Due to a supply chain issue that is beyond our control, Luxel is transitioning to a different source for precursor components of our proprietary LUXFilm^® Polyimide. Specifically, while the components will be supplied by the same company, they will be manufactured in a different facility. LUXFilm^® Polyimide will maintain the same composition and chemical structure, and internal testing on a wide variety of metrics confirms that performance is equivalent.

LUXFilm^® Polyimide has been in use and undergone extensive qualification testing for programs, sometimes spanning decades, and we understand that any change can be cause for concern. We appreciate (perhaps better than most) how sensitive submicron films and their applications can be to small changes and that any change in process can have unexpected consequences. We have extensively tested LUXFilm^® Polyimide produced with material from the new manufacturing facility and compared the results against those from decades of testing to ensure the continuity of quality that users of LUXFilm^® Polyimide have come to expect. A summary of our testing and results is provided below for your review.

Luxel is continuously monitoring our products for quality assurance. If you have a characteristic you consider critical and that is not addressed in our testing, or if this change presents unusual challenges for your application, please let us know by contacting us at TechSupport@luxel.com.

We will continue to deliver LUXFilm^® Polyimide made with components from the original manufacturing facility while supplies last; we anticipate transitioning production to the new source material for products shipped after 01 January 2024. Our products will continue as LUXFilm^® Polyimide and should be considered equivalent in terms of heritage and qualification.

If you need evaluation time prior to switching between LUXFilm^® Polyimide sourced from the two production facilities, please contact Luxel to discuss a testing schedule. Data presented herein should be taken as representative rather than as a product specification.

We measured samples at the Center for X-Ray Optics (CXRO) at the Advanced Light Source (ALS) and the Lawrence Berkeley National Laboratory to verify that the supply change would not add any new elements or appreciably change the density. Results (Figure 1) showed no new absorption lines were seen and modeling indicates consistent ratios of C, H, N, and O as well as consistent density with the new supply.

Broadband visible transmittance of aluminized LUXFilm^® Polyimide shows no significant change in transmittance between supplies, with both able to reach our metrology limit of 2e-9 at an Al thickness of 150 nm.

While LUXFilm^® Polyimide is not typically used as an infrared filter, the infrared spectrum indicates a comparable bond structure (Figure 1).

Standard qualification for LUXFilm^® Polyimide includes burst testing for a range of thicknesses on 5 mm apertures. The pressure is ramped upward continuously until failure. Polyimides prepared before and after the change are not statistically distinguishable.

Bulge testing shows biaxial tensile strength, Young’s modulus, and maximum elongation are equivalent in films made from both old and new supplies of precursor.

LUXFilm^® Polyimide made with the new supply of precursors maintains the low thermal expansion of 3×10^-6 K^-1 at 25⁰ C.
Expected mass loss is <1% at 600⁰ C in air.

Films from the new supply passed gas barrier tests for applications using LUXFilm^® Polyimide, verifying the applicability of the new supply as a gas barrier. He permeability was <10^-8 mbar L s^-1 atm^-1 for a film of 480 nm LUXFilm^® Polyimide coated with 24 nm Al on a 4 mm aperture.

Similarly, leak tests of laser entrance hole (LEH) windows confirm no change in performance. LEH windows with a thickness of 880 nm LUXFilm^® Polyimide on either end of a gaspipe cylinder with 4.1 mm interior diameter passed leak tests at a pressure of 160 kPa. Gaspipes remained leak tight over the three 30 minute pressurization cycles.

Figure 3: Top and side views of a 4 mm-tall gaspipe undergoing testing at 23.2 psi. End caps are 850 nm LUXFilm^® films on a 4.1 mm aperture.

We have made and validated films with thicknesses from 30 nm to 10 µm, verifying that we can still produce the same range of thicknesses.

We have made and validated films up to 300 mm in diameter, assuring that we can produce films of comparable area and quality to that made with our previous supply.

Surface quality has always been a major driver for LUXFilm^® Polyimide, since the polymer is often used for mechanical support of filters that are used for optical blocking. Small defects – bubbles, particles, scratches, etc. – result in pinholes and cracks in optical blocking layers, setting a much lower limit on optical density of filters made with, for example, DuPont’s Kapton products. Depositions of aluminum onto the surface of LUXFilm^® Polyimide from both sources show comparable optical density and pinhole density. Surface quality is equivalent.

Thermal/infrared blocking filters for cryogenic applications frequently employ thin Al depositions onto the surface of LUXFilm^® Polyimide. Discontinuous Al layers, either from poor surface quality or from the growth structure of Al in very thin layers, can behave as low-pass filters (example), making them useless as thermal blocking filters. Figure 4 shows the infrared transmittance for films from the new supply coated with 20 nm to 30 nm Al, with a 2018 data set (with 27 nm to 31 nm Al) for comparison. The 30 nm Al coating on the LUXFilm^® Polyimide made with the new supply falls within the range of the historical data.

Testing following the blueprint of Bhandarkar et al (2015) is ongoing.

Assemblies for pressurized applications (e.g., hohlraums for fusion tests and burst assemblies for strength tests) show no appreciable change in epoxy adhesion or wicking. We do not anticipate any change in reliability, durability, or assembly processes.

As a proxy for durability in a space environment with atomic oxygen and other ionic and radical species, we measured the etch rate of LUXFilm^® Polyimide in an air plasma. The new supply appears to etch slightly slower, at a rate of ~0.8 that of polyimide from the previous supply.

50 nm films as support for transmission electron microscopy (TEM) show LUXFilm^® Polyimide from the new source has comparable to lower attenuation and noise than polyimide from our previous source. Stability in the electron beam is maintained.