Exploring Advanced Rapid PCB Construction Techniques
In the ever-evolving world of electronics, the need for high-speed PCB (Printed Circuit Board) laminates has become increasingly important, particularly for USB 3.x devices. A High-Speed PCB Design Guide, spanning 8 chapters, 115 pages, and a 150-minute read, offers valuable insights into this topic.
Jim Choate, USB technology product manager at Agilent Technologies, recently presented a webinar on compliance testing for USB 3.1 devices. According to Choate, the latest USB chip sets are facing limitations due to the properties of FR-4 PCB laminates, which are commonly used in electronics. A transition to PCB laminates with better dielectric properties than FR-4 is being considered to progress electronics.
The development of electronics over six decades has been driven by advancements in semiconductor manufacturing. From the original Universal Serial Bus (USB) standard, drafted in the 1990s, which supported a maximum signaling rate of 12 Mb/s and powered external equipment, to the introduction of USB 2.0 within a few years, increasing the maximum signaling rate by 40 times to 480 Mb/s, and the subsequent upgrades, USB technology has come a long way. In 2013, the standard was upgraded again, adding an even faster transfer mode whose ceiling is 10 Gb/s.
For USB 3.x, which demands strict signal quality over high-speed serial interfaces, materials that offer low dielectric loss and stable dielectric constants are ideal to minimize attenuation and impedance variability. High-frequency/low-loss PCB materials are recommended to maintain signal quality over USB 3.x interfaces. These materials reduce insertion loss and minimize signal distortion at multi-gigabit speeds common in USB 3.x designs.
Rogers RO4350B is an example of a popular high-frequency laminate used in high-speed digital circuits. It features low dielectric loss, a stable dielectric constant for consistent impedance, better thermal management, and is compatible with standard FR-4 processing, making it a strong candidate for minimizing signal attenuation in USB 3.x applications.
Multilayer PCBs incorporating dedicated ground and power planes help reduce signal noise and provide controlled impedance for high-speed differential pairs in USB 3.x transceivers. Additional PCB design practices such as proper impedance control, minimizing vias, short trace lengths, differential pair routing, and continuous ground planes optimize the benefits of these laminates for high-speed signals.
In summary, using multilayer PCBs with high-frequency, low-loss laminates like Rogers RO4350B, combined with impedance-controlled design and good grounding, is the recommended approach to reduce signal loss for high-speed signals including USB 3.x. This reduces attenuation and preserves signal fidelity essential for USB 3.x data rates.
Jim Choate believes there is enough margin to push USB signal rates beyond 10 Gb/s without abandoning FR-4 for PC motherboards, but repeaters would be necessary. From his experience at Intel, Choate believes that using a material other than FR-4 for a PC motherboard would be a deal-breaker.
The article concludes by asking the reader if 30% lower loss at 10 GHz would be worth it, considering the cost-effectiveness of developing tricks to skirt the limitations of conventional PCB materials versus the premium for a material with far less loss. A case study on a high-speed video board further illustrates the benefits of these high-frequency/low-loss laminates in practice.
Science and technology have advanced significantly in the realm of electronics, leading to the development of high-speed Printed Circuit Board (PCB) laminates, particularly critical for USB 3.x devices. To maintain signal quality over these high-speed interfaces, data-and-cloud-computing-driven research focuses on materials with low dielectric loss and stable dielectric constants, such as the Rogers RO4350B laminate. These advances in technology are improving the performance of USB 3.x devices by reducing signal attenuation and minimizing impedance variability through controlled impedance techniques and high-frequency/low-loss PCB materials.
