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Design tips on FPC boards

Edit:Xing DA Electric Technology Co.,LtdUpDate:Nov 05, 2018

Shape:

First, the basic route must be designed, and then the shape of the FPC should be designed. The main reason for adopting FPC is that it wants to be miniaturized. Therefore, it is often necessary to first determine the size and shape of the machine. Of course, the important component positions in the machine still need to be prioritized (for example: the shutter of the camera, the head of the recorder...), and if it is set, it may not need to be changed greatly even if it is necessary to make some modifications. After determining the position of the main part class, the next step is to determine the form of the wiring. First of all, you should first decide on the need to use the twists and turns. However, the FPC has a certain degree of rigidity in addition to the software, so it cannot really fit close to the inner edge of the machine. Therefore, it is necessary to design and cooperate with the clearance.


Circuit:

There are many restrictions on circuit wiring, especially the need to bend back and forth. If not designed properly, it will greatly reduce its life. It is necessary to use the FPC of the single-sided mechanism in principle. If the line is too complicated and you have to use a double-sided FPC, you should pay attention to the following points:

1. See if you can use the through hole (there is no one). Because the plating of the through holes has an adverse effect on the folding resistance.


2. If the through hole is not used, the through hole in the meandering portion does not need to be plated with copper.


3. Make a zigzag part separately with a single-panel FPC, and then join the two-sided FPC.


Circuit design:

We already know the purpose of using FPC, so we should consider both machine and electrical properties.

1. Current Capacity, Thermal Design: The thickness of the copper foil used in the conductor section is related to the current capacity and thermal design of the circuit. The thicker the conductor copper foil, the smaller the resistance value and the inverse relationship. Once heated, the conductor resistance will increase. In the double-sided through hole structure, the thickness of the copper plating can also lower the resistance value. It is also designed to require a current that is 20 to 30% more margin than the allowable current. However, in addition to the appeal factor, the actual thermal design is also related to circuit density, ambient temperature, and heat dissipation characteristics.


2. Insulation: There are many factors that affect the insulation properties, and it is not as stable as the resistance value of the conductor. The general insulation resistance is determined to have pre-drying conditions, but it is actually used on electronic instruments and dry performance, so it must contain considerable moisture. Polyethylene (PET) is much less hygroscopic than POL YIMID, so the insulation properties are very stable. If used as a maintenance film and solder-resistant printing, the insulation properties are much higher than that of PI.