Prevention and treatment of warpage of PCB board proofing

PCB proofing warpage prevention and treatment methods. As a member of the Shenzhen PCB board production department, everyone will see or encounter the phenomenon of warpage of the circuit board. The warpage of the Shenzhen PCB board will cause inaccurate positioning of the components; when the board is bent at SMT, THT, the component pins are not It brings a lot of difficulties to assembly and installation work, so how to prevent the warpage of Shenzhen PCB board, the following gives you a detailed explanation:


IPC-6012, the maximum warpage or twist of SMB-SMT circuit board is 0.75%, the warpage of other boards generally does not exceed 1.5%; the warpage allowed by electronic assembly plants (double-sided/multi-layer) is usually 0.70 ---0.75%, (1.6mm board thickness) In fact, many boards such as SMB and BGA boards require warpage less than 0.5%; some factories even less than 0.3%;

PC-TM-650 2.4.22B

Warpage calculation method = warpage height/curved edge length

Prevention of Shenzhen PCB board warpage:

1. engineering design:

 

The arrangement of prepregs between layers should correspond; Shenzhen PCB multi-layer core board and prepregs should use the same supplier products; the outer C/S surface graphic area should be as close as possible, and an independent grid can be used;

2. Baking board before cutting

Generally, 6 to 10 hours at 150 degrees, to eliminate the moisture in the board, and to further cure the resin completely, and eliminate the stress in the board; before the material is baked, the board is required for both the inner layer and the double side!

3. Before laminating multilayer boards, pay attention to the latitude and longitude directions of the cured sheets:

The shrinkage ratio of warp and weft directions is different, pay attention to the warp and weft direction before cutting and stacking Shenzhen PCB board semi-cured sheets; pay attention to the warp and weft directions when cutting core boards; generally, the direction of the cured sheet roll is the warp direction; the long direction of the copper clad laminate is the warp direction;

4. Shenzhen PCB board proofing laminate thickness to eliminate stress Cold pressing after pressing the plate, trim the burrs;

5. Baking board before drilling: 150 degrees for 4 hours;

6. The thin plate is best not to be mechanically brushed, it is recommended to use chemical cleaning; use special fixtures during electroplating to prevent the plate from bending and folding

7. After tin-spraying, it is naturally cooled to room temperature on a flat marble or steel plate or cleaned after cooling by an air-floating bed; warping plate treatment: 150 degrees or hot pressing for 3-6 hours, using a smooth and smooth steel plate for heavy pressing, and baking 2-3 times grilled