1. According to provisions of GJB3835, after warping and deformation welding of PCBA in reflow oven welding process, the maximum warping and distortion shall not exceed 0.75%, and the warping and distortion of PCB with fine-spacing components shall not exceed 0.5%.
2. PCBA with obvious warping, if the multi-layer PCBA has deformation stress, including reinforcement of metal frame installation, chassis platform screw installation, chassis guide rail guide groove insertion and other reverse deformation installation (insertion) operation, It is likely to cause damage or fracture to the metallization holes of printed wires such as high-density IC and other components leads, BGA/CCGA solder joints and relay holes of multilayer PCB.
3. PCBA with distortion or bowing up to 0.75% shall be installed in accordance with the following provisions if it is confirmed that the deformation stress does not cause component damage and reliability problems and it needs to continue to be used.
Install (insert) and screw fastening directly on the chassis platform, guide groove, guide rail or pillar should not be carried out to avoid further damage to components and metallized holes caused by the reverse deformation stress of PCB assembly installation.
Local bedding measures (electrical or thermal conductive materials) shall be taken at the place where the distortion and bending deformation gap is the largest, without affecting installation reliability and ensuring the main thermal or conductive channels. The warping part can be installed and fastened only under the condition that the deformed printed circuit board assembly does not bear the reverse deformation stress.
4. The rigidity and deformation capacity of the materials selected for the PCB installation structure and reinforcement frame shall not cause distortion or bow deformation or reverse deformation of the PCB.
5. For the multilayer PCBA with obvious distortion or bowing, or the distortion (bowing) less than 0.75%, especially the PCBA equipped with high-density IC, BGA/CCGA components, correction or anti-deformation installation of PCB should be strictly prevented.
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Zhejiang NeoDen Technology Co., Ltd
Post time: Jun-02-2021