Re: Si5351A blown (IC1) QCX transceiver.


Gwen Patton
 

I splurged and got myself a hot air station. They aren't tremendously expensive. I think I paid about $65 for mine.

When doing SMT work, I have either an iExtruder solder paste dispenser or a tiny manual dispenser I got from Tindie. Then I use syringe-able solder paste and apply to the pads, carefully put the chip onto the pads with a pair of tweezers (I use a lighted magnifier or a LCD microscope), and heat it with the hot air station. When the solder melts, surface tension will practically SUCK the chip into alignment. Let cool, then clean off the flux that was in the solder paste with isopropyl and a swab. I use disposable foam swabs for electronics work, as they don't leave little wisps of cotton fiber everywhere. They get torn up on the board, but don't leave bits for the most part.

If you get a hot air station, removing a chip is easy. Apply some flux (I use Amtech NC-559-V2-TF Tacky Flux in a syringe), then heat the part while holding it with tweezers. When the solder melts, lift the chip off. Then clean up the pads with solder wick and your iron, and clean the board. Then you can apply fresh solder paste to the pads, and hot air solder the new chip in place.

I get the tacky flux from Rossmann Group in New York, a certified Amtech dealer. It's really good flux. I mostly use that for soldering iron work. https://store.rossmanngroup.com/amtech-nc-559-v2-30-cc-16160.html
I get either MG Chemicals T3 solder paste for larger pads, or Chip Quik T5 solder paste for really tiny pads. The really small syringe applicator I have is for the T5. When working with paste, that number matters. The smaller the number, the larger a syringe needle you need for it to flow properly.

https://www.i-extruder.com/en/
https://www.tindie.com/products/avandalen/disper-micro-dot-solder-paste-syringe-dispenser/
Chip Quik T5: https://www.amazon.com/gp/product/B00D2I88PG/
MG T3: https://www.amazon.com/gp/product/B00M1RC0YY

I have 3 soldering irons. A TS-100 with an ILS tip  for fine work, a cheap but temp controlled mains iron from Banggood for connectors, PCB enclosures, and large heat sinks, and a Dremel Versa-Tip butane iron for outdoor work.

TS100: https://www.amazon.com/gp/product/B06XBFTKMY
ILS Tip: https://www.amazon.com/gp/product/B072J75BRT/
https://www.banggood.com/MUSTOOL-MT883-80W-Electric-Solder-Iron-Station-Adjustable-Temperature-180-480-or-392-896-Auto-Sleeping-110V-or-220V-EU-or-US-or-UK-Plug-Option-p-1553736.html
WEP/Kohree Hot Air Station: https://www.amazon.com/Kohree-Rework-Station-Solder-Digital/dp/B00JVM3WBC  (There's a bunch of these under different names. The one I bought is no longer on the site.)

I also have a ReFlowR programmable soldering hotplate that I've never actually used. Maybe someday I'll find an actual need for the thing. Not worth posting a link, it's no longer being made.

73,
Gwen, NG3P

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