So, I finally got around to trying to build a FOB.
I figured I’d try dispensing the solder (Chip-Quik) without a stencil first.
No way can I dispense solder on the Attiny25 or the Nordic pads. I have a yellow “needle” on the syringe. Maybe I’d do better with something smaller, but as I recall when I tried smaller needles I couldn’t dispense paste. But maybe I tried too small.
Anyone have experience with a tiny tip using Chip-Quick?
I figured I’d try dispensing the solder anyway, and reflow even though the solder bridged the chip pads.
I didn’t have an problems getting the solder on the 0402 pads.
During reflow, on 0402 tombstombed–I was able to push it pack down while still on the hotplate. All the passives turned out great–none of those skewed parts I’ve seen on just about every FOB I bought from SparkFun.
The chips were a different story. Not surprisingly, there were solder bridges. I didn’t think I could “solder wick fix” the bridges on these parts, since a lot of the pads go under the chip. But, using wick on the edges that didn’t have adjacent passives that blocked the soldering iron, I was able to clean things up.
I tried removing parts so I could get wick into to fix the bridges on the Nordic pads. Finally, I removed the Nordic and used the wick to clean up the pads. I wasn’t careful enough a couple of the pads had very little land area and came off the board when I just cleaning them up to try again.
I’m going to try again, but this time I think I’ll do two reflow passes. First time, just the chips, then clean up wick. Then add the passives.
If that doesn’t work, I’ll try a finer needle to dispense the solder on the pads with no bridges.
Next, I’ll order up a stencil.
So, you’re a better man than me!