The soldering process went on mostly well, no tombstones, no misplaced components and no excesive solder...however, some bugs were found and caused me a couple of hours of annoyance:
- 3V6 and 5V voltages missing. For some reasong the switching power supply L7980 didn't deliver the said voltage. After some time of examination, I found the root cause, and it couldn't have been more stupid than it was - feedback resistors R60/R61 and R62/R63 were converesely set. So, instead of 5 or 3V6 volts at the output, the voltage divider was set to 0.75V. The reason of this folly is that in my Assembly Drawing the resistor designators were misplaced. Replacing the said resistors solved the problem.
- Short circuit at 3V3 RF. After I got SMPS to work, I noticed increased heating of the chips. Soon, I realize that 3V3 at the PLL of MAX2871 is shorted. To find out the location of the short, I lifted the U8 chip (LP5907) and broke it by accident. But at least, I've found the cause of short circuit. Under the MAX2871 chip there is a ground pad and 3V3 trace very close to it. For some reason, solder mask doesn't cover it completely. So, during the soldering, some paste went over it and made a short. Reworking the MAX2871 solved the problem. However, I've lost LDO chip and have to replace it now.
- 6-ball BGA didn't solder. This one was really anoying. The small RF logarithmic detectors LMH2110 didn't solder to their place, so I needed to do it manually. First, they are increadibly small (IC size smaller than 0603) and it was Sisyphus work to put them on their place. I managed to loose two of them just by clasping them a bit too hard with my tweezers. Second, I couldn't solder them easily because, I assume, the solder balls are lead-free. I wasn't able to heat them up with my hot air gun (nor reflow oven) because the air flow was set too low because any higher air flow would blow them away :/. I plan to use hot plate next time when I solder them, that is, when the new batch arrives because I lost all those that I had :(
- Filter lost. Simple as that, I lost the filter LP0603A1880ANTR.
These are all bugs I found so far. I examined the board and believe that it main parts should work properly. I could test out the VCO, attenuator and switches, but I cant solder the Teensy on board before all my reworking is done. So, when new detectors arrive, I'll give it a test try.