Daily Archive for May 14th, 2012

ubbcom: Etching Really Small Things

It’s almost time for me to graduate, so I decided to take a little time this weekend to do something other than freak out about making sure I have everything taken care of.

I was staring at a breadboard on my desk and it occurred to me that I’m always ripping up my MAX232 chip and associated components to save space for one project while putting it back so that I can use serial communication for the next project. So, I thought, why not make a decent breakout board that uses one of the FT232RL USB Serial drivers that I have lying around?

The design is very simple; it’s basically the same schematic as Sparkfun’s FT232RL breakout board. However, unlike that board, it’s designed so that it sits in the middle of the breadboard, using only 2 rows (and 4 pins). It also allwos one to use USB to power the breadboard.

First, I wanted to test to see if I could actually etch an SSOP28. They have an extremely fine pitch, so I knew it would be quite difficult to etch them. Using MITERS’s lamination method, I tried it out and had some decent success. I only have a picture of the final etch, but I’m convinced that with a little refinement (not to mention fixing the blatant bugs in the design), this design is totally etchable with minimal manual intervention. I had to clean up a few toner-transferred traces with a knife, but overall, the transfer process went well; the laminator applies a perfect, even amount of heat to the board and toner as it passes through and only takes a few seconds. For a design with such a small pitch, one of the issues is that the toner smooshed and covered a slightly larger area than it should have.

After I cleaned up the traces, I etched the board with very good results. It took a while (probably 15 minutes) to clear out the tiny little spaces between the SSOP traces, but it definitely worked in the end.

I’m going to re-route the board and etch a prototype that should theoretically work, hopefully, maybe, if the stars are aligned.

ubbcom’s github repo is here.