So the reflow test went better than I’d hoped, the stencils were a bit hard to use since they’re unframed but the biggest issues was the roughness of the edges and using a hard edge to scrape the paste.
I did one board with the stencil, and the rest i did by hand with a syringe.
The hotplate QK680
Already to go!
all pasted and components laid out (prototype in the background)
I hand soldered the CPU on one of the boards a few days ago, then pasted the rest
Enough junk ?
Ready to burn up, this is what you do when you’re learning the solder profile, you make three of them with chips that are very hard to source…
Used 120C warm up for 0 seconds, then 185C-190C for the melt, with a short hop to 200C for about 20 seconds. I reckon 190-195C indicated is where its melting.
Clck for bigger image, paste by hand . If only my eyes had zoom mode, eh krytie ? it looked a lot tighter when i was placing them !
Things will straighten out by themselves later, maybe.
Starting to melt
little uneven here, but once it’d finished flowing it was all good, i touched up the chip with an iron later.
moved it too soon
you can see bits of the paste left behind, this was much much worse with the lead free paste, it ended up with 100’s of solder balls unmelted underneath the components that caused shorts, this just cleaned away.
couple of bridges, too much paste, and uneven dispersal, easy to remove with some copper wire.
prototype board, i forgot to do a via under the chip, hence the wire. this one i hand soldered… cut it a bit deep too.
proto and first run,and it worked! its a double sided board, but given its just a couple of components i’ll hand solder those. i wish i’d populated that tiny 3v<>5v level convertor on the other two boards. I just really didn’t believe it’d actually reflow and it did.
some of the boards i cut, and test layouts, its a lot harder to solder with a cnc’d board and no solder mask with a tight polygon pour, so i removed a lot of it.
it was much easier reflowing than hand soldering, and i knocked out the three prototypes much quicker than i had the hand soldered ones. I reckon i could have done all 16 and only taken another 30 minutes of placing.