Step 6: Reflowing
After reading a few articles on the reflow ovens used in industry, I realized that the method I was using was clunky and far from ideal.
In a perfect situation, a reflow should minimize time spent above the solder melting point, while still reaching a temperature somewhat above this melting point. The shorter the time, the less brittle the solder. Reaching the correct temperature ensures the solder "sticks" correctly. Also, the board must be the same temperature across its area so it does not warp.
When you plot these criteria against time, you get what's called a reflow profile. I have created one for the average home oven, which I've uploaded. Please ignore the "Soak" step - it is unnecessary due to the slowness of the oven.
So here's a quick run through of the profile: the board goes in the oven cold, and is kept in while the oven approaches the reflow temperature. This ensures the board is the same temperature everywhere (because the oven heats up slowly, giving the heat enough time to penetrate and soak all areas). As the reflow temperature is reached and surpassed, the solder melts. Once the correct temperature above the solder melting point is reached, the door is opened and a fan is used to gently draw hot air away from the face of the oven, which shortens the time the solder is liquid by speeding its cool-down.
An oven thermometer is used to 1) ensure accurate temperature readings, allowing for shorter times spent with the solder liquid, and most importantly 2) to make sure the oven does not reach a temperature that is much hotter than what it reports (some can go over by 20F or more).
THE ACTUAL STEPS:
Well, the time has finally come. Place the PS3 board on a counter top like you did when you prepped it for the low temp bake and check to make sure it is level. Then, put it on a pizza tray.
Put the motherboard in on the middle rack, towards the front of your oven. Place the thermometer you hopefully purchased in the oven, where you can see it through the door. Turn the temperature up to 500 degrees Fahrenheit. Relax. The oven will not reach this temperature. Take a seat on the floor and watch the thermometer. Once the needle rolls to approximately 460F, turn off the oven an throw open the door. The thermometer will rise a few degrees before it falls. Do not panic.
Take a box fan, osculating fan (set to not osculate), or similar, put it on its lowest setting, and place it OUTSIDE THE EDGE OF THE OVEN DOOR TO THE LEFT OR RIGHT, NOT DIRECTLY IN FRONT, WITH THE FAN BLOWING AIR AWAY FROM, I REPEAT, AWAY FROM THE OVEN, AND NOT NOT NOT INTO IT. The idea here is the pull hot air from the face of the oven, without creating any significant disturbance to the motherboard within. This will speed up the cool down, as explained in the theory. Once the board is close to room temp, feel free to remove it.
Congratulations! You've re-flowed your PS3.