In the field of consumer electronics, the core pursuit of FPC design is "thinness" - the thinner the substrate, the smaller the bending radius, and the more it can fit into the narrow body space. But in the fields of power batteries, industrial control, and automotive electronics, there has been a fundamental shift in design constraints: engineers are no longer concerned about "whether they can be thinner by 0.5 μ m", but "whether they can withstand 100000 bends without breaking", "whether they can carry 3A current without significant temperature rise", and "whether they can maintain dimensional stability in temperature cycles from -40 ° C to 125 ° C.

The selection of copper thickness for FPC directly determines the current carrying capacity, impedance control, and mechanical bending performance of flexible circuit boards. In the field of power batteries, FPC, as a collection line, needs to withstand high currents. Copper thickness of 2oz (about 70 μ m) or above is usually used in the FPC of power batteries for new energy vehicles, mainly to cope with the temperature rise challenge when high currents pass through. What these scenarios require is not thinner substrates, but stronger 'skeletons'. The 50-125 μ m PI substrate demonstrates irreplaceable value in this engineering requirement.

2、 Engineering logic of 50-125 μ m thick substrate

In the thickness spectrum of FPC substrates, different thicknesses correspond to different engineering positions. 12.5 μ m oriented towards high-density interconnect (HDI) products, pursuing ultimate thinness and lightness; 25 μ m is the standard specification in the field of consumer electronics; 50-125 μ m is positioned for industrial grade high reliability applications.

3、 From PI to Copper Coating: The Technical Path of Roll to Roll Vacuum Magnetron Sputtering

The copper layer preparation of 50-125 μ m PI copper plated film adopts roll to roll (R2R) vacuum magnetron sputtering process. Using high-purity oxygen free copper, a conductive layer of high-purity oxygen free copper is deposited on the surface by vacuum magnetron sputtering, giving the surface of the PI film material the conductive and thermal properties of a metallic material, inheriting the original chemical and physical properties of the PI film.

Copper plating is performed on a thick substrate of 50-125 μ m, with a relatively wide process window. Compared with ultra-thin substrates of 6 μ m or 4 μ m, thick substrates have a larger thermal capacity and higher mechanical strength. They have better tolerance for temperature and tension fluctuations during sputtering, making it easier to ensure the uniformity and adhesion of the copper layer. After professional testing, the adhesion of the PI copper plating film of Advanced Institute Technology has reached 5B level (the highest level of ASTM D3359 standard).

4、 Copper layer thickness: performance range from 10 μ m to 25 μ m

Based on 50-125 μ m PI substrate, copper plated film products with different copper layer thicknesses can be prepared by precise control of sputtering and electroplating process parameters. The thickness of the copper layer varies from 10 μ m to 25 μ m, and different thicknesses correspond to different performance focuses:

Note: The thickness of the copper layer is the nominal reference value, and the specific performance is subject to the actual product specifications.

5、 Key performance: Technical foundation for thick substrate and thick copper layer

6、 Core application scenarios: from power batteries to high current FPC

7、 Selection considerations: from copper layer thickness to application scenarios

8、 Conclusion

The essence of 50-125 μ m PI copper plated film is to strike an engineering balance between the thinning and structural strength of the PI substrate. It does not pursue "extreme thinness", but rather "strong enough" - exchanging thicker PI substrates for higher current carrying capacity, better dimensional stability, and stronger environmental resistance. In engineering scenarios where FPC is required to carry high currents, withstand mechanical stress, or undergo high-temperature processes, 50-125 μ m provides a reliable guarantee that thin substrates cannot replace.

For FPC design engineers, understanding the engineering logic behind the thickness range of 50-125 μ m - the need for thicker copper layers for current carrying capacity, stronger "skeletons" for high reliability, and more stable dimensions for harsh environments - is more valuable than simply comparing thickness values. On this thickness platform, customizing products with different current carrying capacities by adjusting the thickness of the copper layer (from 10 μ m to 25 μ m) is a key step in transforming "thick substrates" into specific engineering solutions. From power battery BMS to satellite payloads, from car engine compartments to industrial control cabinets -50-125 μ m PI copper plated film is pushing the application boundary of FPC from "consumer electronics" to "industry and aerospace".