Meter board, double-sided PCB etching

With the success of the SSOP breakout experiment, I was eager to try it on a larger scale.   If everything goes well, I may end up making all of the boards in-house!  This would be awesome, because I make a lot of mistakes and wasn't looking forward to the one-month turnaround times just to learn my board was crap.

The next most-simple board I have planned is the meter bridge.  It's a simple matrix of 77 LEDs, to be controlled by a TLC5940 PWM LED driver chip and a 74HC595 shift register.  In order to fit everything within the front panel of a 1U rack unit, I've opted to move the chips onto a daughter board that will backpack onto the front-facing meter board.  

The meter board is a simple affair, but absolutely requires a two-sided PCB due to the nature of a matrix.  Step one:  design the board.

Front and back of a board for 7 10-LED bargraphs and a single 5mm LED at the top of each column.

Some close-ish traces, but after doing the SSOP I felt confident.

Several people suggested printing both sides and aligning them  face-to-face, taping the paper together on one side, and ironing them both at once.  This sounded a lot better than the one-side-at-a-time technique I had imagined, and in practice it worked perfectly.

Hey, cool.

 I'll solder it up tomorrow night, but dang I am excited about this.   I chose the right drill size this time (1/32") and everything just came together.  Assuming everything is good, this is a major win for my productivity - all of those LEDs and their associated 150+ wires were a total mess on two breadboards.  Consolidating all of that down to just 18 pins is wonderful.  If the soldering goes well, I'll prototype my control chips and then make the daughter board for this, further reducing the pin count to 5.  Yes!