Since 2015, FlexTech has funded three projects with ITN Energy Systems, based in Littleton, CO. 

The projects all draw on a unique concept of using thin, flexible ceramic sheets as both a substrate for functional devices and as an integral part of the hermetic packaging to support paper-thin FHE products. 

Each program was increasingly sophisticated, enabling a larger variety of functions to be integrated into a common package. Independent functions such as energy storage, energy harvesting, or printed microelectronic circuits are deposited on their own ceramic substrate and the layers vertically stacked and interconnected into a monolithic structure that combines several functions in the smallest possible package volume.

The ITN projects provide excellent examples of the power of collaborative research and development to help de-risk investments in next-generation electronics. All the projects were conducted with technical contributions from small and large businesses as well as university partners. The programs were funded by the U.S. Army Research Laboratories (ARL), directed by industry leaders and managed by SEMI FlexTech with the focus on utilizing the advantages of flexible hybrid and printed electronics (FHE) to create lighter-weight, lower-power, more conformable electronics than available commercially today. Markets ready to take advantage of FHE developments include healthcare, aerospace, mobility, consumer electronics, industrial electronics. 

ITN was founded in 1995 to focus on researching and developing technologies related to aerospace, energy and the environment for defense and commercial marketplaces. Its business model employs collaborative R&D projects to explore, develop and validate promising next-generation clean energy technologies with an emphasis on tackling the manufacturing challenges that enable low-cost, high-volume production of thin-film devices on flexible substrates. Those technologies that meet the technical and business requirements of the market are commercialized via focused, spin-out companies with five such spin-outs formed so far. The work on ultra-thin batteries needed by the SEMI FlexTech community readily slid into their portfolio of projects. 

Project 1 – a New Solid-State Lithium Battery

The first project kicked off in 2016, with ENrG, and successfully supported the development and validation of novel Solid-State Lithium Battery (SSLB) products with total packaged thickness ranging from 50-250 microns. The SSLB proved to have substantial advantages in form factor and performance when compared with both commercial-off-the-shelf batteries and emerging technologies. For example, the SSLB provided more than double the operating time in a substantially smaller package in powering an audio device supplied by SEMI FlexTech partner companies. 

By avoiding the use of liquid electrolytes, the ITN SSLB also eliminates flammability issues while still allowing the benefits of lithium-based battery chemistry. 

The SSLB boasted many attributes attractive to the FlexTech community, including: 

• Ultra-thin form factor, i.e. <250 microns thick, mAh class packaged batteries;
• High volumetric energy density, i.e. baseline products with ~500 Wh/l and a roadmap to >1,000Wh/l;
• The ability to support high current pulsing, i.e. current pulses at 4-10C rates, in support of demanding FHE duty cycles;
• High-temperature compatibility with solder reflow and other FHE integration schemes;
• Rechargeability with high capacity retention at >1,000 cycles

This new SSLB has formed the foundation of subsequent projects and commercialization efforts. 

Project 2 – Adding Energy Harvesting Based Recharging Capability 

The second SEMI FlexTech-funded project proposed a novel self-recharging battery with the addition of Lucintech’s cadmium telluride (CdTe) photovoltaics (PV), which was also deposited on thin yttria-stabilized zirconia (YSZ) substrates. Because the CdTe supports a superstrate configuration, the SSLB can function as the back sheet for the PV package, thereby dramatically decreasing overall package thickness. The resulting flexible integrated power pack provided up to 0.25 Wh of energy storage and ~0.2 W of PV generating capacity in a total package of fewer than 250 microns. 

As part of that effort, the ITN Team identified an effective power-management circuit that was ultimately compatible with die thinning and form factors very attractive to FHE. Consequently, the PV and SSLB were interconnected into a common power bus that enabled FHE to be operated with either the PV, SSLB or some combination of the two. 

ITN is seeing great interest in this product and both developing a version with substantially higher capacities than the project entertained for a UAV platform while ramping to low volume with support from NextFlex, a member of the Manufacturing USA network, and formed in 2015 through a cooperative agreement between the U.S. Department of Defense (DoD) and FlexTech Alliance.
 

Figure 1 Monolithic integration of function layers atop of SSLB for high-performance microelectronics device

Project 3 – Integration with Processing and Sensor Systems

The third FlexTech-funded project builds further on that foundation. In this project, the ITN Team is maturing the technologies to create a battery with an integrated processing and sensor system, nicknamed BiPASS. In addition to SSLB layers, the BiPASS package integrates printed circuits on YSZ employing high-performance, silicon-based bare die micro-electronics and/or thin-film sensors into the common packaging.  

The initial demonstration integrates a commercial lithium battery charge control circuit within the SSLB packaging to create a monolithically integrated power module. There have also been promising developments of the University of Rhode Island’s metal oxide (MOx)-based thin film gas sensors that have dramatically increased sensitivity when deposited on thin YSZ. The resultant sensor achieves ppb detection of trace explosives gases that can be powered by SSLB.  

Along the way, ITN’s partners Molex and SunRay Scientific matured several aspects of FHE circuit printing and integration on both PET and YSZ, including new materials and processes for conductive traces, and bare die attachment with fine features. The project is in its final stages and the ITN Team now has a promising roadmap to integrate power, microelectronics, and thin-film sensors/sensor systems into a single paper-thin package.
 

Figure 2 Mockup of the Charge control circuit on SSLB

Commercial Scale-Up Strategy

Since the initial demonstrations were completed, ITN has been actively maturing a commercial scale-up strategy based on significant market-pull and interest from several companies. A new venture to commercialize this next generation SSLB is in process. As part of those discussions, ITN is in active discussions with potential strategic partners to support the transition to high-volume production to access additional markets, many of which are cost-sensitive and need a higher degree of production maturity. 

In the meantime, ITN’s limited volume SSLB production line is already supporting medical device customers. In addition, a baseline SSLB (~2.5 mAh capacity) has been developed and tested in several new applications, including wearables, sensors and smart labels.

“Based on the acceptance of these projects in the market, I believe all three projects have provided significant value to the SEMI FlexTech community,” said Brian Berland, chief technology officer at ITN. “In addition, the connections and visibility we have gained within the industry by partnering with SEMI FlexTech have been invaluable. We are excited to continue this journey with new and additional projects. In the meantime, we are hopeful that our ongoing discussions with investment partners will support our commercializing of these components.”