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Space Saving with RC Circuit

Space Saving with RC Circuit

A space and money saving solution for reducing component count in photo-detector (PD) devices for optical communication systems

Our Integrated Resistor Capacitor (IRC™) chip provides a number of benefits to the device OEMs by reducing the number of components used in PD devices for optical-fiber communication. Because of the very large demand for PDs, this innovation offers OEMs a great opportunity to conserve resources while improving their productivity.

The Challenge:

High Demand in the Market: Need an integrated component solution for photodetector (PD) devices with lesser cost and a compact design.

Photodiode devices, like a Receiver Optical Sub-Assembly (ROSA), used to detect light transmitted through fiber optical cables are typically compact in design. The basic components inside are a light sensor (PD and header) an amplifier (TIA), capacitor(s), and a resistor. The capacitor and resistor are used to protect and enhance the sensitivity of the photodiode by reducing electromagnetic noise.

The photodetectors designs may vary, but the market demands each design be smaller and cheaper than the last. Once Tecdia understood the OEMs’ roadblocks we divided their challenges into categories based on the form and function of the components, the circuit connections, and the installation process.

The challenge we faced was to integrate a parallel plate capacitor with a thin film resistor in a small easily wire bondable configuration metallized on the same ceramic chip face. Also an open space had to remain on that face for mounting a photodiode chip while still leaving the chip small enough to fit in the center of the device. Changes in the wire bond connections were made to compensate for the relocation of components. The end product from this venture was the three in one IRC (Integrated Resistor + Capacitor) on a ceramic chip that can also serve as a submount for the photodiode as shown below.

The Solution:

Utilize Tecdia’s “Thin Film” expertise to develop an all-in-one design.cs__ssirc_contents_Link

Illustrated below are before and after circuit designs of a typical application. The circuit on the left without the IRC consists of six discrete components and four pin terminals linked by one or more wire bonds. On the right is a design that has the IRC mounted in the center and the photodiode mounted on the IRC. Thanks to our integrated thin film components the discrete components have been reduced from six to four, and the number of wire bonds from eight to six.
To achieve this new component we capitalized on Tecdia’s technical knowledge and experience in manufacturing single layer GBBL ceramic chip capacitors, thin-film chip resistors, and optical submounts. Tecdia is comprised of multiple business units that cover a wide variety of technologies and crafts, providing rich interdisciplinary resources for this task which is why we were able to develop this unique component.

IRC Design

The Result:

The design of the photodiode device has a simplified layout with open spaces. The production engineer has fewer components to install and connect. Inspection sees higher yields (reduced risk of electrical shorts from excess epoxy and installation errors). Purchasing and material departments have less stock to buy and manage. Marketing has a more robust product (fewer components and wire connections). Finally, the OEM has a lower cost and environmentally friendly product.

Client Information

【Client Industries】
Manufacturing of optical device & module manufacturing such as ROSAs, BOSAs, Optical Transceivers