Epec Manufactures Embedded Resistor PCBs for High-Speed Electronics Applications

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Epec Engineered Technologies, a provider of engineered solutions for printed circuit boards, cable assemblies, and custom electronic components across multiple industries, provides PCB manufacturing with embedded resistors for high-speed applications, addressing design complexity and miniaturization in electronic systems.

High-speed PCBs are used across applications ranging from smartphones and medical devices to military radar and satellite systems. As integrated circuits have advanced from simple transistor-based designs to complex chips with millions of components, circuit boards have required higher functionality within limited space. Epec identifies miniaturization as a key challenge, where reduced space inside devices limits the placement of passive and active components. To address this, passive components such as resistors, capacitors, and inductors are embedded directly into PCB layers.

The company works with substrate manufacturers, including Ticer Technologies and Ohmega Technologies, which produce thin-film embedded resistor copper foils used in PCB fabrication. Epec's experience with these materials supports the development of embedded resistor solutions.

Epec explains that embedded resistors differ from surface mount resistors (SMTs) by being integrated into the PCB structure as planar resistive elements formed within the circuitry, eliminating the need for solder joints.

The company identifies several design impacts associated with embedded resistors:

• Removing discrete SMTs increases available routing area by reducing the space required for interconnecting traces and vias, allowing additional functions or smaller board sizes.
• Shorter wiring lengths reduce complexity in connecting passive components to integrated circuits, supporting more compact board designs.
• Embedded resistors reduce parasitic capacitance, electromagnetic interference (EMI), cross talk, and noise from nearby circuitry, while enabling placement under integrated circuit pins to reduce inductance.
• Embedding resistors improves board integrity, supporting stability across frequency ranges, longer lifecycle, and reduced signal reflection through improved impedance matching.

Epec also references the use of OhmegaPly®, a thin-film resistor conductor material from Ohmega Technologies. The material is laminated to dielectric layers and processed to form planar resistors within the PCB. Due to its thin-film structure, it can be embedded within layers without increasing board thickness or occupying surface space. The material has a low resistance temperature coefficient and operates across a wide frequency range, with testing beyond 20 GHz and lifecycle performance exceeding 100,000 hours at 110°C.

Applications referenced by the company include surface resistors on HDI circuit boards, embedded pull-up resistors in aerospace systems, and series and parallel termination resistors in BGA packages.

Epec outlines process considerations for embedded resistor manufacturing within subtractive PCB fabrication. The process involves etching resistive materials using copper sulfate solutions, followed by copper removal using alkaline etchants. The company notes that CAD operators require training due to differences between additive thick-film and subtractive thin-film processes, where resistor elements and terminations are defined using different techniques.

For design implementation, Epec states that material manufacturers provide standard design parameters for stability and tolerance management. Engineering teams work with these parameters to align embedded passive designs with specified requirements.

The company references industry standards related to embedded passive devices, including IPC-4821, IPC-4811, IPC-2316, and IPC-6017, which define specifications, design guidelines, and qualification requirements for printed boards containing embedded passive components.

Epec provides printed circuit boards for multiple industries, where embedded resistors are used in applications requiring high-speed PCB performance.

Click here to learn more about the embedded resistors in high-speed PCBs.