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Having nothing to do in my workshop, I decided to practise my skills a bit. I digged up a scrapped graphics card from the junk box and decided to try to desolder the RAM-chips (BGA) after seeing how "easy" it looks when Louis Rossman does it.

I applied flux around, launched the hot air station, and started to heat. Realizing after a few minutes that nothing at all had happened, I tried a combo of 1) other nozzles, 2) higher temperature and 3) more airflow.

At the last point I had 400 degrees celsius and 90% airflow. Zero reaction. Even heated on the back side, no reaction.

Finally I gave up and simply pried off the chip to see how the solder balls were laid out, so I could use that info for the next chip (which went just as badly).

Then I tried the 400C / 90% setting straight upon the solder balls of the pried off chip, but the solder did not even melt. My next approach was to use the soldering iron at 350C straight on the balls, with and without a wick, but not even that melted the solder.

What I had to do was to apply a large blob of fresh solder to the iron tip, drown the solder balls in it, and then - finally - I was able to remove some of the balls with the wick. Note: some of the balls, not all of them because they did not melt.

What the hell is this BGA-ball kind of solder anyway, that does not melt?

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    \$\begingroup\$ Having nothing to do in my workshop? Do you mean you should have been tidying it up and found some intersting scrap? Or is that just me. \$\endgroup\$
    – Chris H
    Apr 11, 2017 at 13:06
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    \$\begingroup\$ @ChrisH Occupational hazard! :-) \$\endgroup\$
    – winny
    Apr 11, 2017 at 13:34
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    \$\begingroup\$ Is there any chance your temperatures were in Fahrenheit and displayed as centigrade? \$\endgroup\$
    – KalleMP
    Apr 11, 2017 at 13:53
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    \$\begingroup\$ @laptop2d *crappy RoHS lead-free solder \$\endgroup\$
    – winny
    Apr 11, 2017 at 19:07
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    \$\begingroup\$ @winny RoHS lead free solder is terrible stuff \$\endgroup\$
    – Voltage Spike ♦
    Apr 11, 2017 at 19:36

4 Answers 4

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Thermal inertia is playing against you. Also take into account that lead-free solder needs temperatures in excess of 220°C to melt down (compared to 180°C for tin-lead solder), so the thermal gradient will be quite high to begin with.

Because of this, I would recommend preheating the board to 120°C by using one of the following methods:

  • A preheating plate, or
  • An oven

Then apply hot air to desolder the BGA chip.

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    \$\begingroup\$ What’s wrong with your ° sign? \$\endgroup\$
    – Michael
    Apr 11, 2017 at 18:50
  • \$\begingroup\$ Nothing that I'm able to see myself... But thank you for raising the flag, i'll look into it. \$\endgroup\$
    – Enric Blanco
    Apr 11, 2017 at 18:54
  • \$\begingroup\$ Better now after editing? \$\endgroup\$
    – Enric Blanco
    Apr 11, 2017 at 18:56
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    \$\begingroup\$ I think you used Ordinal indicator instead of degree sign at first. \$\endgroup\$
    – Mołot
    Apr 12, 2017 at 8:14
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BGA have a very good thermal contact with PCB- total cross section of all balls is a quite large figure. So before solder type, all PCB is sinking the heat from your BGA. So you have to preheat all of it to 150C, then power flow will become much lower (delta T is lower) and then you will not need more than 300-350C.

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I think you should measure the temperature of your rework station nozzle and soldering iron with a pyrometer. You think your nozzle was at 400°C and your iron at 350°C, but I'm willing to bet they really weren't that hot. Any reasonable solder will melt above 300°C.

On a practical note, if you want to salvage BGA components and don't mind to destroy the PCB in the process, a small gas torch heating the backside of the PCB works wonders: larger chips just fall off by themselves, and a gentle shaking of the PCB removes the smaller SMD components as well. Don't try this inside though (or while wearing nice clothes), as it takes some practice to avoid overheating the PCB. Fumes from burning PCB are toxic and the smell is very long lasting.

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    \$\begingroup\$ With my hot air station at verified 400C i am also not able to remove contemporary bga chips from often 8 layer boards, so i am willing to bet that his station reaches far more than 300C. Regarding your gas torch advice, i would rather recommend an industrial style hot air gun. Enough energy output and somewhat regulated temperature. Useful for preheating too \$\endgroup\$
    – PlasmaHH
    Apr 11, 2017 at 19:28
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I think it is standard lead-free solder.

Your problem with desoldering could be related to many factors.

  • mass of copper in PCB layers
  • quality of soldering station
  • quality of hot-air station
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