How to avoid printed circuit board warping

1. Reduce the effect of temperature on board stress
Since [temperature] is the main source of board stress, as long as the temperature of the reflow oven is lowered or the speed of the board heating and cooling in the reflow oven is slowed down, the warpage of the PCB can be greatly reduced. However, other side effects may occur, such as solder shorts.

2. Use high Tg sheet
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 of the material, the faster the board starts to soften after entering the reflow oven, and the time it takes to become a soft rubber state. It will also become longer, and the deformation of the board will of course be more serious. The use of a higher Tg sheet can increase its ability to withstand stress and deformation, but the price of the corresponding material is also relatively high.

3. Increase the thickness of the circuit board
In order to achieve lighter and thinner thickness of many electronic products, the thickness of the board has been left at 1.0mm, 0.8mm, and even 0.6mm. Such a thickness should keep the board from being deformed after passing through the reflow furnace, which is really a bit difficult. The PCB factory recommends that if there is no requirement for lightness and thinness, the board can preferably use a thickness of 1.6mm, which can greatly reduce the risk of warpage and deformation of the PCB board.

4. Reduce the size of the circuit board and reduce the number of panels
Since most reflow ovens use chains to drive the circuit board forward, the larger the circuit board will be dented and deformed in the reflow oven due to its own weight, so try to put the long side of the circuit board as the board edge. On the chain of the reflow furnace, the concave deformation caused by the weight of the circuit board itself can be reduced. This is also the reason for reducing the number of panels. That is to say, when passing the furnace, try to use the narrow side to be perpendicular to the furnace direction, which can achieve the lowest The amount of concave deformation.

5. Use the oven tray fixture
If the above methods are difficult to achieve, the last thing is to use the oven tray (reflow soldering carrier/template) to reduce the deformation of the circuit board. The principle that the oven tray fixture can reduce the warpage of the PCB board is because the material of the fixture is general. Aluminum alloy or synthetic stone will be used to have high temperature resistance, so the PCB factory will let the circuit board pass through the high temperature thermal expansion of the reflow oven and the cold shrinkage after cooling down. The tray can play the function of stabilizing the circuit board. After the temperature of the plate is lower than the Tg value and starts to recover and harden, the original size can be maintained.

If the single-layer tray fixture cannot reduce the deformation of the circuit board, you must add a layer of cover to clamp the circuit board with the upper and lower trays, which can greatly reduce the deformation of the circuit board through the reflow oven. . However, this oven tray is quite expensive, and you have to add labor to place and recycle the tray.

6. Use Router instead of V-Cut's sub-board
Since V-Cut will destroy the structural strength of the panel between the boards, try not to use the V-Cut sub-board, or reduce the depth of the V-Cut.

Any other question, please RFQ.