Graphite-based Direct Metallization for Fabrication of Complex Interconnect Designs

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Introduction

The technology trends are unmistakable, such as the need to move into higher functionality while reducing footprint of the PWB substrate. In turn, this triggers circuit designs with smaller vias, blind, buried and stacked vias, as well as any-layer technology. In addition, there is a call-out for more flexible and rigid-flexible printed circuit boards. Complicating matters for the fabricator is the proliferation of material sets designed to support the low-loss, high-frequency market segment. With all of these changes, along with heightened emphasis on end-product reliability and productivity, metallization performance is under the highest scrutiny. 

Direct Metallization

Direct metallization of boards is a predominant process in flex circuit and microvia manufacture. This conveyorized process is fast and efficient. However, in North America, direct metallization is not as common as in overseas marketplaces, most likely reflecting the higher percentage of flex and microvia in the production mix. Regardless, direct metallization processes (most) offer lower consumption of resources over conventional electroless copper. This includes reduced rinse water and waste treatment concerns, lower power consumption as well as fewer chemical processes to maintain. For most direct metallization systems including graphite based processes, the equipment footprint is quite small when compared to a conventional electroless copper line of equal productivity. This is indeed an advantage with respect to capex utilization and return on assets.

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Editor's Note: This article originally appeared in the May 2014 issue of The PCB Magazine.

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