Improved Inner Layer Etching by Simultaneous Cupric Regeneration Copper Recovery System

摘要

It is not the purpose of this paper to demonstrate the effects that a tightly controlled etchant can have on the etched panel, it has long been established that tighter control limits are a major factor towards improving etch quality. However the purpose of this paper is to present an alternative method of controlling Cupric Chloride compared to conventional chemical dosing systems and the benefits it provides the board fabricator.For those who are unfamiliar with the use of Cupric it is most commonly used for etching copper frominner layer circuitry.While copper is initially required to activate the etchant, as the copper content increases cuprous ions areformed and the etchant becomes less active. If allowed to increase too high the etchant will no longerremove the copper. A simple illustration to describe what happens is the use of sugar in a hot beverage. Theliquid is able to dissolve sugar but if you are a sweet tooth and too much sugar is added the sugar will notfully dissolve.You can either add more liquid or stop adding sugar; either way there is a saturation level that cannot beovercome.The Cupric has a relatively wide operating window and will produce good quality with undercut withinacceptable limits. Where the product is not complex or fine line and undercut control is less crucial theprocess is often run with manual testing and dosing and this may be perfectly acceptable.