Board bending and warping are common issues when a PCB goes through the reflow furnace. To prevent the PCB from bending and warping during this process, the following detailed explanations may be helpful:
1. **Reduce the Influence of Temperature on PCB Stress**
Since “temperature” is a major source of stress for PCBs, reducing the temperature of the reflow furnace or slowing the heating and cooling rates can significantly decrease bending and warping. However, be aware that these adjustments might lead to other issues, such as potential short circuits.
2. **Use PCB with High Tg**
Tg, or glass transition temperature, is the point at which the material transitions from a glassy to a rubbery state. A lower Tg means the PCB material softens more quickly in the reflow furnace, increasing the likelihood of deformation. Using a PCB with a higher Tg enhances its ability to resist stress and deformation, although higher Tg materials tend to be more expensive.
3. **Increase PCB Thickness**
To meet the demand for lighter and thinner electronic products, PCB thicknesses have been reduced to 1.0mm, 0.8mm, or even 0.6mm. Such thin boards are more prone to deformation after reflow. If there are no stringent requirements for reduced thickness, opting for a 1.6mm thick PCB can significantly lower the risk of bending and warping.
4. Reduce the PCB board size and number of panels. Since most reflow furnaces use chains to move the PCB board, a larger PCB design can lead to denting and deformation due to its weight. To mitigate this, position the long side of the PCB board along the edge of the chain in the reflow furnace. This alignment helps minimize depression and deformation caused by the board’s weight. Reducing the number of panels also helps to achieve minimal depression and deformation.
5. Use furnace tray fixtures. If the above methods are impractical, employing furnace trays can help reduce deformation. These trays minimize bending and warpage by stabilizing the PCB board during thermal expansion and contraction. Once the PCB board cools below its Tg value and hardens, the tray helps maintain its shape. If a single-layer tray is insufficient, adding a cover to clamp the PCB between upper and lower trays can significantly reduce deformation during reflow. Note that furnace trays are expensive and require manual handling for placement and recycling.
6. Use a router instead of V-Cut for sub-boards. V-Cut can compromise the structural strength between PCB boards, so it is advisable to avoid V-Cut for creating sub-boards or to minimize its depth.
1. **Reduce the Influence of Temperature on PCB Stress**
Since “temperature” is a major source of stress for PCBs, reducing the temperature of the reflow furnace or slowing the heating and cooling rates can significantly decrease bending and warping. However, be aware that these adjustments might lead to other issues, such as potential short circuits.
2. **Use PCB with High Tg**
Tg, or glass transition temperature, is the point at which the material transitions from a glassy to a rubbery state. A lower Tg means the PCB material softens more quickly in the reflow furnace, increasing the likelihood of deformation. Using a PCB with a higher Tg enhances its ability to resist stress and deformation, although higher Tg materials tend to be more expensive.
3. **Increase PCB Thickness**
To meet the demand for lighter and thinner electronic products, PCB thicknesses have been reduced to 1.0mm, 0.8mm, or even 0.6mm. Such thin boards are more prone to deformation after reflow. If there are no stringent requirements for reduced thickness, opting for a 1.6mm thick PCB can significantly lower the risk of bending and warping.
4. Reduce the PCB board size and number of panels. Since most reflow furnaces use chains to move the PCB board, a larger PCB design can lead to denting and deformation due to its weight. To mitigate this, position the long side of the PCB board along the edge of the chain in the reflow furnace. This alignment helps minimize depression and deformation caused by the board’s weight. Reducing the number of panels also helps to achieve minimal depression and deformation.
5. Use furnace tray fixtures. If the above methods are impractical, employing furnace trays can help reduce deformation. These trays minimize bending and warpage by stabilizing the PCB board during thermal expansion and contraction. Once the PCB board cools below its Tg value and hardens, the tray helps maintain its shape. If a single-layer tray is insufficient, adding a cover to clamp the PCB between upper and lower trays can significantly reduce deformation during reflow. Note that furnace trays are expensive and require manual handling for placement and recycling.
6. Use a router instead of V-Cut for sub-boards. V-Cut can compromise the structural strength between PCB boards, so it is advisable to avoid V-Cut for creating sub-boards or to minimize its depth.
