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Microwave Printed Circuit Board Concept

Microwave Printed Circuit BoardConcept

A microwave circuit refers to any electrical or electronic device which operates on microwaves or uses microwaves for its operation. Some examples include radar systems, satellite dishes, cell phone towers, and TV antennas among others. Such circuits are designed to operate at specific frequencies or bandwidths so that they do not interfere with each other.
A microwave is an electromagnetic wave of frequency between 1GHz and 30GHz. It falls under the band B, C, D, and E in IEEE standards. Microwaves occupy a large part of the entire RF spectrum as compared to other frequencies. The global demand for communication devices such as routers, DSL, and mobile phones has increased significantly due to technological advancements such as internet connectivity being provided by these devices and advancements in technology by small-sized electronic components that can operate at high frequencies. As a result, there is an increase in demand for microwave circuit design services.
Microwave PCBs have to meet certain requirements that have not changed even though the designs have.

Understanding The Concept

So, what is microwave PCB? Simply put, it’s a pc board that incorporates circuitry optimized for frequency bands in which microwave signals are most commonly used. As the boards are designed specifically for such frequencies, they offer superior performance over traditional boards in terms of both design and reliability. Besides, their smaller size and lower overall weight make them perfect for use in applications where space and transportation costs are at a premium.

Microwave Printed Circuit Board Concept
Microwave Printed Circuit Board Concept

Why Microwave Technology?

The microwave portion of telecommunications is used for point-to-point voice and data communications. You can also use it for two-way radio, cable television, and telegraphy in a limited range of frequencies. As it allows information transmission at high speeds over long distances, it is very common in military organizations. For these reasons and more, microwave technology plays an essential role in today’s technological world.

As such, it was important that an efficient way to transmit microwaves be developed, the result was a device called a microstrip line. In short, when combined with other components, microstrip lines are what allow microwaves to travel great distances while maintaining optimal signal strength.

A microstrip line consists of three main parts, including a metal foil, dielectric material, and a ground plane. Metal foil serves as an antenna, and the dielectric material acts as a waveguide. Whereas the ground plane provides electrical shielding. These three elements are placed on top of one another and bonded together using heat or pressure, which creates a single unit known as a structure.

What Are The Factors That We Need To Consider While Selecting The Right Board?

Choosing a board for microwave design is not an easy task. There are several factors that we need to consider such as frequency, applications, and modes of use. There are three main types of boards, including through-hole, single-sided, and multi-layer boards. It is also very important that you pick out a board that matches your frequency range.
For example, you need a board with wider spacing between conducting tracks at higher frequencies than low frequencies. So, make sure that you select the right one depending on your frequency range.
The next thing that you need to look into is your application or project needs. Depending upon your requirement, you can go ahead with either through-hole or SMD-style component placement methods.
The final step in choosing a microwave PCB will be deciding on the thickness of the copper traces before the Circuit board fabrication process. You will have to choose according to your project needs whether thin or thick copper traces would be best suited for your application. But, keep in mind that thicker copper traces provide better current carrying capacity but they are more expensive than thinner ones. So, again it all depends on what kind of budget you have set aside for your project.
Every board has its unique features, so do check out every detail before buying one. A well-known feature of these boards is their ability to withstand high temperatures without getting damaged. This makes them ideal for high-temperature environments like ovens, motors, etc.
Another advantage of using these boards is their small size which makes them easy to handle and transport from one place to another. They also come with different pin configurations like double row, single row, and even no pin configuration options. Some of them also offer the ground plane on both sides which helps in reducing noise levels due to capacitive coupling.
In addition to all these advantages, most of these boards are made up of epoxy glass material that provides insulation against electric fields and other environmental factors.

Installation of Components onto A Microwave PCB

Let’s now take a quick look at how we can install our components onto a microwave PCB. First of all, get yourself ready by wearing safety glasses and gloves so that you don’t end up hurting yourself during installation. Make sure that you have gathered all the tools required for installation beforehand.
Next, remove any existing solder mask and protective coating from the surface of your board. Make sure that there is no dirt or dust present on it as well. If necessary clean it thoroughly with acetone and then wipe dry with a lint-free cloth or paper towel.
After doing so you can proceed to install the components onto it just like any other circuit board out there. Remember to always start with your smallest components first and work your way up to larger ones. Before soldering it is recommended that you apply a thin coat of flux on all surfaces where you are going to be placing your components. Then apply a little bit of solder paste on each pad and lastly place your component in position and heat it with a soldering iron.
Make sure that you inspect for proper alignment of your parts and if needed apply extra flux or reposition it until everything looks just right. Once you are satisfied with your results, it’s time to apply a generous amount of solder over all your components. Once you have done so, wait for it to cool down and that’s it.

How Do I Choose My Microwave PCB Manufacturer?

Before you start shopping for a company to make your circuit boards, there are a few things you should know. Here’s a quick rundown of some key questions you should ask yourself as you’re shopping around, such as:
• Does your board require special materials?
• Do you need services outside of just PCB manufacturing?
• How many layers do you need?
• What sort of electrical isolation is needed between high-voltage and low-voltage areas on your board?
• How much space will you need for mounting components?
Once you have answers to these questions, it will be easier to find a vendor that can meet all of your needs. Of course, in order to get accurate information from vendors about their capabilities, you may need to provide them with more details about your project than what we’ve provided here. They must understand exactly what kind of design you’re working with so they can give you honest feedback about whether or not they’re able to work with it.

What Is Hybrid Microwave Circuit

A hybrid microwave involves a thin film or thick film technology to construct different microwave circuits using a medium that can transmit signals. The medium, in this case, is mostly sapphire, alumina porcelain, ceramics of high level, or quartz.
There are two types of hybrid microwave circuits, passive and active. Passive hybrid circuits consist of passive elements like resistors, capacitors, inductors, and filters. Whereas active hybrid circuits use active devices like transistors, diodes, etc.
Active hybrid circuits have better performance than passive ones, but their fabrication process is more complex than passive ones because they contain semiconductor elements, unlike passive elements. Thus it is easier to fabricate passive hybrid circuits than active ones.
There are various factors affecting the microwave circuit design such as size, power consumption, cost of materials used, and the operating temperature. These factors must be considered while designing a microwave circuit.
Understanding the Lumped Componentization of a Microwave Circuit
A lumped component model is one of several techniques used to analyze and design high-frequency microwave circuits. It was originally developed for analysis and design in communication systems. It is characterized by using lumped elements (e.g., resistors, capacitors, inductors) instead of transmission lines or other forms of circuit elements whose behavior is dominated by distributed parameters like permittivity and permeability.
In addition to being useful for analysis, lumped element models are also useful for conceptual designs because they make it easier to visualize components and their interconnections. The concept of lumped element models is very similar to that of ideal transformers used in a single-sideband modulation. In this model, an ideal transformer represents an actual transformer with losses and non-ideal characteristics asleakage reactanceare replaced by zero values.
The equivalent circuit consists of an impedance connected between port 1 and the ground, plus a series capacitor representing the leakage reactance and shunt conductance. This technique is often referred to as lumped parameter modeling. Other examples include bridge networks used in an RF filter design and the current source inverters used in active filters.
Would like to know more about the Microwave PCB conceptor printed circuit board assembly? Email us at sales@pnconline.com

PCB Design

Possible Problems & Solutions in a PCB Design Process

Whatever electronic and digital device you have, it depends on a printed circuit board for signals transmission to help it operate. These devices need a well-designed structure and manufacturing, but you have to encounter many issues in this case that we will discuss here.
Any issue in the design of a PCB would cause delays in its manufacturing, so you must know how to avoid them. Similarly, some problems happen before the design that designers can avoid through proper strategies.

PCB Issues before Its Design

The designer should consider certain steps for a successful design, such as project management and its timeline. You should allocate the project resources and time like there should be enough time to edit your design according to the rules. Sometimes the designers miss certain schedules in a hurry, delivering an incomplete design having many errors.
The designer should be an expert in using the latest design tools. You must have a complete library of CAD materials and should also know the basic design rules. Though these steps look minor, they should be in hand before starting a PCB layout. Now, we will discuss some common PC design issues, so let’s begin.

Component Problems

Sometimes the designers choose the wrong components just to speed up the process, but it can affect a circuit board’s effectiveness. Designers often go for an existing circuitry or select an old and familiar library as it’s convenient for them. But, it becomes a problem when such components or parts are not feasible due to their price or they are not available. So, the designers should be well-informed in terms of design libraries and should choose the Printed Circuit Board parts wisely.

Issues with Physical Parameters

The designers often choose familiar things related to materials, board layout, and outline, as well as the stack-up for layers. However, the prices of such materials may change, besides, their availability can also become an issue. Such changes can affect the design rules according to a different substrate. Likewise, the outline of the PCB also changes due to the design and fabrication limits. So, the designer should discuss all design parameters with their manufacturer before designing the layout.

Locating the PCB Components

A PCB has different components and their footprints should be well-placed on a PCB for precise manufacturing, and it’s called the DFM or Design for Manufacturing for a circuit board manufacturer. If you ignore the DFM, it would result in a high-cost and less effective PCB.
There are certain DFM rules to follow in terms of distance between the components and the circuit board’s edges, the distance between different components, and spacing between various features of the board and components.
There should be enough space around the test points to help a circuit board get tested automatically. You should also consider the placement of the parts that get hot as it can result in thermal issues, affecting a PCB’s performance. Moreover, the high-frequency components should be located in such a way as to have powerful signals.

Routing Issues of Traces

Another PCB design issue is regarding the incorrect trace routing. Like, the widths of the traces and their distance should be correct. The designer should discuss these parameters with their manufacturers to have a precise trace width. Moreover, the weight of the copper should also be correct for perfect routing.
At the same time, the designers should input these values into the design rules while working through CAD. By having well-planed rules and design limits, you can avoid issues regarding a controlled impedance or routing. You can also reduce the burning of traces that occurs due to a lack of copper in case of high currents. You can also eliminate poor signals, and poor copper balancing that happens on the layers of a PCB.
Similarly, the issue of the thin high-voltage traces is also there. Sometimes the trace of a circuit board needs a high voltage that a small trace of less width can’t handle. So, you must calculate the trace width through PCB software, like CAD which has a width calculator for PCB traces.
The designer also has to consider the suitable rise in the temperature for certain traces that helps them to evaluate the current capacity of the trace to choose a compatible copper weight
Moreover, you need high-frequency routing for high-speed signals. Trace routing is not an issue in the case of microcontroller PCBs because they do not need high-speed signals. But, the trace paths need attention for the high-frequency circuit boards because of the address bus and external data.

PCB Design
Possible Problems & Solutions in a PCB Design

Ground Planes and Power Issues

Most designers ignore a network that delivers the power and sometimes they don’t even think about it. If you don’t have a well-designed ground, it would result in poor signals with the noise and EMI emissions. So, the designer should focus on these issues with proper planning after discussing them with the manufacturer. You should know the precise configuration and planes’ location in the layer stack of a PC BOARD.
The design of the ground planes is important to avoid the blockage of signals’ return paths. Moreover, you can also control the interference of the ground and analog with each other by considering these points. Both ground and analog are different in terms of circuitry.
The electric devices involve the linear and switching regulators in terms of voltage. There is low energy by linear regulators, but they are less costly and many PCB designers use them for this reason. But, the linear regulators are not easy for low-noise applications that use high power.
Whereas the switching regulators involve more complicated designs than linear regulators. They are effective in terms of energy, but they need a detailed design for a PCB. So, you have to be careful in this case and should follow the datasheet rules strictly.

System Design Issue

A PCB is just a part of a large electronic device having a specific system that a designer has to consider. However, most designers focus on just the design of a circuit board. Such ignorance can cause several issues during the PCB assembly, such as incompatible wires and board connectors, inaccessible human interfaces or switches, and the lack of space for repair or system debugging. So, the electrical engineers should focus on the design of the full system instead of just a circuit board.

Wrong Usage of Decoupling Capacitors

The electrical parts of a circuit board need stable electricity without interruption. The hardware of a PCB involves decoupling capacitors for stable voltage and this decoupling happens on the rail that supplies the power. You must place the decoupling capacitors close to the pin for maximum and stable current to help it pass through the decoupling capacitors before it reaches the pin.
All these issues are technical that affect the hardware of circuit boards. You must solve these issues to have an effective and functioning product or device.

How to Find the Design Resources for PCB

You can avoid or eliminate the above problems by accessing suitable design resources. You can easily find them online from different companies that offer PCB design, manufacturing, and also provide calculators to calculate specific design parameters. Such companies also offer PCB design and manufacturing services other than just guiding you in a PCB design.

Frequently Asked Questions

What Is Meant By PCB?
PCB is an abbreviation of Printed Circuit Board. It is used in electrical devices to provide them with signals or current to operate. Printed circuit boards are used in different industries, including networking, electronics industry, gadgets, aerospace, and much more.
What Is DFM In A PCB?
DFM is Design for Manufacturing which means you have to have a special layout design for a PCB to be manufactured correctly. You will have to face many issues if there is no DFM.
What Are PCB Design Issues?
PCB design involves different issues regarding its components, power supply, routing, design parameters, decoupling of capacitors, layers stuck-up, copper weight, etc.

Final Thoughts

Any issue in the design of a PCB would cause delays in its manufacturing, so you must know how to avoid them. PCB design involves different issues regarding its components, power supply, routing, design parameters, decoupling of capacitors, layers stuck-up, copper weight, etc.
The designer should consider certain steps for a successful PCB design, such as project management and its timeline. You should allocate the project resources and time like there should be enough time to edit your design according to the rules. Sometimes the designers miss certain schedules in a hurry, delivering an incomplete design having many errors.
All these issues are technical that affect the hardware of circuit boards. You must solve these issues to have an effective and functioning product or device. You can avoid or eliminate the above problems by accessing suitable design resources. You can easily find them online from different companies that offer PCB design, manufacturing, and also provide calculators to calculate specific design parameters.
Would like to know more about the PCB design process or PC Board assembly? Email us at sales@pnconline.com

PCB Design, Selecting the Right PCB Trace Widths?

Every PCB designer has a series of decisions to make PCB Design as they translate an abstract schematic into a functional, reliable, and manufacturable PCB assembly. Placing the components on the    PCB is usually the first step, connecting those components with copper conductors to create the circuit is the next.  To connect the components, the layout designer must interpret the circuit netlist and turn that netlist into actual copper traces, subject to constraints of both manufacturing technology and the laws of physics.  One of the most important considerations for the designer is the appropriate trace width for each of those connections. The width of each trace determines both the real-world performance of the circuit and the overall size and number of layers of the PCB.

To balance circuit performance and PCB size, the designer needs to balance four considerations:

  • The manufacturer’s minimum trace width and spacing
  • The size and pitch of the component pads that the trace will connect
  • The amount of current flowing through the trace
  • Whether the trace is part of a controlled impedance circuit

Minimum Trace Width and Spacing

The manufacturer’s minimum trace width and trace spacing will define the smallest trace width that can be used for all signal traces that do not carry significant current or have impedance constraints.  The minimum trace width is typically used as the default for the layout, since using the minimum trace width will result in the smallest possible PCB and the most flexibility in routing.

For a standard Printed Circuit Board, fabrication minimum trace widths/spacing is typically 5 mil (.127mm). PNC’s High Density Interconnect (HDI) PCB trace width/spacing can be as narrow as 3 mils (.076mm)

Trace Width vs Pad Width

Another consideration when selecting trace widths is that the trace should be smaller or equal to the pad width. For the most part, if working with the minimum trace widths, this will not be an issue, however, care must be taken when laying out the traces and pads for high current applications.

High Current Traces

Once a designer has placed the components in the layout, they will often focus next on creating the power and ground traces to the active components.  This is because the current carrying traces need to be appropriately sized and routed.   Signal traces, which are typically at the minimum trace width, can be more easily routed around the larger power traces.

Copper PCB traces, like any conductor, have an internal resistance that is proportional to the conductor length, and inversely proportional to its cross-sectional area. Since the copper on a layer is of a uniform thickness, the width of the trace determines its cross-sectional area.  There will be both a voltage drop along the trace as well as heating of the trace due to the power dissipation.  If a PC Board trace is not sized appropriately to carry the current required by the circuit, the trace can fail due to overheating, or the high voltage drop along the trace can cause intermittent circuit problems as the current and thus the voltage drop in the trace varies over time.

Designers often create an internal copperlayer with multiple buses of various voltages.  Since that layer consists only of power busses, the buses can be quite wide.  The designer will then connect the individual components to the bus using vias rising to the component’s power pins.  A bus based design reduces voltage drop at far from the power supply while reducing the width of the short connector trace to the same size as the component pin pad.

In the days before the internet and sophisticated PCB layout software,  designers would use the pages of current vs trace width tables  in IPC 2152 “Standard for Determining Current Carrying Capacity in Printed Board Design”  Now there are online calculators  based on those tables that take in to consideration all of the factors involved in determining the appropriate trace width for a specific current and allowable temperature rise of the trace due to the power dissipation. Many full featured Printed Circuit Board layout applications have the calculations embedded in their design rules.

If a PCB is intended for high power applications such as motor control or an LED power supply, a copper layer thicker than the typical 1 oz can be used but note that it is difficult to etch fine traces and pads in thicker copper.  Make sure to check with the PCB fabricator about their capabilities. PNC has experience with thick copper layers and can provide advice to the designer about what is possible.

Controlling Trace Impedance

The last consideration in selecting trace widths is the impedance of the trace, which becomes a factor in high frequency signals such asDDR busses, video such as HDMI, and high speed serial communication like USB and Gigabit Ethernet. At these high frequencies, not only the trace resistance, but the capacitance and inductance of the trace become significant factors.

Designing controlled impedance (CI) circuits is beyond the scope of this post, because designing a controlled impedance circuit requires taking into account the dielectric constant of the PCB, the length and routing of the trace in addition to the width of the trace.  However, trace width is one of the most easily controlled elements of impedance controlled circuits,so the trace width on individual controlled impedance circuits may be different from the width of other low frequency signal traces, and those traces may be finetuned after the prototype PCBs are tested.

The design of controlled impedance circuits is described in detail in IPC-2141A “Design Guide for High-Speed Controlled Impedance Circuit Boards”, and many of the formulas are available in online calculators or as options in PCB layout applications. When designing high speed circuits, it also pays to work with a PCB manufacturer like PNC that has expertise in fabricating PCBs with precise and consistent dielectric properties.

Schedule a Design Review with your PCBA manufacturer

 The designers at PNC have experience with both high power and high-frequency RF and microwave PCB layout designs.  Because they work closely with the manufacturing team, they know what is possible to achieve with the thick copper layers used in today’s compact LED and motor controllers,  and they know what it takes to maintain consistent dielectric properties in the substrates, needed for predictable RF performance. Let them help you with your design.