Prevention and treatment of warpage of PCB proofing
As a professional PCB board production staff, everyone will see or encounter the phenomenon of circuit board warping, Shenzhen PCB board warping will cause component positioning is not accurate; plate bending in SMT, THT, component pins are not complete, It will bring a lot of difficulties to the assembly and installation work, then how to prevent the warpage of the PCB board in Shenzhen? Let me give you a detailed explanation:
IPC-6012, SMB--SMT circuit board maximum warp or distortion of 0.75%, other board warp generally does not exceed 1.5%; electronic assembly plant allowed warp (double / multi-layer) is usually 0.70 ---0.75%, (1.6mm plate thickness) In fact, many boards such as SMB, BGA board requires warp less than 0.5%; some factories even less than 0.3%;
Warpage calculation method = warp height / curved length
PCB board warpage prevention:
1. engineering design:
The inter-layer prepreg arrangement should correspond; Shenzhen PCB board multi-layer core board and prepreg should use the same supplier product; the outer C/S surface area should be as close as possible, and a separate grid can be used;
2. Pre-feeding baking sheet
Generally 150 degrees 6-10 hours, the water vapor in the board is eliminated, the resin is completely cured, and the stress in the board is eliminated; the baking sheet before opening, whether it is inside or both sides is needed!
3. Pay attention to the warp and weft direction of the cured sheet of the laminate before laminating the laminate:
The ratio of warp and weft shrinkage is not the same. Before the lamination of Shenzhen PCB board prepreg, pay attention to the warp and weft direction; when the core board is blanked, pay attention to the warp and weft direction; the direction of the solid sheet is the warp direction; the long direction of the copper clad is the warp direction;
4. Shenzhen PCB board proofing laminate thick to eliminate stress After the pressure plate is cold pressed, trimming the raw edges;
5. Boiler before drilling: 150 degrees 4 hours;
6. The thin plate is preferably not mechanically brushed, it is recommended to use chemical cleaning; special fixture is used for plating to prevent the board from bending and folding.
7. After spraying the tin, it is naturally cooled to room temperature on the flat marble or steel plate or the air floating bed is cooled and cleaned; the warping plate treatment: 150 degrees or hot pressing for 3-6 hours, using a smooth and smooth steel plate, 2-3 times baking grilled