A quick guide to GPU VRAM swaps for beginners

I did two mods on dead 3090s last winter and the preheat advice is spot on. I tried my first one with just a hot air station and a cheap silicone mat and the whole board flexed when the chip came loose. Second board I preheated properly from underneath and the difference was night and day. The memory chips basicly floated off once everythign was soaked through.

The pad cleanup got me too. I thought I'd done a decent job with braid untill I checked with a loupe and found a couple pads with solder bunched up at one edge. Replaced the paste, reseated the chip, no boot. Took it apart again, flattened everything properly, and it posted first try.

One thing I'll add is that GDDR6X reflows way faster than the paste on my station suggested. I scorched the mask around one chip because I was hanging around waiting for something to happen that had allready happened. Now I probe the corner with tweezers constantly and the second I feel any give I stop adding heat. Also agree on practicing on junk boards first. I wrecked a couple of dead motherboards before touching anything I actually cared about and that saved me a lot of grief. My reballing still looks rough compared to factory but it works.

I'd push back on the constant tweezers probing bit. On my second card I did that and ended up nudging the chip sideways before the joints under the middle had let go, which put a small scratch across the mask and two slightly bent pads. Since then I just watch the solder at the edges, when it goes dull and wet looking and the chip visibly settles, it's ready. No touching needed. The probing gives you a false sense of control when the real answer is patience with the temp.

The thing that actually saved my first board was a cheap k-type thermocouple taped under the memory area. I was guessing at preheat temps by feel before that and kept either cooking the mask or giving up too early. Once I could see the underside number climbing I knew when to stop waiting and start working, and the chips came off way cleaner. Also learned the hard way to reflow the new chip with the stencil already taped down, not after. Trying to align it while the paste is live is a mistake you only make once.

One thing about reballing that took me way too long to accept is that the alignment doesn't have to be perfect when you place the chip. My first attempt I spent ten minutes nudging it into position with tweezers, and the moment the solder went liquid the whole thing pulled itself square anyway from the surface tension. Now I just get it roughly centered, let the paste do the work, and check the edges after it cools. The one exception is that a warped board will fight you on this, so check that the card sits flat on the bench before you even start.