Any PCB may be deformed if it goes through the furnace, which is related to PCB substrate, copper attachment area and CTE. Simply put, the thinner the plate, the easier it is to deform.

If LZ suspects the deformation of the shield, the PCB deformation caused by thermal expansion and cold contraction after reflow soldering can be verified without shielding, but I think this force is very small, even if the deformation degree in the middle is far greater than that at both ends. So that's not the point.

This problem can be solved from the following points:

1. fixture-1. 1 fixture flatness problem, are there any bugs during processing or design?

1.2 Whether the first part of fixture has the phenomenon of top lung after the first part is produced.

2. This possibility is relatively large, that is, the copper bonding area of the whole PCB is extremely uneven in the whole category, resulting in distortion caused by different expansion coefficients of each part after heating. Because this force depends on the distribution of copper, it is extremely irregular and uniform in appearance, which is slightly different from the efficiency of ordinary warping smiling faces. I used to call it the punt phenomenon or the impeller phenomenon. Ningbo dejia electronic professional pcb aluminum substrate