PCB design & shape affect warpage of manufacturability

1.Design principles shape：
    PCB design for the general shape of the aspect ratio is not too large rectangle, large aspect ratio, or a larger area of the board, prone to warpage. Larger board can save material, but because the quality of warping and other factors make it in the production and transportation are more difficult and require special fixtures fixed, so in principle the use of more than 23cm × 30cm board; for SMD SMB PCB components, for its size, thickness, chamfer around and around vertical and parallel precision, require more stringent. This is because of the different sizes and types of placement machines to the specific requirements of the SMB will be slightly different, SMB's size is too large or too small, the board can not Mounter well fixed, this will placement accuracy, speed, welding quality adversely affected, causing problems in manufacturing; and in severe cases can lead to the production of SMB can not be processed with automatic placement equipment.

2. PCB warpage requirements
    PCB size is too large, in addition to increasing the production and transportation of inconvenience outside automated insertion line, if the PCB level, can cause inaccurate positioning, components can not be inserted into the hole and surface mounted stick-chip board on the plate, and even crashed inserted automatically installed. Loaded on board after soldering components bending element foot is difficult to cut flat tidy. The board can not be fitted into the socket on the chassis or inside. At present, the PCB has entered into the era of surface mount and chip installation, assembly plant on the warping degree requirements must be more strict. Because for PCB warpage is not serious, the use of plug-in components when you can rely on to overcome part of the deformation component leads; and PCB warpage to mount components, since no lead, only to rely on the element itself adaptation, which can cause cell rupture, welding unreliable and other issues.
    Rigid PCB, the PCB surface mounting for maximum allowable warpage and distortion of 0.75%, 1.5% allow various other boards. For 1.6mm thickness PCB, double-sided or multilayer regardless, warpage is usually 0.70 to 0.75%, many SMT, BGA board required is 0.5%. Warpage test method is to put on the PCB by the test platform to test the needle into the largest local warping to the length of the test needle diameter, divided by the curved edge of the PCB can be calculated the warping of the PCB.