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who's applying photoresist film ?

who's applying photoresist film ?

2008-12-17 by Adam Seychell

I'm curious how many people here are applying their own dry film 
photoresists. I've stumbled upon a method that seems to work half 
reasonably. Rather that discuss it here I wrote up a web page.
http://members.optusnet.com.au/~eseychell/PCB/photoresist/index.html
I'm interested in what other techniques people use since I've never 
tried one of those office hot roll laminators. Are these machines "fool 
proof" or have they got problems like bubbles and wrinkles ? The film's 
stickiness makes it difficult to work with.

Adam

Re: [Homebrew_PCBs] who's applying photoresist film ?

2008-12-17 by DJ Delorie

Adam Seychell <a_seychell@...> writes:
> I'm curious how many people here are applying their own dry film 
> photoresists.

I am, but if I can get the laminator hacked, I may switch from wet to
dry.  I'll have to try and see which is more reliable.

I did a solder paste screen using aluminum foil and dry film, it seems
to have worked well but I haven't tried to apply paste with it yet.

> I've stumbled upon a method that seems to work half reasonably.

I use the wet method, which I've described here before.  It works
reasonably well but it's a bit messy and labor-sensitive.

Re: who's applying photoresist film ?

2008-12-17 by jcarlosmor

I am using a medium size office laminator without any problems. The 
film adheres so well, so I beleive that the correct temperature is the 
key for success. I had noticed also that bubbles or wrinkles are mainly 
due to operator human error by manipulating the film, just before 
entering the hot rolls, not the process itself inside the laminator.  
However, large PCBs in the horizontal axis are more prone to wrinkles 
because it is harder to keep the film flat with the hands at those 
sizes. It would be very useful to adapt some kind of roll support or 
clamp to a structure containing the laminator itself, to emulate a more 
professional laminator with a flat film entering the hot rolls. Your 
wet method seems very well, but there are more steps to follow than in 
the dry method.

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-17 by Adam Seychell

jcarlosmor wrote:
> I am using a medium size office laminator without any problems. The 
> film adheres so well, so I beleive that the correct temperature is the 
> key for success. I had noticed also that bubbles or wrinkles are mainly 
> due to operator human error by manipulating the film, just before 
> entering the hot rolls, not the process itself inside the laminator.  
> However, large PCBs in the horizontal axis are more prone to wrinkles 
> because it is harder to keep the film flat with the hands at those 
> sizes. It would be very useful to adapt some kind of roll support or 
> clamp to a structure containing the laminator itself, to emulate a more 
> professional laminator with a flat film entering the hot rolls. Your 
> wet method seems very well, but there are more steps to follow than in 
> the dry method.

Yea it can be a bit labour intensive as DJ mentioned. The water can make 
it a bit of a mess too. Originally I was applying it cold and heating 
after it with hot air, but this cause serious problems with trapped 
water which leads to poor adhesion. Seems my method hasn't much value 
after all. The new squeegee board thing I'm using was an attempt handle 
large sheets of photoresist without it all tangling up. I suppose the 
water method helps with bubbles and the dreaded trapped particles.
My new method takes me about same time and effort to make a cup of 
brewed tea, so I'll stay with it for time being.

I've seen the the professional dry film laminating machines, and they 
have lots of rollers. 2 heated rollers for lamination, 2 protection 
backing film removal rollers, and 2 rollers that carry the photoresist. 
I assume all rollers are all carefully aligned to avoid wrinkles and 
film warping. Two human hands cannot archive that control. I too found 
actual temperature isn't all that critical. It does need to be above 40C 
though using the wet method.

Adam

Re: [Homebrew_PCBs] who's applying photoresist film ?

2008-12-17 by Markus Zingg

I do, but I never tried the wet method cause doing it the "dry" way 
works just fine as long as I use a sheet of paper between the film and 
PCB while feeding this "stack" into the laminator as I documented in the 
files section sometimes back. Funny, I can't seem to find the file in 
the filesection anymore, and I'm currently in a hurry. So, if others are 
interested I try to find the original photos I made of the process and 
post them again.

Markus

Adam Seychell schrieb:
Show quoted textHide quoted text
>
> I'm curious how many people here are applying their own dry film
> photoresists. I've stumbled upon a method that seems to work half
> reasonably. Rather that discuss it here I wrote up a web page.
> http://members.optusnet.com.au/~eseychell/PCB/photoresist/index.html 
> <http://members.optusnet.com.au/%7Eeseychell/PCB/photoresist/index.html>
> I'm interested in what other techniques people use since I've never
> tried one of those office hot roll laminators. Are these machines "fool
> proof" or have they got problems like bubbles and wrinkles ? The film's
> stickiness makes it difficult to work with.
>
> Adam
>
>

Re: who's applying photoresist film ?

2008-12-17 by jcarlosmor

I think that your wet method will be very valuable for soldermask, 
which is harder to adhere and process without bubbles or wrinkles than 
photoresist. In fact, DuPont and ThinkTink make recommendations to 
use "wet" methods improvements prior to laminate if problems arise, 
specially when a vacuum laminator is not available (the common case in 
hobby or small shops situations).

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-17 by Markus Zingg

Huh?

The soldermask resist I have is much thicker than the one I use for 
etching and as a result VERY easy to apply.

Unfortunately I don't know exactly what it is. I so far buy it from 
Bungard which is a small quantities supplier for stuff like that in europe.

Markus

jcarlosmor schrieb:
Show quoted textHide quoted text
>
> I think that your wet method will be very valuable for soldermask,
> which is harder to adhere and process without bubbles or wrinkles than
> photoresist. In fact, DuPont and ThinkTink make recommendations to
> use "wet" methods improvements prior to laminate if problems arise,
> specially when a vacuum laminator is not available (the common case in
> hobby or small shops situations).
>
>

Re: who's applying photoresist film ?

2008-12-18 by jcarlosmor

I am using Vacrel soldermask from DuPont. Do you have a reference or 
part number regarding the soldermask from Bungard that you use? Thanks.

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-18 by Adam Seychell

jcarlosmor wrote:
> I am using Vacrel soldermask from DuPont. Do you have a reference or 
> part number regarding the soldermask from Bungard that you use? Thanks.
> 
> 
Does the finished result look professional ?
I bought some of that green liquid photoimageable solder mask but its a 
2 part system and must be applied by a screen mesh, then baked 40 
minutes at 75C before UV exposure. It develops in 0.9% sodium carbonate 
just like with dry film solder masks and dry film photoresists. Haven't 
even tried it yet.
Your dry film solder mask looks a lot more attractive.

Re: who's applying photoresist film ?

2008-12-18 by trevwhite74

Hi, I have just ordered some dry film solder mask from the following
link. I think I remember talking to a rep who said this stuff is
pretty good. I shall hopefully try it over the next few weeks. 

http://www.megauk.com/dry_film_laminators.php

> Does the finished result look professional ?
> I bought some of that green liquid photoimageable solder mask but its a 
> 2 part system and must be applied by a screen mesh, then baked 40 
> minutes at 75C before UV exposure. It develops in 0.9% sodium carbonate 
> just like with dry film solder masks and dry film photoresists. Haven't 
> even tried it yet.

I nearly bought some of this photoimageable solder mask because they
sell it in several colours but the process does seem a quite a hassle.
I think I shall get round to trying it at some point but the green
film seems the most practical for now. 

Trev

Re: who's applying photoresist film ?

2008-12-18 by jcarlosmor

Since Vacrel is a dry film soldermask it gives a professional look, but 
several two-part liquid photoimageable soldermask are also very good. 
�what kind or brand of LPI did you purchase? The main disadvantage with 
LPI is the high energy required for imaging, in comparison with dry 
film.

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-18 by Adam Seychell

trevwhite74 wrote:
> 
> I nearly bought some of this photoimageable solder mask because they
> sell it in several colours but the process does seem a quite a hassle.
> I think I shall get round to trying it at some point but the green
> film seems the most practical for now. 
> 
thanks for the link. The prices are kind of on the high side. Their 
\ufffd2625 dryfilm laminator was a bit off putting.
I couldn't see liquid solder masks on their site. What was the pricing 
when you were looking at it ?

I'll try my liquid stuff first. Problems I see using liquid mask is you 
first need to make screen printing frame and buy/make a squeegee too. 
Mixing would require a 0.1g resolution electronic scale (possibly a $20 
  eBay pocket scale). A fan forced home kitchen oven could probably do 
the 75C bake. I'm assuming you'd clean all equipment with developer 
solution. All this sounds like a lot of hassle. Maybe with a some 
patients one could get the process down pat. The sales guy said its 
pretty easy when you get the hang of it.

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-18 by Adam Seychell

jcarlosmor wrote:
> Since Vacrel is a dry film soldermask it gives a professional look, but 
> several two-part liquid photoimageable soldermask are also very good. 
> \ufffdwhat kind or brand of LPI did you purchase? The main disadvantage with 
> LPI is the high energy required for imaging, in comparison with dry 
> film.


The 780 H Series LPI solder mask its made by http://www.eternal.com.tw
Data sheet (not available online) states 350~450mJ/cm^2 exposure energy.
Comparing to my dry film photoresist of 60~100mJ/cm^2.
So yea, exposure energy requirement is factor 5 over the photoresist. 
Not a problem, I can handle a 5 minute wait per side.
Have you used LPI before ?

Re: who's applying photoresist film ?

2008-12-18 by trevwhite74

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@...>
wrote:
> thanks for the link. The prices are kind of on the high side. Their 
> £2625 dryfilm laminator was a bit off putting.

I do not think their prices are great but bit of a niche market I
suppose. I checked out a normal cheap laminator from Maplin that I
picked up for £10 a while back. The temperature switches in it have a
window between 110C and 130C I think. They are around that temp
anyway. This film requires 110 - 115C so fingers crossed I should get
away with a normal laminator. If I need to I will build a better temp
controller for it. 

> I couldn't see liquid solder masks on their site. What was the 
> pricing when you were looking at it ?

http://www.megauk.com/screen_printing.php

if you search the page for order code 41-2002 hopefully this will show
you which stuff I was looking at. The stuff costs £51 + VAT and delivery. 

> I'll try my liquid stuff first. Problems I see using liquid mask is you 
> first need to make screen printing frame and buy/make a squeegee too. 
> Mixing would require a 0.1g resolution electronic scale (possibly a $20 
>   eBay pocket scale). A fan forced home kitchen oven could probably do 
> the 75C bake. I'm assuming you'd clean all equipment with developer 
> solution. All this sounds like a lot of hassle. Maybe with a some 
> patients one could get the process down pat. The sales guy said its 
> pretty easy when you get the hang of it.
>

I do think the process is a lot more involved for the liquid stuff but
for some reason I wonder if the results might work out more
intersting. I am not going to use a screen when I do it. LPKF have a
process called ProMask that actually rolls the ink on. I wonder if
something similar can be done. On www.lpkfusa.com there is a video of
how they apply the ProMask stuff. Might help?

I am going to use a nice pizza oven. I picked one up on Ebay for £20.

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-18 by Markus Zingg

Bungard only sells one soldermask laminate, so calling them and asking 
for a price / ordering should do. The nice thing is that they sell rolls 
of 25m only which is then somewhat affordable. Then, I use a lot more 
photoresist than soldermask per PCB (actually 3 times more -> inner and 
outer layers, and also for makeing the stencil). I also never had to 
remove soldermask because it did not laminate well (as oposed to the 
resist where it happens rarely). In other words, the somewhat higher 
price buying this @ bungard does not add that much to the overal 
material cost to create a PCB.

HTH

Markus

jcarlosmor schrieb:
Show quoted textHide quoted text
>
> I am using Vacrel soldermask from DuPont. Do you have a reference or
> part number regarding the soldermask from Bungard that you use? Thanks.
>
>

Re: [Homebrew_PCBs] Re: who's applying photoresist film ?

2008-12-19 by Adam Seychell

trevwhite74 wrote:

> I do think the process is a lot more involved for the liquid stuff but
> for some reason I wonder if the results might work out more
> intersting. I am not going to use a screen when I do it. LPKF have a
> process called ProMask that actually rolls the ink on. I wonder if
> something similar can be done. On www.lpkfusa.com there is a video of
> how they apply the ProMask stuff. Might help?

My LPISM looked a bit viscous to roll on with a disposable roller. The 
ProMask kit is a little out of reach at US$650.00 :)
I'm thinking it might be easier to screen print it as recommended. The 
main problem I see with screen printing is the clean up.
I'll have to make a screen frame up, probably out of hard wood. The mesh 
  can be bought off the roll from any screen printing supplier. Its 
common for people to make their own frames. I got number 120 mesh.
I think you just stretch the mesh over a frame and then glue it with epoxy.

> I am going to use a nice pizza oven. I picked one up on Ebay for \ufffd20. 
What will this oven be used for ?  I thought you were getting dry film 
which doesn't need baking.

Re: who's applying photoresist film ?

2008-12-19 by trevwhite74

--- In Homebrew_PCBs@yahoogroups.com, Adam Seychell <a_seychell@...>
wrote:
 
> What will this oven be used for ?  I thought you were getting dry film 
> which doesn't need baking.
>

I believe you still need to cure the Dry Film. I am trying to dig out
the datasheet  but I think once developed the boards needs 60mins in
the oven...actually it says they can be cured under UV instead but i
am not sure the results are as good as then oven from reading the
datasheet. 

I also have the oven for when I tin boards using solder paste and some
other things.

Trev

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