Puma board for FreeEMS

[nitrousnrg]

I overlooked PCBNEW BOM, becaue it can't be as customized as the schematic BOM tool.

I think I didn't mention it, but the chinese guys asked for a drill file, which can be generated in File->Fabricaton outputs

About the pcb, I put it in the (stock, standard, not modified) oven, reflows perfect, but I've put too much solder paste to the mcu. Many, many pins are bridged, I'll tell the story later in some place

[jharvey]

Cash Olsen sells Kester 236 in a hypodermic needle that seems to work well for putting on enough, but not to much. Here's his page.

http://kd5ssj.com/

I forget the needle size, it's quite small. I usually clean the needle ID with a single strand of stranded telephone wire. So it's probably under 22ga.

[EssEss]

most places include a solder stencil for free (or free if you ask for it - some places do not advertise this fact) .. just do that next time. piece of cake.

[jharvey]

Hmmm, if we can do SLA, why don't we see similar tech for solder past? Wouldn't that be great if you could simply buy an ink cartridge for you bubble jet printer and you've got your solder mask... Anyone know if such a thing exists?

[EssEss]

not to hijack further, but I doubt it. it's not fast enough.
if you've ever seen a high volume assembly line, there are usually multiple pick-n-place machines per paste machine and the paste machine is throttled down .

I could only imagine that a 'paste squirter' machine would move equally slow since you're constrained to the movement of material. I also imagine it's highly wasteful since metering would not be very exact. afaik sla is completely different process anyways - which can be much faster since you're steering a beam vs. moving an extruder head (not sure what technology that it)

[jharvey]

I know one fellow with eyes that are less than par. He doesn't fret the bridging, he just puts some solder wick on it after he finds a bridge. The big thing is to do a continuity check to find bridges. The wick picks up the excess, while the solder in-between the pad and lead will stay. Perhaps you can do the same.

[Fred]

I know one fellow with eyes that are less than par. He doesn't fret the bridging, he just puts some solder wick on it after he finds a bridge. The big thing is to do a continuity check to find bridges. The wick picks up the excess, while the solder in-between the pad and lead will stay. Perhaps you can do the same.

Be careful doing continuity checks, a multimeter can easily kill a sensitive IC like this. Visual inspection and being careful in the first place is FTW.

Fred.

[nitrousnrg]

1. I agree with essess, stencils should be enough, afaik.
2. Visually the MCU looks good, crystal too, but I tested them anyway, at least on critical pins.
3. As it turns out, I need a better soldering iron. Also, I learnt that VDD1 and VDD2 are internally connected.

I could test the SM loading tonight if I've had the capacitors of the PLL and crystal circuits. They weren't listed in my original BOM, so I'm putting through hole capacitors, 2 for the crystal, 2 for the PLL. That will happen tomorrow, I don't even have those values in a TH version..

Also, a friend should have showed up here with his camera... I'm kinda worried about him.

[jharvey]

Just in-case you haven't see the plastic stencils, this company makes them.

http://www.pololu.com/catalog/product/446

I've used them, and on low qty / low cost, they do OK. I see many advantages of steel stencils. These do OK for hobby and hand populated proto's.

[nitrousnrg]

PUMA BOARD ACTUALLY WORKS!!!

After soldering the FT232 and the second regulator, the firmware was loaded pretty nicely, no warnings, nothing wrong :-)

Now its time to keep soldering and start testing the rest of the circuits!!!