PCB Tech - Prevent reflow problems in the production of PCB circuit boards

Board bending and board warping are prone to occur when the PCB goes through the reflow furnace, so how to prevent the PCB board from going through the reflow furnace from bending and plate warping, the following is a detailed explanation for everyone:
1. Reduce the influence of temperature on PCB circuit board stress
Since "temperature" is the main source of PCB board stress, as long as the temperature of the reflow furnace is reduced or the rate of heating and cooling of the PCB board production in the reflow furnace is slowed, the bending and warpage of the board can be greatly reduced. happen. However, other side effects may occur, such as short circuits.
2. PCB with high Tg board
Tg is the glass transition temperature, that is, the temperature at which the material changes from the glass state to the rubber state. The lower the Tg value of the material, the faster the PCB board starts to soften after entering the reflow furnace, and it becomes soft rubber state The time will also be longer, and the deformation of the PCB board will of course be more serious. The use of a higher Tg board can increase its ability to withstand stress and deformation, but the price of the relatively high material for the production of PCB boards is also relatively high.
3. Increase the thickness of the PCB circuit board
In order to achieve the purpose of lighter and thinner for many electronic products, the thickness of the PCB board has left 1.0mm, 0.8mm, or even 0.6mm. Such a thickness must keep the PCB board from deforming after the reflow furnace, which is really a bit It is difficult for others. It is recommended that if there is no requirement for lightness and thinness, it is best to use a thickness of 1.6mm for the PCB board, which can greatly reduce the risk of bending and deformation of the board.

4. Reduce the size of the PCB board and reduce the number of puzzles
Since most of the reflow furnaces use chains to drive the PCB board forward, the larger the PCB design size, the PCB board will dent and deform in the reflow furnace due to its own weight, so try to treat the long side of the PCB board as the edge of the board. Putting it on the chain of the reflow furnace can reduce the depression and deformation caused by the weight of the circuit board itself. The reduction in the number of panels is also based on this reason. Reach the lowest amount of depression deformation.
5. Used furnace tray fixture
If the above methods are difficult to achieve, the last is to use the furnace tray to reduce the amount of deformation. The furnace tray can reduce the bending and warpage of the board because whether it is thermal expansion or cold contraction, it is hoped that the tray can fix the PCB board. After the temperature of the PCB board is lower than the Tg value and starts to harden again, the size of the garden can be maintained.
If the single-layer pallet cannot reduce the deformation of the PCB board, a cover must be added to clamp the PCB board with the upper and lower pallets. This can greatly reduce the problem of PCB board deformation through the reflow furnace. However, this furnace tray is quite expensive, and manual labor is required to place and recycle the trays.
6. Use Router instead of V-Cut to use the sub-board
Since V-Cut will destroy the structural strength of the panel between the PCB boards, try not to use the V-Cut sub-board or reduce the depth of the V-Cut.