The traditional process of achieving multiple thicknesses on a single board
At present, the same flexible PCB has multiple thicknesses, and it’s made by superimposing materials. As shown in Image 1.
There are three thickness specifications for the same piece of product. The thickness 1 is the terminal area, because the terminal part needs to be contacted, under normal circumstances.It must be made by using double-sided copper or two single-layer copper superposition. The thickness 2 area needs to be bent under normal circumstances, so the product thickness requirements will be thinner. The thickness 3 is the pad area, if this area is soldered on both sides, it must be made by using double-layer copper or two single-sided copper structures, and if it is single-sided soldered, it is made with single-layer copper.
In other words, This structure are normally made by using the method of superimposing materials. The material-to-material stacking process is complex, and it is necessary to select a variety of material thicknesses, the structure is shown in Image 2.
In order to achieve the required thickness of the product, the product is filled with PI substrate in the product portfolio, and the structure of the product is made up to 9 layers by adhesive bonding. Material and labor costs have increased significantly. In order to ensure the conduction of the upper and lower copper layers, the product manufacturing process will also change, and the holes should be drilled first, and then the copper plating should be used to achieve the purpose of using hole conduction to achieve the conduction of the upper and lower layers. This complicates the manufacturing process, and the manufacturing process of copper circuit board holes is relatively complex (Through electroplating operations), and quality abnormalities are not easy to find, the quality hazards are prone to occur.
In addition, if the pad area of the product needs to be soldered on both sides, the structure will be more complex, as shown in Image 3.
The required thickness for the product is different, and the selected thickness of PI is also different.
At the same time, the terminals of such products are directly plugged and the mold cannot be punched. Therefore, the industry is made in the form of lasers, and the cost is particularly high.
In order to solve the above problems, Flex Plus (Xiamen) Co., specially invent this technology, We named the product we produced in this way: Sculptured flex PCB
The steps of production:
Step1: Provide copper foill. The thickness of copper foil is the thickness of the thickest copper layer in the hollow flexible circuit board to be made;
Step2: According to the copper layer thickness requirements of different functional areas in the hollow flexible circuit board to be made, the copper foil is etched from thick to thin for many times at the position of the functional area to obtain etched copper foil with multiple copper layer thicknesses;
Step3: Reinforce at least one layer of insulating flexible substrate board to etch copper foil to obtain half of the finished substrate;
Step4: The circuit shape of the negative is transferred to the copper layer of the semi-finished substrate by developing, exposing and etching to form the required circuit, and the final required hollow flexible circuit board is obtained.
Sculptured flex PCB production process features:
1. The functional area includes a terminal, a pad and a bending area located between the two, where the copper thickness of the terminal is the thickest and the copper thickness of the bending area is the thinnest.
2. The copper layer at the terminal is protected with dry film, while the copper layer in other areas is exposed to the outside, and the exposed copper layer is etched to the product thickness required in the pad area through the etching process; The copper layer in the pad area is then also protected with a dry film, and the remaining exposed copper layer is further etched to the required thickness in the bend area through the etching process.
3. In the case that the pad needs to be double-sided soldering, the etched copper foil is reinforced with at least one layer of insulating flexible substrate board. And after obtaining half of the finished substrate, the lower protective film is first pasted on the lower surface of the copper layer outside the welding area and hot pressed, and then the line shape of the negative film is transferred to the copper layer of the semi-finished substrate through development, exposure and etching to form the required line, and the final required hollow flexible circuit board is obtained, and then the upper protective film is pasted on the upper surface of the copper layer outside the welding area and hot pressing.
4. Insulating flexible substrate board is PI.
This technology optimizes the product structure, simplifies the structure of the flexible circuit board with multilayer thickness, reduces the production process, and no longer adopts the expensive laser process, thereby saving the cost. In addition, because the conduction of the product is completely virgin copper layer, the conductivity of the product is guaranteed, and the product quality is improved.
Reference: Flex Plus (Xiamen) Co., Ltd. invention patent, Patent number: 201710945041.1
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