When most people think of PC boards, they think of ones that have all sorts of parts soldered to them.  Even though no one was working at my office this week, the landlords did a wonderful job moving the snow out of the way and in to a couple of huge 10-foot piles. Using a stereo microscope, a special small-part soldering iron (Weller Microtouch MT1500), and lots of patience, I soldered all the parts on.

 

I am especially proud of the two small resistors shown below.  The soldering job isn’t the greatest, but considering that these are some of the smallest discrete parts you’ll ever encounter, this will work. These resistors are size “0201”, and named that because they are 0.02” by 0.01” (0.06 x 0.03 mm).  For reference, the pencil tip shown is 0.5 mm in diameter.  These small sizes are difficult to manipulate by hand; I used some super-fine tweezers and a sharp exact-o knife. Once you get the parts in the correct place, the surface tension of the solder makes them want to stick to the iron. Once this happens, the parts quickly overheat and can be damaged in seconds.

 

 

The whole board looks like this:

 

I managed to keep all the power supply components on the left 1/3rd of the board. There is plenty of room remaining for the processor and even my name. The board has one wire jumper, seen just behind the white OLED connector.

 

The component marked “363” is a resistor, just like the other two from the first picture except much bigger. I chose the “1206” size instead of “0201” size so that I could jump over the vertically-running trace.

 

 

I used the same jumping trick with the inductor, although it’s already as small as it can get. This is a technique used a lot in older PC Board designs, but is becoming a lost art as components become smaller and smaller.

 

 

 

So, how does it look in the case? There is still plenty of room left!

 

 

The board was not sanded down to the smallest dimensions possible. It’s also thicker than it needs to be (it’s the standard 0.063”, but there is no reason it couldn’t be thinner). The battery shown above is actually designed to fit a little lower in the case -- I didn’t force it because I didn’t want to accidently damage its terminals.

 

We’re in the home stretch!  Next up - finishing the software, wiring the battery in permanently, and finishing the case. Then, on to the second version.