First, enhance the anti deformability of PCB
The circuit board (PCBA board) deformation is usually from high-temperature reflow (Reflow) caused by rapid heating and rapid cooling (thermal expansion), coupled with the uneven distribution of the parts and the copper foil on the circuit board, more deterioration of the deformation of the circuit board.
There are some methods to increase the resistance to deformation of pcb:
1. increase the thickness of PCB circuit board. It is recommended to use more than 1.6mm of the thickness of the circuit board. If you still have to use 0.8mm, 1.0mm, 1.2mm thickness of the board, it is recommended to use the furnace fixture to support and strengthen the deformation of the board when passing through the furnace. Although you can try to reduce.
2. use high Tg PCB material. High Tg means high rigidity, but the price will rise as well.
3. Epoxy glue (potted) was injected on the circuit board. The ability to resist stress in the vicinity of BGA or on the back of its corresponding circuit board can also be considered.
4. add reinforcement around the BGA. If there is space, can be considered as in building a house in BGA, surrounded by the supporting force on the frame to strengthen its ability to resist stress.
Two, reduce the amount of deformation of PCB
Generally when the circuit board (PCB) is incorporated into the protective casing should by the shell, but because the product is getting thinner, especially the handheld device, often force bending or circuit board produced by falling impact deformation.
In order to reduce the deformation caused by external force to the circuit board, there are the following methods:
1. to strengthen the shell strength to prevent its deformation affect the internal circuit board.
2. add screws or positioning fixing mechanism around the BGA in the printed circuit board. If our purpose is only to protect BGA, then we can force the fixed BGA near the mechanism, so that BGA is not easy to deformation nearby.
3. increase the buffer design of the mechanism to the circuit board. For example, the design of some buffer material, even if the shell deformation, the internal circuit board can still maintain the external stress. But the life and ability of buffer must be taken into consideration.
Three, enhance the reliability of BGA
1. at the bottom of BGA (underfill).
2. use SMD (Solder Mask Designed) layout. Cover the pad with green paint.
3. increase soldering capacity. But it must be controlled in case of short circuit.
4. increase the size of the BGA pad on the circuit board. This will make the wiring of the circuit board difficult, because the gap between the ball and the line can be smaller.
5. using Vias-in-pad (VIP) design. But the pad on the hole (via) must be via filling plating, otherwise the reflow soldering will be bubbles, but easy to cause the ball from the middle fracture. This is similar to the house playing pile is the same reason.