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1. Enhance PCB's anti-deformation ability
The deformation of the circuit board (PCBA board) usually comes from the rapid heating and rapid cooling (thermal expansion and contraction) caused by high temperature reflow (Reflow), and the uneven distribution of parts and copper foil on the circuit board worsens the circuit board. The amount of deformation.
Prevent BGA from falling off
The methods to increase the resistance of the circuit board to deformation are:
1. Increase the thickness of the PCB. If you can, it is recommended to use a circuit board with a thickness of 1.6mm or more. If you still have to use 0.8mm, 1.0mm, 1.2mm thickness boards, it is recommended to use furnace fixtures to support and strengthen the deformation of the board when passing the furnace. Although you can try to reduce it.
2. Use high Tg PCB material. High Tg means high rigidity, but the price will increase accordingly. This must be a trade-off.
3. Add steel bars around the BGA. If there is space, consider building a house with a supporting iron frame around the BGA to strengthen its ability to resist stress.
4. Pouring Epoxy glue (potted) on the circuit board. You can also consider pouring glue around the BGA or on the back of the corresponding circuit board to strengthen its stress resistance.
Second, reduce the deformation of the PCB
Generally speaking, when the circuit board (PCB) is assembled into the case, it should be protected by the case, but because today’s products are getting thinner and thinner, especially hand-held devices, they often suffer from external force bending or falling impact. The resulting circuit board is deformed.
To reduce the deformation of the circuit board caused by external forces, there are the following methods:
1. Increase the buffer design of the mechanism to the circuit board. For example, designing some cushioning materials, even if the case is deformed, the internal circuit board can still remain unaffected by external stress. But the life and capacity of the buffer must be considered.
2. Add screws or positioning and fixing mechanisms around the BGA. If our purpose is only to protect the BGA, we can force the organization near the BGA to be fixed so that the vicinity of the BGA is not easily deformed.
3. Strengthen the shell to prevent its deformation from affecting the internal circuit board.
3. Enhance the reliability of BGA
1. Fill the bottom of the BGA with glue (underfill).
2. Increase the size of the BGA solder pads on the circuit board. This will make the wiring of the circuit board difficult, because the gap between the ball and the ball that can be routed becomes smaller.
3. Use SMD (Solder Mask Designed) layout. Cover the solder pads with green paint.
4. Use Vias-in-pad (VIP) design. However, the vias on the solder pads must be filled with electroplating, otherwise there will be bubbles generated during reflow, which will easily cause the solder balls to break from the middle. This is similar to building a house and piling the ground.
5. Increase the amount of solder. But it must be controlled under the condition that no short circuit is allowed.
6. I strongly suggest that if it is a finished product, it is best to use [Stress Gauge] to find the stress concentration point of the circuit board. If you have difficulty, you can also consider using a computer emulator to find out where the possible stress will be concentrated.
