HDI PCB Design Guidelines With OrCAD X

June 10, 2024

Cadence PCB Solutions

Key Takeaways

Technology enhances miniaturization and performance, allowing for more complex circuitry in smaller spaces while improving signal integrity and thermal management.
HDI PCB layout requires attention to material selection, component packaging, routing strategies, and simulation to ensure effective use of space and functionality.
OrCAD X offers specific tools, such as blind, buried, and micro vias integration, constraint management, and automated via selection, to adhere to HDI guidelines effectively.

One aspect of high-density PCB layout is working with various via types as illustrated here

An enlarged view of vias in a high-density PCB layout

High-density (HDI) PCB layout has become the standard for many circuit applications. The reduced space required for the layout allows designers to miniaturize the design, increase the product's functionality, or achieve both of these goals. However, as expected, there are layout details that designers must be aware of when using high-density interconnect technology. Below, we’ve summarized the key HDI PCB guidelines.

Key HDI PCB Guidelines

Guideline	Description
Materials and Processes	Use new, thinner dielectrics (this may require different impedance calculations and layer stackup configurations). Keep in mind that solder paste masks will have tighter clearances and need more rigid control. Know when and how to use new technologies, such as via-in-pad and coordinate with your manufacturer. Include considerations for signal integrity, such as controlled impedance layers and appropriate reference planes. Ensure the stackup design aligns with thermal management strategies to prevent hotspots and ensure uniform heat distribution.
Components	Incorporate smaller component package sizes with high pin counts and pin pitches of 0.5mm. Use different routing strategies, which might impact via escape patterns.
Routing	Calculate impedance and control trace and space constraints for multiple connection types, including transmission lines, analog, power, etc. Manage sensitive routing with zones or rooms across the board for adherence to different routing constraints. Use multiple via types, including thru-hole, blind and buried, and microvias. Use your CAD’s constraint system to manage these vias and their applications. Use thinner traces to achieve smaller, more efficient layouts. Be careful when handling current capacity and signal integrity.
Simulation	Analyze your HDI designs and run simulations in conjunction with the manufacturer’s requirements.
Vias	Use microvias, blind/buried, and staggered vias for layer transitions to save space and improve density. Consider smaller diameters for finer pitch components, limiting their useful depth. Manage via inductance and resistance, which can be critical in high-speed circuitry. Minimize the use of unnecessary vias to maximize space for routing and minimize signal integrity issues. Consider via filling if thermal or mechanical stability is a concern.

High-Density PCB Layout Benefits and Concerns

Printed circuit boards are shrinking in size to build the next generation of compact electronic devices while increasing the amount of functionality they can support. These changes are accomplished by using high pin-count components with pin pitches of 0.5 mm (or less), necessitating trace widths and spaces of 2 mils or 50 microns for their connections. Multiple via technologies, along with advanced fabrication materials and manufacturing processes, define these designs as high-density PCB layouts.

There are many benefits to using high-density interconnect, or HDI, in circuit board design, along with some expected concerns. The improvements in quality and reliability in HDI designs effectively lower their overall costs, making a high-density PCB layout a desirable option. However, there are some concerns that designers need to consider first before jumping into the deep end of the HDI pool.

HDI Benefits and Concerns

Category	Details
Benefits	Miniaturization: Smaller component sizes reduce circuit layout space. High-density circuitry: Allows for more circuitry with reduced component spacing. Narrow trace width: Increases routing per square inch. Diverse via types: Enhances routing space with thru-hole, blind & buried, and microvias. Thinner dielectric materials: Improves PCB reliability and reduces board thickness. Performance enhancement: Reduces inductance and EMI susceptibility, enhances thermal management, and improves signal integrity.
Concerns	Layer stackup planning: Essential for high signal integrity. Adaptive routing strategies: Requires new approaches due to changes in pin-pitch, line widths, and via types. New manufacturing processes and materials: Involves higher costs and necessitates new vendor relationships. Cost analysis and tradeoffs: Increased complexity may require finding new manufacturers, potentially raising production costs. Design research necessity: Important to research new requirements before beginning an HDI design.

Designers must research potential changes in manufacturing and the resulting new design requirements before starting an HDI design.

OrCAD X has tools specifically designed for HDI PCB design guideline adherence

OrCAD X has tools specifically designed for HDI PCB design guideline adherence.

How OrCAD X Helps Designers Adhere to HDI Guidelines

OrCAD X supports adherence to HDI guidelines by offering design tools to address the unique challenges of high-density interconnect projects.

OrCAD X Feature for HDI

OrCAD X Feature	Description	How It Helps
Blind, Buried, and Micro Vias	Allows the integration of compact vias that do not traverse the entire board.	Reduces the need for through-hole vias, enabling more compact, dense layouts.
Constraint Manager	Enables setting and managing specific design rules tailored to HDI requirements, such as via stacking and spacing.	Ensures compliance with manufacturing capabilities and adherence to precise HDI guidelines.
Automated Via Selection	Automates the process of selecting the appropriate via based on routing context and predefined rules.	Reduces manual errors and speeds up the design process while ensuring adherence guidelines.
Stacked Vias Capability	Provides the ability to create and modify stacked via structures easily.	Supports intricate layer transitions and optimizes vertical space within multilayer PCBs, crucial for high-density interconnects.
Slide Command for Via Adjustments	Allows for the splitting or adjusting of via stacks post-placement.	Facilitates iterative design adjustments crucial for meeting final design requirements and resolving manufacturing challenges.
Interactive Routing Modes	Enables manual routing guidance while automatically adhering to set constraints for spacing and via usage.	Allows for fine-tuning of the PCB layout to ensure optimal manufacturability.
Design for Manufacturability (DFM) Checks	Integrates DFM checks into the design process to identify potential production issues early.	Helps ensure that the HDI PCB can be manufactured without defects, adhering to design and industry standards.

Experience the capabilities of OrCAD X firsthand and discover how it can help you adhere to HDI PCB design guidelines. Sign up for the free trial today and take your designs to the next level with our cutting-edge tools and features optimized for HDI compliance.

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