I also had the same problem while trying to unsolder the HDMI re timer chip using my rework station that has a hot air gun. What I ended up doing was using my Dremel tool with a small grinding stone and removing the top of the chip until I could see the metal substrate that's inside the chip and then I was able to use my t12 soldering iron to remove it since the heat was finally able to get to the solder in the center of the chip. I hope this helps because I had tried everything else until I thought of doing this.