Veco B.V. Analysis of Alternatives. Non-confidential report

2016. — 31 p.Use of ammonium dichromate as photosensitive component in a polyvinyl alcohol photolithographic lacquer system for the manufacturing of mandrels which are used in nickel electroforming processes.This Analysis of Alternatives (AoA) forms part of the Application for Authorisation (AfA) for the use of ammonium dichromate in photolithographic applications. Within this application, ammonium dichromate is used as a photosensitizer in a light-sensitive, isolating, photolithographic polyvinyl alcohol (PVA) lacquer. After exposure to light with an appropriate wavelength, those lacquers undergo crosslinking reactions, leading to an altered solubility in water and make the mandrels on which the lacquer is applied a valuable tool in nickel electroforming processes. Ammonium dichromate containing products are used as mandrels in this electroforming process and are for internal use only.
This summary aims to shortly explain why the use of ammonium dichromate is essential in this specific photolithographic application. It describes the steps and effort involved in finding and approving a replacement for ammonium dichromate in this application and evaluates potential alternatives in detail. The following key functionalities for the use of ammonium dichromate in the given photolithographic application are as follows and discussed in more detai:
- Photosensitizing capacity
- Adhesion to substrate
- Compatible to PVA
- High-resolution and high definition of photo-images
- Life-time of non-exposed lacquer
- Temperature resistance of the resulting mandrel
- Chemical resistance of the resulting mandrel
- Three-dimensional shape of the lacquer on the resulting mandrelAs a result of the R&D efforts, 4 different 4-diazodiphenylamine formaldehyde (1:1) salts, as only reasonable alternative, are reported and evaluated concerning its technical and economic feasibility, as well as the reduction of the overall risk in case of transition. Besides these diazo compounds, only preliminary testing with a few other alternatives was performed. In terms of technical feasibility, 4-diazodiphenylamine formaldehyde (1:1) showed promising results during ongoing testing, but currently does not represent a viable alternative for ammonium dichromate. For the current alternative under development, development steps were initiated in 2013 and are still ongoing. As of today, this alternative has not proven to be suitable, which is discussed in more detail in chapter 5. A wide-ranging assessment concerning the influence of the alternative on the properties of the final product needs to be conducted. Furthermore, process parameters and equipment need to be adjusted and the approval on the customers' side has to be obtained. The robustness and stability of the products have to be checked and monitored in the long term. Finally, the process has to be repeated for each of the various products and customers. At present, the alternative is in the initial phase of the development process where testing of specific process parameters e.g. concentration, development process, and lacquer adhesion is carried out including first preliminary scaled up experiments. As not all parameters of the current setting turned out to be suitable, it is not yet clear when these phases of the development process will be accomplished. According to the current stage of research in 2016, another 2-3 years are estimated if no major drawbacks occur.