What is the difference between TMM3 and TMM10 PCB materials?

TMM3 and TMM10 are both high-frequency PCB materials produced by Rogers Corporation, each tailored for specific applications in RF and microwave circuits. While they share some foundational similarities, they also exhibit distinct characteristics that influence their suitability for various designs. Below is a detailed comparison based on key properties and performance characteristics.

Dielectric Constant (Dk)

- TMM3: Approximately 3.27 ± 0.032 at 10 GHz, providing good performance for moderate-frequency applications.

- TMM10: Has a significantly higher dielectric constant of 9.20 ± 0.23, which supports stable performance in specialized high-frequency applications.

Loss Tangent (Df)

- TMM3: Features a loss tangent of about 0.002 at 10 GHz, indicating low signal loss suitable for various RF applications.

- TMM10: Offers a lower dissipation factor of 0.0022 at 10 GHz, resulting in even less signal degradation and enhanced performance for high-frequency circuits.

Thermal Stability

- TMM3: Provides a thermal coefficient of dielectric constant of +37 ppm/°K, ensuring reasonable stability across temperature variations.

- TMM10: Exhibits a thermal coefficient of dielectric constant of -38 ppm/°K, indicating better stability and performance across a wider temperature range.

Coefficient of Thermal Expansion (CTE)

- TMM3: Has a CTE of approximately 15 ppm/K in the X and Y directions and 23 ppm/K in the Z direction, which is typical for RF materials.

- TMM10: Features a CTE of 21 ppm/K in the X and Y directions and 20 ppm/K in the Z direction, making it better matched to copper, thus reducing the risk of mechanical stress and delamination.

Mechanical Properties

While both materials show good mechanical strength, TMM3 generally offers superior flexural strength with a value of 16.53 kpsi compared to TMM10’s 13.62 kpsi. This makes TMM3 a better choice for applications requiring higher durability under stress, although TMM10 has a similar flexural modulus of 1.79 Mpsi.

Applications

- TMM3: Commonly used in moderate-frequency applications such as RF amplifiers and antenna feeds, offering versatility for many RF designs.

- TMM10: Specifically designed for high-performance applications like advanced telecommunications, satellite communications, and radar systems, where enhanced electrical and thermal properties are critical.

Cost Considerations

TMM10 is generally more expensive than TMM3 due to its enhanced performance characteristics. The decision between the two materials often involves balancing performance needs against budget constraints.

Physical Properties

- Moisture Absorption: TMM3 exhibits lower moisture absorption (0.06% for 0.050" thickness) compared to TMM10 (0.09% for 0.050" thickness), which is beneficial for maintaining performance in humid conditions.

- Specific Gravity: TMM3 has a specific gravity of 1.78, while TMM10 is denser at 2.77.

Conclusion

In summary, TMM3 and TMM10 PCBs serve different roles in high-frequency applications. TMM3 is a cost-effective choice for moderate-frequency designs, characterized by its superior mechanical strength and lower moisture absorption. In contrast, TMM10 excels in high-performance environments that demand superior electrical and thermal properties. The selection between the two materials should be guided by the specific needs of the application, including frequency, thermal management, mechanical strength, and physical properties.