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How to prevent plate bending problem during PCBA processing

Views:17     Author:Site Editor     Publish Time: 2019-05-22      Origin:Site Inquire

When PCBA is processed into a reflow oven, plate bending and plate warping are prone to occur. How to prevent the board from going through the reflow oven and causing plate bending and plate warping. Next, we will introduce the relevant countermeasures:


1.Reduce the impact of temperature on the board stress

Since "temperature" is the main source of stress on the board, as long as the temperature of the reflow oven is lowered or the speed of heating and cooling of the board production in the reflow furnace is slowed down, the bending and warping of the board can be greatly reduced. occur. However, there may be other side effects, such as solder short circuit.

 

2.PCB uses high Tg plate

Tg is the glass transition temperature, that is, the temperature at which the material changes from a glass state to a rubber state. The lower the Tg value, the faster the board starts to soften after entering the reflow oven, and becomes soft rubbery. The time will also be longer, and the amount of deformation of the board will of course be more serious. The use of higher Tg sheets increases their ability to withstand stress deformation, but the price of high Tg PCB sheets is higher.

 

3.Increase the thickness of the board

In order to achieve a lighter and thinner purpose, many electronic products have a thickness of 1.0mm, 0.8mm, or even a thickness of 0.6mm. This thickness is required to keep the circuit board from being deformed after passing through the reflow oven. It is difficult for strong people. It is recommended that if there is no thin and light requirement, the board can preferably use a thickness of 1.6mm, which can greatly reduce the risk of bending and deformation of the board.

 

4.Reduce the size of the board and reduce the number of panels

Since most of the reflow ovens use chains to drive the board forward, the board with the larger PCB design size will be deformed in the reflow oven due to its own weight, so try to use the long side of the board as a board edge. Putting it on the chain of the reflow oven can reduce the deformation of the sag caused by the weight of the circuit board itself. It is also based on this reason to reduce the number of slabs. That is to say, when the furnace is over, try to use the narrow side perpendicular to the furnace direction. The lowest amount of dent deformation is achieved.

 

5.Using the oven tray fixture

If the above methods are difficult to achieve, the last step is to use the oven tray to reduce the amount of deformation. The reason why the tray can reduce the bending of the plate is because the tray can hold the 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 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 problem of deformation of the circuit board over the reflow furnace can be greatly reduced. However, this oven tray is quite expensive, and it has to be manually placed to place and recycle the tray.

 

6.Use the Router instead of V-Cut

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

 

The above is about how to prevent the problem of plate bending in the PCBA processing process. If you have a circuit board product that needs proofing and batch PCBA OEM, please contact Shenzhen Viasion Electronics!


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