Bow and twist in PCB refers to the bending or warping of the printed circuit board. Bow refers to a bending of the board in which the centre of the board is higher or lower than the edges. Twist, on the other hand, refers to a twisting or rotation of the board about its centre axis. Both bow and twist can be caused by a variety of factors, including uneven expansion or contraction of the materials used in the PCB, improper handling or storage, or excessive stress on the board during the manufacturing process. These issues can lead to poor performance and malfunction of the electronic devices that the PCB is used in.
To prevent bow and twist in PCBs, several steps can be taken such as handling and storing the PCBs properly, controlling the temperature and humidity of the manufacturing environment, using appropriate design and materials, implementing quality control measures, and using the correct fabrication and assembly process. These steps help to minimize the stress on the PCB, prevent uneven expansion and contraction of materials, and detect any issues early on.