Q: What are some of the challenges of new vacuum-coated product scale-up? Part 2 of 3

 

By Dr. Charles A. Bishop

 

More R&D to mimic the real world

This is where before embarking on the scale-up it is preferable go back and do some more R&D. Ideally samples should be produced at the real-world speed and deposition rate with all the rest of the process conditions also being identical. This will prove the same product can be produced by the production system. If the samples are as desired, then all that has been lost is some time, but if the samples are different and do not deliver the desired properties, you will have saved much more time, money and aggravation than you would get if you had bought a production system that wouldn’t deliver the product. 

Even if you have a laboratory machine that can wind at production speed and deposition rate, it is likely that in scaling-up the production system will have geometry changes, and these also can pose a risk. The production system is likely to be larger to enable long rolls of substrate to be used. The larger chamber means that some of the process controls may be affected. Particularly for reactive processes where controlling the gas can be critical, the change in distance between the process zone and outside of the chamber can slow down the response time to process changes. The change in time-constant between the detectors monitoring process parameters and the controllers that respond may be too slow preventing the process ever stabilizing. This may require an alternative method of controlling the process being used. This is a risk, and the solution may only be developed using a system of similar dimensions. 

Either way, this means testing out the process during the R&D phase. This can be done by going to a toll-coating company, but this can be viewed as a commercial risk because it requires sharing the process information and, if process changes are required, sharing the process development results with the toll coater. With some system manufacturers, it may be possible to do some trials with them prior to placing the order for the production system, but again this can raise commercial concerns that they too will have some process information learned from the trials.