Ultra thin PCB

Seiko Epson has succeeded in leveraging its proprietary inkjet technology to develop what the company believes is the world’s first ultra-thin 20-layer circuit board.

Multilayer circuit boards are normally produced by using a photolithography process to pattern a copper foil bonded to a base board. However, the industry has struggled to produce thin, lightweight, high-density multilayer circuit boards cheaply because the traditional process requires thick copper layers, the creation of a different photomask for each layer, a complex step for forming through-holes to electrically connect different layers and a large volume of photoresist, developer, etchants, stripping agents and other chemicals.

Against this backdrop, Epson received a grant from the New Energy and Industrial Technology Development Organization (NEDO), an independent Japanese governmental agency, to develop technology for fabricating circuit boards using inkjet technology.

The goal of the three-year project, which was launched in June 2003, is two-fold: to dramatically reduce the energy consumed in the manufacture of circuit boards and fabricate small, lightweight, high-performance circuit boards.

Epson recently succeeded in producing a 20-layer circuit board sample by using an inkjet system to alternately “draw” patterns and form layers on the board using two types of ink: a conductive ink containing a dispersion of silver micro-particles measuring from several nanometres to several tens of nanometres in diameter, and a newly developed insulator ink.

An inkjet-based manufacturing process has many advantages over a traditional photolithography process.

First off, it uses a far lower volume of materials, since patterns are formed only in areas where they are needed, not over the entire substrate. And it is a dry process, so virtually no liquid waste is created. It also involves fewer steps, consumes comparatively little energy and is readily adapted to high mix, low volume production, since no masks are used. What is more, it is well suited to multilayer structures, since interlayers can also be patterned directly onto the board.

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