You will find it soldered onto the board using multiple connections, which sit in between the APU integrated circuit and the board. These connections are made out of solder and serve two purposes: provides physical mounting to the component as well as electrical connectivity to the board. BGA is a type of SMT mounting; it stands for Ball Grid Array. This ball grid array consists completely out of hundreds of tiny solder alloy connections which tend to fail from time to time. Specifically, due to such a high population of them and due heat cycles, your PS4 is exposed to during gaming.
This APU is extremely powerful, and we all know powerful components on circuit boards do tend to run quite hot. APU is cooled down by a heatsink and fan; however, within itself, it still operates at temperatures up to 90C. The problem lies when the substrate temperature raises and the material expands. However, when a console powers down the heat reduces and all the components retract back to their original positions. Of course, we are talking micro levels here, and you won’t see this actual expansion happening. This expansion and retraction aren’t healthy for solder joints. Coupled with factors, such as moisture accumulation in the air and dust contamination, these little solder spheres tend to fail by developing microcracks within the ball grid array.
Even if any one of these connections fail, and there are hundreds of them, APU loses its connectivity with the circuit board. Consequently, your PS4 usually does not turn on at all or malfunctions. Moreover, this can cause artefacts on the screen or video freezing during the gaming session. This is where PS4 reballing procedure comes in.