In PCB proofing, how to reduce or eliminate the deformation caused by different material characteristics or processing has become one of the most complicated problems faced by PCB manufacturers. Next, let the engineer share with you: What are the causes of pcba manufacturer board deformation?
1. The weight of the circuit board itself will cause the board to dent and deform
Generally, the reflow furnace uses a chain to drive the circuit board forward in the reflow furnace. If there are heavy parts on the board or the size of the board is too large, it will appear concave in the middle due to its own weight, resulting in the board. bend.
2. The depth of the V-Cut and the connecting strip will affect the deformation of the jigsaw
V-Cut is to cut grooves in the original large sheet, so the place where V-Cut appears is prone to deformation.
3. Deformation caused during PCB processing
The reason for the deformation of PCB board processing is very complicated, which can be divided into two kinds of stress: thermal stress and mechanical stress. Among them, the thermal stress is mainly generated during the pressing process, and the mechanical stress is mainly generated during the stacking, handling and baking of the plates. The following is a brief discussion in the order of the process.
Incoming copper clad laminate: the size of the copper clad laminate press is large, and there are temperature differences in different areas of the hot plate, which will cause slight differences in the curing speed and degree of the resin in different areas during the pressing process, and will also generate local stress, which will be gradually released in future processing. Deformed.
Pressing: The PCB pressing process is the main process that generates thermal stress, which is released in subsequent processes such as drilling, shape or grilling, resulting in deformation of the board.
Baking process of solder mask, characters, etc.: Since solder mask inks cannot be stacked on each other when they are cured, PCB boards will be placed in a rack to cure the boards, and the boards are easily deformed under the action of their own weight or the strong wind of the oven.
Hot-air solder leveling: The entire hot-air solder leveling process is a sudden heating and cooling process, and thermal stress will inevitably appear, leading to microscopic strain and overall deformation and warping zone.
Storage: The storage of turnkey PCB assembly at the stage of semi-finished products is generally firmly inserted in the shelf, and the tightness of the shelf is not adjusted properly, or the stacking of the boards during the storage process will cause mechanical deformation of the boards.
In addition to the above factors, there are many factors that affect the deformation of the PCB board. I won't list them all here.