UK-based Emerson & Renwick recently delivered a pilot roll-to-roll (R2R) system to CondAlign, a Norwegian company developing conductive films and related products.
CondAlign turns existing materials into high-value products through a patented technology to align particles in polymers. The product can be described as a double-sided tape with anisotropic (through-plane) conductivity.
CondAlign’s business is based on technology & product development before licensing to customers. Therefore, the specifications for the machine cover a broad range of materials-handling and production requirements. The new pilot R2R coater features the patented CondAlign technology implemented.
CondAlign works with a range of products to customers from several market segments. This can be electrically conductive tapes and substrates as well as thermal-interface materials to the electronics industry, biocompatible films to the healthcare sector, and membranes for gas- and liquid separation. The application areas will define the required material properties for each film such as conductivity, elasticity, light weight, softness, transparency, adhesiveness, resilience to harsher environments or biocompatibility. The production process also requires high accuracy, and the thickness of the film is often less than 100 µm.
The machine can run coating thicknesses from 5 to 3,000 µm with an accuracy of less than +/-2 µm. This required accuracy meant that all machining and assembly had to be to the highest level. The E&R team also added motor control to the calender nip roller, that adjusts the height based on a sensor on either of the rollers. The software and motor adjust compensate for the small amount of variation remaining in the setup.
The main challenges faced in upscaling the CondAlign technology, from a prototype to this pilot line:
- Accurately handling film thicknesses from 5 µm to 3 mm
- Producing films to +/- 2-µm tolerances
- Coating onto release-coated substrate with low surface energy
- Pumping fluids at a broad range of flow rates and viscosities
- Prevent particles from aggregating in the solution before coating
- UV-curing of thick samples
Achieving even particle distribution in the sample, requires that the particles be dispersed in a liquid polymer until coating on the substrate. A storage tank with variable speed agitator, keep particles in suspension.
The machine cures the samples with two UV-LED lamps, providing curing from the top and bottom of the sample. When running at the maximum sample thickness of 3 mm, there were concerns that the UV would not penetrate to cure the whole sample. For this reason, the second UV lamp is capable of being reversed so it illuminates from underneath the sample.
Another issue is the tendency of some of the polymers, once coated onto the film, to retract into "islands’"rather than remain as a homogenous layer, leading to visual defects in the final product. To address this, E&R incorporated a modified version of their slot-die applicator, which allows CondAlign to position the applicator at varying distances from the calender nip according to which polymer is being used and which eliminates this phenomenon as a result.
More info: www.eandr.com