Homebrew PCBs

I made prints on 76µ (3mil) polyester drawing paper, I bought them 20 years ago to make PCB, using a pen plotter and UV exposure. This paper is very stable with temperature and moist.

Placing one sheet on top of the other (not face to face)give a perfect alignment.
It is not possible to get a good alignment when putting sheet face to face ..
Some via are misaligned by up to 30 mil.
There is only one explanation, the optic inside the printer is not perfect.

Has anyone of you already faced this problem ?



      

[Non-text portions of this message have been removed]

Try printing a grid, for example 10 x 10mm, across the page and measure it
to see what is actually happening.  If there is a linear error in one
direction you can sometimes compensate for it in software depending on the
software used.

Is the error symmetric? If the artwork is run in the center of the printer
will it be acceptable?

If you are using a laser printer, I would put some marks on the film before
printing and check their dimensions afterwards.  The heat of the fuser can
really put a lot of stress on the media.
Bertho
==========================================

From: Michel Baguet    Sent: Saturday, July 05, 2008 02:15

I made prints on 76� (3mil) polyester drawing paper, I bought them 20 years
ago to make PCB, using a pen plotter and UV exposure. This paper is very
stable with temperature and moist.

Placing one sheet on top of the other (not face to face) give a perfect
alignment.
It is not possible to get a good alignment when putting sheet face to face
..
Some via are misaligned by up to 30 mil.
There is only one explanation, the optic inside the printer is not perfect.

Has anyone of you already faced this problem?