My Advanced Realistic Humanoid Robots Project

I soldered on 30ga wrapping wire for testing the PCB. The 3 on the front are 5v+ from microcontroller that tells this IC to be in "on" mode, ground from microcontroller, and PWM from microcontroller. The 2 on the back side are +8v and 0v/gnd from the batteries. This was shockingly quite hard to attach these. It's all so dang tiny. Every time I soldered on 8v+, the 0v would fall off because the rear pads of the chip both get hot together. Ended up having to use uv cure solder mask to tack...

I was informed that even unused pins on the chip should have copper landing pads to solder to which will even out the forces when the whole pcb goes molten and chip is trying to auto center! It makes sense! So I added those.

On the big output landing pad on the left, I separated the attachments to each individual pin for the chip's motor output phase rather than have the landing pad be one big blob. This encourages auto centering. Something I had not considered before until someone pointed it out. Such a simple change but so obvious now that I had it pointed out to me!

Here is a revision to my schematics where I run the trace that I had been running under the IC chip instead going around everything to avoid going under the IC chip and the problems that creates. This creative rerouting of that trace also meant I had to get clever with my other traces to compensate and so I had to have one trace jump over another trace at one point and to do this I used a 0 ohm resistor as a jumper bridge to cross over with. In addition to these changes, I also moved the...

So the corner of the PCB that peeled back from the chip was a problem I decided not to tackle with a heat gun. I just don't feel too comfortable using a heat gun at this stage. Instead, I decided to remove the capacitor in the way and just hand solder the chip back on. That went smoothly. Problem solved. That said, to remove the capacitor I envisioned using hot tweezers to grab both sides and lift it off. I did a search online to see if such a device exists and sure enough it does so I...

I soldered on the rest of the SMD components. I noticed the PCB peeled back off the chip in one corner though so I plan to use kapton tape to tape off everything but that corner, use a couple alligator clips to pinch the PCB onto the chip tightly so it can't move, and then use hot air from a heat gun to reflow that corner so it reattaches to the PCB. Once that is done, I will attach jumper leads to the 6 inputs/outputs so I can run a full proper test of the whole circuit using a lab power...

I wanted to be able to get in there and test this board for shorts and check all traces for continuity with my multimeter but felt its leads were too big for this tiny of a board setup. So I came up with this idea to use alligator jumper cables to attach sewing needles to the multimeter probes thereby making the sewing needles the new probes. This way I could get into the tiniest areas and run the tests I wanted. It worked pretty well! I have now tested everywhere quite thoroughly and...

Ok so I had multiple failed attempts to solder the chip on. Despite pretinning the PCB, on both attempts when the solder went molten the chip did not center itself and lock into place as would be expected but instead slid out of position significantly both attempts. After the first attempt I assumed it was the outlet bus/landing pad on the left side of the board that was to blame - it being a larger solder mass than the other solder masses on the other edges of the board - causing the chip...

Ok I managed to apply the UV solder mask today and it seems like it worked quite smoothly. I used the tip of a small sewing needle to spread it over the trace and then held the UV light on it for 10 seconds to play it safe. I used transparent UV solder mask so you can still see the trace but its a bit more murky/cloudy when you see it. I used the tip of an exacto knife to put little scratches on the UV solder mask to test its thickness by feel and test its durability a bit to scratching. And...

Ok so the Relife RL-UVH902 UV fast cure solder mask order has arrived and so has my order for a Relife UV curing light to cure the solder mask quickly and effectively. So now I just need to solder mask off that little trace that goes under the half bridge IC chip.