Assembly and Trouble Shooting of v0.2 Circuit.
The first issue that needed to be addressed on this board before soldering was the unfortunate placement of a trace on the OPA818 circuit that could be at risk for shorting to the thermal pad of the part: To prevent shorting, a thin strip of Kapton tape was used to mask this trace off. This trace should be addressed in the next board layout.
On to soldering... this was my first ever attempt using a stencil for solder paste. I should have photo-documented the process better, but here is a shot of the framed stencil with some paste spreading:
Next time I don't think I will go with the framing, since it was a little bulky and may have caused slight gaps due to warping; some of the pads seemed to have maybe a bit too much paste and some even bled together - as evidenced by the several bridges after reflow.
Here is a map of issues I had during soldering:
- 1 - solder bridges, cleaned up with wick
- 2 - extra paste around jumper footprints shorting gaurd to center trace, also cleaned up with wick (provide extra relief in future layouts)
- 3 & 4 - more bridging on these fine pitch parts
- 5 - too much paste after stencil, wiped off and reapplied by hand before reflow
- 6 - this 2220 PET cap is too fragile, tension from solder adhesion causes cracks, solution (next time around): design custom footprint too avoid tensions; XOR choose ceramic cap, probably not C0G tempco.