Building SMD-DIP adaptors from scratch

You know that crap office joke about "You don't have to mad to work here, but it helps!"? - well, you could paraphrase it about building and soldering with surface-mount chips, and you wouldn't be far wrong. However, don't let anyone tell you it can't be done. It can.

One way to make life easier is to build up a few SMD-DIP adaptor boards. I decided to try and make some adaptor boards like this so that I could play with some SMD-only components on my breadboard. Specifically, I had a Cirrus CS4344 192KHz 24-bit Stereo DAC and a THAT2162 Dual Blackmer VCA which I'd like to have in an easier to use form. The Cirrus DAC is a TSSOP10 package which is pretty small even for a surface mount. The VCA isn't so bad.

I use toner transfer paper ("Press-n-Peel") paper for making PCBs. If you use boards with fairly lightweight copper you can make very fine traces. I've done 25mil (25/1000ths of an inch) without too much bother. The traces on the boards below are this width.

Designing the adaptors and transferring the design to the PCB wasn't too hard. Note that I rearranged the pinout on the larger VCA layouts to make life easier when doing the PCB design. This let me get the QSOP16 package between the legs of a standard 16 pin DIP. I wasn't sure how well this would work, so I did an alternative layout with a 0.6inch DIP too, and did multiple copies so that if one didn't etch correctly, I'd still have a usable one.

Once I'd done that, I used the sponge technique to etch the board.

After that, I just had to check them and solder them up. I left etch resist on the parts of the board that I didn't want to solder to act as a soldermask. The worst part is the initial tacking of the corners of a surface mount device, since as soon as you poke it with a soldering iron it slides off somewhere else and you have to reposition it and start again. Some people glue their SMDs down first before soldering to avoid this, and I'm starting to see why. Anyway, once you've done the corners, you just lie the solder along each row of pins and slide the soldering iron along it. Afterwards, clean up up any bridges with solder wick. Finally, test the board for shorts again.

There, told you it was possible!

Links

Pulsar - have all sorts of useful information about toner transfer PCB production on their site. Dead handy.

BD micro - Useful surface mount soldering tutorial, with video.

Seb Francis - has a page about surface mount soldering too. Good list of the tools you'll need.