In the precise and lengthy production process of rigid flex circuits,the expansion and contraction value of the material will have different degrees of slight changes after going through many heat and humidity processes. However, based on Capel’s long-term accumulated actual production experience, the changes are still regular.
How to control and improve: Strictly speaking, the internal stress of each roll of flexible rigid composite board material is different, and the process control of each batch of production boards will not be exactly the same. Therefore, the expansion and contraction coefficient of the material Mastery is based on a large number of experiments, and process control and data statistical analysis are particularly important. Specifically, in actual operation, the expansion and contraction of the flexible board is staged, and the following editor will talk about it in detail.
1. First of all, from material cutting to baking plate, the expansion and contraction at this stage is mainly caused by the influence of temperature: To ensure the stability of expansion and contraction caused by the baking plate, first of all, the consistency of process control is required. On the premise of uniform material Next, the heating and cooling operations of each baking plate must be consistent, and the baked plate should not be placed in the air to dissipate heat because of the blind pursuit of efficiency. Only in this way can the expansion and contraction caused by the internal stress of the material be removed to a considerable extent.
2. The second stage occurs during the pattern transfer process. The expansion and contraction at this stage is mainly caused by the change of the internal stress orientation of the material: To ensure the stability of the expansion and contraction during the line transfer process, all baked boards cannot be processed. Grinding operation, directly through the chemical cleaning line for surface pretreatment.
After lamination, the surface must be flat, and the board surface must be allowed to stand for a long time before and after exposure. After the line transfer is completed, due to the change of the stress orientation, the flexible board will show different degrees of curling and shrinkage. Therefore, the control of line film compensation is related to The control of the precision of the combination of soft and hard, and at the same time, the determination of the expansion and contraction value range of the flexible board is the data basis for the production of its supporting rigid board.
3. The expansion and contraction in the third stage occurs during the pressing process of the rigid flex circuit boards. The expansion and contraction in this stage are mainly determined by the pressing parameters and material characteristics: The factors affecting the expansion and contraction in this stage include the heating rate of the pressing, The pressure parameter setting and the residual copper ratio and thickness of the core board are several aspects.
In general, the smaller the residual copper rate, the greater the expansion and contraction value; the thinner the core board, the greater the expansion and contraction value. However, it is a gradual change process from big to small, so film compensation is particularly important. In addition, due to the different nature of flex board and rigid board material, its compensation is an additional factor that needs to be considered.
The above are the three stages of controlling and improving the expansion and contraction of the rigid flex circuits carefully organized by Capel. I hope it will be helpful to everyone. For more circuit board issues, welcome to consult us, whether it is in flexible circuit boards, flexible rigid boards or rigid PCB board, Capel has corresponding professional experts with 15 years of technical experience to assist your project and promote your project to go smoothly.
Post time: Aug-21-2023
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