material gains
As Today’s PCBs Become Increasingly Advanced, the Original Principles Remain So Right
Could optical interconnects and graphene change the view?

Many things, including the electronics industry, have changed beyond recognition over the past 40 years or so. It’s all the more incredible how little the PCB has changed in its makeup since its inception, and thus fitting that PCD&F named its Hall of Fame after the printed circuit inventor, Paul Eisler. His radio, the first commercial product to contain a PCB, is on display at the Science Museum in London. It was made in 1945, containing a simple and straightforward PCB designed to implement point-to-point connections. Things have become more sophisticated, of course, as human nature provides both the push from engineers’ curiosity and the pull of market demands.

The main goal of early PCBs was to replace traditional soldered wire connections. This helped streamline assembly, reduce wiring errors, and increase reliability. The PCB’s arrival also facilitated automation of electronics product assembly. In early PCBs, the role of the substrate was barely considered, except to separate the conductors. Now, the substrate properties are the most important aspect where high signal frequencies are present. In other ways, it’s surprising how little has changed, as the constituent parts remain the same: a composite core, comprising a reinforcement and a resin binder, and copper conductors.

Of course, much has been done to boost and optimize the properties of the entire assembly. With efficient thermal transfer a key demand in high-power circuits, unreinforced materials have come to the fore that remove the effects of glass as a thermal insulator.

As far as conductive layers are concerned, alternatives to copper could offer improvements such as greater signal integrity and reduced attenuation, especially when handling high data rates. Graphene offers interesting properties, including excellent electrical conductivity, as well as high strength and flexibility in very thin films down to one atom thick. Of course, graphene is being positioned for many applications, including supercapacitors for energy storage, high-efficiency lighting, and even in higher-performing replacements for silicon-based ICs. On the other hand, board-level optical interconnects using miniature photonic modules can deliver freedom from the loss mechanisms of copper, while also increasing the bandwidth per interconnect. These gains could deliver greater performance, with a significant reduction in PCB size and thickness, driving miniaturization, as well as reducing material consumption.

While adapting to capture the benefits of alternative technologies such as graphene and photonics, the PCB will almost certainly remain the primary substrate and interconnect medium for electronics for many years. It is very difficult to improve the underlying concept. PCBs produced today deliver tremendous performance and functionality, with only a few dollars’ impact on the BoM for a device like a smartphone.

Predictability and repeatability are further strong points. Material suppliers can provide ECAD vendors with accurate data about material properties that let product designers know exactly how the choice of PCB material will affect the operation of the circuit and engineer the composition and dimensions to achieve the performance needed. This is as true for specialty high-performance products as for general-purpose materials such as traditional FR-4 variants.

It’s been said the PCB is the last aspect of a project to be designed and the first to be needed. Its importance is often overlooked. But as we push performance limits, the PCB is a key component and an important factor in determining whether the end-product will meet those requirements. Right now, supply and costing challenges must also be considered.

We can expect the global supply problems to become less severe as producers return to normal work patterns. This is of little comfort to OEMs and EMS businesses seeking materials and assemblies to meet immediate demands. It’s one of the factors driving calls for more PCB production to be done in the US or Europe. This is not a short-term fix but rather a vision to protect industries against trade and shipping problems in the future.

Currently, Asia is by far the dominant region in PCB manufacturing. It produces over 90% of the world’s PCBs, while manufacturing in the US and Europe accounts for a little over 6%. I’ve already drawn attention to the value of the supply infrastructure and subject expertise in areas such as materials technologies needed to sustain PCB manufacturing, wherever it is done. Driving any significant shift in volume demands these types of facilities also be present in the new location. It will not happen quickly, or easily.

There are some successful examples. Clusters of low-loss and medical-focused PCB manufacturing in Switzerland, for instance, show local manufacturing can be highly effective for specialty items in small volumes. However, supply and pricing issues also would affect local manufacturing, so it’s difficult to make a case for moving production of high-volume, price-sensitive boards to the West when they are being made so economically to the high standards we have come to expect.

Ongoing improvements are certain to happen, but it’s hard to see how the PCB that we know and recognize will ever be superseded in its role.

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