Small is Beautiful

Hybrid microelectronics can deliver maximum performance from miniaturised solutions in the most demanding environments – making them ideal for application on high-reliability aerospace and defence platforms, says Richard Smith, chief engineer at TT Electronics.

Hybrid microelectronics have evolved from simple component integration to highly sophisticated system-in-package solutions, driven by persistent demand for miniaturisation, higher performance, and enhanced functionality. For design engineers, these trends represent both challenges and opportunities. Moving beyond traditional component selection toward advanced materials science, heterogeneous integration, and innovative packaging techniques brings potential for optimisation, but it requires a depth of knowledge and understanding to translate these breakthroughs into practical solutions for mission-critical applications. This complexity can be particularly difficult to manage for higher-level system suppliers, where the electronics is just one part of the broader solution. 

So, let’s take a deeper dive into the trend toward hybrid microelectronics. Primarily, it is about achieving maximum performance from miniaturised solutions by eliminating the layers of unnecessary packaging required for die and other components to survive the surface-mount assembly process used to create traditional printed circuit boards. Instead, engineers can take a fully bespoke approach, working with bare semiconductor die and integrating passive components and ceramic substrates to create a highly customised application-specific package. This approach offers significant advantages in size, weight, and performance, while ensuring durability in high-reliability applications that demand exceptional environmental protection. Increasingly, design engineers operating in the defence and aerospace sectors are embracing hybrid microelectronics tailored to the exact requirements of harsh environments.

Overcoming hybrid design challenges

Hybrid microelectronics are mainly used in low to medium-volume applications where performance rather than price is the key consideration. Size, for example, might be the critical technical specification, reflecting a compact or unusual-shaped form factor into which the electronics must fit. Alternatively, weight might be the primary priority, especially in aircraft, spacecraft, or defence systems, where every gram matters because it improves fuel efficiency. Sometimes, engineers are trying to get the maximum power out of a small package, which introduces thermal challenges, making heat dissipation crucial. When performance is uppermost in the minds of design engineers, bespoke hybrid microelectronics really come into their own.

Increasingly, then, system suppliers in the aerospace and defence sector are looking to partner with companies that can help them develop the hybrid microelectronics they need. At the start of this relationship, technical teams from both sides will meet to scope out key criteria, including high-level performance requirements, application context, regulatory and standards frameworks, technology direction, and volume and lifecycle expectations. 

Once the requirements are understood, the detailed design activity will start. Depending on the customer's preferred approach, the relationship between the two organisations may be close, with the supplier working as an extension of the customer's in-house design team. Alternatively, it might be hands-off, with the supplier working in a more traditional subcontracting approach.  Whatever the approach, the supplier will complete detailed design, often through multiple iterations of development and validation, before providing the customer with a fully qualified and compliant solution. This is where the expertise of the electronics supplier ensures reliability is designed in from the outset, then verified with extensive testing, which would typically include: electrical and electronic testing under operational loads, and extensive temperature cycling and high-G centrifuge testing to simulate the high mechanical stresses that might be encountered in launch or flight. Meanwhile, hermetic seal integrity checks can be performed to ensure no moisture is present within the sealed package, which could lead to degradation over a long lifespan. For critical applications such as aerospace and defence, qualification testing includes the destructive sampling of many components: several parts from every batch produced may be destroyed to prove the reliability of the remaining units. In short, no stone is left unturned in ensuring the high-reliability performance of the microelectronics.

Another critical responsibility of the electronics supplier is future-proofing – providing insight into how hybrid microelectronics might evolve over time. This requires having a firm grasp on a number of new technologies and trends that have come to the fore. While aerospace and defence are relatively conservative markets with long-duration platforms, those system suppliers that champion innovation are always open to new approaches that can improve size, weight, and power performance, provided they are proven. Historically, many of these advances have been developed in other markets, such as automotive and telecommunications, and are then evaluated and refined for high reliability in harsh environments.

Hybrid microelectronics – where next?

Now, let’s have a look at some of these critical developments to understand how hybrid microelectronics might develop in the near to medium-term. Advanced materials offer many opportunities, and engineers are exploring different ceramic substrates to improve thermal and mechanical properties.

Power density and thermal management are also areas of development, with an increasing emphasis on higher power density in smaller footprints. This requirement could lead to advanced cooling structures and heat-dissipation techniques, such as vapor chambers. Meanwhile, engineers are increasingly focusing on CTE matching - the process of selecting materials with similar thermal expansion properties - to prevent mechanical stress and cracking during extreme temperature fluctuations, ensuring long-term reliability in high-reliability aerospace and defence environments. Finally, there is a continued desire for greater integration of hybrid microelectronics to combine multiple functions, such as analog, digital, RF, and power electronics, into a single package for optimised high-reliability performance.

These research and development efforts are likely to lead to hybrid microelectronics finding increasing application across multiple sectors. Within aerospace and defence, deterrence and protection systems require high power density at high altitudes, while the electrification of aircraft means avionics and flight control systems will require more lightweight electronics. Satellite power and communications modules also demand ultra-reliable, radiation-tolerant electronics for long-duration missions – and these capabilities can be built into hybrid microelectronics.

Delivering excellence for all applications

Whatever the requirement or application, the key to success comes with partnering with an electronics solutions specialist that can oversee the design and manufacture of bespoke, high-reliability technologies for the most extreme environments.

TT Electronics is a global provider of design-led, advanced electronics technologies for performance-critical applications in specialised markets and can manage the hybrid microelectronics process from start to finish, overseeing development, prototyping, testing, and production as required. Services include turnkey circuit layout and packaging design based on customers’ electrical schematics, and performance and environmental requirements. TT Electronics can also supply design and manufacture in compliance with MIL-PRF-38534 Class H and engineering and programme management support. 

A broad range of packaging and technologies includes hermetic and non-hermetic packaging, multi-layer thick-film printing on ceramic (AIO and AIN), and high- and low-temperature co-fired ceramic (HTCC and LTCC). Other options include thin film, surface mount, bare die and wire bonding (or mixed SMT), and chip and wire.

This portfolio of technologies and services, which provides a genuine whole lifecycle approach, has been proven to deliver multiple benefits to clients over the years – from adding value at the front end to product optimisation, accelerating speed to market, and longer-term reliability. 

Modern avionics systems rely on compact, high-reliability electronics capable of integrating multiple mission-critical functions within constrained aerospace platforms.