PCB proofing warpage prevention and treatment methods. As the personnel of Shenzhen PCB production department, we will see or encounter the phenomenon of PCB warpage. Shenzhen PCB warpage will cause inaccurate positioning of components. When the board is bent in SMT and tht, the component pins are not neat, which will bring many difficulties to the assembly and installation. So how to prevent Shenzhen PCB warpage? Here is a detailed description:

For ipc-6012, SMB -- SMT, the maximum warpage or twist is 0.75%, other boards are generally not more than 1.5%; the allowable warpage (double-sided / multi-layer) in electronic assembly plants is usually 0.70-0.75% (1.6mm thick). In fact, many boards, such as SMB and BGA, require the warpage to be less than 0.5%; some factories even require less than 0.3%;

PC-TM-650 2.4.22B

Warpage calculation method = warpage height / edge length

Prevention of PCB warpage in Shenzhen

1. Engineering design:

The results show that the arrangement of interlayer prepreg should correspond to each other; Shenzhen PCB multilayer core board and prepreg should use the same supplier's products; the outer C / s surface graphic area should be as close as possible, and independent grid can be used;

2. Baking plate before blanking

In general, 150 ℃ for 6-10 hours to remove water vapor in the board, further solidify the resin completely and eliminate the stress in the board; before opening the material, the drying board is required for both the inner layer and both sides!

3. Pay attention to the warp and weft direction of the cured sheet before laminating the laminate

Due to the different shrinkage ratio of longitude and weft, attention should be paid to distinguish the warp and weft direction before lamination of Shenzhen PCB semi curing chip; the warp and weft direction should also be paid to the core board blanking; generally, the roll direction of the cured chip is the warp direction; the long direction of the copper clad laminate is the meridional direction;

4. Shenzhen PCB board proofing lamination, stress relief, cold pressing after pressing plate, trimming burr;

5. Drying plate before drilling: 150 ℃ for 4 hours;

6. It is better to use chemical cleaning instead of mechanical grinding and brushing; special fixture should be used to prevent bending and folding of plate

7. After spraying tin, cool the flat marble or steel plate naturally to room temperature or air floating bed for cooling and then clean; warping plate treatment: 150 ℃ or hot pressing for 3-6 hours, using smooth and smooth steel plate for heavy pressing and baking for 2-3 times