The reason for the warpage of printed circuit boards is that the substrate used may warp on the one hand, and warpage due to thermal stress, chemical factors, and improper process during processing on the other hand. So, what are the preventive measures for warpage of printed circuit boards?
1. Prevent substrate warping caused by improper inventory method.
(1) During the storage of copper clad laminates, if the humidity of the storage environment is high, the copper clad laminates will increase warping due to moisture absorption. Therefore, for copper clad laminates without moisture-proof packaging, pay attention to the warehouse conditions, minimize the humidity in the warehouse and avoid bare copper clad laminates.
(2) Improper placement of copper clad laminates will increase warpage. If it is placed vertically or the copper clad board is pressed with heavy objects, the warping deformation will be increased. Solution: Improve the storage environment and prevent vertical storage and avoid heavy pressure.
2. Avoid warping caused by improper circuit design or improper processing technology.
For example, the pattern of the conductive circuit on the circuit board is unbalanced or the lines on both sides are obviously asymmetrical, resulting in large stress and warping; high processing temperature or large thermal shock during the manufacturing process cause warping, etc.
Solution: For circuit boards with a large area of copper in the circuit pattern, it is best to mesh the copper foil to reduce stress.
3. Eliminate substrate stress and reduce board warpage during processing.
Because in the process of processing, the substrate will be subjected to the action of heat and various chemical substances for many times. For example, after the substrate is etched, it needs to be washed with water, dried and heated, and the thermal shock received when the hot air is sprayed with tin is large. These processes may cause the board to warp.
Solution: Since stress is the main cause of substrate warping, if the board is baked before the copper clad laminate is put into use, the function of the baking board is to fully relax the stress of the substrate, which is beneficial to reduce the warping deformation of the substrate during the manufacturing process.
4. During wave soldering or dip soldering.
the soldering temperature is too high and the operation time is too long, which will also increase the warpage of the substrate. Solution: To improve the wave soldering process, the cooperation of the electronic assembly factory is required.
