PCB Technical - Causes and solutions of PCB board deformation

Causes and solutions of PCB board deformation

With the continuous development of surface mount technology in the direction of high precision, high speed, and intelligence, there are also higher requirements for the flatness of PCB boards. PCB board deformation is a very annoying thing for many assembly factories. Today I will share some reasons and solutions for PCB board deformation with you!

Analysis of the causes of PCB board deformation:

1. When the circuit board is designed, the copper skin is unevenly distributed and warped after pressing.

2. The circuit board is impacted by the external heat and cold, and the situation of sudden cold and sudden heat.

3. The quality of the circuit board is poor.

4. The size of the puzzle is too large.

5. The circuit board is irregular.

The solutions given for the causes of PCB board deformation:

1. Lower the temperature

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 circuit board in the reflow furnace is slowed, the occurrence of board bending and warpage can be greatly reduced.

2. Use high Tg plates

Tg 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 circuit board starts to soften after entering the reflow furnace, and the time to become soft rubber state will be longer. Of course, the deformation of the plate will be more serious, and the use of a higher Tg plate can increase its ability to withstand stress and deformation.

3. Increase the thickness of the PCB board

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 the number of puzzles

Most of the reflow furnaces use chains to drive the PCB board forward. Try to put the long side of the PCB board as the board edge on the chain of the reflow furnace, which can reduce the depression and deformation caused by the weight of the PCB board itself. The decrease in numbers is also based on this reason. That is to say, when passing the furnace, try to use the narrow side perpendicular to the direction of the furnace to achieve the lowest depression deformation.

5. Used furnace tray fixture

Whether it is thermal expansion or cold contraction, the tray can hold the PCB board and wait until the temperature of the board is lower than the Tg value and start to harden again, and it can still maintain the original size. If the single-layer pallet cannot reduce the deformation of the PCB board, add a layer of cover and clamp the PCB board with the upper and lower pallets, so that the problem of PCB board deformation through the reflow furnace can be greatly reduced.

6. Use real connections and stamp holes instead of V-Cut sub-boards

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

The above are the reasons and solutions for the deformation of the PCB board shared by the editor, I hope it will be helpful to everyone!

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