Is Advanced Packaging the Next Large Leap for Mission-Critical Microelectronics?

Bringing the United States back to the forefront of creating the most powerful technologies on the planet starts with the tiniest element, the microchip. The U.S. is making substantial investments in commercial companies to onshore semiconductor supply chains, while simultaneously funding select defense contractors to make the mission-critical microelectronics needed to position our military as the best in the world. Northrop Grumman is one of them.

The U.S. government’s microelectronics needs have evolved significantly over the decades: from vacuum tubes in the 1960s to Gallium Arsenide (GaAs) and Silicon (Si) discrete components in the 1980s and 1990s, then to Silicon Germanium (SiGe) and Gallium Nitride (GaN) discrete components in the recent past. Now, we have entered the era of Advanced Packaging. This is the next microelectronics evolution to enhance and extend the performance of modern military and commercial systems, with power and performance shaping the industry for decades to come.

Fabrication and packaging of microchips onto advanced substrates is critical to the future of defense microelectronics. (Image: Northrop Grumman)

To understand the evolution of the industry, it’s important to look back at some pivotal moments in time. In 1969, the historic mission to put a man on the Moon succeeded, and microelectronics played a crucial role in capturing that iconic feat. Without advancements in microelectronics — specifically from technologies derived from Westinghouse and TRW, both heritage Northrop Grumman companies — this monumental achievement would not have been possible. This success earned Northrop Grumman an Emmy Award for the imagery and significantly influenced the future of microelectronics manufacturing. Westinghouse, a Mid-Atlantic area technology giant of its day, and TRW, an aerospace company out of Southern California in the 1950s-1990s played pivotal roles in many of the microelectronics technologies that are still being developed and modernized at what is now Northrop Grumman’s Microelectronics Center. Today, Northrop Grumman continues to innovate across microelectronics domains, including RF, imaging, optics, communications, and instrumentation.

Recognized for decades, Northrop Grumman has been at the forefront of semiconductor technology development, progressing from early cell phone chips and bulky circuit boards to designing and manufacturing the world’s fastest chip — the Terahertz chip — smaller than a grain of sand.

3D chip stacking is a critical technology for miniaturizing advanced defense microsystems. (Image: Northrop Grumman)

Speed is one thing, Size, Weight, and Power (SWaP) constraints are another. To stay ahead in the rapidly evolving technology landscape, one must not overlook a critical aspect of manufacturing — Advanced Packaging (AP). It’s an area Northrop Grumman began focused investments in just before the COVID-19 pandemic, knowing it would be a key component of the manufacturing process for future defense systems. AP supports the integration of diverse technologies into compact System-in-Package (SiP) designs and enables miniaturization critical for modern devices. Advanced interconnect innovations like Through-Silicon Vias (TSVs) and micro-bumping further boost efficiency allowing microelectronics to meet increasing demands for performance and functionality.

Wafer-Level Integration

The realm of defense microelectronics has many unique needs, including the frequency, power, and reliability at which these devices operate. Components are often asked to perform with higher functions and survive more harsh environments than what commercial companies typically produce or aim to offer. Defense microelectronics must operate across vast power and frequency ranges, with the nation’s security depending on each function. This requires a wide breadth of capability, and dedication to quality and reliability from inspection to lifetime test, utilized at each step of the AP process.

Further advances in packaging and chip-stacking technologies are now at the forefront of microelectronics innovation for engineers working to reduce U.S. defense systems’ size, weight, power, and cost (SWaP-C). These systems are lighter, faster, more efficient and therefore, more affordable, without sacrificing the goal of enhancing national security.

For decades, photolithography processes have driven the pursuit of increasing transistor densities on wafers at a staggering rate, known as Moore’s Law. As reducing node sizes becomes more costly, the adoption of AP is driving new progress in microelectronics systems, making them ‘More than Moore.’ AP enables greater technological functionality in a smaller final product, resulting in enhanced performance, increased miniaturization, and improved system reliability — significantly benefiting military users and contributing to the success of their missions.

Northrop Grumman has been deploying Advanced Packaging and chip integration technologies, such as the Diverse Accessible Heterogeneous Integration (DAHI) platform, to serve critical national needs. (Image: Northrop Grumman)

These critical design and manufacturing processes fit more capability into increasingly smaller and more dense form factors by assembling combinations of Known Good Die (KGD) from various semiconductors, fabs, and designs onto increasingly advanced substrates and directly bonding chips together in vertical (3D) stacks. A wide variety of functions can be integrated into a single, compact package that would have otherwise required multiple large component assemblies to achieve in legacy systems without AP.

AP technologies start with the ability to fabricate and test electrical interconnects from the chip to the outside world. These interconnects are formed by fabricating solder bumps copper pillars or solderless gold or copper bond pads onto the outer surface of the wafer. These interconnects are later bonded to other chips, interposers, or substrates to create the package.

The required size of these interconnects continues to decrease as system functional requirements increase the need for high signal and data transfer rates between each chip. Northrop Grumman’s MicroLine, located in Apopka, FL, offers flexible capabilities and various interconnect sizes and materials to meet the needs of analog, digital, mixed-signal, and other applications. This includes the ability to bump 300-mm wafers onshore with both lead and lead-free materials.

Extreme close-up of solder bumps on wafer. (Image: Northrop Grumman)

To ensure high yields and reliable microelectronics products, whole wafers are inspected using an Automated Optical Inspection (AOI) tool. This equipment is unique to the U.S. and a key differentiator for Northrop Grumman’s Microelectronics Center. This equipment screens for defective die, measuring 100 percent of interconnects for height, diameter, and coplanarity.

Northrop Grumman has extensive history in developing and deploying 2-dimensional, 2.5-dimensional, and 3-dimensional (2/2.5/3D) advanced assembly capabilities that excel in high-performance applications to meet defense and national security requirements, including assembly of multiple semiconductors using die-level and wafer-level integration processes.

Thermal Management

AP deployment also requires innovative thermal management solutions, which are essential for the reliable operation of multiple high-performance chips in smaller footprints. Efficient heat dissipation techniques help maintain optimal operating temperatures, preventing overheating, ensuring longevity, and allowing even higher performance levels to be extracted from the semiconductor die within the package. Defense companies are heavily invested in the successful implementation of these technologies as battlespace conditions can melt chips or entire microelectronics systems if not designed with the mission-critical features warfighters need.

A crucial aspect of Northrop Grumman’s Microelectronics Center is the onshore manufacturing capabilities that allow delivery of a secure end-to-end product. Northrop Grumman has three U.S. government-accredited trusted facilities, which means defense products directly impacting national security are manufactured with full confidence that all data, designs, and other critical information will remain secure.

These microelectronics designs, aimed at being perfected with AP processes are sought after by defense and commercial, alike. AP facilities are now open access suppliers for such services, while continuing to provide singular chips to customers. This is a revolutionary opportunity for commercial companies and defense contractors seeking specific microelectronics solutions for military applications.

Advanced Packaging, often the unsung hero of this technological progress, allows the integrating of diverse components into highly efficient, compact devices that meet the rigorous demands of modern defense systems and are pivotal to the success of the nation’s microelectronics renaissance. As Northrop Grumman continues to expand capabilities, it is driving forward a mission to develop cutting-edge technologies and create the end-to-end supply chain on U.S. soil. Through its focus on Advanced Packaging, Northrop Grumman ensures these innovations continue supporting and enhancing national security.

This article was written by Matt Hicks, Director of Foundries, Test and Advanced Packaging, Dave Shahin, Sr. Manager of Advanced Packaging, Sean Dunphy, Manager of Product Engineering and Production Control, and Lesley Cheema, Advanced Packaging Program Manager, all at Northrop Grumman (Apopka, FL). For more information, visit here .