Analysis of a Customizable Flexible Circuit Video Interface Solution
Sierra Circuits, a renowned PCB design and manufacturing company, has announced the launch of a cutting-edge rigid-flex high-speed digital video board. This innovative board, designed with meticulous attention to detail and stringent specifications, addresses the challenges of high-frequency signals, complex routing, and mechanical reliability.
Design Constraints & Critical Specifications
The board's design is underpinned by several critical factors, including precise impedance control, trace and via dimensions, stackup and materials, and signaling and EMI/EMC considerations.
Impedance Control
To maintain signal integrity, Sierra Circuits employs a 2D numerical solution of Maxwell’s equations for accurate impedance calculation. This method takes into account parameters like dielectric height, dielectric constant, trace width, thickness, and target impedance.
Trace and Via Dimensions
The board adheres to IPC Class 3 specifications, which require minimum trace and spacing dimensions, and reliable via pad sizes with tear-dropped via pads to reduce the risk of conductor separation under thermal/mechanical stress.
Stackup and Materials
The rigid-flex stackup is carefully designed using tools like Sierra Circuits’ PCB Stackup Designer. This ensures mechanical flexibility in the flex regions and electrical performance in rigid parts, critical for maintaining signal integrity in high-speed digital video.
Signaling and EMI/EMC Considerations
Tools such as Sigrity X are used for detailed signal integrity (SI), power integrity (PI), and electromagnetic compatibility (EMC) analyses. These help optimize decoupling capacitor placement, analyze crosstalk, and ensure noise margins.
Applications
The board's high-speed digital video capabilities make it suitable for various applications, including video capture cards, display driver interfaces, medical imaging devices, and aerospace video systems. Its design aligns well with the demanding environments and reliability standards of military and medical equipment.
Manufacturing and Routing Challenges
The board's high-density components and BGA packaging necessitated careful via-in-pad design to address drill-to-copper challenges. The board is a 10-layer board, consisting of an 8-layered rigid-flex connected to a 2-layered rigid-flex. The routing complexity, particularly in the flex areas, required meticulous routing to meet impedance and spacing constraints.
The board's design also had to balance board rigidity with flexibility, necessitating precise control over material selection and layer stackup to avoid delamination or cracking over operational life. Ensuring sufficient thermal dissipation while maintaining controlled impedance in delicate flex sections was another challenge.
Key Features
- High-speed digital video signals with precise impedance control
- IPC Class 3 compliant for high-reliability across harsh environments
- Advanced electromagnetic simulation tools for signal integrity and power integrity analysis
- Fine pitch with 0.5 mm packaging and via-in-pad design for a smaller form factor
- FPGA of 325 pins with a 0.5 mm pitch, configurable after the circuit board is manufactured
- Automatic optical inspection (AOI) for quality verification and defect detection
- SRAM of 40 MHz and NAND flash of 25 MHz with TSSOP packaging
In conclusion, Sierra Circuits' rigid-flex high-speed digital video board represents a significant leap forward in high-frequency signal handling, complex routing, and mechanical reliability. Its design and manufacturing rigor ensure top performance in critical video applications often found in demanding industrial, medical, and military fields.
[1] IPC-2223 Standards for Rigid-Flex and Multi-Layer Flexible Printed Circuits. (n.d.). Retrieved from https://www.ipc.org/standards/ipc-2223-standards-for-rigid-flex-and-multi-layer-flexible-printed-circuits [2] Sigrity X. (n.d.). Retrieved from https://www.sigrity.com/ [3] Sierra Circuit's PCB Stackup Designer. (n.d.). Retrieved from https://www.sierraware.com/products/pcb-stackup-designer/
- The Sierra Circuits' rigid-flex high-speed digital video board, designed with a controlled impedance using a 2D numerical solution of Maxwell’s equations, is a fine example of technology integration in data-and-cloud-computing applications.
- The board's manufacturing process, which includes the use of advanced electromagnetic simulation tools like Sigrity X, demonstrates the potential of technology in addressing the challenges of high-density components and BGA packaging in data-and-cloud-computing environments.
