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Aligning artwork

2005-11-18 by Mike Young

This evening, I got both board edge lines on the silkscreen transfer to 
completely overlay their corresponding 1.6 mil "traces" in the copper for 
its full length of 2.6". These are 1 pixel wide lines, printed at 600 dpi on 
a laserjet. To be clear, this is toner transfer, using Pulsar paper. While I 
don't expect this to be typical or even repeatable, very good alignment is 
easily possible without great effort.

I use common pins in the board corners to align the double sided artwork to 
the board, and later the silkscreen. The pins are a very close slip fit, 
almost an interference fit, in 24 mil holes. That makes them about AWG 22 
ga. In Eagle, I put a via with a 24 mil hole in three of the corners, and 
add a wire circle at the centers on the dimension layer so they print on the 
silkscreen also. This only works if you drill before etching.

Wear cotton gloves when handling the artwork to minimize skin oil transfer. 
To make up the sandwich, pre-pierce the holes in the artwork. Place one side 
on the pins facing in, push the board on, and follow on with the other 
side's artwork. Tape them in place before removing the pins; low tack 
masking tape works best for me. Laminate and process as usual.

That's all. Easy alignment with no eyestrain or jangled nerves.

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