I didn't realize this thread had kept going... I just wanted to give an update: my heat gun + "bend the springs" fix is still going strong. Been watching Youtube vids like a boss, and no sign of trouble. The days of dealing with a failing nVidia GPU are but a distant memory. Its been 3.5 years now; I think we can officially call that a "permanent" fix.
I'm too lazy to re-read this thread (plus I don't feel like arguing anymore), so I'll just add a few things. First - many of you are conflating heat-gun temperatures with reflow oven temperatures. My best advice would be to NOT fixate on the absolute numbers, and instead approach the issue from a heat-transfer perspective. Also - I now use this heat gun/ringstand setup to manufacture and sell my own electronics. Here is my method (which I have written down on an index card and taped to the wall):
1. Put a Hershey's Kiss shaped dab of MG Chemicals 4860P solder paste in the dead center of every pad.
2. Turn on the heat gun at 800*f to pre-soak the base plates. Turn the gun off when the base plate temp reading is 160*C.
3. Wait until the baseplate cools to 60*C, then add the PCB and let it soak.
4. Turn on the heat gun at 800*F and heat for 1 min 10 sec. The solder will just begin to flow at this point.
5. Increase the temp to 820*F and heat for another 15 sec.
6. Turn the heat gun off and very quickly move the PCB from the hot aluminum plate to the ringstand's cast iron plate for cool down
I have a 3" spreader nozzle on the Steinel, and I use a spacer tool to make sure the end of the nozzle is exactly 22.3mm from the surface of the aluminum base plate (which is sitting on the cast iron ringstand base). If I move the nozzle any closer, it will blow away the 0603 caps. This setup is what I use to reflow a double-side board that is 51mm long and 8.5mm wide (approx. the size of your pinky finger). The most thermally massive component on the board is probably a SOT-223. This is what I do for a living now; I'm not making this stuff up to trick some random strangers on an internet forum.
If what you say is true that you need to set your H.G. to 450 deg C., then basically this means I can try "reflowing" at low (350 deg) until I am blue in the face
My best overall advice is to not focus on the absolute numbers. The temperature setting, airspeed, nozzle type, nozzle distance, heat profile, etc. will have to be determined empirically. The process I've just outlined for making my own products will obviously not reflow a BGA. I know all the future lurkers are desperate for some exact, enumerated instructions for reflowing a BGA, but the truth is that you'll just have to experiment. I guess the good news about the BGAs is that it's so thermally massive that it's almost impossible to overcook them in situ. I remember once when I had the Harbor Freight gun maxed, at point blank, and I nuked the GPU until I heard something pop. You know, that unmistakable sound when an electrolytic or other small passive suddenly explodes. Luckily, it had no perceivable negative effects.
The ultimate takeaway from this thread should be the knowledge that you CAN solder with a heat gun, and you CAN use it to fix a faulty GPU. The temperature you set the gun to is borderline irrelevant; what matters is getting the heat energy into the solder. And don't forget to preheat. Preheating is critical. I use an old toaster-oven for preheating in many soldering/brazing/welding operations. Large pieces of thermally massive cast iron can also be used for this purpose. In other words, heat a chunk of cast iron (like a 45lb barbell plate) in your kitchen oven, then remove it, carry it to your garage, place it on an insulated surface, and put your laptop on top so it can soak.
Home
Help
Search
Login
Register
