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How to prevent circuit board bending and warping

92 Published by FASTPCBA 7月 24,2019

How to prevent circuit board bending and warping

 1, Lowing temperatureeffects on circuit board stress

Since temperature is the main source of circuit board stress, so simply lowering the temperature of the reflow oven or slowing the temperature rise and cooling of the board production in the reflow oven can greatly reduce the occurrence of circuit board bending and warping. However, there may be other side effects, such as solder short circuit.

2, Circuit board uses high Tg substrate material

Tg is the glass transition temperature, that is, the temperature from glass state material to rubber state one. The lower Tg value material, the faster the board starts to soften after entering the reflow oven, and the time to be soft rubbery state will also be longer, and the deformation degree of the circuit board will absolutely more serious.Using higher Tg ratio substrate material can increase their ability to withstand stress deformation, but the price increases at the same time.

circuit board

PCBA

3, Increasing circuit board thickness

In order to achieve lighter and thinner purpose, many electronic products have thickness of 1.0mm, 0.8mm, or even 0.6mm.Which is much hard to keep the circuit board from not being deformed after through the reflow oven. It’s recommended the board can preferably use thickness of 1.6mm if there is no requirement of light and thin, which can greatly reduce the risk of bending and deformation of the circuit board.

4, Reduce the size of the circuit board and the number of panels

Since most of the reflow ovens use chains to drive the circuit board forward, the board with the larger circuit board design size will be depressed deformed in the reflow oven due to its own weight, so try to use the long side of the board as a board edge and put it on the chain of the reflow oven can reduce this problem. It is also based on this reason to reduce the number of panel. That is to say, trying to use the narrow side perpendicular to the furnace direction during wave soldering thereby lowest degree of depressed deformation is achieved.

flexible PCB

flexible PCB

5, Using the oven tray fixture

If the above methods are difficult to use, the last method is to use the oven tray to reduce the deformation degree. The reason why the tray can reduce the bending of the board is because the tray can hold the circuit board regardless of thermal expansion or contraction. After the temperature of the board is lower than the Tg value and then hardened again, the original size can be maintained.

If the single-layer tray can not reduce the deformation degree of the circuit board, it is necessary to add a layer of cover to clamp the circuit board with the upper and lower two-layer trays, so that the deformation problem decrease of the circuit board over the reflow furnace. However, this oven tray is quite expensive, and it has to be manually placed and recycle the tray.

6, Using the Router instead of V-Cut

Since V-Cut will destroy the structural strength of the panel between circuit boards, try not to use the V-Cut board or reduce the depth of the V-Cut.

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