Page 172 - PCMI Journal December 2020
P. 172
PCM Educational Session for Colleges and New Staff Presented by: David M. Allen, Emeritus Professor of Microengineering, Cranfield University, UK
11/23/20
Coating
§ The objective of photoresist coating is to provide a protective surface stencil that can protect from (resist) the action of chemical etching.
§ The stencil pattern is achieved by photo-exposure of the light-sensitive coating via uv flood exposure through a phototool or uv laser exposure (also known as laser direct imaging or LDI).
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Resolution v. coating thickness § In general, liquid photoresists will give coating
thicknesses between 2 μm and 15μm.
§ Dry film photoresist thicknesses are generally between 10
μm and 100μm.
§ The finest features will be resolved in the thinnest photoresists but the stencil gains increased strength with thicker coatings.
Note the compromise
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Issue 136 December 2020 PCMI Journal 172
