Lesson learned - I physical damaged the Teensy 3.1 MINI54 chip

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Ewing

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Hello all,

As the title states, I physically damaged my Teensy 3.1 while trying to remove solder paste . . . with the end of a paper clip . . .

While I am an engineer (chemical and biological systems) and a fairly skilled programmer, I am still learning about proper procedure and best practices with electronics.

In case others reach this post:
  • I successfully soldered the Teensy 3.1 to the OctoWS2811 Adaptor and got the BasicTest_UserMod sketch running with an Adafruit NeoPixel 8X8.
  • I then started worrying about the long term effect of all the excess solder paste, so I used a chem-wipe to try and remove the residue.
  • When the chem-wipe failed, I switched to a brown paper towel wrapped around a small slotted screw driver--to this point the assembly continued to work and I was able to test several other sketches . . .
  • But then I went the extra distance and started really removing solder paste with the end of a paper clip . . .

I started to troubleshoot the failure to upload a sketch:
  • I checked that the board was getting the correct voltage
  • I checked that the program pin was being pulled to 0V when the button was pressed
  • I searched high and low for any article or posting that referenced the issue
  • I tried both Mac and Windows machines
  • Then I decided to actually look at the board . . .

Teensy31_Damage.jpg

My scratching did remove solder paste, but it also damaged at least a few of the 8 pins on that side of the chip.

I now have a soft brush and some rubbing alcohol to try with the next board.

Hope this helps someone in the future (as an object lesson of what not to do), and if anyone has any suggestions or other comments then I would be happy to read your replies. Thanks
 
use 90% (or better, I use 92%) isopropyl alcohol next time. Just sit the device in a bath of it over night in a sealed container, and take it out in the morning. In a couple hours it should be clean and ready to go.
 
Thanks defragster,

I put it under the scope and didn't see any obvious bridges or other debris, but I gave it a shot with solder wick anyway (on both the microcontroller and the MINI54). Unfortunately, I still cannot upload sketches. Under the scope it looks like I bent, deformed and shorted the pins on the MINI54, so . . . I decided to try using the edge of a scalpel to "ease" the pins apart--it didn't work. (I thought to use the conductivity setting on my multimeter to check if the pins really were shorted, but the probes do not have fine enough tips to target those individual pins).

I'll try again with my second board tonight and then follow xxxajk's advice and let it soak in isopropyl alcohol. Thanks again
 
I do that all the time putting on QFN parts. After using the heat gun to melt the solder paste, I'll flood the pins with sticky flux and run a very fine tipped soldering iron along the pins and the solder cleans up perfectly. I use Amtech SynTECH solder paste, it's supposed to have a shelf life of 6 months with no refrigeration, but my current tube expired in 5/31/2010 but still works fine and I don't bother to keep it in the fridge the last few years. For flux I use MG Chemicals No Clean Paste flux I get at Frys for about $10/syringe. If you're going to do much work with QFNs, a hot air pencil and some solder paste will be the best investment you can make. I use a really cheap coffee cup warmer for a pre-heater and that made soldering them even easier.

Or maybe that's not a QFN, but the flod with flux really does help to with solder bridges. If it's got leads, cover the pads with sticky flux and then place the part in the flux so it doesn't move much and get one corner pin soldered. Usa a magnifying glass to make sure it's in the right place and the do an opposite corner. After that, the flux tends to make it easier. As does skinny solder, I have some .010 diameter solder I got surplus once and it really makes a difference for tiny stuff like that.

Ira
 
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