TOKYO -- Oki Printed Circuits has developed a mass-production technology for printed circuit boards with a maximum board thickness of 3.5mm (30 layers) to support next-generation 1,000-pin fine-pitch LSIs.

The components, which have a pin pitch of 0.35mm, are expected to see use in various consumer devices such as smartphones. Mass production commenced this month on PCBs for socket boards used in LSI function testing devices.

As mobile devices such as smartphones grow smaller and more powerful, the LSIs inside them have also grown ever smaller, with pin pitch falling from 0.50 mm or 0.40 mm to 0.35 mm. Development has also begun of highly functional LSIs having more than 1,000 pins to achieve the performance needed to transmit large volumes of data at high speeds. Boards needed to test the functionality of such next-generation LSIs must support reduced pitch, better handle signals associated with the increased number of pins, and ensure a stable power supply and grounding for the increased number of signals. These requirements necessitate more layers, OKI says.

In response, OKI developed its new FiTT method, which is capable of forming through vias of ultrafine diameters (finished diameter 0.10mm) with a pitch of 0.35mm in substrates with a maximum board thickness of 3.5mm, which reportedly is not possible with existing build-up or through via methods.

The firm says the development was made possible by high-precision laminating technologies, which minimize layer-to-layer registration offsets to within 40µm, and high-precision drilling technologies, which use systems for adjusting via hole positions down to the micron level and optimize drill shape and drilling process steps. This technology ensures a stable power supply and grounding connections, even with large number of layers for through via configurations, thereby achieving the high signal quality required by the circuit boards used in LSI function testing devices.

OKI Printed Circuits plans to take an active approach to expanding its printed circuit board business to handle narrow-pitch multi-pin LSIs beyond the reach of previous methods. The company will target the market for LSI tester socket boards. OKI Printed Circuits is also working to develop next-generation printed circuit boards (with pitches of 0.30mm or less) as part of efforts to develop products to match customer requirements.

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