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Method for hybrid printed circuit boards with BCB waveguides for board-to-board optical and electrical interconnections

IP.com Disclosure Number: IPCOM000010675D
Publication Date: 2003-Jan-08
Document File: 3 page(s) / 59K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for hybrid printed circuit boards with benzocyclobutene (BCB) waveguides for board-to-board optical and electrical interconnections. Benefits include improved performance, improved ease of manufacturing, and improved support for future technology.

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Method for hybrid printed circuit boards with BCB waveguides for board-to-board optical and electrical interconnections

Disclosed is a method for hybrid printed circuit boards with benzocyclobutene (BCB) waveguides for board-to-board optical and electrical interconnections. Benefits include improved performance, improved ease of manufacturing, and improved support for future technology.

Background

        � � � � � The most common polymer waveguide is based on acrylics. They are thermoplastic materials with a glass transition temperature (Tg) of approximately 100°C. When the processing temperature is higher than the Tg, the acrylic materials become liquid and start to flow. Therefore, the acrylics waveguides usually deform and cause significant optical signal loss due to optical property degradation after solder reflowing. Acrylics also absorb moisture (moisture absorption 2-3% weight), which degrades the optical property of the waveguide. In addition, acrylics have a high curing shrinkage. As a result, acrylics-based waveguides are not suitable for PCB applications.

        � � � � � A requirement exists for a reliable optical/electrical hybrid printed circuit board (PCB) for board-level optical and electrical interconnections. PCBs with waveguides for optical interconnections are in the development stage. No conventional solution solves the optical property degradation due to the deformation of the waveguide after solder reflowing.

General description

� � � � � The disclosed method is a hybrid printed circuit board (PCB) integrated with BCB waveguide arrays for board-to-board optical and electrical interconnections. These waveguides transmit optical signals from the optical source, such as a vertical cavity surface emitting laser (VCSEL), on one package to an optical receiver (photodetector) on another package. Due to the low optical absorbance and the extremely stable optical property of BCB waveguides, the disclosed PCB boards provide good optical transmission for future high-speed board-level optical and electrical interconnections.

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved performance due to low optical loss because of low shrinkage after curing

•        � � � � Improved performance due to minimal degradation of optical properties, especially at high temperatures

•        � � � � Improved performance due to BCB’s low dielectric constant and dissipation factor

•        � � � � Improved ease of manufacturing due to the ease of fabricating BCB waveguides into BCB PCBs

•        � � � � Improved support for future technology due to high compatibility with future high-speed BCB-based PCBs

Detailed description

� � � � � � � � � � � The disclosed me...