The deformation of the PCB board, also known as the degree of warpage, has a great influence on the welding and use. Especially for communication products, the single board is installed in a plug-in box. There is a standard spacing between the boards. With the narrowing of the panel, the gap between the components on the adjacent plug-in boards becomes smaller and smaller. If the PCB is bent, it will Affect the plugging and unplugging, it will touch the components. On the other hand, the deformation of the PCB has a great influence on the reliability of BGA components. Therefore, it is very important to control the deformation of the PCB during and after the soldering process.
(1) The degree of deformation of the PCB is directly related to its size and thickness. Generally, the aspect ratio is less than or equal to 2, and the width to thickness ratio is less than or equal to 150.
(2) Multilayer rigid PCB is composed of copper foil, prepreg and core board. In order to reduce the deformation after pressing, the laminated structure of the PCB should meet the symmetrical design requirements, that is, the thickness of the copper foil, the type and thickness of the medium, the distribution of graphics items (circuit layer, plane layer), and the pressure relative to the thickness of the PCB. The center line of the direction is symmetrical.
(3) For large-size PCBs, anti-deformation stiffeners or lining boards (also called fire-proof boards) should be designed. This is a method of mechanical reinforcement.
(4) For partially installed structural parts that are likely to cause PCB board deformation, such as CPU card sockets, a backing board that prevents PCB deformation should be designed.