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For Packaged PICs, It’s Always About The Bond

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Silicon photonic (SiP) devices and photonic integrated circuits (PICs) are revolutionizing telecom/datacom markets. The growing capabilities of PICs have also spawned new approaches to advanced computing and myriad new market opportunities that legacy technologies cannot address. PIC Magazine spoke with the experts at Palomar Technologies to learn how die bonding continues to evolve and play a central role in SiP and PIC manufacturing.

The universality of some semiconductor processes points to their essential nature across technological platforms. Even as device form factors, lithographic innovations and defect management techniques come and go, there remain some steps that are always needed including the requirement to place finished die inside a receptacle that will protect it and enable its functionality.

While semiconductor manufacturing across technologies is considered the most complex of any industry, the potential for ICs to transform every major aspect of the human experience drove innovation like little else in the last 50 years. Today's devices are quite literally orders of magnitude better than previous generations; even as per unit costs shrank, performance has soared. PIC and SiP devices are now entering the growth ramp that microelectronic devices faced decades ago. Like their microelectronic counterparts, PICs today face growing pains to automate and address unique testing requirements.

Much as we have seen within silicon logic and memory device manufacturing, PIC producers are keenly aware of the need to finely tune process steps and material formulations to aid in defect elimination and quality control. The test and measurement sector of PIC and SiP manufacturing has also stepped up with ways to automate and improve product quality, reliability and repeatability. These advances help reassure end users than a PIC device can be as reliable as any commercial microelectronic IC.



Die bonding is a prime example of how a technology that has been a part of semiconductor production predating automation has continued to evolve and bring value to complex systems including PIC manufacturing. In a recent conversation with Palomar Technologies' Kyle Schaefer, product marketing manager, PIC Magazine technical editor Mark Andrews spoke about ways that die bonding has evolved, and how advances in the field can contribute to balancing the need for high throughput with process control. PICs of all types are traversing the sometimes perilous path between R&D, low rate production and high volume manufacturing.

Because PICs and SiP devices are still maturing technologies, many manufacturers are also relatively new, seeking efficient means to transition from R&D or proof of concept into production. Given the different developmental stages that PIC manufacturers find themselves, almost all need an economical means to transition from one stage to another. Having process tools that work in R&D as well as in production is an astute investment strategy, a fact that Schaefer says characterizes most Palomar Technologies customers.

One such customer is Bay Photonics that operates out of the Epic Centre, a business incubator serving the counties of Devon and Somerset in South West England, UK. The Epic Centre is part of the Torbay Development Agency that encourages and fosters new business ventures and manufacturing within the region. While not all companies operating out of the Epic Centre are developing photonic devices, many are, and according to Epic Centre Director Wayne Loschi, purchasing the Palomar Technologies 3880 Die Bonder was a decision made after 13 months of various tenant companies using the bonder for many wide-ranging requirements. The purchase was a ‘natural' decision after administrators saw how many companies were utilizing the tool at many different levels of product development.

Schaefer said one Bay Photonics staffer who truly put the bonder through its paces was John Coombes, senior process & development engineer. Coombes' company moved into the Epic Centre to further develop their capabilities as a PIC assembly and packaging house. The company's objective is to reduce their customer's investment in the direct costs of packaging and assembly for proof of concept devices, prototypes, pre-production devices and production PICs.

“With Bay Photonics recent move to Epic we have challenged the Palomar 3880 on-site here with a range of devices requiring exploitation of its multiple process capabilities, from epoxy dispense to daubing of glass paste and attachment of multiple piece parts to create a photonic subassembly. Bay Photonics - working with Palomar on the Palomar 3880 Die Bonder - has shown that it is a great working platform with good flexibility for handling innovative Photonics enquiries,” Coombes said.

“It has allowed Bay to present bumped PICs and place them with good accuracy onto a tile with specific pad locations and attach with thermosonic and eutectic attachment methods using sinter materials to investigate potential methods and materials.”

“The die bonder consistently demonstrated its powerful programming, high level of tooling process control and intelligent pattern recognition capability from dispensing to picking and placing of die and SMD components though to accurate offset placement of glass blocks attached using the Palomar controlled eutectic nest in a specific position. Furthermore, the flexibility offered with its processing capabilities and tooling array has given Bay confidence in the machine's capabilities; it offers a great platform for innovation,” Coombes concluded.