Pushing the Limits

Adaptability in all aspects is the PCB industry’s greatest strength.

“Change is inevitable – except from a vending machine.” – Robert C. Gallagher

It’s an amusing quip (although perhaps increasingly incongruous given the rapid adoption of contactless payments) that lets me comment on some of the transformations we have experienced in the PCB industry over recent years. Some challenges, such as thermal management, had receded for a time but are now back and more urgent than ever. Others, like the constant demand to support faster and faster signal speeds, demand that we continue to extend the limits of performance from the materials and techniques at our disposal.

The PCB’s role has become hugely more significant and influential as electronic systems have gotten more complex, more performance hungry, and more mission critical. It has extended from providing basic mechanical support and connectivity to becoming a comprehensively engineered part of the system.

The electronics industry of today is vastly different from the way things were as recently as the 1980s. Thermal management was a great challenge, largely due to the inefficiency of circuits such as linear power converters and power amplifiers. The adoption of much more efficient switched techniques, as well as exponentially smaller chip fabrication processes, solved that challenge for a while.

But thermal management is back on the agenda today, particularly in lighting and power conversion. With the adoption of solid-state lighting in buildings, outdoors and automotive applications, controlling the LED die temperature is essential when engineering light engines to ensure consistent chromaticity and the desired reliability. In power conversion, while efficiency continues to increase courtesy of new topologies and component technologies, our relentless desire to make all things smarter and more connected, wherever we live, work and travel, is raising the overall demand for electrical energy and power. But the overall size of the system is important too, to meet legacy form factors in markets such as residential lighting and to satisfy user demands for the smallest, slimmest product outline.

All this has moved designers to rely increasingly on technologies such as insulated metal substrates (IMS) as an elegant solution that can be included in designs from the beginning and not added as an afterthought – as is so often the case with a heat sink. IMS is a relatively new innovation in the PCB world and manufacturers’ product ranges have quickly become diverse and differentiated to help designers find the right balance of parameters such as thermal performance, cost, size, weight and reliability for their applications.

On the other hand, the perennial demand for increased high-speed signal capability continues to challenge board designers. The PCB industry has responded with advanced, low-loss substrate materials and innovations such as ultra-thin copper foils that minimize skin effects. The critical point to consider here is, perhaps, not so much the physics of skin effect, but the processes that must be developed to produce such ultra-thin materials with consistent parameters and at affordable cost.

More challenges come from the general trend toward higher voltages in key applications such as electric vehicles and the conversion, distribution and storage of energy from renewable sources. The push toward higher system voltages enables lower I2R losses and thinner conductors. However, as voltages used push beyond 600V, there is increased demand for substrate materials that provide a high comparative tracking index (CTI > 600V) to maintain electrical insulation in environments of electrical stress, humidity and contamination.

Also to consider is the adoption of wide-bandgap power semiconductor technologies like gallium nitride (GaN) and silicon carbide (SiC). SiC, in particular, can withstand higher die temperature – typically up to 200°C – and operate from higher rail voltages than their silicon predecessors, and so demands improved PCB properties to ensure the best system performance.

In addition, the smart revolution is driving complex electronic systems, such as industrial controls, vehicle trackers, smart meters and power systems, into harsher environments that contain natural humidity. Accordingly, conductive anodic filament (CAF) formation between conductors has become a major concern that has drawn response from the PCB industry. Closely spaced PCB interconnects and other design parameters, substrate choice and process are all factors that can promote CAF failure.

Revolutions in the PCB industry today are few, although evolution is continuous. While the underlying recipe is mainly the same today as it has always been, combining glass weave, copper foil and epoxy resin, substrate performance has changed beyond recognition. Material chemistries continue to advance, offering improved properties, and new processes such as 3-D printing are absorbed.

As well as being adaptable from an engineering perspective, the industry has shown adaptability and resilience in the supply chain. Market demands have led to China becoming the world’s largest PCB manufacturing nation. Now, geopolitical changes and new cost pressures are reshaping the landscape again as material production and board manufacturing moves toward southeast Asia and Thailand and Vietnam in particular. It’s reckoned that about one-third of production could migrate into this region in the coming years.

Change is inevitable and growth is prolific. The global PCB market has already grown to exceed $80 billion, through its ability to adapt and meet customers’ changing needs. Endowed with that flexibility, it’s expected to rise above $120 billion in the next few years.

Alun Morgan is technology ambassador at Ventec International Group (ventec-group.com); alun.morgan@ventec-europe.com.