May 30, 2013
Freescale makes some nifty accelerometer chips, like the popular MMA8452, for which Sparkfun, USA sells a breakout board. But unfortunately (for hobbyists) they all come in hard-to-solder tiny little packages, like the 16 pin QFN which is just 3 mm x 3mm across.
After a few unsuccessful attempts to solder the MMA8452 chip at home, I found a better candidate - the MMA7660 which has a DFN-10 package. As you can see from the schematic below, the latter has only 10 pins, and the pins extend to the sides, which makes it easier to solder.
[From Freescale MMA8452/MMA7660 datasheets, for illustrative purpose.]
I was able to successfully solder the MMA7660 on to DFN-10 prototype board using a hot air rework station.
I basically followed the technique shown in the video below:
- Apply flux and tin the pads.
- Place chip on tinned pads - align correctly, apply flux.
- Heat the chip with the hot air gun.
- Solder exposed pins on the sides.
- Reheat the chip with hot air gun to reflow the solder.
- At each stage, inspect pads with magnifier for shorts, and use flux generously.
Sjaak solders a QFN chip, attempts a BGA chip:
A couple of photos of the chip after soldering:
So why torture yourself soldering these microscopic chips when you can buy breakout boards?
A few reasons to consider, especially if you are trying to make a product that you might sell:
- Cost: The breakout board is usually 4-5 times more expensive than buying the chip.
- Size: If you are designing a PCB yourself, it's going to be much more compact if you just use the chip and not the whole breakout board.
- Bragging Rights: When you walk into a bar and announce that you hand soldered a DFN-10 chip, that will surely make you popular. Right? Right? ;-)