For photonic integrated circuits (PICs), packaging is still an issue. Applications using photonic technology are at the eve of a potential breakthrough in communications, medical and optical networking for data centers applications. However, low-cost / high-volume production is still hampered by complex and costly packaging technology. Finding an affordable solution to photonics packaging could be paramount. To quote Barwicz et al: “Cost is more than a commercial consideration. It can define the accessibility of a technology and, in turn, its societal impact.” (1).
As a result, much effort is put on research to find efficient and effective packaging technologies for PICs. Among others, solutions include "pluggable optics," “heterogeneous integration,” and a technology shift from "active to passive alignment". Another viable solution is to adapt and modify existing packaging solutions from the semiconductor industry towards photonics. An example of such an adaptation, is presented in this paper, which is the near-hermetic air-cavity plastic (ACP) packages produced by injection-molding of low moisture liquid crystal polymer (LCP) in the so-called "butterfly" layout. The traditional butterfly package is a hermetic metal package that is often used in photonic applications (2). The butterfly package layout is widely used in the photonics industry not only because of its hermeticity and good thermal conductivity, but also because there are few alternative packages solutions available. Unfortunately, this package is relatively expensive, especially considering that some of its characteristics, such as hermeticity, are not always necessary.
In 2005, RJR Technologies pioneered an air-cavity RF-power package using LCP injection molding technology (3) (4). For decades, the semiconductor industry used ceramic packages to provide the benefits of an air-cavity enclosure. RJR’s ACP package solution effectively replaced most ceramic packages in the RF Power market by providing customers with the same electrical and higher thermal performance at reduced costs and faster time-to market. This was not only true for this market, but also for any electronic application that requires the use of an air-cavity package. As such, this technology can also provide a cost down solution for photonics while maintaining good thermal conductivity and providing near-hermetic performance. On top of the lower cost price, these packages can also be produced in strip format, thereby allowing strip-level assembly processes, a potential further cost-down in current assembly process of photonic devices where production is essentially still "piece by piece."
References
1. T. Barwicz, T.W. Lichoulas, Y. Taira, Y. Martin, S.Takenobu, A. Janta-Polczynski, H. Numata, E,L. Kimbrell, J.W. Nah, B. Peng, D. Childers, R. Leidy, M. Khater, S. Kamlapurkar, E. Cyr, S. Engelmann, P. Fortier, N. Boyer, „Automated, high-throughput photonic packaging“, Optical Fiber Technology, Vol 44, Pages 24-35, (2018).
2. R. Uppal, „Optoelectronics and Photonics Assembly and Packaging Technology”, International Defense Security & Technology [Online]. Available: https://idstch.com/technology/photonics/optoelectronics-and-photonics-assembly-and-packagingtechnology/. [accessed: Feb 25th 2023].
3. D. Zyriek, W. Salhuana, R. .Bregante, “Solutions for Low Cost, Near Hermetic Air Cavity Packages”, IMAPS US Device Packaging Conference 2023, Fountain Hills, Arizona, March 1316, (2023).
4. J.W. Roman, R.J. Richard, “A Moisture Resistant Air Cavity Plastic Microwave Power Package Capable of Eutectic Die Attach” Proceedings of JEDEX Conference, San Jose, California, (2003).
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