Use Valid Parts

• Availability? If not, these should be designed out to avoid timescale and budget increases.
• Recommended for use? Manufacturers are discontinuing or replacing parts continuously. Design out these parts.
• End-of-life? Just because you used a part on your last PCB design doesn’t mean you should use it again.
• Check before you create: When deciding on a part, do you check its status before adding it to your CAD library?

Footprint errors

• Your ECAD library: This must be verified, as your ECAD library forms the foundations of your products. Please do not take short cuts with your ECAD library, and don’t commit the cardinal sin of every engineer having their own library. If your foundations are unstable you will pay the price later in the product lifecycle, which will end up costing much more to rectify down the line.

Communication

• Can you build it? Don’t design in isolation. Communicate with your PCB manufacturer and PCB assembler: they will be more than happy to work with you. Your CAD system will allow you to design anything if you define unrealistic rules. Your design may look fantastic but if it can’t be made, you’ll be wasting your time.
• Fail to plan, plan to fail: Resist the temptation to just dive into laying out your PCB. Take a step back and review the challenges you are facing. How do the functional blocks of the schematic interrelate and how could they fit onto the board? Once defined, review with the engineer before you have to make wholesale changes. Then and only then look at the detail.
• Review and then review again: Define your milestones and perform smaller reviews regularly. Catch those issues as early as possible before they have a major impact on your PCB design.

• The late design change: You have just finished, you have created all the manufacturing files, and can breathe a big sigh of relief. It’s nearly the end of the day and then it happens: the late design change and the pressure is on. Make sure you understand the impact of the change, and don’t take any short cuts. ‘Less haste, more speed’!

The post Common PCB Design Mistakes appeared first on Quantum CAD.

Simultaneously, the designers need to account for the possible effects of high-speed signals in a PCB layout, considering that increasing clock frequencies and decreasing rise times may result in fluctuating signal or signal integrity issues.

You must use higher frequencies to overcome this issue. Hence, higher frequencies, ranging from 50MHz to 3GHz, have become a staple in designing PCBs.

Implementing effective high-speed PCB design is vital to meet and support real-world demands.

However, there are three main hurdles to overcome in dealing with high-frequency boards. These are:

1. Signal integrity
2. EMI/EMC
3. Dielectric loss.

Since signal transmission issues are remarkable when a PCB works with high-speed signals, an outstanding high-speed PCB incorporates different components and routing while deflecting signal integrity issues simultaneously.

Here at QuantumCAD, we’re experts in a range of custom PCB design processes – including high-speed PCB design.

Using our expertise in the field, this article will explain crucial factors to consider during the high-speed PCB design process, including the impact of wiring topology, taking care of signal integrity, and more.

What is a high-speed signal in a PCB?

Signal frequencies ranging between 50MHz and 3GHz are considered high-speed signals, such as clock signals.

In principle, a clock signal is ideally a square wave. Yet, the “LOW” level cannot instantaneously become a “HIGH” level or contrariwise.

Rather, the clock signal must adhere to a specific rise and fall time because of what appears to be a trapezoid in the time domain. Notably, the amplitude of the higher frequency harmonics of the clock signal is contingent on the rise and fall time. Specifically, if the rise time is longer, then the magnitude of the frequency harmonics will be shorter.

The impact of wiring topology on signal integrity

When signals transmit along the line on a high-speed PCB, signal integrity issues can occur.

The impact of wiring topology on signal integrity gets recognised in the fluctuating and inconsistent signal arrival times at each node. Plus, the timing at which the reflected signals arrive at a certain node is also irregular.

These inconsistencies result in the decline of signal integrity.

Generally, the Star Topology is used to prevent signal integrity issues. With the star topology, you can manipulate the signal transmission and reflection delay by controlling several equivalent lengths to improve signal quality.

Before using a specific topology, it’s imperative to consider the signal topology node conditions, the working principle executed, and the wiring difficulty.

Different buffers pose different effects on signal reflection. This means that, although generally helpful, the star topology may not solve certain devices’ signal delays, such as the digital address bus connection to FLASH and SDRAM.

On the other hand, on a daisy chain topology, the signal is generally communicated between the DSP and the SDRAM, ensuring the signal’s quality.

FLASH does not have a high loading rate, meaning that, in high-speed simulations, paying attention to the waveform at the FLASH is unnecessary as long as the waveform at the node, where the high-speed signal is transmitted, works efficiently.

Additionally, routing is essentially tricky, but unlike the daisy chain topology, having a massive sum of data address signals in a star topology makes routing extra challenging.

When do we need to take care of signal integrity in high-speed PCB design?

In principle, on a PCB, a signal should travel unimpaired and undamaged from a source (Tx) to a load (Rx), but this is not always the case.

More often than not, the signal gets to the load with a few losses, either by impedance mismatch, crosstalk, attenuation, reflection, or switching issues.

1 – Signal integrity

Signal Integrity (SI) is the measure of signal distortions and fluctuations in the high-frequency domain. Signal integrity enables the generation of practical solutions to predict and understand the critical issues revolving around the high-frequency field.

Rather than simple wires, high-speed PCB design requires traces to visualize as transmission lines.

Once the highest operating frequency in the design gets identified, it’s easier to target the pathways used as transmission lines for better signal transmission. These transmission lines must undergo digital and analog analyses to ensure functionality.

2 – PCB substrate

Another factor that you must consider in high-speed PCB design is the substrate material to be used.

Each PCB substrate has a unique dielectric constant (εr) value. This value determines the length at which signal traces can pass as transmission lines. With this available data, the PCB designers can manipulate and prevent signal integrity threats.

Specifically, with the dielectric constant (εr) value, designers can examine and evaluate the velocity (Vp) at which the signal flows and propagation delay (TPD).

Even more so, it’s crucial to take into account how insertion loss increases with signal frequency. The insertion loss (per inch) gets measured for FR-4 (glass epoxy) and high-frequency Rogers RO4350B material.

In sum, higher insertion loss may lead to more attenuation.

3 – How to suppress electromagnetic interference

Since the PCB is the source of Electromagnetic Interference (EMI), the high-speed PCB design is directly related to the Electromagnetic Compatibility (EMC) of various electronic products.

Giving enough focus on EMI/EMC shortens product development cycles and accelerates time-to-market rates.

Considering the EMC, it is important to consider its three key elements:

1. The source of radiation
2. The route of transmission
3. The victim.

The propagation route gets sectioned off into space radiation propagation and cable conduction.

It’s imperative to look at how it spreads first to suppress the harmonics. Power Supply decoupling, together with the necessary matching and shielding, is required to address conduction propagation.

One way to solve the problem of EMC radiation through conduction is by Filtering.

Additionally, you can consider the problem from the source of interference and the victim. For interference sources, consider using an oscilloscope. Using this, check whether the rising edge of the signal is too fast or whether there is reflection or overshoot, undershoot, or ringing. If there are any, consider matching.

Additionally, avoid using the subharmonic, 50% duty cycle signal that only demands more high-frequency components.

Finally, in terms of victims, consider measures such as land acquisition to address the problem.

Conclusion

With the continuous progression and advancement in our modern world, High-Speed PCB design is necessary and essential to keep abreast with our developing times.

Contact us

Is your business in need of expert high-speed PCB design services to keep up with the increasing product demand?

QuantumCAD can help.

With over 25 years under our belt in designing custom PCBs, numerous qualified PCB designers, and experience in working with some of the biggest brands, including Jaguar and Ericsson, we can deliver a custom high-speed PCB that suits your needs.

Contact us today to speak to a PCB expert.

The post The impact of high-speed PCB design appeared first on Quantum CAD.

What is a Flexible PCB?

Flexible printed circuit boards, also called flexible PCBs, are regarded as printed circuit boards which are flexible and can be bent once or multiple times to fit a product’s requirement. Noting this, there are still significant differences between rigid PCBs and flex circuits when considering design, fabrication and functionality.

A flexible printed circuit consists of a metallic layer of traces – which is usually copper – bonded to a dielectric layer – which is usually polyimide.

The thickness of the metal can vary; it can be extremely thin (<.0001″) to extremely thick (> .010″), and the dielectric thickness can vary from .0005″ to .010″.

Often an adhesive is used to bond the metal to the substrate, but other types of bonding such as vapor deposition can also be used to attach the metal.

Copper tends to readily oxidize so normally the exposed surfaces are covered with a protective layer. Gold or solder are the two most common materials because of their conductivity and environmental durability. For non-contact areas, a dielectric material is used to protect the circuitry from oxidation or electrical shorting.

We’re experts in all things related to flexible pcbs, including flexible PCB design. Keep reading to discover the advantages of flexible PCBs and get in touch with us to get your PCB designed by our specialist team.

What are the advantages of flexible PCB?

Now you know the answer to the question ‘what is a flexible pcb?’ you can start looking at some of their advantages.

An advantage of a flexible PCB is that the number of material combinations that could go in a flexible printed circuit are nearly endless; current, capacitance, chemical and mechanical resistance, temperature extremes and type of flexing are just some of the criteria that impacts the material selections that best meet the functional needs.

This makes flexible PCBs a great solution to a product packaging problem.

Further advantages of flexible PCBs are:

• Flexible circuits allow unique designs which solve interconnection problems
• Flexible PCBs require fewer connection and solder joints, which lowers the cost and improves product reliability
• The ability to fold and form flex circuits enables a package size reduction due to a decrease in weight and space. This considerable weight reduction is a benefit over wire harnesses, and rigid assemblies.
• The thinness of the material makes flexible circuitry the best candidate for dynamic flexing applications up to millions of flexures.
• Flexible circuits dissipate heat at a better rate than any other dielectric materials, meaning that flexible PCBs are a great option to be used in high temperature applications.

You might be surprised that today’s flex circuits are so good at getting rid of heat, especially because the boards are getting smaller and smaller. Size is not important. Instead, the real key is surface-to-volume ratio, and flex circuits offer an excellent surface-to-volume ratio.

Additionally, the circuit’s compact design allows for a shorter thermal path, which prevents the build up of heat. Recently consumer electronics giant Samsung’s probe into its Galaxy Note 7 exploding was found to be overheating. This helps you understand how dangerous it can be when a device doesn’t dissipate heat well.

In addition, flex circuits make the installation and repair both practical and cost effective, and with flexible PCBs, replacing the circuit board and wires is relatively straightforward.

Plus crucially, flexible circuits eliminate human error which is common in wire assemblies. This means that using flexible PCBs ensures that the manufacture of your PCB is least likely to go wrong.

Due to their many advantages listed above, we use flexible PCBs in our custom PCB design process for a range of projects.

Although you should now be able to answer the question ‘what is a flexible pcb?’, you may still not know when different types of circuit are needed. Keep reading to find out more.

When is a double-sided flexible circuit needed?

A double-sided flexible circuit is required when the circuit density and layout can’t be routed on a single layer, Maybe Ground or power plane applications being used for shielding applications.

There may be a dense surface mount assembly preventing all routing on one side, however component assembly is available on both sides.

When is a multilayer flexible circuit needed?

As with a double-sided flexible circuit, a multilayer circuit is used instead of a single layer, where the circuit density and layout can’t be routed on a single layer.

The benefits of using a multilayer flexible circuit are:

• A dense surface mount assembly
• Increased circuit density
• Controlled impedance with shielding
• There can be unbonded regions to increase flexibility
• EMI/RFI shielding
• Ground and power plane applications required for shielding applications

When should you use flexible rigid PCBs?

A flexible rigid PCb has an easier assembly in the final product in comparison with other flexible boards. This maximises the space by reducing the need for interconnects between individual rigid boards.

It’s advised to use flexible rigid PCBS when you’re either using high density dual side components or when controlled impedance is required.

Common materials for flexible PCBs

Flexible Base Film

A bendable film that acts as an insulating (dielectric) base material and coated with a dielectric cover layer on the top:

Base Copper Thickness

This is for use as electrical conductors with conductive pathway printed on the base film:

Solder Mask

A thin lacquer-like layer of polymer that is applied to the copper traces of a printed circuit board (PCB) for protection against oxidation, and to prevent solder bridges from forming between closely spaced solder pads. Flexible solder mask is essentially the same epoxy-based material as used on rigid PCBs but with the addition of a flex agent:

Surface Finish

The surface finish forms a critical interface between the component and the PCB. The finish has two essential functions, to protect the exposed copper circuitry and to provide a solderable surface when assembling (soldering) the components to the printed circuit board.

Stiffeners

When working with flexible PCBs there are times when certain parts of the flexible PCB need to be rigid. We do this by adding mechanical support to the parts of the PCB that require it. This mechanical support is called a PCB Stiffener.

Contact us

At Quantum CAD, we’re experts in designing a range of flexible PCBs that suit your needs.

We’ve been designing leading PCBs for clients in a wide range of industries for more than 25 years, meaning that we are well equipped to handle your request.

Interested in speaking to a PCB expert to get your project started?
Contact us today

The post What is a flexible PCB? appeared first on Quantum CAD.

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There is now a growing demand for high-power PCBs. This is because modern and up-to-date electronic devices need to operate at faster speeds due to their more advanced components that need to combat current needs and complexities.

This blog is going to discuss what high-power PCBs are, what they’re used for, and the challenges in designing them.

What are high-power PCBs?

As previously mentioned, high-power PCBs are those that are designed to withstand higher currents and temperatures.

They are typically made from copper because copper has low resistivity and therefore makes for an excellent conductor. Copper has been used as an electrical conductor since the early 1800s, and due to its high level of electrical conductivity, it’s still the first choice for any electrical connector.

What are the differences between high-power and regular PCBs?

• The material choice – Because high-power PCBs experience extra stresses on its thermal conductivity, the material choice will differ depending on whether you’re designing regular or high-power PCBs.

• The coefficient of thermal expansion – For high-power PCBs, this must be selected in a way whereby the expansion or contraction of the material caused by the additional high-power doesn’t cause mechanical stress on the PCB.

• High-power PCB material must also have low loss, as a high-loss PCB generates more heat.

In the custom PCB design process, there are extra considerations that have to be made when designing high-power PCBs over regular PCBs. See this list of considerations further down.

How many amps can a PCB handle?

There are numerous manufacturing possibilities for a PCB, including copper thickness, number of layers, the material used, and more.  However there are general guidelines in the public domain surrounding track widths to carry specific currents to take advice from.

The chart below shows an IPC chart offering simple information on 1oz copper.

Designing high-power PCBs

PCBs that are used for RF applications, amplifiers or power conversion circuits will need careful consideration in terms of key design elements.

These include thermal conductivity (TC), thermal expansion (CTE) and material losses.  Calculations at the start of the project are critical in choice of PCB topology and materials.

When designing high-power PCBs, both thermal design and heat dissipation must be optimised, which is a significant challenge for designers.

In addition, designing high-power PCBs require further considerations than when designing regular PCBs because both thermal design and heat dissipation must be optimised, which is a significant challenge for designers.

These additional considerations are:

• Safety – Heat dissipation and short circuits are both potential safety hazards that need to be considered in the design process.

• Planning the layout – When designing high-power PCBs, you need to allow sufficient space between the components for copper pours, increased via sizes and trace widths.

• Trace widths – You should use a trace width calculator to ensure the high-power PCB has the capacity to carry the sufficient current required.

• Copper pours – Use copper pours wherever possible to aid heat dissipation.

• Double up on layers – By doubling up on layers of copper pours stitched together with vias, you will achieve greater heat dissipation.

• Thermal reliefs or Solid floods – Use thermal reliefs on all non-power nets. However, high-power nets are better with solid copper to pads. Note that these may need to be hand soldered.

• Thick PCBs – Thick PCBs create more space which allows heat to dissipate more effectively, resulting in the potential to reduce the overall board size.

• Materials – Remember to select the appropriate material for your application. As mentioned FR4 is the most commonly used material in PCB manufacturing, but if a high-power PCB has requirements that can not be achieved using FR4, materials such as Rogers substrates, pedestal PCB, insulated metal substrates (IMS) and copper INVAR.

Contact us

With the multiple things that need to be taken into account when designing high-power PCBs, it’s essential that you know exactly what you’re doing.

Another option is to use an expert, like us, to design your high-power PCB for you.

With over 25 years of experience, our specialist team has the skills to design your high-power PCB.

Simply get in touch with us to speak to one of our PCB experts and start your project today.

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