How to avoid the occurrence of rocker or plate bend in the reflow oven during the production of the pcb board

2019-09-28 18:35:59 460

1: The effect of lowering temperature on the stress of PCB circuit board

        Since temperature is the primary source of plate stress, the board factory can greatly reduce plate bending and plate warpage by reducing the temperature of the reflow oven or increasing and cooling the plate during reflow. furnace. However, there may be other side effects such as solder shorts.

2: Use high Tg material PCB circuit board

       Tg is the glass transition temperature, which is the temperature at which the material changes from a glassy state to a rubbery state. The lower the Tg value, the faster the sheet begins to soften after entering the reflow oven, and the shorter the time to become a soft rubber state. It will also get longer and the deformation of the board factory board will of course become more serious. The use of higher Tg plates increases their ability to withstand stress and deformation, but the price of the material is relatively high.

3: Increase the thickness of the PCB board

        In order to achieve a lighter, thinner purpose, many electronic products have a thickness of 1.0 mm, 0.8 mm, or even 0.6 mm. The thickness of the plate must be maintained in the reflow oven and cannot be deformed. A little difficult. It is recommended that if there is no thin and light requirement, the board should be able to use a thickness of 1.6 mm, which can greatly reduce the risk of bending and deformation of the board.

4: Reduce the size of PCB board and the number of boards

        Since most reflow ovens in PCB circuit board factories use a chain to drive the PCB board forward, the larger PCB board size will be deformed in the reflow oven due to its own weight. Therefore, try using a longer PCB board side. . The board of the PCB. When placed on the chain of the reflow oven, the deformation of the groove due to the weight of the board itself can be reduced, and for this reason, that is, when the furnace is finished, the number of panels is also reduced, and the number is narrower. One side is used to cross the direction of the furnace as much as possible. A minimum degree of dent deformation can be achieved.

5: Use tray fixture fixture

          If the above method is difficult to achieve, the final step is to use a reflux carrier/template to reduce the amount of deformation. The PCB board factory is able to reduce the bending of the board because of thermal expansion or contraction. It is desirable that the tray can hold the PCB until the temperature of the PCB is below the Tg value and then harden again, and the size of the garden can be maintained.

  If the single-layer tray can not reduce the deformation of the PCB board, it is necessary to add a layer of cover layer, and clamp the PCB board with the upper and lower layers of the tray to avoid the problem of deformation of the PCB board, which can greatly reduce the number of reflow furnaces. However, this tray fixture is very expensive and must be placed manually to place and recycle the tray.

6: Use Router instead of V-Cut

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

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