starting point. Avoid looking at the light that comes out 
of it (or the bulb itself!), that UV absorbing glass is there for a 
reason.

And, 
     Sunlight as a UV source?

     I've had it be good enough for some things, and sorely inadequate 
for others. Spend a few bucks on the halogen light mentioned above and 
it'll be consistent day/night, winter/summer. You can always move up from 
there.

     ack! gotta go do work...
     -Gary

Hello Jon,

  Monday, January 28, 2008, 10:28:09 PM, you wrote:

%<
> Although it is expensive, get a Stauffer transmission test scale,
                                  Stouffer www.stouffer.net
> (ST-7 or ST-21) at a professional photography store (hard to find

Actually the best scale is T2115  @  $6.10 ordinary one or
                           T2118C @ $15.15 calibrated
Both are 21 step 1/2" wide by 5" long

Years ago i bought T2115 and to date used it only 3 times.

(visit my blogg on the link below)

-- 
 Best regards,
 Zoran A. Scepanovic
 zastos@...
 http://zastosen.blogspot.com

*********
After you use everything you know and can find out to make what you're
certain is the right decision, and it's too late to change things or
back out -- you'll find out something that would have reversed the whole
thing for you, if you'd only known in time.
*********

Please be advised what was said may be absolutely wrong, 
and hereby this disclaimer follows.  
I reserve the right to be wrong and admit it in front of the entire world.



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