Tag Archives: PCB Fabrication

PC Board Electrical Schematic and Its Functionality?

Whatever we create, including a PC Board,is a picture or an idea that we convert to paper in the form of a diagram. You can’t proceed with manufacturing without a proper PCB layout or schematic.

An electrical schematic is a conceptual plan or drawing that helps understand the physical aspect of a PCB in terms of assembly.
The basic purpose of electrical schematicsis to have design communication.It should help manufacturers clearly understand it.Besides, the schematic directs you to makea PCB layout.

Schematics involve specific elements which are essential to understand, such as:

  • REFDES or reference designates
  • Symbols representing the components
  • Outputs
  • Nets

To know schematics in detail, you have to understand the above elements.

REFDES or Reference Designators-Identifying Labels

Identifying labels or reference designators help understand components because they describeso much about them. If REFDS is precise, it helps a reader to identify the types of the components and symbols,depicting every component.
So, each electrical component or part has a standard symbol.However, onlyspecific schematics follow such standards.
In some cases, reference designators can fully describe the component type, like when there is a generic box with pins itrepresents a passive component.

At the same time, reference designators also connect to theBOM, and bill of materials. Every Printed Circuit Board component needs a part number that BOM shows. Besides, it also helps find the area or location where components should be installed.
The format of the reference designators consists of a code in the form of a letter that describes the component, and its type having a specific number.

Symbols Representing Components

The electrical schematic has specific symbols of the physical components of PCB assembly in terms of soldering. They also describe the circuit boards’ structures, such as test points and vias.

The symbols are specific shapes or they are diagrams to indicate the type of PCB components. There are symbols for all electrical components like capacitors, diodes, resistors, and transistors.

The symbol of each component consists of pins that help in creating the electrical connections. The pins of all schematic symbols have specific numbers,depicting the physical components.

Designers can assign either a single symbol or multiple symbols to represent a single component of a PCB. Whereas the components having several pins are assigned many symbols to create a readable electrical schematic.

When a component is having multiple symbols, each symbol representing the same component has a similar designator.

Electrical Components-Resistors

PCB has many electrical components, including resistors. The U.S designers use a zigzag line to describe a resistor. Whereas its symbol is a rectangle according tointernational standards.On the other hand, the letter R in schematics isa representation of the resistor.

CapacitorSymbols and Letter

Capacitors have two types, includingpolarized capacitors and non-polarized, and both have different symbols. The curved line is a symbol of a negative terminal of a polarized capacitor. Whereas the plus sign denotes a positive terminal of a polarized capacitor.Whereas the letter C defines a capacitor in schematics with REFDES.

Inductor Symbol and REFDES Reference

Inductors are also important passive components of a PCB, and their construction involves a series of curves.Manufacturers use a coil of wire to make inductors. Whereas the letter L defines a capacitor in schematics with REFDES.

Diode Symbol and REFDES Reference

Some other PCB electrical components within the PCB design include diodes that permit the current to travel in just one direction. The diode has different types, including

  • Zener diodes
  • LEDs or light-emitting diodes
  • Schottky diodes

Zener diodesprevent the reverse flow of a current. However, the reverse flow can happen at a certain electrical power level.
There are also LEDs or light-emitting diodes which emit light when having a forward flow of a current.
The Schottky diode has simple features,but it switches quickly and the voltage drops in a lower forward direction.
Other than LED, the letter D or L defines a capacitor in schematics with REFDES.

Transistors Symbol and REFDES Reference

Transistors involve the flow of current at the primary terminal and they function like switches. The basic types of transistors include:
Bipolar Junction Transistors-BJTs: It is a current managing device that helps a current flow either into one base pin or out of it, changing to high currents passing through emitters and collectors.

Field-Effect Transistors-FETs: The FE transistor is another current-managing device that helps voltage turn on the current on the pin, via source pins and adrain. Various drawings indicate transistors and the letter Q and M define a resistor in schematics with REFDES and also represent the MOSFET. However, some designers use the letter T in the wrong way.
Variable Resistors’ Symbol andREFDES Reference

Variable resistors have two categories:

  • Potentiometers-three terminals
  • rheostats-two terminals

The function of the variable resistors is to customize resistance according to users. An arrow across the resistor represents the rheostats, whereas an arrow on the side of the resistor shows potentiometers.

There are also varistors or voltage-dependent resistors which resemble the variable resistors, but they are denoted by a line across them.The symbols of the resistors include R, VR, and RV, depending on the type of the resistor.

IntegratedCircuits, Symbol, and REFDES Reference

A single-package circuit developed with a semiconductor is an integrated circuit. You can also consider such circuits asamplifiers, processors, power regulators, and memory of a device. The shape of the integrated circuit is like a rectangle or a square that you can install on a PCB. It is a box with power inputs and outputs or pins and sometimes a board has many boxes.

The symbolof the integrated circuit in a schematic is the IC or the U.

Resonator, Crystals, and Oscillators, Symbol and REFDES Reference

PCB also has resonators, crystals, and oscillators, which give a consistent frequency output. These elements are different in terms of circuitry and characteristics but they have a commonfunction.

Some Other Symbols

There are also several other symbols to show interconnections on a schematic having labels to find their electrical nets.
Mostly there is no reference designator for non-component symbols, however, some have symbols like TP or test points, and X, and MH on REFDES.

Understanding Nets in Schematics

The wired connections on the printed circuit boards are what designers call nets. They are lines that connect symbol pins to the nets. You have to properly label the nets while making schematics to help manufacturers identify them. Specific symbols depict thenets to the same or different pages when you don’t draw them as connections, such as interpage and intrapage symbols.

Try not to overlap the nets to have good readability, however, you can’t ensure it every time. A dot or a circle on a schematic diagram shows two nets’ connection. If there is no DOT in a schematic, it means there is no connection between the nets. Whereas advanced drawings have wire hops to show that the nets don’t connect.

Outputs of Schematics-Netlists & BOM

The schematic diagram has two important outputs, including BOM, and netlists. The netlist is a file that designers use to understand routing and parts’ placement on a PCB. The format of thenetlists can vary in symbols. The name of the nets is presented in the netlist, showing thelocation of connectionsbetween the PCB parts. Netlist also has an output tool to give names to the nets which were without names.
Generally, there are several tables in a netlist, listing the PCB components and their names, net names, and some other essentials. Sometimes the netlists include additional information to help you understand the SPICE.

Bill of Materials-BOM

Bill of materials shows data in the form of a spreadsheet,matching the REFDES in schematicshaving a number and a physical component. Designers use different formats for BOM outputs, depending on the nature of schematics and your requirements in terms of output.
There can be many reference designators with independent partnumbers to help with manufacturing. Some detailed BOMs consist of specific part numbers of a company, quantities of components at different locations on a PCB, and the part numbers for different vendors. In other words, BOM has essential information to understand schematics and develop it through different steps, including SMT assembly.

Final Thoughts

You must know that the electrical schematic is a drawing that helps understand the physical aspect of a PCB in terms of assembly. The main aim of electrical schematics is to have design communication and help manufacturers construct the PCB. It should help you clearly understand parts and assembly. All electrical components have standard symbols. But, only specific schematics follow such standards. Different software help make electrical schematics that you can explore online.
Would like to know more about Electrical Schematics or printed circuit board assembly? Email us at sales@pnconline.com

Ultimate Guide to PC Board Thickness

Ultimate Guide to PC Board Thickness

Printed circuit boards are vital parts of electronic technology and you have to focus on various factors to design or buy them. PCB thickness is the most important factor in this case. However, the weight, profile, and components of PCB also matter a lot.
PCB thickness can influence its function, affecting resistance and conductivity. The application of a circuit board determines its thickness and there are different levels of thickness in this regard.

A-Thickness Of A Standard PCB

A standard printed circuit board has different types, like one-sided having one layer of copper or double-sided boar with two layers of copper. Whereas multiple layers are also in practice. The double-sided PCB has a substrate layer between two layers.
Generally, a standard circuit board is 1.57mm or 0.0065 inches as it used to be the thickness of the plywood in old circuit boards. Later, multilayered PCBs emerged and the designer had to make their thickness according to the connectors. So, the designers need a standard thickness of 1.57mm.
The board thickness also ranges from 0.008 inches to 0.240 inches, and you can select any thickness between these figures to match the PCB application. You can give your requirements to the manufacturer or can hire an engineer to evaluate PCB thickness for a specific application.

Copper Thickness Of A Standard PCB

You also have to consider the copper thickness as it helps get the desired PC Board thickness and influences its function. Like, one square foot area of the circuit board needs an ounce of copper which becomes 1.37 mils. But, it can vary, depending on your needs according to the current that passes through the board.
Most circuits come up with 1oz copper i.e. equal to one ounce. However, it can be 2oz if the circuit board needs high currents. Designers often increase the track’s thickness which results in higher current points. Moreover, they don’t add anti-welding masks because they want to reinforce the track during assembly, like with tin.
Sometimes laminate manufacturers use an intermediate thickness of copper just to lower the price, like 0.75 oz. But, such a practice is technically not so good. Experts don’t recommend this because the PCB thickness also reduces during mechanical or chemical cleaning. The popular copper thickness is 0.5oz, like in the case of two-sided laminates.

Trace Thickness In PCB

You have to specify the trace thickness while making the Gerber files to avoid overheating. Trace thickness is the trace width that can tolerate the temperature difference ranging from the standard to maximum operating temperatures. In other words, the trace width should be enough to bear increased temperatures. Besides, PCB width calculators are available to find the trace width.

 

Ultimate Guide to PC Board Thickness
Thickness guide of PC Board

B-FR4 Thickness Of A Standard PCB

FR4 is the flame retardant material which is a fiberglass sheet with epoxy lamination. FR4 shows the quality of the laminate in PCB. Generally, it’s the base material for Printed Circuit board Fabrication.
The rigidity occurs due to epoxy that resists fire, and engineers prefer it for its low cost. The dielectric strength of FR4 is high, moreover, it is lightweight and also resists heat and water. So, they are compatible with different environments.
The FR4 thickness lies between 3 and 10 inches, and it can cause an increase in PCB thickness. You have to evaluate the FR4 thickness by considering the board components and space.
Design Parameters of an FR4 Board Thickness
Generally, the designers prefer thick boards because thin FR4 boards get damaged faster, especially when they are large, besides, the grooves are missing. Whereas thicker boards provide more flexibility and also include grooves.
Should Be Flexible
Thin circuit boards are more flexible than heavy or thick boards, especially in the medical field’s control unit. But, thinner circuit boards cause lots of issues during soldering that results in bending. Eventually, several other components also get curved, damaging a board’s connections.
Compatible Impedance
PCB thickness is crucial while constructing multilayer boards became you have to match the impedance. Besides, you also have to consider each layer’s capacitance. The board won’t function if its impedance is not compatible.
Edge Connectors
The edge connectors also directly influence the PCB thickness, especially when there is FR4. An incompatible mating part of the connectors can result in PCB damage. So, you must be clear about materials before PCB manufacturing.
PCB Weight
More thickness means more weight and increased shipping costs. So, you have to keep in mind the weight of the circuit board that determines the weight of the final product. Experts find thinner layers better than the others, however, one should go for a standard PCB thickness.
C- Core Thickness of Standard PCB
The core is a PCB layer having FR4 between copper layers or foils. The core of a standard PCB involves certain items of which copper should be precise. It’s a fiber mesh layer having resin, moreover, it has incurred FR4 as well.
The core thickness of the standard PCB becomes hard to select during a multilayer PCB design. However, sometimes PCB remains effective even if the core thickness is not compatible. But, the end product should perform high for which PCB should have accurate thickness. The designer must consider this factor and share the right details with the manufacturer.
The weight of the core thickness goes from 1 to 3 ounces depending on the requirements. The weight also includes copper layers that can be on both sides. However, if both sides’ weight differs, it would cause additional expenses and poor results. The core thickness with the desired copper weight is also possible through pre-preg sheets.
D-Two-Layered PCB Thickness
Printed circuit boards with multiple layers are getting popular these days. They include glass fabric based on epoxy having copper coils. A multi-layered PCB can bear high loads, however, its thickness remains only 63mm.
Complex PCBs need wiring, resulting in more layers, so PCB thickness becomes up to 93mm. The thickness of a standard PCB also gets influenced by foil lamination, if the lamination consists of 4 layers, 0.031 would be the PCB thickness. The thickness would become 0.062 if the foil lamination includes 6 layers.
Likewise, the thickness becomes 0.062 to 0.125 for 8 to 10-layer PCB. Your requirements can also demand half, one, or two-ounce copper foil.
PCB Thickness Allowance
Also known as PCB thickness allowance, it is the tolerance for PCB manufacturing substances. It can be more or less than the average amount of material. Designers consider certain parameters for it, such as the IPC guidelines. Such design parameters help manufacturers have the flexibility to develop a circuit board that performs well.

FAQs

What Is The Importance Of Knowing PCB Thickness?
You have to focus on the circuit board thickness because both electronic devices and boards have a tendency to shrink. So the board has to be thin and lightweight to help manufacturers place it into the device. The weight of the final product also matters as thicker circuit boards can increase the weight of the device, resulting in increased shipping costs.
How Many Layers Are There In A Standard PCB fabrication?
There are various types of standard printed circuit boards, including one-sided having one layer of copper or double-sided board with two layers of copper. There is also PCB with more than two layers called a multi-layered PCB.
What Is FR4 In A Standard PCB?
FR4 is the flame retardant material which is a fiberglass sheet with epoxy lamination. FR4 shows the quality of the laminate in PCB. Generally, it’s the base material of a rigid circuit board.
What Is Core Thickness In A Standard PCB?
PCB layer with FR4 between copper layers or foils is known as the core. The core of a standard PCB consists of various elements, including copper that has to be accurate. PCB core is a fiber mesh layer having resin, moreover, it has incurred FR4 as well.
What To Consider While Designing A Standard PCB?
Designers have to focus on various factors to design or buy a printed circuit board. PCB thickness is the most important factor, but the weight, profile, and components of PCB also matter a lot.
What is Trace Thickness In PCB?
Trace thickness is the trace width that can tolerate the temperature difference ranging from the standard to maximum operating temperatures. You have to specify the trace thickness while making the Gerber files to avoid overheating.

Wrap Up

Now, you know how important it is to consider PCB thickness in different ways. PCB thickness can influence its function, affecting resistance and conductivity. The application of a circuit board determines its thickness and there are different levels of thickness in this regard. You can have a good circuit board by choosing the board thickness wisely, depending on its application.
Would like to know more about printed circuit board assembly? Email us at sales@pnconline.com

Physical and Electrical Partitioning In PCB Design

Physical and Electrical Partitioning In PCB Design

Partitioning your design into physical and electrical sections can significantly reduce the number of through-holes you need in your PCB, thereby increasing production speed and cutting down on manufacturing costs. Here, we will explain what physical and electrical partitioning are how they are used in PCB design, and how to create effective partitioning schemes in your PCB designs.
As you work on your next PCB design, you may be wondering how to implement physical and electrical partitioning in your design. These two factors are equally important to making the finished product successful, and both have a huge impact on the success of your design project as a whole. Stay with us if you’re looking to save time and money while producing high-quality products, read on!

Layout Considerations

When you’re laying out a Printed Circuit Board, you have two different considerations, such as physical, which is how your components are laid out on your printed circuit board; and electrical, which has to do with where you’re going to put all of your wires. These two can be grouped when it comes time for assembly.
For example, if you plan to use surface-mount parts that require soldering instead of wire-wrapping, then you will want to make sure that there is enough space between these parts so that they can be easily soldered onto your PCB. If you don’t leave enough space between them, then there won’t be room for solder paste. The solder paste is a sticky substance used to hold down SMT parts during pcb assembly.
This makes soldering difficult or impossible and the same logic applies to wiring. If you don’t leave enough space between components, then your wires may not fit without being bent too much or getting in each other’s way. This can cause problems when it comes time to solder everything together, as well as with heat dissipation, and too many wires crammed into one area might block airflow and cause overheating issues.
On top of that, you also need to consider things like trace width and spacing. Trace width refers to how wide your traces are (the lines connecting individual pads on your PCB), while trace spacing refers to how far apart they are from each other. Trace width should always be smaller than trace spacing because having wider traces means more copper is needed per unit length which means higher cost and greater weight.
Traces are usually made using either a single solid line or multiple lines connected by vias. Single solid lines tend to be faster but less reliable than multiple lines connected by vias, but they’re also easier to design and cheaper. Vias are holes drilled through layers of material that allow traces on different layers to connect.However, vias increase complexity and cost. There are several tools available to help designers create their circuits. Some free software options include EagleCAD, Kicad, Altium Designer, and CAD. However, regardless of what software you choose to use, remember that layout is only half of the process.

Physical and Electrical Partitioning In PCB Design-Content Image
Physical and Electrical Partitioning In PCB Design-Content Image

Overlapping Impedance Nets & Ghost Nets

To create a circuit board with electrical & physical separation, you must insert impedance nets into your design. There are three different ways you can do that, including overlapping impedances, creating ghosts, or through a virtual ground plane. In some designs, more than one method is used. So, let’s see how and when to use them.

An overlapping impedance net has part of it on one side of a barrier, and part of it on another side. A ghost net is used when you have two nets that need to be separated but you don’t want them physically separated because they are too close together or because they are too important for each other. A ghost net is just a virtual representation of an actual physical connection that exists between two parts of your circuit board.

A good example of why you might use a ghost PC board net instead of separating your nets with some physical method is if you have 2 power supplies that need to share ground. They can share ground by having their grounds tied together through some kind of wire.But, since they’re both supplying power independently, we don’t want them tied directly together at all times, but only when there is a current going through either one or both supplies. So what do we do? We create a ghost ground plane where we tie their grounds together. This way, when none ofthe supplies is active, there’s no connection between them, and when either supply is active, there isa connection between them.

An electrical partitioning net does exactly what it sounds like. It partitions electrical signals from each other. In a design where you want to physically separate your nets, you can do that by creating an impedance plane that separates them. But, then how do you keep them electrically isolated? That’s where a physical partitioning plane comes into play. This is just another name for a ghost ground plane, but instead of being used for sharing grounds between two supplies, it’s used for keeping two parts of your circuit board electrically isolated from each other while still allowing communication between them.

One last thing about these three methods is thatyou can’t use one without using at least one of the others. If you have a wall between two sections of your circuit board, there has to be some way for those sections to talk to each other. Otherwise, they wouldn’t be able to pass power or data. So, if you have a wall, you need ghosts or an impedance plane on both sides of it. And if you have ghosts, there needs to be a wall somewhere too.

Why Would You Ever Choose One Method Over Another?

Well, overlapping impedances are good when you don’t need high-frequency performance because they introduce more inductance than either of the other two methods. Ghosts are good when you don’t care as much about electromagnetic interference or EMI because they don’t create as much capacitance as either of the other two methods.

Whereas the physical partitioning nets are good when you want to keep your layout compact or if you have a design that’s already laid out and you can’t change it, as having a wall between two sections of your board is going to require some rework if it doesn’t already exist.
So, you need to decide if you want your partitions at a high frequency or low frequency. For a high-frequency circuit board, you’ll need to use overlapping impedances or ghosts; for a low-frequency circuit board, you can just go with physical partitioning nets.

Solving Unplanned Overlaps

It’s not uncommon for two different circuit boards or two different designs within a single board to overlap. Unplanned overlaps are hard to solve, but these tips will help you create better schematics so that you can avoid them.
Before you design your next PCB, make sure you follow all of these guidelines for PC Board Fabrication. By doing so, you’ll be able to identify overlaps before they occur and reduce your chances of creating any issues when manufacturing your product.
If you don’t have access to specialized tools or software, consider using some online tools like Google Sketch Up to help with your schematic design. These free programs allow you to build 3D models of your circuits, as well as export them into other applications like Eagle CAD or Altium Designer. This allows you to easily view how your components will fit together on a printed circuit board.
You should also use both software and hardware layout techniques to ensure that there aren’t any unplanned overlaps between your PCBs. While it may seem easier to just use one method, it’s important to understand how each technique works so that you can spot potential problems early on. For example, if you only use software-based layout techniques, then you might miss physical overlaps that would prevent a component from fitting onto your board.
Similarly, if you only rely on hardware-based methods, then you might overlook electrical conflicts that could lead to shorts or failures during testing. The best way to get around these kinds of issues is by using both types of layouts simultaneously. You can use a program like Altium Designer to lay out your circuit board, then print out an image of what you’ve created. Then take that printed image and place it over your actual PCB. This ensures that you catch any unplanned overlaps before they cause problems later on down the line.
Just remember, even though it takes more time upfront, double-checking everything twice is always worth it. With that said, there are still times when the overlap errors do slip through. When you find yourself in a situation where you need to resolve an issue like this, we recommend you double-check it. As it would become much easier to fix an error than it would be otherwise. You can also get professional help in this regard.
Would like to know more about physical and electrical partitioning in your designs or pcb assembly services? Write us at sales@pnconline.com

Tips for RF PCB Design

Tips for RF PCB Design

With so many things to consider when designing an RF PCB, it can be hard to know where to start. How do you choose the right layout? What tools should you use to get the job done? RF PCB design has its own set of challenges that need to be addressed to get the most out of your circuit. There are some best practices you can use to ensure that your design will function optimally and run smoothly.
The best PCB design solution can be the difference between success and failure for your product, so you want to make sure that you are getting it right the first time around. Our guide will walk you through all of the steps necessary to create an RF design that works and that makes your product even better than you envisioned.

Tips for RF PCB Design
Tips for RF PCB Design

Surface Mount Capacitors

Use surface mount capacitors when space is limited. You can incorporate them into your RF Printed Circuit Board design with no impact on performance. Try to keep track of how much space they’ll take and make sure there’s still enough room for other components on the board, like resistors and coils. The surface mount parts are more fragile than through-hole components and require an extra level of care when handling.
Consider using larger surface mount parts wherever possible, or incorporating test points into any sensitive areas if smaller parts are required. Remember that small surface-mount parts have very thin leads that could break off easily. Make sure you know what size of solder tip will be needed before moving forward with your design. If it’s too small, it could damage the delicate leads on these devices. It may also be difficult to attach them to boards after soldering as their leads are so small that they tend to slide around during assembly. When in doubt, use a slightly larger part.

Differential Pair Transformer Coupling

Choosing proper circuit components is an important part of designing and building circuits. When creating transmitter/receiver pairs, several factors influence how well each device will perform. The goal of any transmitter or receiver circuit is to accurately convert an input voltage into an output voltage with minimal noise and distortion.
These parameters are known as gain, linearity, bandwidth, noise figure, NF, return loss, RL, and intercept point, IP. A low NF results in more power being transferred from input to output. The IP value represents how much power can be handled by the front end of a given device before distorting or saturating it, all while maintaining its linearity characteristics.
In other words, if a device has high gain but poor linearity, then it may still have acceptable levels of IP. But if a device has high gain and poor linearity at lower power levels, then it won’t have good IP numbers. In general, devices with higher gains have lower bandwidths, however, there are exceptions to every rule. For example, some amplifiers have very high gains but also operate over wide frequency ranges.

Microstrip Transmission Lines

These are transmission lines in which all of their circuit elements, including those forming half-space planes, and terminations, such as capacitors and transformers, are fabricated on metal strip circuits. The strip circuit is usually etched onto an epoxy substrate using photo etching or electroplating techniques. The micro-strip designs have become very popular for many PC BOARD applications because they can be packaged in small cases with relative ease due to their thin profile. They also have good impedance matching properties over a wide frequency range.

Reference Planes, Power Planes & Ground Planes

Radio-frequency circuit boards or RF designs are often more sensitive to ground loops and signal integrity issues than regular designs because RF circuits and components are particularly susceptible to noise. One way that experienced designers combat these types of issues is by strategically adding power planes, reference planes, and ground planes to their board layouts.
Reference planes: The reference or signal planes can allow designers to focus on specific sections of a circuit without having to worry about interfering signals from other portions.
They also provide a convenient place for designers to add vias between layers of copper, which helps improve both signal quality and thermal performance. Reference planes can be especially useful when they’re directly connected to a component’s ground pin, which allows them to act as an extension of that component’s ground plane.
Power planes: they should always be connected directly to an external source of power, otherwise, they could cause voltage drops across adjacent traces and components.
Ground planes: They should always be connected directly to an external source of the earth, otherwise, they could cause the voltage rises across adjacent traces and components. It’s important to note that many high-speed applications use multiple ground planes at different potentials, so it may not be feasible to have just one global ground plane. However, it’s generally best practice to keep each section within a single board connected through at least one shared global ground plane.
By using separate grounds for different sections of a design, designers can avoid parasitic effects and increase the overall reliability by ensuring all parts of their designs have access to low impedance paths back to an external earth point.
In addition, it’s crucial to ensure that any ground or power planes are spaced far enough away from any active circuitry in order to minimize crosstalk. Generally speaking, there should be at least 1/10th of a millimeter between active circuitry and any nearby reference or power planes. The distance requirements become even more stringent with higher frequencies. When operating above 30 GHz, there should ideally be no less than 0.3 mm of separation between any ground or power plane and active circuitry.

Vias – Size, Shape & Placement

Vias are required in order for us to make electrical contact with traces on different layers. There are three types of vias, including plated through, blind, and buried. A plated through via connects one layer’s copper trace directly with another via’s copper trace or traces. A blind via creates electrical contact but no physical connection between two layers and a buried via provides both an electrical and physical connection.
Placement is generally determined by where it will be soldered or how many layers are involved. For example, if there are four or more layers involved then we recommend using plated through vias because they offer better conductivity than a blind via. If there are only two layers involved then we recommend using either type of visa, depending on its location relative to other components.
As far as shape goes, choose from square, round, or rectangular options that match your pcb fabrication layout requirements. Circular vias may also be available upon request, however, these have a higher cost associated with them due to their complexity and are not always necessary. We use wire-bondable vias wherever possible because they provide a faster assembly process. The above diagram illustrates each type of via along with its respective shape and size.

Isolating an RF trace

It is essential to isolate an RF trace from high-speed signals, including HDMI, USB differential pairs, or crystals’ clock traces. Experts do it through a method known as via stitching where vias are stitched around the RF traces to keep them away from other parts on the circuit board. But, there should be proper isolation as improper isolation can affect PCB function.

RF Circuit Board Insulation

Insulation is one of the most important factors for minimizing the signal loss in an RF transmission. If you want to ensure that your signal reaches its destination without any hiccups or interference, it’s crucial that you use good quality material for your board’s insulation, and choose one with at least 5-mil thickness.
One of our favorite options is Taconic TFEP as it offers superior heat resistance and can withstand temperatures as high as 350 degrees Celsius. It also has great mechanical properties and will last for years to come. Another great option is Rogers, which boasts similar properties but has a slightly higher temperature resistance.
You’ll also want to make sure that you’re using a good adhesive when attaching components to your board. This will ensure that everything stays intact even in tough conditions. If you want to ensure that your signal reaches its destination without any hiccups or interference, it’s crucial that you use a good, quality material for your board’s insulation.
You can create a flawless RF circuit board by considering all the above design guidelines.

Final Thoughts

RF PCB design has its own set of challenges that need to be addressed in order to get the most out of your circuit. There are some best practices you can use to ensure that your design will function optimally and run smoothly. You have to consider material, traces, surface mount capacitors, isolation, insulation, reference, ground, and power planes, vias size and shape, coupling, and micro-strip transmission line.
Would like to know more about RF design or pcb assembly services? Email us at sales@pnconline.com

Design Elements Influencing SMT Assembly

Design Elements Influencing SMT Assembly

Smart devices should perform well to satisfy consumers who want high-density devices. The Surface mount technology or SMT helps develop high-end electronics. The process of SMT involves soldering which goes through different problems due to PCB pads, reflow technology, stencil design, quality of the soldering paste, and different technical parameters.
SMT manufacturing involves many challenges and different design elements influence it. The supplier needs Gerber files and design data for the placement of components. Gerber files help configure different SMT manufacturing machines and develop stencils for placing the solder paste on the circuit board. The manufacturer and designer should discuss the design parameters and elements for precise SMT manufacturing.
So, different elements affect the quality of SMT that we will discuss below.

Making Bill of Materials (BOM)

SMT has various features and BOM is one of them. The flow of soldering has close contact with the bill of materials. You have to consider the below factors to create a high-quality SMT.
• Components packaging should be compatible with mounting requirements.
• The component figure should be according to the SMT requirements to get the desired shape with precise dimensions.
• The PC BOARD pad soldering should be compatible with the reflow technology to prevent its oxidation and the same applies to the solderable ends of the elements. If these two factors get polluted, it would result in defective solderings, such as solder beads or pseudo soldering. The same is true regarding the humidity sensor and PCB administration.

Design Elements Influencing SMT Assembly
Design Elements Influencing SMT Assembly

PCB Pad Design

PCB design highly influences the manufacturing of SMT in terms of quality. According to HP research, 80% of SMT manufacturing defects occur due to the poor design of a PCB. So, the designer should focus on essential factors, including the folder mask, layout of components, type of the substrate substance, thermal pad design, assembly techniques, component packages, the position of vias, optical positioning, and the transmission boundary.
If the PCB pad design is poor, it would result in deflected soldering even if the mounting position is fine. Like, tombstoning or disposition of components can happen. You can avoid these issues by considering the key aspects while designing the SMT pad, such as the distance between the pads, residual size of the pads, width and symmetry regarding pads, and avoiding through-hole vias.

Printing of Solder Paste

The paste of solder should have a compatible printing technology, or it will affect soldering. A poor printing of solder paste results in a deflected PCB that you have to revise. During the printing of solder paste, you should consider three essential elements, such as solder paste, scraper, and stencil

Quality of The Solder Paste

Solder paste is an integral part of reflow soldering, and it’s a combination of alloy and flux. Precise soldering joints depend on the powder of alloy, whereas the flux removes oxidation from the surface to ensure high-end soldering. Even, the paste of solder having 50 percent of solder of alloy can be enough if it has high quality. Two key factors of soldering paste, including storage and application, determine its quality. Make sure to store the solder paste at appropriate temperatures ranging from 0 to 10 degrees.

PCB Stencil

The pad of the PCB should have evenly applied solder paste through a stencil, which is a major factor in Printed Circuit Board printing. Moreover, the eminence of the stencil affects the printing eminence. The stencil is designed through different techniques, including laser cutting, and chemical corrosion. You can design stencils by considering certain characteristics, such as:
• The thickness of the steel sheet
• Aperture design
• Mark points
• Anti-solder ball processing
• Direction of printing
• Type of scraper in terms of shape and material

Printing Parameters

You have to consider essential parameters of printing for precise results, such as frequency, scraper speed, scraper pressure, stencils down release speed, and its cleaning mode.
Both pressure and speed of scraper should be well-balanced, like not so low or so high. If these values are not balanced, it would result in defective printing, thus influencing the manufacturing.

Right Equipment

There should be accurate equipment to have high-level printing of the soldering paste. A small space and high-density PCB should follow the right printing rules for a stable process.

Understanding PCB Support

The printing of the soldering paste depends on the PCB support, as its lack can result in an uneven soldering paste. So, it is important to have uniform PCB support to keep the PCB and stencil close enough.

Components Mounting

The mounting of the PCB parts or components depends on different elements, including the right pressure for mounting, the quality of the components, and their precise location. Components should be according to the BOM, and mounted on the PCB at the right place, following the right dimensions. At the same time, the mounter should be precise in this case to ensure a stable mounting of the components onto the PCB pads.
The mounting angle should be correct, besides, the mounting pressure should be suitable, like not too high or low. You can evaluate mounting through different elements, such as the thickness of the board, components’ package, mounted z-axis, and nozzle’s pressure.

Quality of Reflow Soldering

The temperature curves of the reflow soldering should be well-set to have high-quality soldering of areas to be welded. An increased temperature can affect the PCBA due to heat occurring at a fast rate. It would cause PCB deformation, damaging the components. Besides, the soldering paste has a solvent that gets volatile, splashing out the metal composites as tin’s plating balls. Engineers apply nitrogen reflow soldering to get rid of oxidation, enhancing the quality of soldering.
Moreover, make sure that the reflow soldering is compatible with the PCB substrate, size, material, weight, and thickness. Besides, it should be according to the reflow oven’s structure, and the temperature zone’s length should also be considered.
SMT assembly is easy to optimize by having the best PCB design and software to analyze it. The right design software helps you to set assembly standards without missing any factor.

Additional Information

The solder paste is applied to the pads through a machine by holding the stencil tightly on the PCB. Then components are placed according to the footprints with the help of optic technology. The engineers inspect the placement of the components through an optic machine to make sure it’s free from flaws, and this should be done before reflow soldering. Sometimes the x-ray technology is used for inspection which is essential before PCB testing. Such inspection helps detect poor solder joints, as well as short circuits that happen during the reflow soldering.
The placement machines are unable to hold a PCB if the PCB edge is crowded with components, and this can influence SMT manufacturing. You also have to consider the tooling strips for miniature PCBs. The tooling strips should be at least 6 mm to help a machine have a proper grip during the PCB assembly. You can also give the V-score on the tooling strips to separate the parts easily in the later stage.
Keeping the SMT components in one direction can also reduce the flaws and helps have placement the components in one go. So, the selection of the components and their placement affects the SMT assembly, making it smooth or horrible.

Frequently Asked Questions

What is PCB?
PCB is an abbreviation of Printed Circuit Board. It is used in electrical devices to provide them with signals or currents to operate. Printed circuit boards are used in different industries, including networking, electronics industry, gadgets, aerospace, and much more.

What is SMT in PCB?

SMT stands for Surface mount technology, and it helps develop high-end electrical devices.

What is Soldering in PCB?
Soldering is a manufacturing technique in PCB where two metals are connected through another material’s fusion. It should be precise because poor soldering results in a device malfunction.

What Are Important Characteristics Of A Stencil Design In PCB?
Stencil design depends on certain characteristics, such as the thickness of the steel sheet, aperture design, mark points, anti-solder ball processing, the direction of printing, and the type of the scraper in terms of shape and material.

Final Thoughts

Smart devices should perform well to satisfy consumers who want high-density devices. The Surface mount technology or SMT helps develop high-end electronics. The process of SMT involves soldering which goes through different problems due to PCB pads, reflow technology, stencil design, quality of the soldering paste, and different technical parameters.
SMT manufacturing involves many challenges and different design elements influence it. PCB design highly influences the manufacturing of SMT in terms of quality. According to HP research, 80% of SMT manufacturing defects occur due to the poor design of a PCB.
The PCB designer should focus on essential factors, including the folder mask, layout of components, type of the substrate substance, thermal pad design, assembly techniques, component packages, and the position of vias, optical positioning, and the transmission boundary.
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