What are the opportunities and challenges that leading PCB manufacturers should be ready for, with the arrival of 5G? To find that out, Rahul Chopra of the EFY Group spoke to Erich Schlaffer, project leader research & development, AT&S, Austria. The excerpts follow…
EB: Is there a need to relook at manufacturing processes and technologies when making 5G (mobile communication) products?
PCB manufacturers will now need to distinguish between sub-6GHz and the 5G mmWave (above 28GHz) range. When we look at the sub-6GHz range, there is no big impact on the PCB manufacturing process. But when we look at frequencies above 28GHz, the impact of the losses generated by the PCB and the signal integrity have to be addressed by new materials and processes. PCB manufacturers will need to put in a lot of effort to reduce signal losses and interference, e.g., by optimising the dielectric layer with respect to the material (low dielectric constant) or thickness, the material transitions (interfaces), or also the copper roughness.
With copper, the major challenge is that while smoother copper offers advantages for high frequency (HF) applications, somewhat greater roughness improves the adhesion of the PCB traces on the basic material. For this reason, AT&S conducted an extensive study of commercially available copper foils for HF applications. The geometry (profile) of the tracks also affects signal delays at higher frequencies and has to be optimised. In addition, we investigated the effects of different metals (copper, gold and nickel) on the skin effect in the GHz range, and are developing new surface materials accordingly to get optimised results.
EB: What are the problems that manufacturers or OEMs will face if they do not adopt new manufacturing processes?
As explained, the established processes and materials will be limited to fulfilling the needs of the high frequencies related to the 5G standard. So there must be a technology and paradigm change on the side of the component vendors and PCB manufacturers.
EB: Will there be a requirement to rethink the ‘design for manufacturing’ principles too? If yes, can you share some that will be affected a lot?
Yes, we believe there will a major impact on design models! The new mobile communication standard needs drastic footprint reduction. Plus, low power consumption, higher diversification and more complexity will be demanded by 5G applications. The design of the RF antenna and the digital logic can´t be connected by cables anymore.
So, new, highly integrated connection technologies will be needed. At the end, all-in-one packages and modular solutions will be required. For 5G applications, a hybrid PCB structure combining high-speed layers (RF-optimised) and standard layers may offer a performance and cost optimised solution.
EB: What are the changes required in manufacturing processes for the 5G wave?
The structuring related processes need a new ‘mindset’. For the higher frequencies, one of the key priorities is to avoid roughness of the copper layers. In addition, simulation skills need to be considered, to support design for manufacturing.
EB: Will there be a need to reskill (train) the manufacturing team too?
Of course, new processes and the handling of new materials need skilled operators. Data preparation, increased simulation and measurement tasks, as well as the handling of the new sensitive production steps, will need well trained manufacturing teams.
EB: Will there be a need to upgrade or buy new types of manufacturing equipment too?
Yes, to both those options – we need to upgrade existing machines to fulfill the increasing RF requirements. In addition, new processes, simulation and measurement equipment are needed to close the gap between a digital logic based PCB and a high speed
EB: What are the kinds of industries in which you expect to see the highest requirement for 5G high-speed PCBs?
The 5G market will provide significant growth opportunities over the next few years –spread across infrastructure, devices and services. The 5G enabled digitalisation revenues will show growth rates upwards of 20 per cent until 2026, and will cover markets like mobile communication, automotive, retail, media, agriculture, public transport, financial services, etc. Both infrastructure and the end user devices will need powerful PCBs.