Photoresist processing for improved resolution having a bake step to remove the tackiness of the laminated photosensitive layer prior to contact imagewise exposure
US5391458A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 18, 1992 |
| Grant date | Feb 21, 1995 |
| Priority date | — |
| Expiry date | Dec 18, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH05K2203/1105
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A method is provided for forming a high-resolution photoresist layer on a substrate, such as a metal-clad circuit board blank. A dry film is used which comprises a support sheet, a negative-acting, alkaline aqueous developable photoresist layer in direct contact with the support sheet, and a protective sheet. The protective sheet is removed and the photoresist layer is cut sheet laminated to the substrate. Then the support sheet is removed. The photoresist layer is baked until its exposed surface is non-tacky. Artwork is laid directly in contact with the non-tacky exposed surface, and the photoresist layer is exposed to actinic radiation through the art work. The photoresist layer is then developed in alkaline aqueous solution. The photoresist layer is highly resolved. Subsequent processing steps, such as plating or etching and stripping yield a printed circuit board having highly resolved lines and spaces. Photoresists of specific formulation are found to be bakeable to a non-tacky surface with minimal loss of photospeed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.