Homebrew PCBs

Hi Jim

Thanks very much for the in-depth tutorial.  I didn't know you could 
put one layer of resist over another like that.

When you mention heathing with the aluminum plate, you must mean 
between the burner and the board itself, not on top of the board, 
right?  (I thought you had to use pressure to press on the film, but 
from your explanation, it sounds like you can get away without it).

The pressure you use when actually touching the film must not be 
that great?

Also, I don't have very dependable sun here where I live.  I use a 
regular UV lamp, which seems to work best for me after about 20 
minutes, even though the manufacturer says 10-12.  I've heard bug 
lights can offer better exposure times too, but I have yet to try.
 

Thanks for the help!

-Josh


--- In Homebrew_PCBs@yahoogroups.com, "Jim Klitzing" <wb6myc@...> 
wrote:
>
> Josh,
> 
> Water makes the resist adhere quite well w/o bubbles, but it 
causes 
> two problems for me; ther first is the one you described, and the 
> second is the tendency for the resist to 'lump' instead of melt 
when 
> developed, leaving ragged edges.
> 
> I have a laminator, and it works well for the thinner board 
material, 
> but you do have to place the board into a carrier for this to work 
> properly.
> 
> On thicker board material, where I cannot use a laminator, this is 
my 
> method for applying it sucessfully:
> 
> This product is a 3-layer laminate, consisting of a photo-
sensitive 
> polymer layer between two protective layers of clear plastic 
film.  
> It can be used without process equipment or exotic chemicals, and 
> develops easily in a slightly caustic soda solution.
> 
>  Here is my own procedure for applying this resist:
> 
>          I.      Cut your board to size, clean and dry the copper 
> surface
> 
> ·        Whatever your finished board size will be, make it about 
> 1/4" larger all the way around. This will allow you to do a final 
> trim later to remove any ragged edges or other defects after 
etching. 
> These defects tend to appear right at the edges of the board.
> 
> ·        Wearing latex gloves is helpful; you must clean any oils, 
> corrosion or other defect from the copper. One way to do this is 
to 
> use a scouring powder (like Kleen-King) and water. Very fine steel 
> wool is also OK. If the copper surface is already in good shape, 
> clean with soap and water only and dry.
> 
> 
> 
>      II.     Prepare the laminate and apply it to the the board
> 
> ·        Cut a piece of the laminate stock into a sheet about 1/2 
> inch larger than your board all the way around.
> 
> ·        Lay the laminate flat on a cool surface, and with the 
point 
> of a needle or Xacto knife, pick away at a corner until the 
> protective layer begins to separate.
> 
> Note: You will be able to separate the first protective layer only 
on 
> one side of the laminate, the other will not peel away until the 
> laminate is heated and cooled later on in the process.
> 
> .        Heat a 3/8" thick aluminum plate to 125f. Lay the board 
on 
> it, and when it comes to temp, apply the resist 1/4" at a time, 
> moving your finger side-to-side to apply it evenly, while 
continuing 
> to peel back the protective layer as you go. Trim off the excess 
> material.
> 
> ·        Warm the board slowly using a hot plate and that piece of 
> 3/8" aluminum plate. Move the temp up from room temp to 150f (max) 
> over 15 minutes, allowing the resist to cure to the board; Allow 
to 
> cool gradually. Test for proper curing by peeling back the outer 
> protective layer at the edges; if it comes away clean, it's OK; if 
> the resist comes with it, it's not cured yet. Do not remove the 
outer 
> layer entirely, just test the edges.
> 
> .	I find that one layer of this material is not enough 
> protection (I got a lot of pin-hole penetration through the 
resist), 
> so I always add a second layer of resist, this time at room 
> temperature. Peel away the protective layer over the first layer a 
> bit at a time, and apply the second layer a bit at a time, peeling 
> it's first layer as you go. Cure the board again as in the 
previous 
> step.
> 
> 
> III.      Expose
> 
> ·        Using a negative image of your artwork, expose the board 
> with the proper light. I use a glass picture frame to hold the 
> artwork and board together, and expose it in direct sunlight for 
> about 15 seconds. Store in a cool, dark place for 15 minutes to 
allow 
> the polymers to set.
> 
> IV.      Develop and etch your board
> 
> ·        I use Arm & Hammer washing soda (not baking soda), 1/2 
> TEAspoon (TSP) per 8 oz of water.
> 
> ·        Peel away the other protective layer remaining over the 
> photo resist, and pour developer over the board until the done, 
then 
> rinse immediately. The resist should slowly melt away. If it comes 
> off in clumps, strands or gobs, the resist did not cure properly.
> 
> ·        Now you can etch your PC board
> 
> ·        Resist can be stripped with Acetone, or if you don't like 
> Acetone, you can use a more concentrated developer solution (2 
> Tablespoons per 6 oz of water). Allowing either to sit on the 
resist 
> for a few minutes will cause the resist to bubble up and lift away 
> from the copper.
> 
> ·        Don't forget the final water rinse.
> 
> ·        Trim the board to size (this is where the ragged edges 
> disappear).
> 
> Hope this helps.../ Jim
> 
> 
> --- In Homebrew_PCBs@yahoogroups.com, "joshdewinter" 
> <joshdewinter@> wrote:
> >
> > Hi
> > 
> >   MG Chemicals now sells a "Negative Photoresist Film" (product 
> #416-
> > DFR5) that I believe may be Riston.
> > 
> >   I have tried it several times now with mediocre results.  The 
> > traces turn out good when they turn out.  The problem I'm 
getting 
> is 
> > actually getting the film to stick to the board uniformly before 
> > exposure.
> > 
> >   Someone suggested using water between the board and the film 
to 
> > allow rolling of any bubbles out from underneath with your thumb 
> > after positioning, then drying it in an oven at about 200 
degrees 
> for 
> > 10 min to get it to stick.
> > 
> >   They were right, it worked great...until I tried to dry it.  
> Small 
> > mutations formed, sometimes in the form of lines, sometimes what 
> look 
> > like small blobs.  They aren't bubbles per se, but somehow there 
> are 
> > areas of the film that appear to stick to the board at a deeper 
> level 
> > than the surrounding film, or maybe they are melting and 
deforming.
> > 
> >   The manufacturer recommends using a laminator to apply the 
film, 
> > which I tried initially, but it appears to have the same 
problem.  
> My 
> > laminator is adjustable heat, and I've tried from hi to low with 
> > similar results.  I haven't as yet put the board between any 
> > protective sheets when laminating like you might to laminate 
paper 
> > items...I'm going to try that next (the manufacturer never 
> > specifically said to do it).
> > 
> >   Here are their instructions: 
> > 
> >   http://www.mgchemicals.com/techsupport/416dfr_inst.html
> > 
> >   I clean the board ahead of time with steel wool, alcohol and 
> > acetone.  I am using clean gloves throughout.
> > 
> >   Can anyone help me with any tricks to get this stuff to adhere 
> > uniformly?
> > 
> >   Thank you so much in advance!
> > 
> > 
> > -Josh
> >
>