How thick is Rogers RO4003C?

Substrate Thickness Options for Rogers RO4003C

Rogers offers their RO4003C laminate in a range of standard thicknesses to suit different design requirements. The standard thickness options for RO4003C are shown in the table below:

These thickness options span from 0.008″ (0.203 mm) for very thin, flexible substrates up to 0.060″ (1.524 mm) for thicker, more rigid boards. The most commonly used thicknesses are 0.020″ (0.508 mm) and 0.030″ (0.762 mm).

In addition to these standard thicknesses, Rogers also offers custom thicknesses of RO4003C laminate for specialized applications. Custom thicknesses can be ordered in 0.001″ (0.025 mm) increments. The maximum thickness available is 0.120″ (3.048 mm).

Factors Affecting Choice of Substrate Thickness

There are several factors that designers need to consider when selecting the appropriate thickness of RO4003C substrate for their PCB. The key factors are:

Electrical Performance

The thickness of the substrate impacts key electrical properties of the PCB. Thinner substrates allow for finer feature sizes and tighter coupling between conductors, which is advantageous for higher frequency operation. Thicker substrates provide more mechanical stability and allow higher power handling.

The dielectric constant (Dk) and dissipation factor (Df) of RO4003C also vary slightly with thickness. Thinner laminates tend to have slightly lower Dk and higher Df than thicker laminates. The table below shows the nominal Dk and Df values at 10 GHz for different thicknesses:

Mechanical Strength and Rigidity

Thicker substrates provide more mechanical strength and rigidity to the PCB. This is important for boards that will be subject to physical stress or vibration. Thinner substrates are more flexible, which can be desirable for some applications but may require additional mechanical support.

The table below shows the nominal flexural strength of RO4003C at room temperature for different thicknesses:

Manufacturing Considerations

The choice of substrate thickness also impacts the manufacturability of the PCB. Very thin substrates can be challenging to handle and process, especially for large panel sizes. Thin laminates are also more prone to warping and damage during manufacturing.

Thicker substrates are generally easier to manufacture but require wider minimum feature sizes. Thicker boards also take longer to drill and may be more expensive to manufacture.

Cost

In general, thinner RO4003C laminates are more expensive than thicker ones on a per-area basis. This is because the raw materials represent a larger portion of the total cost for thinner laminates. However, thinner PCBs may have a lower total cost if they enable a smaller overall circuit size.

RF Performance Considerations

For RF and microwave PCB designers, the substrate thickness is a critical parameter that affects the impedance and loss of transmission lines. In general, thinner substrates allow for narrower traces and smaller features, which is desirable for higher frequency operation.

However, thinner substrates also result in higher conductor losses due to the decreased cross-sectional area of the traces. Thicker substrates have lower conductor losses but may not support the required feature sizes at high frequencies.

The optimal substrate thickness depends on the frequency band and circuit architecture. The table below provides general guidelines for selecting RO4003C thickness based on frequency:

These are just rough guidelines and the actual optimal thickness will depend on the specific design constraints and performance requirements.

Selecting RO4003C Thickness for Your Design

With all of these factors to consider, how do you go about selecting the appropriate RO4003C substrate thickness for your PCB design? Here is a general process to follow:

1. Determine the frequency range and critical performance requirements for your application. This will help narrow down the range of suitable thicknesses.

2. Consider the mechanical requirements and operating environment of the PCB. Thicker substrates may be needed for boards that will experience high stress or vibration.

3. Evaluate the manufacturability of different thickness options based on your PCB fabricator’s capabilities and guidelines. Get their feedback on any special requirements or challenges for very thin or thick substrates.

4. Use RF simulation software to model the performance of transmission lines and other critical structures on different substrate thicknesses. Optimize the design as needed to meet specs.

5. Compare the total cost of different thickness options, factoring in both material and manufacturing costs. In some cases a thinner substrate may have a higher per-area cost but result in an overall cheaper board.

6. Consider any other application-specific requirements that may drive the substrate thickness, such as weight or thermal management needs.

By systematically evaluating all of these factors, you can select the RO4003C substrate thickness that best meets your design goals and constraints.

FAQ

To wrap up, here are answers to some frequently asked questions about RO4003C substrate thickness:

What is the thinnest RO4003C substrate available?

The thinnest standard thickness of RO4003C laminate is 0.008″ (0.203 mm). Rogers does offer custom thicknesses down to 0.004″ (0.101 mm) for specialized applications.

What is the thickest RO4003C substrate available?

The thickest standard thickness of RO4003C laminate is 0.060″ (1.524 mm). Custom thicknesses up to 0.120″ (3.048 mm) can be requested.

Can I use a thicker RO4003C substrate for high frequency designs to reduce conductor losses?

In general, no. While thicker substrates have lower conductor losses, they do not support the finer feature sizes needed for high frequency operation. It’s usually better to use a thinner substrate and optimize the conductor geometry to minimize losses.

Are there any disadvantages to using a very thin RO4003C substrate?

Very thin substrates can be more expensive and challenging to manufacture. They may require special handling and be more prone to damage during fabrication and assembly. Thin substrates also provide less mechanical strength and rigidity.

How does the substrate thickness affect the controlled impedance of transmission lines?

The substrate thickness is one of the main factors that determines the width of PCB traces for a given characteristic impedance. Thinner substrates require narrower traces to achieve the same impedance as wider traces on a thicker substrate. Simulation software is used to calculate the exact trace geometries needed to achieve the desired impedance on a specific substrate thickness.

In summary, the thickness of Rogers RO4003C substrates is a critical design parameter that affects the electrical, mechanical, and manufacturing characteristics of a high frequency PCB. By carefully evaluating the performance requirements and constraints of an application, designers can select the optimal substrate thickness and achieve the best overall results.