Sunday, 3 May 2015

Testing Chinese press-n-peel alternative (again)

With all these guitar pedals we've been making (as well as the PCB fails, wrongly-mirrored SMT designs and just outright failures) in recent weeks, our stock of press-n-peel blue paper has been hit severely.

The last lot we bought online was about £15 for five sheets - nearly three quid a sheet! Today, the cheapest we could find it on eBay was £21 + p&p. That's quite pricey.

Now we've tried alternatives to press-n-peel in the past, and found the old blue paper to give the best results. At least, it did when we used our big £2k-worth of Xerox printer. But that big old beast has gone to BuildBrighton, and the little desktop laser printer we have here at Nerd Towers is a hopeless Brother something-or-other.

Even on blue press-n-peel, the image is flaky, often there are broken traces and touching up with a Sharpie is now a common job. So we thought we'd give some of this cheaper transfer paper a try. The Xerox was great with press-n-peel, and so-so with cheaper, starch-based transfer papers.

But our Brother printer doesn't get the same crisp, sharp lines on blue paper - so perhaps it might actually work better with a different transfer paper? There was only one way to find out...

A quick click around on eBay and five days later, we had an impressive 100 sheets of transfer paper delivered for less than a tenner. That's less than 10p a sheet, compared to over £4 for press-n-peel blue. While that does sound cheap, it could still end up being quite pricey, if it doesn't work!

So what do the results look like?

Here's a "control". We're using the same method for creating these two boards, preparing the copper the same way we usually do, for both transfers, so that the only thing different should be the transfer paper. First up, our regular press-n-peel blue paper:

Straight out of the printer, the image is sharp and clear. Well defined tracks look like we should get a good image. But if you shine the paper towards the light, you can see that the toner has not been laid down as a continuous line of "ink" but appears to be "scaly" and looks like it could get put down in "layers" on the copper board.

The transfer has gone on ok. There are a couple of spots of black toner still left behind on the transfer paper, but most of the mottling is happening on the ground planes, and larger areas where it has been filled in. There are a couple of traces that were cracked, and a few with noticeable gaps in them that need touching up with a Sharpie.

Here's the etched board. Despite the slight raggedy edges where we've had to touch a few traces up with a Sharpie pen, it's not bad at all. There are a few marks in the larger planes, but the 0.3mm traces have all turned out quite well and the overall look of the board is one where the masked copper has remained pretty much intact.

Now with the cheap chinese alternative:

Out of the printer, the image already shows areas that could be affected by pitting - there are gaps in the larger areas and a few traces are already broken.

Compared to the press-n-peel image, there's none of the "scaly-ness" of the blue image - but you can already see that the quality of the yellow printing image isn't as good as the press-n-peel version.

The transfer process was very impressive. A few passes through the laminator, then about a minute in a cold water bath (just as we've been doing with blue press-n-peel for a while) and the entire image is transferred with no trouble at all. Not a grain of toner is left behind on the backing paper. The actual image transfer is far better than press-n-peel - it's just a shame that the printed image isn't as good to begin with!

After etching, the copper board does look a bit of a mess. You can see that the tracks are not particularly well-defined, but they are useable. Large planes appear "pitted" where the toner didn't transfer as a single solid block of colour, and appeared to have large "pin-holes" in the final layer.

After running a multi-meter/continuity test on all the tracks, they appear to at least work. But the overall finish of the board is a much poorer quality than the press-n-peel board.

So there you have it.
Cheap chinese toner transfer paper isn't as good as press-n-peel (at least, not using our scabby not-very-good-for-toner-transfer-Brother-laser-printer). It all goes to back up Steve's insistence that "you get what you pay for".

But at 10p a sheet compared to over £4 a sheet, and both give functional, working results, it's hard not to ignore the price difference. If only we could find a laser printer that would give a decent printed image on the yellow transfer paper, and things might be different!