On Dec 9, 2008, at 7:18 PM, solarwind wrote:

> So I've done quite a bit of research on making your own PCBs. But I do
> have a few questions...
>
> The method is as follows: [description of "toner transfer" method]
> My questions:
>
> 1. What kind of paper works best for this? Glossy paper? What brand?
> Specially designed paper? What are your experiences?

It may depend on your printer.  Probably specially designed paper  
works best, but it's expensive and harder to get.  I've used glossy  
magazine paper (free!), which has worked ok for the NOT fine-pitch  
boards I've made using it.

> 2. What printer should be used? Laser or inkjet? What are your  
> experiences?

For this method, you MUST use a laser printer, because you're counting  
on the melting and adhesion properties of the laser toner.  The people  
talking about inkjets are using a different (photographic) process  
that is better for finer pitches, but more expensive and somewhat more  
complex (see below.)

> 3. When printing designs for fine pitch TQFP component ... where  
> does the
> problem lie - during the ink transfer stage or during the actual
> etching stage?
printing and ink transfer mostly, I think.

> How can this be done more reliably so that no traces
> are broken and everything works out well?

There are lots of theories...  Most people give up at some level of  
complexity, because it has become increasingly easy to get a PCB  
easily made.  (for instance, there are specialized heated lamination  
presses that replace the "clothes iron", and only cost, oh, 2x the  
cost of a single professionally made board...)


> 4. When making double sided PCBs, does the same technique apply

You add registration issues (making sure that the two sides line up  
exactly),
and the lack of plated-through holes for getting signals from one side  
to the other that I mentioned back in my first message.


> 5. Is there anything wrong/incomplete in my method above? Do you guys
> think it'll work? Does anyone have any advice?

I think the chances of someone without any experience being able to  
successfully create a toner transfer board with .4mm pitch packages  
(that's about .2mm lines and spaces, right?) the first time they try  
are almost zero.

> 6. Is it possible to make plated through-holes on your PCB  
> practically?

No.

> http://www.thinktink.com/stack/volumes/VOLVI/copplate.htm

Thinktink is "semi-pro", not amateur...

> http://www.diyaudio.com/forums/showthread/t-45235.html  <= This guy  
> got great results.

He didn't plate his holes, did he?  He made a double sided board where  
the top is mostly ground plane, and soldered some components on both  
sides.  You can make changes to a PCB design so that the only places  
that carry signals from one side to another happen on holes where you  
CAN solder on both sides (and this works BETTER when most of your  
components are SMT, so most of these connections are vias), but it's  
generally a real pain.

The photographic method for making PCBs is very similar to toner  
transfer, except that you start with a PCB blank treated with a  
photosensitive resist, which is then exposed to a light source  
(usually UV) and "developed", which removes part of the resist.  After  
that the board is etched and drilled as normal; since the resist is  
applied professionally and "intimately" to the copper, it is more  
reliable that trying to transfer a resist pattern to the copper via  
amateur techniques.

> I really don't want to waste $50 getting my PCB professionally [made]

You'll spend that much on materials to make your home-made PCB too,  
though you'll end up with more than you need for ONE pcb...   In the  
end, I suppose it depends on whether you want to make "PCB  
fabrication" part of your hobby or not...

BillW

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