Q-bus I/O project

I would recommend against that. Not unless you are trying to create a commercial product where you *must* be RoHS to conform to the requirements of the bureaucrats. Use real solder -- the job will be much easier and the result more reliable. Real solder is still available, including solder paste. I asked one of the technicians at work about this stuff a while ago -- they know all about this question since they have to use RoHS when doing rework on modern designs. And what I just said is what they told me (i.e., don't, unless you are forced to). They also told me that real solder works just fine on lead-free parts. I tried that and can confirm this is correct. I would think a pick & place robot would be a fairly straightforward derivative of a 3d printer. But is that really needed? Placing the parts isn't all that terrible. The trouble is the soldering. I have read (and posted here in the past) a nice article (in German) on the use of a toaster oven with some clever temperature control as an IR reflow soldering machine. I haven't tried this yet, but it sounds like a good scheme, and would allow the use of BGA parts at least in moderate sizes. At least one of the moderate cost small volume PCB fab shops will deliver solder paste screens along with the finished boards if you ask for it. paul