Homebrew PCBs

Hello everybody.

After browsing on youtube for some interesting movies about CPLD's I came across this video:

http://www.youtube.com/watch?v=WTuF28TqwT0&feature=related

How well does this stuff work in practice?

With kind regards,

Bart

Good thing too this guy hides the traces with soldermask, rarely seen
such an ugly board....

What "stuff" specifically do you refer to?

ST

On Wed, Sep 2, 2009 at 3:08 PM, boombox666<boombox666@...> wrote:
> Hello everybody.
>
> After browsing on youtube for some interesting movies about CPLD's I came across this video:
>
> http://www.youtube.com/watch?v=WTuF28TqwT0&feature=related
>
> How well does this stuff work in practice?
>
> With kind regards,
>
> Bart
>
>
>
>
> ------------------------------------
>
> Be sure to visit the group home and check for new Links, Files, and Photos:
> http://groups.yahoo.com/group/Homebrew_PCBsYahoo! Groups Links
>
>
>
>

If you refer to the green soldermask in the video, that is real soldermask for industrial PCB making. However, the last shot on the finished PCB shows very poor finish, because is almost for sure that the datasheet for that soldermask states that it must be baked in an air-forced oven before imaging with UV. Also, it must be applied by screen printing, not manually with a card. If the user follows all the steps according to the manufacturer you end with a professional board, since the soldermask in the video is "the real thing" used in industry.

In my tests for a PCB resist ink, I've found a very good UV curable
ink that functions well as a soldermask.

I can eject this and cure it no problem with an Epson R280.
Originally I wanted to use it as a binder for a 3d printer but it's
very expensive ($100 a cartridge) but it seems to work great so far.

Anyway, I hope to release it as a soldermask product instead but I'm
trying to determine longer term stability/if it clogs inkjet heads.
If someone wants to try it out, I can send you a prefilled cart at my
cost to evaluate.  Email me off list and show me your current inkjet
pcb setup to qualify.

You need a massive UV lamp to cure it.  With a 100W mercury lamp, it
only takes 10 seconds but I'm trying to find a cheap solution.  I
found some 1W UV Led torches but don't have results yet.  It takes
about 8hrs in direct sunlight to dry otherwise.  Those cheap UV
fluorescent tubes don't work well either.

Henry

On Wed, Sep 2, 2009 at 12:53 PM, jcarlosmor<jcarlosmor@...> wrote:
>
>
> If you refer to the green soldermask in the video, that is real soldermask
> for industrial PCB making. However, the last shot on the finished PCB shows
> very poor finish, because is almost for sure that the datasheet for that
> soldermask states that it must be baked in an air-forced oven before imaging
> with UV. Also, it must be applied by screen printing, not manually with a
> card. If the user follows all the steps according to the manufacturer you
> end with a professional board, since the soldermask in the video is "the
> real thing" used in industry.
>
>

jcarlosmor wrote:
>  
> 
> If you refer to the green soldermask in the video, that is real 
> soldermask for industrial PCB making. However, the last shot on the 
> finished PCB shows very poor finish, because is almost for sure that the 
> datasheet for that soldermask states that it must be baked in an 
> air-forced oven before imaging with UV. Also, it must be applied by 
> screen printing, not manually with a card. If the user follows all the 
> steps according to the manufacturer you end with a professional board, 
> since the soldermask in the video is "the real thing" used in industry.

I've recently been playing with Liquid Photoimageable Solder Mask 
(LPISM). Your right, it needs a proper bake before exposure or it gets 
damaged in the developer.

* LPISM part A and B are mixed on a metal spatula (typ. 1 gram)
* screen printed (polyester mesh 125 thread/inch)
* baked 80C 20min,
* UV exposed (2 minutes from 4 x 8W UV BL tubes)
* developed (10g/l Na2CO3 @ 35C, manual paint brush agitation)
* baked 150C 20min.

notes:
* All equipment is readily cleaned in the developer tray.
* It goes a long way, 1 gram of LPISM does your typical 10 x 10cm PCB.
* A PCB holding jig is required for double sided printing.
* working in a artificial lighting area seems safe.

The link below is of a board I did recently. I know its quite ugly, but 
I'm only just learning about this solder mask stuff.
http://members.optusnet.com.au/eseychell/revH_photo.jpg

I'd like to know what experience people have with dry film soldermasks. 
Might be lot more practical for hobbyist.

> I'd like to know what experience people have with dry film soldermasks. 
> Might be lot more practical for hobbyist.
>

I use the dry film from megauk.com. You apply it with a laminator and then uv expose the area you want to keep. A developing agent then removes the areas that were not exposed to uv ( pad areas ). The film is then cured in uv and an oven and does produce a great finish. 

I have experienced some 'blisters' in initial application but I think this is just down to a clean environment. 

I have added a picture in the album 'Dry Film Solder Resist Mask board' to show my results. 

Trev

I have a UV box with 99 LEDs, 395nm.  Regular dry film takes about 5
minutes exposure; what would that work out to with your ink?  Does
your ink come in spray cans?  I think a spray-on ink would work well
with our existing photomask setups.

Adam Seychell <a_seychell@...> writes:
> http://members.optusnet.com.au/eseychell/revH_photo.jpg

How did you solder-coat that?

> I'd like to know what experience people have with dry film
> soldermasks.

I've thought of using etch resist as a soldermask, but I don't know
how well it would hold up.  A spray can of UV-cure something would be
nice.

If you have an Epson Printer, you can just print it out and cure it.
No wasted ink or extra exposure step needed.  That way and placement
accuracy is much better.  It only comes in tiny little very expensive
syringes but I've been refilling some empty black cartridges to do
some testing.  If you're interested I can have you do some testing.
H

On Wed, Sep 2, 2009 at 5:05 PM, DJ Delorie<dj@...> wrote:
>
>
> I have a UV box with 99 LEDs, 395nm. Regular dry film takes about 5
> minutes exposure; what would that work out to with your ink? Does
> your ink come in spray cans? I think a spray-on ink would work well
> with our existing photomask setups.
>

On Thu, 2009-09-03 at 09:44 +1000, Adam Seychell wrote:
> 
> The link below is of a board I did recently. I know its quite ugly,
> but 
> I'm only just learning about this solder mask stuff.
> http://members.optusnet.com.au/eseychell/revH_photo.jpg
> 
> I'd like to know what experience people have with dry film
> soldermasks. 
> Might be lot more practical for hobbyist.
> 

Adam,
Your first board with LPI soldermask looks really good. I would prefere
to buy boards from you than from some boardhouses out there. I used a
lot of dry film soldermask but i don't like it (neither riston) and
won't recommend it. It can seem a good option for the homebrew but the
LPI options out there seem even better and also easier to get.

Comparable to riston the vacrel (dry film soldermask from dupont) is
laminated at same 110�C, and developing time in Na2CO3 is also the same
along with temperature and concentration (same tank and procedure for
both, but increase time for never fail results), but exposure time on uv
lamps is about the double i used 10seconds for riston and 19s for
vacrel, on same vacuum exposure unit and same high contrast photoplotter
film. The cure was 2hours on 100W uv lamps, but should be less uv and
some oven heating. The lamination pressure should be superior to riston
but the expensive and far from good bungard laminator was already stupid
painful to operate.

I won't recommend it because:
* I really hate the smell of it. When heated has really nasty gases, not
even strong exhaustion ventilation remove the smell.
* Is very very difficult to laminate. I used a big very expensive (like
a good car) professional laminator that always laminate riston without
problems and still soldermask always had bubbles on it. 
* Is not a thing to put on a oven. That air bubbles can lift the
soldermask or your components when heated. The air bubbles are tricky
also in low pressure environments. 
* It gives a ugly very thick finish. Is so thick it looks like a pvc
sheet glued above like a stencil. 
* Hard to remove if a problem in application occurs. If you misalign the
artwork or over/under expose/develop, for example , you can only remove
it in 15min acetone dipping and scrubbing. After cure is impossible to
remove. 
* Is very expensive and hard to get. Any low quantity application method
of dry film has considerable wast, when using expensive dry film the
wast is a budget hole.

You know i am a big fan of your lamination method, after understanding
how a professional laminator works every laminator i can afford seems
just more trouble than results. But i don't know if your laminating
method will work good enough with dry film soldermask.

BTW, you should rename your method to 'Painless Dry film lamination
method for the homebrew (with water)' , wet lamination is spraying hot
water between the hot rubber roll and dry film to replace microscopic
air bubbles by water which will disappear in some hours because the
dryfilm is water soluble.

Henry Liu <henryjliu@...> writes:
> If you have an Epson Printer, you can just print it out and cure it.

I have an R280 but it's not converted for PCB use.  I use it to print
photofilms and do glossy photos.

> That way and placement accuracy is much better.

How?  How can the printer know where the copper is, so it can print in
the right spots?  With film I can visually align the film to the board
before exposure.

> Henry Liu <henryjliu@...> writes:
>> If you have an Epson Printer, you can just print it out and cure it.
>
> I have an R280 but it's not converted for PCB use. I use it to print
> photofilms and do glossy photos.
>

See my tutorial no modification needed except to your CD tray:
http://www.fullspectrumengineering.com/tutorial.html
You can buy an extra one for $10-15 if you want to keep the original.
Just put in the new cartridge and it prints it.

>> That way and placement accuracy is much better.
>
> How? How can the printer know where the copper is, so it can print in
> the right spots? With film I can visually align the film to the board
> before exposure.
>

In Altium and Eagle you can print the soldermask layer.  Invert it to
print black where you want no soldermask.

The Stainless Steel PCB CD Stencil gets your alignment into the
printer every time:
http://www.fullspectrumengineering.com/pcbstep2.html

If you want to do boards bigger than 3.5x2.5 then you are on your own.

Simao is right, I use Adams method too. I use Adam's Wet lamination then press it with laminator, Thanks Adam, I use his  tutorial for my blog..you can see at
http://nastelroy.wordpress.com/2009/01/21/membuat-pcb-photoresist/

I have try many times to make soldermask for my board, but get bad result. I use silkscreen method to get my soldermask
--- On Wed, 9/2/09, Simao Cardoso <simaocardoso@...> wrote:

From: Simao Cardoso <simaocardoso@gmail.com>
Subject: Re: [Homebrew_PCBs] Re: Solder mask liquid,
To: Homebrew_PCBs@yahoogroups.com
Date: Wednesday, September 2, 2009, 7:57 PM






 




    
                  On Thu, 2009-09-03 at 09:44 +1000, Adam Seychell wrote:

> 

> The link below is of a board I did recently. I know its quite ugly,

> but 

> I'm only just learning about this solder mask stuff.

> http://members. optusnet. com.au/eseychell /revH_photo. jpg

> 

> I'd like to know what experience people have with dry film

> soldermasks. 

> Might be lot more practical for hobbyist.

> 



Adam,

Your first board with LPI soldermask looks really good. I would prefere

to buy boards from you than from some boardhouses out there. I used a

lot of dry film soldermask but i don't like it (neither riston) and

won't recommend it. It can seem a good option for the homebrew but the

LPI options out there seem even better and also easier to get.



Comparable to riston the vacrel (dry film soldermask from dupont) is

laminated at same 110ºC, and developing time in Na2CO3 is also the same

along with temperature and concentration (same tank and procedure for

both, but increase time for never fail results), but exposure time on uv

lamps is about the double i used 10seconds for riston and 19s for

vacrel, on same vacuum exposure unit and same high contrast photoplotter

film. The cure was 2hours on 100W uv lamps, but should be less uv and

some oven heating. The lamination pressure should be superior to riston

but the expensive and far from good bungard laminator was already stupid

painful to operate.



I won't recommend it because:

* I really hate the smell of it. When heated has really nasty gases, not

even strong exhaustion ventilation remove the smell.

* Is very very difficult to laminate. I used a big very expensive (like

a good car) professional laminator that always laminate riston without

problems and still soldermask always had bubbles on it. 

* Is not a thing to put on a oven. That air bubbles can lift the

soldermask or your components when heated. The air bubbles are tricky

also in low pressure environments. 

* It gives a ugly very thick finish. Is so thick it looks like a pvc

sheet glued above like a stencil. 

* Hard to remove if a problem in application occurs. If you misalign the

artwork or over/under expose/develop, for example , you can only remove

it in 15min acetone dipping and scrubbing. After cure is impossible to

remove. 

* Is very expensive and hard to get. Any low quantity application method

of dry film has considerable wast, when using expensive dry film the

wast is a budget hole.



You know i am a big fan of your lamination method, after understanding

how a professional laminator works every laminator i can afford seems

just more trouble than results. But i don't know if your laminating

method will work good enough with dry film soldermask.



BTW, you should rename your method to 'Painless Dry film lamination

method for the homebrew (with water)' , wet lamination is spraying hot

water between the hot rubber roll and dry film to replace microscopic

air bubbles by water which will disappear in some hours because the

dryfilm is water soluble. 




 

      

    
    
	
	 
	
	








	


	
	


      

[Non-text portions of this message have been removed]

DJ Delorie wrote:
>  
> 
> 
> I have a UV box with 99 LEDs, 395nm. Regular dry film takes about 5
> minutes exposure; what would that work out to with your ink? Does
> your ink come in spray cans? I think a spray-on ink would work well
> with our existing photomask setups.
> 

Hi, I have both a homemade 395nm LED light box and a basic commerical UV 
BL tube exposure box. Using LED exposure, my photoresist dry film takes 
70 seconds, while the LPISM doesn't even properly cure at 30 minutes.
 From limited experiments, the exposure period from UV BL tubes takes 
about 2~4 minutes for the LPISM. So my conclusion is LED's don't work on 
photoimagable solder masks.


Adam

Simao Cardoso wrote:
>  
> 
> On Thu, 2009-09-03 at 09:44 +1000, Adam Seychell wrote:
>  >
>  > The link below is of a board I did recently. I know its quite ugly,
>  > but
>  > I'm only just learning about this solder mask stuff.
>  > http://members. optusnet. com.au/eseychell /revH_photo. jpg 
> <http://members.optusnet.com.au/eseychell/revH_photo.jpg>
>  >
>  > I'd like to know what experience people have with dry film
>  > soldermasks.
>  > Might be lot more practical for hobbyist.
>  >
> 
. It can seem a good option for the homebrew but the
> LPI options out there seem even better and also easier to get.

Thanks very much for sharing your experiences with dry film solder 
masks. After trying out the LPI I think with some experimenting the 
process can be made cheap and reliable in a hobbyist setup. I was going 
to get prices for dry film solder mask, but if I'm faced with the 
problems you describe then I won't bother. The LPI soldermask is 
available in much lower minimum order cost. I paid AU$70 for 1kg, and 
split that with a someone else. 500g will last me a life time. I'd agree 
that dry film would be far far more expensive.

With some simple home made jigs , the LPI solder mask should be a fairly 
painless process.

All solder mask data sheets (liquid or dry film) I have read mention 
pre-drying the PCB before applying solder mask . This suggest to me 
that unlike photoresist, wet laminating dry film solder mask will simply 
not work.



> 
> BTW, you should rename your method to 'Painless Dry film lamination
> method for the homebrew (with water)' , wet lamination is spraying hot
> water between the hot rubber roll and dry film to replace microscopic
> air bubbles by water which will disappear in some hours because the
> dryfilm is water soluble.
> 

Ok, thanks for the suggestion. I need to update the article a little, It 
can be simplified.
When I was experimenting various manual lamination methods, I found if 
the film is applied cold then it traps too much water and *sometimes* 
causes adhesion problems. It would appear initially that no water is 
trapped , but after heating to complete the bond, I often saw pail marks 
appearing through the dry film.  I found fine traces often lift off the 
copper where these marks were located. It had me puzzled for a while. I 
tried copper micro etching, various post heating times and temperatures 
to try improve adhesion. It was only when applying hot water when I 
discovered it was trapped water causing the problem. This is the main 
reason why a squeegee board is necessary for my method.
I'm not sure what the minimum temperature is, but its likely over 35C.

Adam

I'm using the Solder Mask UV Film from Think and Tinker -- with outstanding results.  I've never had a problem.  No smell, nothing.
I simply laminate it, expose it for 50 seconds using a image made on a laser printer with clear acetate.  Develop it in Washing Soda.  Expose it again for 15 mins, then bake it for an hour in a toaster over.

Hard as a rock.

The only issue I've had is trying to find something that sticks to it, so I can stencil the labels.

fredbutz wrote:
>  
> 
> I'm using the Solder Mask UV Film from Think and Tinker -- with 
> outstanding results. I've never had a problem. No smell, nothing.
> I simply laminate it, expose it for 50 seconds using a image made on a 
> laser printer with clear acetate. Develop it in Washing Soda. Expose it 
> again for 15 mins, then bake it for an hour in a toaster over.
> 

What is your light source ? Using LPI solder mask, I found a 2 minute 
exposure requirement from 4 x 8W BL tubes box. My UV LED box (15x15mm 
pitch grid, 395nm LED) will actually cure the solder mask after ~7 
minutes, but it leaves a mat finish after developing. The datasheet 
states that inadequate exposure intensity, will cause dullness after 
developing. Do you have this problem ?  I can easily mechanically buff 
the solder mask to return it's luster.

The 150C 60 minute post baking completes the cure. Only methylene 
chloride based paint strippers will remove solder mask, but will also 
attack the epoxy base.

fredbutz wrote:
>   
> I'm using the Solder Mask UV Film from Think and Tinker -- with
> outstanding results. 

If you look close between two near traces, is the dry film glued to the
laminate or is air between? Around any copper trace don't you see air
trapped there?
Riston is applied to a perfect flat surface, dry film soldermask is very
thick almost solid and applied to a not flat surface leaving always some
air around the copper traces. 

> I've never had a problem. No smell, nothing.

It works, we made hundreds of working boards with it. But comparable to
LPI is a bad choice in price and availability and is not easier to use.
Is only better to traditional screened soldermask. We got also problems
caused by wrong temperature and pressure parameters, and bubbles from
misaligned and with wrinkles dry film rolls, re-reeled by bungard for
lower quantity.  
Anyway I simple don't like it, and find the finish ugly because is too
thick. And for the homebrew is just too expensive.

> Hard as a rock.
> 
> The only issue I've had is trying to find something that sticks to it,
> so I can stencil the labels.

Any proper legend ink will do, dry film soldermask is still epoxy.

--- In Homebrew_PCBs@yahoogroups.com, "fredbutz" <fredbutz@...> wrote:
>
> I'm using the Solder Mask UV Film from Think and Tinker -- with outstanding results.  I've never had a problem.  No smell, nothing.
> I simply laminate it, expose it for 50 seconds using a image made on a laser printer with clear acetate.  Develop it in Washing Soda.  Expose it again for 15 mins, then bake it for an hour in a toaster over.
> 
> Hard as a rock.
> 
> The only issue I've had is trying to find something that sticks to it, so I can stencil the labels.
>

I understand that nothing smell when you laminate the PCB, but are you sure that nothing smell when the PCB is baked? I think that you toaster oven is functioning at a temperature very lower than expected.

I have used Think and Tinker soldermask too. Vacrel soldermasks smell horrible above 60 degress centigrade that is the point when they start to react to heat. You cannot tolerate the smells for more than 3 seconds as they are very aggresive, and severe irritation occurs.

http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/tech_bulletins/tb0054.pdf

No, I bake them for 1 hour at 100C.  No smell.  Hard as a rock.
I'll measure the oven next time though to be sure.


--- In Homebrew_PCBs@yahoogroups.com, "jcarlosmor" <jcarlosmor@...> wrote:

>
> --- In Homebrew_PCBs@yahoogroups.com, "fredbutz" <fredbutz@> wrote:
> >
> > I'm using the Solder Mask UV Film from Think and Tinker -- with outstanding results.  I've never had a problem.  No smell, nothing.
> > I simply laminate it, expose it for 50 seconds using a image made on a laser printer with clear acetate.  Develop it in Washing Soda.  Expose it again for 15 mins, then bake it for an hour in a toaster over.
> > 
> > Hard as a rock.
> > 
> > The only issue I've had is trying to find something that sticks to it, so I can stencil the labels.
> >
> 
> I understand that nothing smell when you laminate the PCB, but are you sure that nothing smell when the PCB is baked? I think that you toaster oven is functioning at a temperature very lower than expected.
> 
> I have used Think and Tinker soldermask too. Vacrel soldermasks smell horrible above 60 degress centigrade that is the point when they start to react to heat. You cannot tolerate the smells for more than 3 seconds as they are very aggresive, and severe irritation occurs.
> 
> http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/tech_bulletins/tb0054.pdf
>

--- In Homebrew_PCBs@yahoogroups.com, "fredbutz" <fredbutz@...> wrote:
>
> No, I bake them for 1 hour at 100C.  No smell.  Hard as a rock.
> I'll measure the oven next time though to be sure.
> 

Did you had free time to check your oven temperature? Or do you have an industrial oven, with ventilation, exhaust fans and so on? I was wondering if DuPont changed something in Vacrel to emit lower fumes, but no, the Soldermask fumes are same aggresive. I can assure you that if you intend to cure at the specified temperature you will have a lot of trouble with other members of your home, apart of you! The smells are insopportable.