Umm you really should not to this!! unless you want to destroy it, 350 C is very very hot never mind 400C considering SnAgCu (lead free) has a melting temperature of 222☌, compared to the regular SnPb (tin Lead) sphere of 183☌ going above these temps by more than 5 deg does not make the solder stick better. If not, keep going up until you can lift the chip. If it lifts, that's the temperature you need to hit. Wait ten seconds, and try and lift the chip up with a flathead screwdriver. This is called a BGA lift, and just follow this profile up to 350C. Its very beneficial to get a test board and figure out just how hot you need to go on your machine before the solder melts. *Another Note* These machines are not exactly the same, my 381C may actually be outputting air at 360C, where yours may be doing 400C. You need to let it sit for at least 15 minutes without being disturbed. At this point, it is incredibly crucial to not touch or move the board. When it reaches 90C, I turn the unit and the griddle off. Hold for 60 seconds - Increase the temperature to 195C - Hold for 60 seconds - Increase the temperature to 291C - Hold for 40 seconds - Increase the temperature to 350C - Hold for 20 seconds - Increase the temperature to 381C - Hold for 20 seconds - Decrease the temperature to 291C -Hold for 10 seconds - Drop the temperature to 90C as fast as the unit will go. This is the heating profile that I follow (All temperature increases are in 3 deg/sec, which is one press of the up/down button on the unit a second): - Turn on the unit and wait for it to reach 90C. Note that the griddle is on at 400F for the whole time. You always wait for the unit to reach the temperature before you start timing. The lowest temperature the unit can go to is 90C, so after I turn it on I wait to time until the actual temperature (bottom number) reaches 90. Make sure that the air pressure is at 5 1/2 (thats the dial in the bottom right of the unit). So after ten minutes of pre-heating the board, I begin the hot air reflow.
the vicious cycle continues until you get micro fractures in the chips and your console is dead for good. which leads to more pressure, which leads to more broken joints. The issue with this is that more pressure inevitably leads to more broken joints. The idea is that you can over tighten the bolts causing the heatsinks to exert more pressure on the processors, pressing the broken solder joints down until they make connections. By removing the stock heatsink clamps, you can hold the CPU and GPU heatsinks on with machine screws. The "X-Clamp" Fix- This fix utilizes the same basic principle as the penny fix. Now this is all good and dandy save the fact that neither the solder balls nor the RAM were meant to take that kind of pressure, and this fix will only lead to more broken joints. The Penny Fix- By putting pennies underneath the GPU heatsink/on top of the RAM chips, the extreme pressure on the RAM BGAs will (in some cases) push the chip down enough that the bad joints make connections. I'm not even going to explain what's wrong with that picture. The Towel Fix- People think that by wrapping their 360 in a towel and running it for excessive periods of time, the internal components will reach the melting point of lead-free solder (217C), and the bad joints under the BGAs will reflow, fixing the problem. The problem behind the Red Rings (9 times out of 10) has to do with cracks, whiskers, and other issues with the solder balls under all of the BGA chips on the 360 MoBo caused by constant heating/cooling cycles.
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