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April 2014 • The PCB Magazine 67 based base materials contain the halogen fluo- rine, nobody is proposing to eliminate these base materials. The alleged problem with tetra- bromo bisphenol-A is the potential formation of dioxines during the incineration of base materi- al scrap. Alternative chemistries for tetrabromo bisphenol-A include phosphorus-based com- pounds, sometimes with added inorganic fillers. However, these phosphorus compounds are not universally accepted. Another approach consists of building inherent flame-retardency into the epoxy resin in the form of aromatic rings. Alternative Metallization Technologies There are a number of Z-axis metallization processes that are less wasteful than the tradi- tional plating processes. A traditional through- hole metallization process such as panel plate/ tent and etch deposits copper not only in the through-hole but also on the surface where it is not needed, consuming plating chemistry and generating an etching waste stream. Likewise, the pattern plate process requires extra steps for metal etch resist plating and etch resist strip- ping. In contrast, the ALIVH (any layer intersti- tial via hole) process uses no plating and etch- ing to metallize the vias but uses a copper paste that is only applied to the via. The B 2 it process is another such example: the metallization in the Z-axis to interconnect adjacent metal lay- ers consists of multiple step screen printing of a silver paste by which cone-shaped bumps are formed that poke through the dielectric during multilayer lamination and make contact with the next metal layer. PCB GREEN TECHNOLOGIES IN PCB FABRICATION continues karl dietz is president of karl dietz consulting, llc, offering consulting services and tutori- als in the field of circuit board & substrate fabrication technology. to view past columns or to reach dietz, click here. dietz may also be reached by phone at (001) 919-870-6230. The Impact of Miniaturization on Fab Processes by Real Time with...IPC aPEX EXPo 2014 editor andy shaughnessy caught up with sanmina's Brian nelson at ipc apex expo recently and discussed how fabrication pro- cesses are affected by advances in miniaturization. realtimewith.com CliCk To View vIdEo InTERvIEw

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