PCB Tech - Design essentials of FPC circuit board

FPC not only has circuit board design performance, but also plays a decisive role in the application field, such as common circuit board welding, LED energy-saving circuit board production and circuit board maintenance, etc. It can be said that today's FPC has penetrated into all walks of life Therefore, it is very important to master the FPC design principles.

In terms of design, FPC materials can be roughly divided into the following aspects

One, style

The basic route must be preset first, and then the FPC style must be preset. The main reason for using FPC is that it wants to be small-scale. It is customary to vote on the size and style of the machine first. Of course, the position of the tightly closed components in the machine must be set first (for example: the shutter of the camera, the sensor head of the sound recorder, etc.). If it is set, even if it may be necessary to perform many corrections, it does not need to be large. Change. After voting for the position of the main parts, the next step is to vote for the wiring form. First of all, you should first vote on the part of the application of the round-tripping, but the FPC should have much rigidity except for the software, so there is no way to really fit the inner edge of the machine, because this needs to be preset to correspond to the gap that has been sold.

Second, the circuit

There are many restrictions on circuit wiring, especially where it needs to go back and forth. If the preset is not suitable, it will greatly reduce its life span. In principle, FPC with a single-sided mechanism is required for the partial use of the shuttle. If double-sided FPC must be used due to the complicated circuit, the following points should be paid attention to:

1. See if holes can be formed without having to penetrate (common sense of circuit board maintenance). The electroplating that forms voids will have a bad influence on the bending resistance.

2. If the holes are not formed by penetrating, copper plating is not required to form holes in the local penetrating hole.

3. The single-sided FPC is used to additionally manufacture the part of the tuck, and then it is combined with the double-sided FPC.

Three, circuit pattern essentials

FPC should also consider the performance of the machine and the insulation of the circuit board when designing.

1. The current volume, thermal pre-design, the thickness of the copper foil used as appropriate for the conductor part, and the current volume and thermal pre-design undertaken by the circuit are all related. The thicker the conductor copper foil, the smaller the resistance value, which is inversely proportional. Once heating, the resistance value of the conductor will increase. In the double-sided hollow structure, the thickness of copper plating can also reduce the resistance value. It is also preset that the amount of current required to exceed the allowable current by 20 to 30% with a 100% margin. But in fact, the thermal preset is not only related to the appeal factor, but also related to the density of the circuit, the surrounding temperature, and the special nature of heat dissipation.

2. Insulation: There are many factors that affect the special properties of insulation, and it is not as firm as the resistance of a conductor. Ordinary insulation resistance values have pre-drying conditions when voting, but they are actually used on electronic spectrographs and dried, so they must include considerable nutrients. Polyethylene (PET) has a lower hygroscopicity than POLYIMID, so the special insulation properties are very firm and stable. If used as a guarantor film plus solder resist printing, after the nutrient is reduced, the special insulation properties are much higher than that of PI. .

Generally speaking, when designing FPC circuit board s, the above factors must be dealt with well, so that the circuit boards designed in this way have high-efficiency transmission performance and controllable performance.