In the design of multi-layer insulation components (MLI) for spacecraft, the thickness of each layer of material directly affects the weight budget of the entire satellite. Engineers face a recurring engineering choice: how to find the optimal balance between thermal control performance, mechanical reliability, and weight?

Traditional MLI uses a 25 μ m or thicker aluminum coated PI film as the reflective layer - reliable in performance but substantial in weight. If the thickness of the substrate is reduced from 25 μ m to 12.5 μ m or even 7 μ m, the weight reduction effect is significant. However, thinner substrates require significantly higher process control in post-processing steps such as vacuum evaporation, slitting, and bonding, which poses a challenge to mass production yield.

25 μ m is located at a special position. In the product spectrum of PI aluminum plated film, 25 μ m (approximately 1mil) is the industry consensus "standard thickness". It does not place extremely high demands on processing technology like thinner specifications, nor does it make unnecessary compromises on weight and flexibility like thicker specifications. It is precisely this "just right" that makes 25 μ m the most widely used and trusted specification in high-end applications such as aerospace thermal control, electronic shielding, and precision optics.

2、 Why 25 μ m: Industry Consensus from MLI to FPC

In the application system of polyimide film, 25 μ m is one of the most basic thickness units - the vast majority of PI film manufacturers use 25 μ m as the core specification in their standard product lines. The reason why 25 μ m has become the industry standard is due to its comprehensive advantages in multiple engineering dimensions:

3、 PI Al: Engineering Logic of Material Combination

The core value of 25 μ m PI aluminum plated film comes from the synergistic effect of PI substrate and aluminum coating - each contributing irreplaceable performance to the other.

4、 Vacuum evaporation: "growing" optical grade aluminum layer on a 25 μ m substrate

The aluminum layer preparation of 25 μ m PI aluminum coating film adopts vacuum evaporation process - in a vacuum environment, high-purity aluminum wire or aluminum block is evaporated into gas by heating, and then deposited on the surface of PI film to form a coating.

Process maturity:The 25 μ m substrate has high mechanical strength and heat capacity, good tolerance to temperature and tension waves, easier to ensure uniformity and adhesion of the aluminum layer, and high stability in mass production.

5、 Aluminum layer thickness: performance span from 0.5 μ m to 1 μ m

Based on a 25 μ m PI substrate, aluminum plated film products with different aluminum layer thicknesses can be prepared by precisely controlling the evaporation process parameters. The thickness of the aluminum layer varies from 0.5 μ m to 1 μ m, and different thicknesses correspond to different performance focuses:

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

6、 Key Performance: Technical confidence with 25 μ m specification

7、 Three major application scenarios: from spacecraft to precision optics

8、 Selection considerations: from aluminum layer thickness to application scenarios

9、 Conclusion

The essence of 25 μ m PI aluminum plated film is an engineering product that finds the optimal balance point in high-end applications such as aerospace thermal control, electronic shielding, and precision optics. It is not the thinnest or thickest, but it is the "just right" choice in most high-end application scenarios: sufficient to meet the thermal control performance and reliability requirements of spacecraft MLI, support the electromagnetic shielding and flexibility requirements of FPC, maintain high yield and controllable cost in mass production.

For engineers, understanding the engineering logic behind the thickness of 25 μ m - why it is 25 instead of 12.5 or 50- is more valuable than simply remembering a specification. On this thickness platform, customizing products with different properties by adjusting the thickness of the aluminum layer (from 0.5 μ m to 1 μ m) is a key step in transforming the "standard answer" into specific engineering solutions.