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I bought a $50-$60 hot air rework station on ebay, im trying to learn micro soldering and when I try desoldering a random chip on a board, it wont come off, I seen youtube videos saying that when using 350 degrees temperature the chip should come off within 30sec, not working with me, not even after 2min. is the problem due to the cheap rework station? note: im also not using flux as atm don't have any.

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    \$\begingroup\$ Nothing aids learning like cheap tools. \$\endgroup\$ – Harper - Reinstate Monica Dec 14 '19 at 3:30
  • \$\begingroup\$ That's a completely ordinary price for something which would work just fine, so while an issue with it can't be ruled out it's probably ok. Try using a smaller nozzle and more airflow. Try removing something small like an SMD resistor, chips (especially QFN's) may have a thermal pad pulling a lot of heat into the interrior of the board. And be careful what the board is sitting on, it can get pretty hot. Try to practice on scrap or even a solderable proto board, rather than what you are tying to fix. \$\endgroup\$ – Chris Stratton Dec 14 '19 at 3:47
  • \$\begingroup\$ It also helps to pre-heat the whole board to 150 - 200 °C prior to hitting the chip with hot air. Especially if the chip has a large thermal pad underneath. \$\endgroup\$ – jms Dec 14 '19 at 4:57
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The time to remove a part depends on the thermal mass of the board it is connected to and the power (temperature and flow rate) of the hot air. If you have a chip connected to a big ground plane, it can take a long time to remove, especially at lower airflow. 2 minutes is not unreasonable, especially for a lower power hot air rework station, a big ground plane and lead free solder.

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