Who Manufactures PCBs Using TMM6 with EPIG Nickel-Free Surface Finish?

Introduction

In high-frequency circuit design, achieving the right balance between electrical performance, mechanical reliability, and manufacturability is often challenging. Rogers TMM6—part of the TMM® (Thermoset Microwave Materials) family—addresses this challenge by combining many of the desirable features of ceramic substrates with the ease of soft substrate processing techniques.

TMM6 is a ceramic, hydrocarbon, thermoset polymer composite designed for high plated-through-hole (PTH) reliability in stripline and microstrip applications. With a dielectric constant of 6.00 ± 0.08 and a low dissipation factor of 0.0023 at 10 GHz, TMM6 offers a unique Dk value that fills an important gap between lower-Dk PTFE materials and higher-Dk ceramic substrates.

Unlike PTFE-based materials, TMM6 is a thermoset resin that does not soften when heated, enabling reliable wire bonding without pad lifting or substrate deformation. Its coefficient of thermal expansion (CTE) closely matched to copper ensures exceptional plated-through-hole reliability, while its thermal conductivity is approximately twice that of traditional PTFE/ceramic laminates, facilitating effective heat removal.

This article provides a comprehensive overview of TMM6 laminate properties, a detailed 2-layer PCB design example, and key sourcing information for engineers and procurement professionals.

What Is Rogers TMM6 Laminate?

Rogers TMM6 is a thermoset microwave material from the TMM series, which includes a wide range of dielectric constants from 3.0 to 10.0. TMM6, with a Dk of 6.0, is specifically designed for applications requiring a higher dielectric constant than traditional PTFE materials but without the brittleness or processing challenges of pure ceramic substrates.

Key Differentiator: Thermoset Resin with Ceramic-Like Performance

TMM6 offers several unique advantages over both PTFE-based and ceramic substrates:

Complete Material Properties Table

The following table consolidates all electrical, thermal, mechanical, and physical properties of TMM6 laminates into a single comprehensive reference.

Notes:
1. Prolonged exposure in an oxidative environment may cause changes to dielectric properties of hydrocarbon-based materials. Rogers recommends evaluating each material and design combination for fitness over the entire product life.
2. The design Dk is an average from multiple tested lots on the most common thicknesses. Contact Rogers for detailed information.

Typical values are a representation of an average value for the population of the property. For specification values contact Rogers Corporation.

Features and Benefits Summary

Exceptional Thermal Stability

TMM6 exhibits a thermal coefficient of dielectric constant (TCDk) of only -11 ppm/°K—exceptionally low for a Dk 6.0 material. This ensures that the dielectric constant remains stable across a wide temperature range (-55°C to +125°C), critical for applications operating in extreme environments such as satellite communications and aerospace systems.

Copper-Matched CTE for PTH Reliability

TMM6's CTE values (18/18/26 ppm/K in X/Y/Z) are closely matched to copper (17 ppm/°C). This match minimizes thermal stress on plated-through-holes during temperature cycling, resulting in:

High PTH reliability – Excellent performance in thermal shock applications

Low etch shrinkage – Dimensional stability during fabrication

Reduced pad lifting – Reliable soldering and wire bonding

High Thermal Conductivity

With a thermal conductivity of 0.72 W/m/K, TMM6 offers approximately twice the thermal conductivity of traditional PTFE/ceramic laminates (typically 0.26–0.35 W/m/K). This facilitates efficient heat removal from power amplifiers and other high-power RF circuits, extending component life and improving reliability.

Thermoset Advantages Over PTFE

Unlike PTFE-based materials, TMM6's thermoset resin:

Does not soften when heated – Enables wire bonding without pad lifting

Does not require sodium napthanate treatment – Simplifies electroless plating

Resists creep and cold flow – Maintains dimensional stability under mechanical stress

Offers consistent performance across processing temperatures

Standard Offerings

TMM6 laminates are available in a comprehensive range of thicknesses, panel sizes, and copper cladding options.

Standard Panel Sizes & Claddings

2-Layer PCB Design Example Using TMM6

To demonstrate the practical application of TMM6, the following is a complete 2-layer rigid PCB design case.

PCB Design Specifications

Design Observations

This board (85.6 mm × 99.75 mm) features a moderate component count (23 components) with only 2 nets, suggesting a dedicated RF or microwave functional module. Key observations include:

50 mil (1.27 mm) dielectric thickness – Provides robust mechanical strength and reliable impedance control for microwave circuits

EPIG surface finish (Nickel-Free) – Electroless Palladium Immersion Gold finish offers excellent wire bondability and solderability without nickel, which can be problematic for some RF applications (no magnetic/nickel interference)

No solder mask – Preserves the thermoset material's low-loss characteristics; avoids unwanted dielectric effects

No silkscreen – Maintains a clean RF surface; avoids contamination

TMM6's Dk of 6.0 – Enables circuit miniaturization compared to lower-Dk materials; compact filter and coupler designs

TMM6's thermoset properties – Reliable wire bonding and PTH reliability

IPC-Class-2 compliance – Ensures reliability for commercial and industrial applications

Manufacturing Process Highlights

No specialized processing – TMM6 can be fabricated using all common PWB processes; no sodium napthanate treatment required

Chemical resistance – Resistant to etchants and solvents used in PCB production

Excellent PTH reliability – CTE matched to copper ensures reliable plated-through-holes

Fine-pitch capability – 4/6 mil trace/spacing supports high-density RF designs

100% electrical testing – Guarantees functional integrity of every board

Typical Applications

- RF and microwave circuitry

- Power amplifiers and combiners

- Filters and coupler

- Satellite communication systems

- Global Positioning Systems Antennas

- Patch Antennas

- Dielectric polarizers and lenses

- Chip testers

Conclusion

Rogers TMM6 laminates offer a compelling combination of high dielectric constant (6.00 ± 0.08), low loss (0.0023 @ 10 GHz), and exceptional thermoset reliability—all without the specialized processing requirements of PTFE-based materials. With CTE matched to copper (18/18/26 ppm/K), thermal conductivity of 0.72 W/m·K, and a thermoset resin that enables reliable wire bonding, TMM6 is ideally suited for demanding RF and microwave applications.

Key advantages include:

High Dk of 6.00 – Enables circuit miniaturization compared to lower-Dk materials

Low loss (Df = 0.0023) – Maintains signal integrity in microwave circuits

Thermoset resin – No softening when heated; reliable wire bonding; no pad lifting

CTE matched to copper – Excellent PTH reliability; low etch shrinkage

High thermal conductivity (0.72 W/m·K) – Efficient heat removal; approximately 2× better than PTFE/ceramic laminates

No PTFE processing – No sodium napthanate treatment required; all common PWB processes

Wide thickness range – Available from 0.015" to 0.500"

TCDk of -11 ppm/°K – Exceptionally stable Dk across temperature

Chemical resistance – Resistant to etchants and solvents

Whether used in power amplifiers, satellite communications systems, or microwave test equipment, TMM6 provides a reliable, high-performance foundation for demanding high-frequency circuit designs.