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RF Circuit Board Design – Top Challenges, Solution and Tips for smooth process!

By | Date posted: | Last updated: February 9, 2022
RF Circuit Board Design

RF circuit board design is seeing increased usage whether it is in medical, industrial or communication devices. Simply put, RF signals are high-frequency analog signals. The RF frequency range is usually from 300 kHz to 300 GHz. This is as opposed to Microwave frequency range, which is anything above 300 MHz.

Even though RF PCBs have a wide range of advantages, compared to high-speed digital-signal board design, RF circuit board design also comes with its unique set of challenges. Let us look at these challenges in some detail as also look at effective tips that help designers mitigate these challenges effectively.

Challenges associated with RF Circuit Board Design

  • Sensitivity to noise – RF signals are highly sensitive to noise and lead to ringing and reflections. What is important is to ensure that the signal is properly terminated. It is also advisable to optimize the return path and ensure proper grounding is maintained.
  • Impedance Matching – Essentially frequency and tolerance are inversely related The higher the frequency, the smaller is the tolerance. If the total length of he trace is greater than the critical length i.e 1/16th of the wavelength of the signal, impedance control needs to be undertaken.
  • Return loss – It is imperative that return loss be minimized. In the absence of a good design, the return signal will go through power planes, or through multiple layers of the PCB. In such cases it will not be impedance controlled. For this reason, it is important that there are ground planes underneath the signals that can provide an impedance-controlled path. With ground planes, ground loop currents are minimized and also RF leakage into circuit elements is minimized.
  • Crosstalk – High Frequency designs also suffer from crosstalk. Crosstalk, in fact, is directly proportional to edge rates of the active line. Here the coupled energy from the active line is superimposed on the victim line. With board densities rising, so does the issue of crosstalk. To counter this, it is important that adequate space is left around the signal trace. Also it is important that traces are kept as small as possible. Also it is important that high-speed signals are routed as far apart. Reducing the dielectric spacing between the line and its reference plane, is yet another effective measure. Similarly, terminating the line on its characteristic impedance also limits crosstalk.
  • Other signal losses – Other signal losses include skin effect loss as also dielectric loss. PCB designers therefore need to look at laminate properties such as:
    • Dissipation Factor
    • Dielectric Constant Value

FR4 material for PCBs or laminate, for example, has a high dissipation factor. Insertion losses are therefore higher when using FR4. Also, the dielectric constant value of FR4 can vary up to 10 percent. In turn, this impacts impedance. High frequency laminates have more stable frequencies.

Coming to the Dk value itself, in microwave circuits the Dk value is linked to the size of circuit elements. It is therefore possible for a designer to reduce the circuit size by choosing a laminate that has a higher Dk value.

Effective Tips for RF Circuit Board Design

There are a number of effective tips that help in creating better designs and improving anti-interference. Some of these include:

  • Usage of inner layers as power ground layers. By doing this you will provide shielding and reduce spurious inductance. Reducing the length of the signal wire reduce cross-interference.
  • Turning the circuit layout 45 degrees. By doing this, high-frequency signal emission and coupling will be reduced. Short layout lengths work better for through holes. Also, the layout between layers should be vertical in order to reduce signal interference. It is also beneficial to increase copper on the ground layer.
  • Packaging important signal traces. This goes a long way in increasing the anti-interference ability of the signal. When it comes to signal traces it is also recommended to avoid loops and use a chrysanthemum link instead.
  • Bridging the decoupling capacitor. It is important to lay out the RF first and make the RF signal 50 ohms.
  • The importance of isolation cannot be overstated.

Incorporating these seemingly small suggestions can go a long way in creating far more effective designs and improving overall efficiency.

Mer-Mar Electronics is a certified and leading PCB manufacturer that gets things done in lesser turnaround time. We are committed to accurately reflecting your PCB design specifications as well as meeting the industry standards. We at Mer-Mar Electronics, assist our customers from initial design to mass production & delivery; as one of the leading electronics manufacturing services (EMS) providers. To know more contact us at sales@mermarinc.com or call us on (760) 244-6149.

Top 7 Must-Know Rules to Consider for Aerospace PCB Design!

By | Date posted: | Last updated: December 23, 2021
aerospace pcb design

When it comes to manufacturing printed circuit boards for aerospace electronics, they need to have an extremely high degree of reliability. More so, as these need to operate in harsh environmental conditions! Since such mission-critical operations do not allow for any scope for error and need to stick to strict operating standards, there are some stringent guidelines that need to be followed.

Rules to consider when it comes to aerospace PCB design:

1. High Quality Components

Now this clearly makes sense. Since you do not have any scope for malfunction and maintenance interventions aren’t a possibility, it is imperative to use high quality materials and components.

For instance, one of the materials that is recommended to be used includes anodized aluminum as it helps in heat dissipation. In fact, its thermal conductivity is far higher than that of traditional materials.

2. Thermal Management

With aerospace PCB design What is required is effective thermal management. Therefore, you need to ensure proper heat dissipation without using external heat sinks. This can be done in several ways, including:

  • Use of heavy copper technology that allows heat dissipation without needing any additional cooling systems.
  • Use of thermal vias.
  • Use of materials such as Pyralux AP, FR 408 and other such materials.
  • Ensuring there is a reasonable distance between components to allow for heat dissipation.

3. Strict adherence to reference standards

There are fixed reference standards to be followed when it comes to PCBs for the aerospace industry. These include:

  • IPC 6012DS that lays down the performance standard for rigid PCBs for aerospace as well as military applications
  • AS/EN 9100, which is a series of standards developed by IAQG specifically for the aerospace industry.

4. Use of Conformal Coating in Aerospace PCB Design

Given the harsh operating conditions for aerospace PCBs, conformal coating is a step that cannot be avoided. Some of the conformal coatings include:

  • Electrolytic Nickel Gold
  • ENIG
  • HASL
  • Lead-free HASL

Such conformal coatings offer protection against heat, humidity and more. Once the conformal coating has been applied, the use of an acrylic based spray is prudent, as it protects the PCB from contamination as well as short circuits.

5. Routing Guidelines

It is important to choose the size of PCB traces so that they can handle the current load as also to ensure effective heat dissipation. It is recommended that the angles on the traces are less than 45°, so that the signal transmission is uniform. Additionally, it is important to separate components that operate at low frequencies from the ones that operate at high frequencies. This will ensure that the signal quality isn’t compromised. Also, the clock signals need to have proper physical shielding. It is also important to follow the rules to reduce crosstalk.

6. Use of flex and rigid-flex PCBs

The use of flex and rigid-flex circuit boards is widespread when it comes to the satellite, aviation and aerospace industries. However, as compared to industrial applications they are made of polyamide as opposed to FR-4. The advantages that it offers include:

  • It can adapt to small spaces.
  • It is light.
  • It is heat resistant.
  • It has high durability.

In fact, flex and rigid-flex PCBs offer high resistance to vibrations and shocks besides offering great mechanical and electrical connections. In addition, they work well in limited space applications. With their use, secure connections can be managed offering polarity and contact stability.

7. Aerospace PCB Design Testing

Above everything, what is required is robust testing. In fact, you need to go through a whole lot of testing loops to ensure that the design is reliable and will work well in the aerospace environment, which means working in zero-gravity in a vacuum as also working in extremes of temperature, depending on whether they are working on a low-orbit or geostationary satellite.

To sum up

With aerospace PCB design and manufacturing, the aim must be to offer high reliability even in the most difficult operating conditions. To this end, right from design to selection of right materials can all ensure that the PCB offers a failure-free operation. A robust board will ensure that it can resist g-force vibrations, thermal issues and more.

Mer-Mar Electronics is one of the leading aerospace PCB design and manufacturing companies that specialize in building ITAR compliance aerospace PCB assembly. We are committed to accurately reflecting your design specifications as well as meeting the aerospace industry standards. We at Mermar Electronics, assist our customers from initial design to mass production & delivery; as one of the leading Aerospace electronics manufacturing services (EMS) providers.

Latest Trends in Medical Grade PCB Design and Manufacturing!

By | Date posted: | Last updated: December 23, 2021
medical grade pcb design

The medical industry has shown an unprecedented evolution in the development of medical devices. As the new diseases take birth, we need to brace up to the situation and upgrade the equipment to handle any sort of challenges. Very rightfully, PCB design and manufacturing companies have been tirelessly developing devices for testing novel diseases. New trends have emerged in building medical device electronics. Innovation & flexibility have become the standard principles of PCB design and manufacturing. PCB manufacturers have been quick to find ways to innovate and adapt to the changing landscape in the medical industry.

In this article, let us find the latest trends in medical PCB design and manufacturing and how your CM can best respond to the emerging trends in the medical industry.

Trends in Medical PCB Design

The medical industry is dynamic with several advancements happening in the market. Recent advances that are currently in the market include robotics, wearables, machine learning, and AI-based software, higher resolution computer vision, and more. One needs to keep up with the latest innovations and PCB design trends.

High-power boards, open & transparent communication and other factors are quickly reshaping the medical-grade printed circuit boards.

Some of the latest trends in the foreseeable future are listed below. Choose a CM that keeps up with these latest Medical PCB design trends.

  1. Smaller the better

    The printed circuit boards for medical device electronics are becoming smaller and denser. The component placement density has increased. This is reducing the margin of error on the boards facilitating the adaptability in PCB designs. Thin and lightweight PCBs help you in heat dissipation.

  2. High power boards

    There has been an increasing demand for high-power boards. It can accommodate more abundant components. Typically, higher voltage levels operate in the range of 24 to 48 volts. Thermal design should be optimized, and heat dissipation should be minimized for high-power boards.

  3. Non-standard PCB Form-Factor Designs

    With more health awareness among the people, many have been attentive to their body and mental health. They have been investing in self-monitoring health devices for exercise, wellness, and other medical conditions. This has led to non-standard Printed circuit board form PCB design factor.

  4. High-density Interconnect (HDI) Boards

    Smaller boards that provide higher functionality and tighter interconnectivity paths with very less area for traces. And for the same reason, many medical boards go for the deployment of HDI boards.

  5. Flex Structures

    Flexible electronics with special manufacturing needs have to be incorporated into the PCB designs and this has picked up momentum in recent years. These are excellent options since you have space, weight, and size limitations. These are also better-suited for high-temperature and high-density applications.

  6. IoT Usage

    IoT is everywhere. Device interconnectivity is much needed for improving medical systems. We need smart data transfer which would be made easier with the help of IoT. Hence designing PCB assemblies for IoT is now a much-needed necessity. IoT-ready PCBs should also meet rather stringent standards and regulations that govern their manufacturing.

  7. Spread of COTS Components

    There are commercial-off-the-shelf components (COTS) that help in speeding up and improving the design process. You can achieve a higher degree of reliability and efficiency with these. But make sure you receive PCB products from a reputable source.

PCB Manufacturing Trends in Medical Systems

We are currently living in a world that is undergoing a fourth industrial revolution where the physical and digital boundaries are blurred. The communication systems and software have to improve the manufacturing speed and efficiency. To ensure optimal medical-grade PCBs, we need to incorporate the latest manufacturing PCB trends.

  1. PCB Design Intent

    The best way to incorporate the design intent throughout your PCB build process is to collaborate with the right CM partner early on in the development.

  2. Digital Twin Technology

    Under PCB manufacturing, digital twin technology helps you to prevent waste and also mitigate development costs. You can identify any potential errors even before the first board is out in the market.

  3. Optimize DFM and DFA Usage

    Optimize your medical PCBA development to meet a high yield rate. Also, let your CM use DFA and DFM standards and guidelines.

  4. Transparency

    Maintain open and transparent communication with your CM from the beginning so that you can have seamless collaboration between your CM and you for your medical-grade PCBs.

  5. Agile Manufacturing

    PCB manufacture can incorporate PCB design changes iteratively with minimal production disruptions.

Challenges while designing Medical PCB devices

Several key standards and regulations have to be complied with and adhered to while designing medical electronic devices to ensure the safety of both medical professionals and patients.

  1. However, any major technological breakthrough takes years to see the light and make an impact in the market. This is because, while we make improvements in the product design, there would be longer intervals to get the distribution approvals as one needs to make sure that all the necessary safeguards are in place.
  2. Raw material supplies also dry up and it also becomes difficult to procure. Even customer demands change and reshape product design and development.

Summary

PCB design and manufacturing trends are likely to disrupt the current market trends and would show positive momentum in terms of design innovation, reliability, and performance. PCB industry as a whole is evolving but more specifically in the medical industry niche.

You can go for a certified and experienced CM for building high-quality and error-free PCB assemblies for medical systems. The CM should be able to meet the rigorous medical industry standards as they would be of utility where human lives are at stake.

Mer-Mar Electronics is a certified and leading PCB manufacturer that gets things done in lesser turnaround time. Our team works on medical-grade PCB development for delivering high-quality equipment with superior support. To help you get started, we furnish some information for DFM checks and you would be able to easily see and download DRC files. Get in touch with us to know more about our medical PCB design and manufacturing services.

How to Prevent the Causes of Device Failures using high-speed PCB?

By | Date posted: | Last updated: April 2, 2022
high speed pcb

With speed emerging as a crucial factor in product performance, designs are often known to have a number of high-speed interfaces. It is therefore not surprising that signal as well as power integrity issues are often seen which in turn lead to device failure. In fact it is becoming increasingly important for design engineers to take into account the analog features of high speed PCB design.

To achieve signal Integrity of SI as it is popularly called, PCB paths need to be well-defined. In turn these well-defined paths allow that the signal is delivered from the driver to the receiver at the right time. On the other hand, if the design has poor SI, it is not likely to deliver the signal at the right time. A poor SI is also known to cause radiated emissions that are higher than acceptable. Issues in design can also lead to device failure causing it not to function at all.

PCB Design elements that aid in achieving high speed SI:

Transmission line behavior at high-speed frequencies- With clock rates and signal speeds increasing, the PCB trace lengths are on the same order of length as the edge rates passing them. Delays and losses therefore need to carefully weighed. The most common transmission line impedance to achieve is 50 Ω. To achieve the required impedance the PCB Material, its trace width in each layer need to be identified. The two commonly used transmission lines include the stripline as well as the microstrip. While stripline has the signal trace in between two reference planes, in the case of microstrip, the signal trace is routed on the outer layer. It is the signal speed requirement as well as the design complexity that determines whether stripline or microstrip needs to be used. Overall, microstrip is known to offer a faster signal path.

While considering signal trace, it is also important to choose a short trace with an not disrupted reference plane. The advantage with this is that current can travel to the receiver and return through the path of least impedance. The common return path problems include the following:

  • Discontinuity in reference plane
  • Change of layer of routed signal with no reference plane underneath

In turn, the above leads to signal reflection and ringing. Signal reflections can be a function of the driver, transmission line or receiver impedance. If the signal encounters a change in the impedance of the PCB, (known as impedance discontinuity), the signal can reflect back to its source and this can result in the distortion of the signal. In case of multiple reflections, ringing is a consequence. On the other hand if the driver, transmission line and receiver have the same impedance, the problems of reflection and ringing will not occur.

Another problem that arises is that of crosstalk. This is a result of coupling of signals and can occur if multiple signals couple if they are routed too close. Crosstalk can be prevented if the trace and return paths are twice the trace width away from other signals. Ringing can also increase crosstalk.

Factors need to remember for high speed PCB Design

  • Termination Topology
  • Lengths of traces
  • Speed of signals
  • Shape of traces, among others

In order to maintain SI, therefore, the following need to be kept in mind:

  • Identify high speed signals.
  • Ensure that the highest speed signals are on the top and bottom layers.
  • Signal traces should be kept one dielectric away from the return path.
  • Ensure good ground references are given
  • Maintain greater than 2x line width rule for inter-pair spacing.
  • Ensure there is more than 3x line width spacing from other interfaces.
  • Right- angle turns need to be avoided
  • Number of vias need to be minimized
  • High speed signals need to be kept away from noisy signals.

Power integrity

A power delivery network or PDN provided inside the system that complies with the power supply conditions, leads to power integrity. Compared to SI, Power Integrity is more difficult to visualize as there are numerous nodes and each node can impact the overall impedance. Issues related to PI are therefore harder to troubleshoot. A through study of Pi both in the pre & post layout PCB design and PCB manufacturing stage is therefore imperative. PI study today involves studies for loading at high frequencies.

The key in PI analysis is to treat power rails as transmission planes and analyze their characteristic impedance. The other issue is that there is different impedance in different frequencies and therefore components as well as placement locations need to be carefully worked on.

If you have any requirements or inquiries related PCB manufacturing, Get a quick quote or simply drop an inquiry at sales@mermarinc.com.

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