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Fresh PCB Concepts: Designing a PCB for Telecom Applications

We receive many questions about design guidelines based on the end-user application of PCBs. In this column, we will discuss PCBs for telecommunication applications. How do you design a telecom PCB? How are PCBs for telecom manufactured? What are the material considerations for a telecom PCB? We will also address what is needed for these products to work properly, and how manufacturing a PCB with the correct design guidelines will aid in achieving the desired final application. Here are a few key factors to consider. We also recommend involving your PCB supplier at the time of design to help ensure manufacturability at the lowest possible cost.

Design Considerations

First, let’s discuss the different design considerations for telecom applications based on the environment in which they will be used. Typical uses for telecom applications are indoor equipment, outdoor equipment, and terminal equipment. Each of these uses brings its own set of challenges, which should be considered from design through manufacturing. Table 1 shows some important design considerations.

Table 1: Design considerations.

Material Considerations

Choosing the correct material significantly affects the performance of the product’s required parameters. Here are a few things to consider when selecting materials:

• High-speed (SFP-CN 10G, DDR3 1600MT/s, XGMI 3.125G) ± 48V and 10A current
• Max rate is 10G in the case: Tg 170 and low loss are acceptable
  • This mainly considers the length of the trace of the highest speed signal
  • If the length of the trace ≤ 152 mm, then use these materials: S1000-2, S7038, and TU-872SLK
  • If the length of the trace ≥ 152 mm, then use these materials: FR408HR and Megtron-4/M
  • Thermal reliability, low-loss

It’s necessary to consider the layer counts and whether the material can support multiple lamination processes. Table 2 is a good resource to aid in material selection.

Table 2: Material selection.

With multiple challenging operations—such as back drill of different depths, press-fit technology, and deep cavity milling—it is crucial that the factories used have strong process accuracy and management capabilities. These are just some items to consider. We also recommend having deep discussion with your PCB supplier from the concept stage to ensure excellence and manufacturability are designed into the project.

Overall, when looking at PCBs for a telecom application, it is important to look at where that application will be used (indoor/outdoor/terminal equipment) and the types of materials that will give you the high-performance results required. The design should have considerations for signal integrity, thermal dissipation, and high power integrity.

Jeff Beauchamp and Harry Kennedy are field application engineers at NCAB Group.