A couple of days ago we discussed some cute little PIC 12F chips. As promised, here is a post about hand-soldering one.
Tools we used:
- Soldering-iron and hot-air rework station.
- Curved tweezers.
- Scalpel or hobby knife.
- Kapton tape
- Fine solder (0.5mm thick with rosin core).
- Coffee or strong drink
How-to continues below.
When we added the DFN package to our library, we forgot to remove the soldermask under the middle pad. This pad isn’t connected and has no electrical function. We suspect it cools the chip down and helps position the chip during the reflow soldering to snap the package into place.
We used the scalpel to remove the silkscreen.
We tinned the paths both on the PCB and the package. Be sure to use flux as this will improve the flow of the solder. Don’t use an excessive amount of solder, just wet the pads. After tinning apply extra flux. We used kapton tape to protect the PCB and a trace we accidentally scraped.
We used the hot-air tool to melt the solder on the pads, then carefully put the package in the right spot.
When the airspeed is set high (it always is too high with light objects!!) the chances are the little chip will fly away. We had the best luck with dropping the chip and removing the hot air, wait till the solder has cooled down, and use the hot-air tool again to flow the solder underneath it (aim the nozzle straight on the package to avoid it from flying away).
After using the hot air, use flux to wet the sides of the chip and slide with the soldering iron along the sides.
After soldering the DFN, the remaining parts are easy. We can’t say the satisfaction is as great as your first blinking LEDs project, but it came very close! Ow, just a note: check the DFN before soldering the remaining components to the board, this will save lots of time! ;)
The result is on the top of this post. If someone has a good use for these little PICs leave a comment