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Embedded Resistors in Hi-Speed PCBs

Embedded resistors integrate directly into high-speed PCB layers, eliminating the need for discrete surface-mount components. This approach improves routing efficiency, reduces parasitic effects, and enhances overall signal integrity. By embedding resistive elements within the PCB stack-up, designers can achieve smaller, more reliable circuit boards optimized for high-frequency performance.

High-speed printed circuit boards are foundational to modern electronics, enabling functionality across applications ranging from mobile devices to aerospace systems. As device complexity and performance requirements have increased, traditional discrete component approaches have become a limiting factor in PCB design.

To address ongoing miniaturization and performance demands, passive components such as resistors are now embedded directly into PCB layers. This allows designers to maintain electrical performance while reducing the circuit board size and freeing up valuable routing space.

At a Glance: Embedded Resistors

Embeds thin-film resistors directly into PCB layers, eliminating discrete SMTs and freeing up routing space for higher-density designs.
Improves electrical performance by reducing parasitic capacitance, EMI, and signal reflections while enhancing impedance control.
Uses specialized materials like Ticer by OhmegaTicer and controlled subtractive processes to enable stable, high-frequency operation without increasing board thickness.

Embedded Resistors vs. Surface-Mount Resistors (SMTs)

Surface-mount resistors consist of ceramic bodies with metalized terminations that connect to PCB pads. In contrast, embedded resistors are thin-film planar elements formed directly within the PCB copper layers.

Key Differences:

SMTs require pads, solder joints, and routing connections
Embedded resistors are integrated into the circuit pattern with no solder joints
Embedded solutions eliminate the need for additional assembly steps associated with discrete components

Benefits of Embedded Resistors

Increased Routing Area

Removing discrete SMT components reduces the need for interconnecting traces and vias. This frees up circuit board space, enabling:

Additional functional circuitry
Reduced PCB size for compact designs

Shorter Wiring Lengths

Embedded resistors are incorporated directly into the circuitry, reducing the need for routing between components. This results in:

Simpler circuit board layouts
Reduced manufacturing complexity
Lower overall production costs

Reduced EMI and Parasitic Effects

Closely spaced circuitry can introduce unwanted electrical interactions, including parasitic capacitance and electromagnetic interference (EMI). Embedded resistors help mitigate these effects by:

Reducing parasitic capacitance
Minimizing crosstalk and electrical noise
Improving overall circuit performance

Enhanced Signal Integrity

Embedding resistors within the PCB improves electrical performance across high-speed designs:

Better impedance control and matching
Reduced signal reflection from loads
Stability over a wide frequency range
Increased PCB lifecycle and durability

Ticer Embedded Resistor Technology

Epec utilizes Ticer resistor technology to integrate resistive elements into PCB designs. This material consists of a thin-film NiCr metal alloy sputtered onto copper foil and laminated to dielectric layers.

Material and Process Characteristics:

Thin-film resistive layer embedded within PCB layers
Does not increase the circuit board thickness or consume surface area
Processed using subtractive manufacturing techniques

Performance Attributes:

Low resistance temperature coefficient (<50 ppm)
Stable performance beyond 20 GHz
Long-term reliability exceeding 100,000 hours with minimal resistance shift at elevated temperatures

Manufacturing Process Considerations

Although similar in concept to traditional subtractive PCB fabrication, embedded resistor manufacturing introduces additional requirements.

Process Requirements:

Ticer must be etched in a Cupric Chloride or permanganate solution
Copper over the resistor is removed using an alkaline etchant
These steps require dedicated process capability and investment

Design and Engineering Considerations:

Material suppliers define design parameters for long-term stability and tolerance control
CAD design must account for differences between thin-film subtractive and thick-film additive processes
Resistor geometry and terminations are defined differently than conventional SMT designs

Engineering collaboration is critical to ensure designs meet electrical and manufacturing requirements.

Embedded Passive Standards

Design and manufacturing of embedded resistors follow established IPC standards:

IPC-4821: Embedded passive device capacitor materials
IPC-4811: Embedded passive device resistor materials
IPC-2316: Design guides for embedded passive printed circuit boards
IPC-6017: Qualification and performance specifications for printed circuit boards with embedded passives

Frequently Asked Questions

Quick Links

How do I best specify embedded resistors in Gerber data?
What does impedance mean in this context?
What should I know about vias when using embedded resistors?
What should I know about BGA applications?
What are considerations for copper in embedded resistor designs?
How does removing discrete SMTs impact PCB design?

How do I best specify embedded resistors in Gerber data?

Embedded resistor designs must follow material supplier guidelines for geometry, tolerance, and stability. CAD tools must account for thin-film subtractive processes, where resistor elements and terminations are defined differently than traditional SMT layouts.

What does impedance mean in this context?

Impedance refers to how electrical signals propagate through PCB traces. Embedded resistors help match line impedance and reduce signal reflections, improving overall signal integrity in high-speed designs.

What should I know about vias when using embedded resistors?

Embedded resistors reduce or eliminate the need for vias associated with discrete components, simplifying routing and enabling more compact PCB layouts.

What should I know about BGA applications?

Embedded resistors are commonly used for termination in BGA packages, where space constraints and signal integrity requirements make integrated solutions more effective than discrete components.

What are considerations for copper in embedded resistor designs?

Copper plays a critical role as the base material for thin-film resistive layers like Ticer. Proper processing and etching are required to ensure accurate resistor formation and reliable performance.

How does removing discrete SMTs impact PCB design?

Eliminating surface-mount resistors frees up routing space, reduces interconnect complexity, and allows for smaller, more functional PCB designs without sacrificing electrical performance.

Looking for Embedded Resistors in Your PCB?

Work with Epec's engineering team to integrate embedded resistors into your next high-speed PCB design for improved performance, reduced size, and optimized manufacturability. Contact our engineers today to discuss this technology and how your application may benefit from it.

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