Desoldering Tip When Nothing is Working For You

RE: Desoldering Tip When Nothing is Working For You

koudelad — Tue, 23 Jul 2019 06:05:21 GMT

I used a hobby hot air gun to remove a rotated 48-pin TQFP in my IR thermometer build and it went OK (the chip still works after this rework). Temperature regulation is sometimes useless, if the device has no feedback regulation. I had no idea about the target temperature, but you can see the start of melting the alloy. The only way was to approach to the chip slowly and regulate the target spot temperature by the distance to target.

RE: Desoldering Tip When Nothing is Working For You

jw0752 — Tue, 23 Jul 2019 04:08:42 GMT

Hi Sean,

I use a 260 watt Weller gun for these situations. I allow the tip to get quite hot and then I hit the point I want to desolder. The very hot tip melts the solder before the copper ground plane can conduct the heat away. With my luck using a very hot blower I would damage the circuit board itself. Thanks for sharing your technique.

John

RE: Desoldering Tip When Nothing is Working For You

dougw — Mon, 22 Jul 2019 21:52:42 GMT

I'm surprised your hot air doesn't go higher.

I think my Aoyue goes to 900 degrees, especially when the air flow rate is reduced, although I don't ever run that high as it can damage the PCB at that temperature.

Even though I can get the temperature over a wide area, I still use a small nozzle and cut the pins like you did, so I can minimize the potential collateral damage. (unless I need to save the component for re-use)

RE: Desoldering Tip When Nothing is Working For You

Jan Cumps — Mon, 22 Jul 2019 21:07:43 GMT

Most likely the pins were soldered to the big ground plane.

500°F (260° C) is on the low side for unleaded solder. And the pencil may not have had the capacity to keep the heat with that ground plane involved?