International Business Machines Corporation

Eboney J N Smith

Ashwinkumar C Bhatt

Ross William Keesler

Michael Vito Longo

Brant S Blomberg

A hybrid photolithography process for printed circuit board patterning combines two types of photoresist applications to achieve superior protection of printed circuit board (PCB) 'plated through holes' (PTH). In a first step, electro-deposited (ED) photoresist (also known as 'ED resist') is applied to a fully copper plated PCB including the 'plated through holes' to protect the outer layers and the &#x2018;plated through holes&#x2019; from copper etchant solution. In a second step, the electro-deposited photoresist is imaged (exposed) and patterned (developed). In a third step, after developing the circuit image, a layer of Dry Film resist is applied to the panel of the PCB on top of the developed electro-deposited (ED) photoresist. This Dry Film resist layer will &#x2018;tent&#x2019; the plated through holes by adding an extra layer of protection to the plated through holes. In a fourth step, the dry film resist is then exposed and developed. At this point, the PCB is etched as normal and all subsequent processing remains unchanged.

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Johnson City, NY, United States of America

Eboney J N Smith