So this was attempt to at making a double sided PCB, this time I had thought about it much more carefully and come up with this jig to ensure the acetates were correctly lined up on every side.  I secured one with selotape to one of the plates below.  Then I lined up the vias on the second acetate, added some double sided tape and pressed the other board firmly down on top of it.  By making sure the two board right angles were lined up I was able to reproduce the alignment every time I put the two pieces of acrylic together.  I tested the theory a few times and then proceeded to insert the board.  I taped down one edge so that it wouldn't move around and then taped my jig together.  After exposing in my UV exposure box I developed, etched, cleaned and drilled.  The result was VERY good.  Other than a few shorts because of my routing of wires to close the board was perfect.  The only problem I did find was when it came to removing the tape from the jig.  I think the UV light caused it to break down, leaving lots of sticky residue.  This isn't great as it effects the transparency of the jig.  I think I will have to make a new one and then use a different method of securing.

 Here is the finished board.  Next step was to make the vias from one side of the board to the other.  For this I got a piece of wire and painstakingly soldered and then cut each one.  This took about half an hour to do 100 vias.  I think I will definitely investigate through hole plating at home!

After this I started to populate the board.  First in was the headers which I had to solder from the wrong side.  This was very stressful as I knew one wrong move and I would make a tiny short circuit which would be very difficult to fix.  I managed to get through without making any obvious mistakes so I moved on to installing the matrixes.  I started by testing them all on a breadboard that I set up.  The one by one I added them on to the board and tested as I went along.  I was expecting huge problems with this part of the build however I only had one; a broken track I assume on the covered part of the board. This was easily fixed by a small jumper wire and then I continued with the rest of the displays.

 After my first successful board I started the second, also a double sided board this one was slightly larger and has SMD chips on it.  This obviously required greater accuracy so I took a lot of care when aligning my acetates.   My care paid off as the board came out perfectly!  I have yet to solder in any components but bellow is a little picture of what the finished product should look like.  The next challenge is soldering those SMD chips.

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