I’ve been working on a project recently which requires the use of Logic Level MOSFETs. Unfortunately, the kind of MOSFET I needed only comes in surface mount package which is not much good for breadboard prototyping on its own.
Enter the SparkFun SOT-23 to DIP Adapter Boards:- https://www.sparkfun.com/products/717
This simple modules allows you to “break out” the SOT-23 device to a set of pins allowing you to plug it into breadboards easily AND cheaply. These little boards can be had from SparkFun themselves for a mere $0.95!
Unfortunately, I live in Britain where you pay three times the price for the same thing.
My Solution? Mill My Own SparkFun SOT-23 to DIP Adapter Boards!
Because the guys over at SparkFun are such good dudes, they include the Schematic and Eagle Cad Files for you to download free of charge, so you can make your own – which is exactly what I did.
I took the Eagle Files kindly provided by SparkFun and generated a panel of six SOT-23 to DIP adapter boards.
It took me a couple of attempts to get the spacing right so that I could mill them out cleanly and these are the end results. I gave two of the boards to a friend who wanted to experiment with them which left me with the four boards as shown above.
To date, these are the smallest PCBs with the smallest traces and pads I’ve ever produced on my CNC Machine and I’m more than happy with the results. I don’t use any auto leveling or probing or anything like that. I set my machine up by eye and make adjustments on the fly.
Now I’ve just got to get to grips with soldering the parts on which should be fun!
I fear these boards are too small for my homemade re-flow oven so it’s hand soldering. I think the technique I’m going to go with is to use paste to mount the SOT-23 component and then heat the pads with the iron to get it to flow rather than dabbing at it with solder and soldering iron and making a pigs ear of it lol.
UPDATE #1 – 25th August 2016
I have successfully soldered my SOT-23 MOSFETs to one of my milled adapter boards but it wasn’t easy.
My hands were shaking quite badly so I spent a fair bit of time chasing the MOSFET around the bench when it would spring out of the tweezers. Eventually I got the part lined up on the board but unfortunately the tracks lifted as I attempted to heat up the solder paste.
The second attempt was a roaring success and despite my heavy handedness with the MOSFET to begin with, surprisingly it still worked lol.
Using the Blink Without Delay sketch from the Arduino IDE I was able to test the MOSFET circuit. I have included a schematic image below.