Analysis of a Stiff-Flexible Video Circuit Board Construction
Sierra Circuits Unveils High-Performance Rigid-Flex Video Board
Sierra Circuits, a leading PCB design company, has announced the launch of a new rigid-flex high-speed digital video board. This innovative board, designed to operate at frequencies up to 1 GHz, offers a combination of features that make it suitable for environments requiring high data throughput, precise signal integrity, ruggedness, and flexible mechanical configurations.
Key Specifications
The board, measuring 9 x 14 inches with 26 layers, combines rigid and flex sections. It incorporates an Altera Cyclone III FPGA for video processing and control functions, and features an FPGA with 325 pins and 0.5 mm pitch, which can be configured after manufacturing the circuit board. The board also includes SRAM and NAND flash memory, with the SRAM operating at 40 MHz and the NAND flash at 25 MHz, both housed in TSSOP packaging.
Design Constraints
The design process involved careful consideration of critical constraints. The small form factor of the board and the high density of components and BGA required careful via-in-pad design to address drill-to-copper challenges. The board adheres to IPC Class 2 or 3 standards depending on environmental reliability needs, and uses tear-dropped via pads to ensure mechanical strength and reduce via breakout in harsh conditions.
Applications
This board finds use in demanding areas such as medical imaging equipment, road traffic monitoring systems, automatic vehicle guidance systems, and automatic optical inspection machines, where high-speed video data processing and reliability in harsh environments are paramount.
Manufacturing and Routing
The design and DFM team at Sierra Circuits work closely to evaluate various routing requirements for a particular design. The components were placed based on the shortest routing length, and the SRAM and NAND Flash are placed on the same board with a minimal form factor, requiring dense routing with the length matching.
Controlled Impedance and Via-in-Pad Design
Controlled impedance is critical for signal integrity at high speeds. Sierra Circuits uses a 2D numerical solver based on Maxwell’s equations to accurately calculate impedance for traces, with parameters tailored for microstrip and stripline structures to maintain signal quality up to 1 GHz. The multilayer rigid-flex PCB employs via-in-pad technology to minimize signal path lengths and reduce inductance, which is essential in high-speed digital circuits.
Rigid-Flex Construction
The board is a 10-layer board, consisting of an 8-layered rigid-flex connected to a 2-layered rigid-flex. This construction provides the necessary flexibility and ruggedness for the board's demanding applications.
Quality Assurance
Automatic optical inspection (AOI) is a technique used to analyze standard and complex PCBs, verifying the quality of the board by detecting defects if any. Sierra Circuits aims to deliver high-performance and quality boards, and the rigid-flex video board is no exception.
For more information on the importance of IPC design guidelines, readers are encouraged to check out Sierra Circuits' blog on IPC-2223 standards and design violations for rigid-flex boards. To learn about bend radius calculation, controlled impedance for flex, and other important design techniques, download Sierra Circuits' design guide.
[1] Sierra Circuits. (n.d.). Rigid-Flex PCB Design Guide. Retrieved from https://www.sierracircuits.com/pcb-design-guide
[2] Sierra Circuits. (n.d.). Maxwell Equations for PCB Design. Retrieved from https://www.sierracircuits.com/maxwell-equations-for-pcb-design
[3] Sierra Circuits. (n.d.). IPC-2223 Standards and Design Violations for Rigid-Flex Boards. Retrieved from https://www.sierracircuits.com/ipc-2223-standards-and-design-violations-for-rigid-flex-boards
[4] Sierra Circuits. (n.d.). Medical Flex PCBs. Retrieved from https://www.sierracircuits.com/medical-flex-pcbs
[5] Sierra Circuits. (n.d.). Automatic Optical Inspection (AOI). Retrieved from https://www.sierracircuits.com/automatic-optical-inspection-aoi
The Sierra Circuits' rigid-flex video board, designed for environments requiring high data throughput and precise signal integrity, employs controlled impedance and via-in-pad technology for high-speed digital circuits, supporting data-and-cloud-computing requirements. As a result of its multilayer rigid-flex construction and adherence to IPC Class 2 or 3 standards, the board offers reliability in harsh environments, making it suitable for applications such as medical imaging equipment and automatic optical inspection machines.
