"A K" wrote:
> It's great that this should come up now, as tonight I completed a
> successful toner transfer etch (and subsequent reflow) of 6 boards each
> containing a 4x5 pad BGA with 0.4mm pitch.  Some of the traces were 6
> mil and the yield was 100%.  Toner transfer is definitely doable for
> prototype work and there's nothing like same-day design turnaround.  In
> the past I have used toner transfer to complete double sided 12x12 inch
> boards that would have been rather costly to have made due to the
> dimensions.  So it's doable and once you get the hang of it, a little
> fun.  Don't waste your time with dissolving paper transfer, use the
> slick backing of mailing labels and scuff/rub the waxy surface with a
> paper towel so the toner sticks.  This peels right off instantly after
> you've pressd it to the board and you're ready to etch.  I use one of
> the ubiquitous HP LaserJet 4M Plus printers with EconoMode and RET off.
>  Can't get more basic/inexpensive than that!

Andrew, if you don't mind I'd like to clarify a few things because this is 
something I can definitely make use of (the instant gratification aspect is 
very appealing).

- Which mailing labels are you talking about? Avery, FedEx?
- I'm assuming you're printing on the side that the paper used to be on, 
after you peel the paper off?
- How much do you have to rub the waxy surface in order for the toner to 
stick?
- Do you have a favorite source of copper clad boards?
- For double sided boards, how do you ensure the two sides line up?
- Are there any tricks for the ironing part?

Do you tin your boards after etching?

In the past, I have used the photo method (2001), the plotter method 
(2002-2003, actually made hundreds of boards using this one), and relatively 
recently (2006) the direct toner transfer method. I wasn't very happy with 
the last one, as the toner would often rub off with the paper (plus it took 
a long time).

By the way, what's considered the proper way to dispose of used etchant?

Best regards,

Vitaliy 

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