Mesmoproc - implementation of a maskless electrochemical surface modification process

摘要

The conventional processes used to fabricate microscale interconnections, devices and components use photoresists and a range of developing, etching and stripping chemicals to produce the requisite shapes and features in a process known as photolithography. In conventional production approaches, a photolithography stage is required to pattern each individual substrate. Currently, PCB boards (PCBs) are manufactured by using a copper coated board which is coated with a photosensitive etch resist material. This is typically in the form of a so-called dry film resist, although liquid materials are also sometimes used. Although there are several approaches that can be used to form subsequent patterns and features, etc. a commonly used method requires the resist to be cured by exposing it to ultra violet light through a mask. A pattern is then formed in the resist by removing the material in the unexposed areas. This process is known as development. In PCB board applications, additional copper may then be plated on top of the thin copper coating as required. Once the copper has been plated, the resist is then removed entirely using a range of chemical stripping solutions. Next, the exposed copper is removed using a variety of etching solutions, which are typically very corrosive. This process, therefore, requires multiple steps to create a metallic pattern on a substrate and also involves many chemicals which are all removed. In addition, PCB manufacturing is carried out in tanks where the circuit board and counter-electrode are often placed at some distance from each other, which in some applications increases the energy requirements of the process and reduces the overall efficiency. This is partially due to the use of standard tank designs and efforts to incorporate electrolyte agitation schemes such as eductors and stirrers, which necessitate a large gap between the electrodes. Many of the electrolytes used in PCB fabrication are strongly acidic corrosive agents that have associated health, safety and environmental concerns. PCB manufacturing, therefore, remains an expensive, multistep process involving specialised equipment and infrastructure which generates copious waste and that consumes large amounts of energy, thereby raising operational costs. Due to increasing cost and sustainability issues, as well as growing social and environmental concerns, many companies using photolithography are keen to implement more efficient alternative approaches. One such alternative is to use a maskless approach known as Enface which obviates the need for individual photolithography stages.