To what state should I warm? Here, again, there are indirect signs on which we can navigate. The whole procedure takes about 5-8 minutes. The spread of time is due to the factors listed above. Also depends on the quality of the flux used, the type of solder from which the BGA array on the substrate (lead or lead-free) is made. In the process of strong heating, the flux should decay sufficiently (smoke).
Also an important marker is the visual detection of the melting of solder on the elements located on the chip around the crystal (usually a row of small SMD capacitors). When the solder on them «shimmers» — a sure sign that the balls of the substrate have reached the temperature of their melting, and this is exactly what we need! For more confidence, you can take a tweezer in your free hand and try to slightly move the chip itself: gently push it (literally by a millimeter) to the side and see how it «swings» and due to the forces of surface tension of the molten balls from below, it will get in place. After that, heating can be safely stopped!
Note: some craftsmen use the usual building hair dryer instead of the station or repair the video card with their own hands, «baking» it in a home oven, after wrapping it in foil! Frankly, I’m not a fan of such radical methods of «repair», although (if the guys do it all), then why not? 🙂
During the heating procedure, you can monitor the surface temperature with a thermocouple or pyrometer (infrared thermometer). This will help in the future to better navigate the selection of the right thermoprofile.
P.S. There is service center, where we provide computer repair in Cincinnati.