How to advance and deal with the warping of the PCB board?

IPC-6012, SMB--SMT circuit board maximum warpage or distorted 0.75%, other board warpage is generally not more than 1.5%; electronic assembly plant allows the warping degree (double sided / multilayer) is usually 0.70---0.75%, (1.6mm thickness) actually many boards such as SMB, BGA board for warpage is less than 0.5%; part of the plant even less than 0.3%.

The calculation method of the warping degree = the height / length of the curved side

Prevention of warp of circuit board:

1 Engineering design:

The arrangement of the interlayer semi - curing sheets should correspond to the;

The same supplier products should be used in the multi layer plate core plate and semi - curing plate;

C/S surface area of the outer surface is as close as possible to the surface, can be used as an independent grid.

2 pre baking plate:

Generally 150 degrees 6--10 hours, excluding water vapor in the plate, further make the resin curing completely, eliminating the stress in the plate; opening the pre baked board, regardless of the inner layer or the need for both sides!

3 the direction of the warp and weft of the plate curing sheet should be paid attention to in the front of the multilayer board laminated sheet:

The warp and weft direction is not the same as the shrinkage, and the semi - curing sheet should pay attention to the direction of longitude and latitude; the core board should also pay attention to the direction of the warp and weft.

4 drill before baking plate: 150 degrees 4 hours.

5 laminated thick cold stress eliminating pressure plate, cutting edges.

6 sheet is best not to pass through the mechanical grinding brush, it is recommended to use chemical cleaning; electroplating, the use of special fixture to prevent the plate bending fold.

7 natural cooling to room temperature or air flotation after cooling in the flat marble or steel plate.

Warping board processing: 150 degrees or hot pressing 3--6 hours, using the smooth and smooth weight of the steel plate, 2-3 baking.


 

(Source: )

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