Fine lines in high yield. XCIV. Dry film photoresist components and their functions (Part A)

Non-chemists involved in PWB fabrication are often mystified by the variety of chemistries employed in numerous processing steps such as surface preparation, imaging, development, stripping and plating. This is not helped by the fact that most of the chemical compositions are 'proprietary,' and the suppliers are often reluctant to share even fundamental information in a qualitative way. The compositions of photoresists are no exception to this scenario. So it seems to me it may be useful to cover in this column, in a two part series, some insight into the components of dry film resists and their functions. This is by no means a daring endeavor since it draws on information that resides in the public domain (Ref. 1-9), is somewhat dated, but nevertheless still quite relevant.