Improving copper plating adhesion on glass using laser machining techniques and areal surface texture parameters

• Excimer laser machining is proposed to improve electroless copper/glass adhesion.
• Various structured surfaces are produced by changing operating parameters.
• The factors which affect surface topography are investigated.
• ISO-25178 Part 2 areal parameters are used to measure surface topography.
• Parameter correlations are shown with respect to mechanical scratch testing results.

Glass is a promising substitute substrate material being evaluated for electronic packaging technology. Improving the electroless copper plated layer adhesion of the glass is one of the most important considerations for development of the technology. An excimer laser (248 nm) was used for structured texturing of glass surfaces (to improve adhesion) by changing mask dimensions, laser operating parameters and overlapping pitch spacing, and therefore producing a range of micro-scale features. Electroless plated copper adhesion strength was assessed using quantitative scratch testing, demonstrating that micro-patterned structures can significantly improve copper/glass adhesion. New ISO 25178 Part 2 areal surface texture parameters were used to characterise the surface roughness of ablated glass surfaces, and correlated to the scratch testing results. Highly correlated parameters were identified that could be used as predictive surface design tools, directly linking surface topography to adhesion performance, without the need for destructive adhesion quantification via scratch testing.