Author Topic: A question for those that etch thier own double sided boards...  (Read 1318 times)

CodeMonk

What method do you use to line up both sides perfectly? (Or close at least).

What I currently do is add 4 offset pads outside the PCB area, as shown below.
(The PCB is bordered by the blues lines in this example).



I do a thermal transfer of one side to the copper clad.
I then drill 4 holes through the outer pads the size of a round toothpick.
I use a center punch to mark those holes before drilling so those holes are dead center (I've gotten pretty good at that).
Toothpicks make a snug fit on the holes, so there is no slop.
Then I poke holes through the pads in the printout of the other side.
Sometimes I get things lined up perfectly.
Most of the time however, things are a little bit off and I end up with drilled hole that is not centered in the pad hole (represented by that little red spot on the pad on the board).

So I'm looking for suggestions on improving the alignment of the pads.
Preferably a method that won't require me to buy any new tools or other hardware (I'm pretty broke ATM).
(I know someone here uses a paper cutter to get things lined up, I lack one of those though :(  ).

I was just thinking, instead of using those 4 pads on the outside of the board, use some of the actual component pads instead.

When I am better off financially, I will be having boards made (Currently learning how to use Eagle).

Thanks


newperson

Re: A question for those that etch thier own double sided boards...
« Reply #1 on: March 27, 2013, 01:31:59 AM »
just 1 piece of tape is all that is needed.  leave extra room at the top of film/paper and hold your two pieces toward a light.  line the holes up and tape the top. 

defaced

Re: A question for those that etch thier own double sided boards...
« Reply #2 on: March 27, 2013, 10:36:25 AM »
I do photo resist, print my stuff on transparencies, and line everything up and tape it before I stuff the board in.  You might be able to see through your paper well enough to try this (maybe on a window that gets good sun light where you can use it like a light table).  The problem I have run into is that my laser printer (and apparently others, as I've also read about this online) have a skew to them.  If you're doing a small board it won't be enough to notice, but if you do a large board, or many boards on the same piece of paper, you might notice that the further you get from the center of the holes become more out of alignment.  The solution to this is to change to a printer that doesn't have this (I didn't do that), or flip one of the pieces of paper (which you can't do with the toner transfer method). 
-Mike

John Lyons

Re: A question for those that etch thier own double sided boards...
« Reply #3 on: March 27, 2013, 10:40:26 AM »
I make a two sided pouch with photo paper and some tape.
I line up the images with a light table/window, then tape them.
Slide in the board and iron...
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