There has been no update on this project log for quite some time, but quite a few things have happened in the meantime:
After fixing the issues found in my prototypes of the Bus Logic Board (BLB) (HA-B06), the input and output modules (HA-B08 and HA-B07, respectively), I have ordered a first production run ten of each. Because different solder mask colors were offered for the same price, the boards are now kind of color-coded: The BLB is green, the output module red, the input module blue - which looks very nice. I will add photos to this entry once I get to taking them.
Two BLBs have been populated using traditional soldering so far.
I have started to populate an output controller module this evening, using solder paste and a hot-air station for the SMD parts. This has worked very well, is much quicker than individual hand-soldering under the microscope, and the first test measurements indicated that there are indeed solder joints where they should be, and no undesired bridging.
I dispense the paste using a syringe with a 0.8x20mm blunt needle, and have yet to find out if this is reusable after leaving it alone over night, and continuing to work on it the next evening. The first few drops of paste that came out of the fresh packaging seemed a bit dried, so perhaps this will happen to the remains in that needle as well, in which case I should get some more of those for one-time use.