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smt-assembly

SMT Assembly and Thru-Hole/Chip Functionality

Printed circuit boards are parts of various electronic devices, home appliances, and vehicles. The function of these green chips depends on their material and assembly technology. Each step of PCB assembly is important and needs careful processing considering essential features.
Two methods are popular in PCBA, including, MT and THT. Let’s study them in detail.

Through-Hole Technology (THT)

Traditional PCB has through whole technology, involving both automatic and manual processes. THT is PCB packaging technology that involves pins or leads, besides, you have to insert the chips in the PCB through holes, soldering from below. The technique gives it the name through-hole.
Through-hole technology was more in practice till 1980 and every PCB device had this technology. Then SMT emerged where chips are installed on the surface. However, some PCBs still need through-hole chips, like capacitors and resistors.
THT needs more drilling, however, the device with this technology has a durable bonding with the circuit board.
Let’s look at the important steps of THT.

Installation Of Components

Engineers place PCB components with their hands, however, it needs precision depending on the design.
PCB Inspection
PCB inspection is crucial because most devices need flawless PCBs to work well. Most of the through-hole process is manual, so you have to make sure that the assembly is without any mistakes.
Printed Circuit Board Soldering
Soldering of components is also important as you have to fix the components manually. This is the last part of assembly, and the manual work makes it more reliable than SMT.

Why Is THT Still In Use?

Though THT is an old PCBA technology, you still need it for certain reasons, such as:

  • Even a hobbyist can assemble a circuit board with THT by using a soldering iron. It involves less hassle because the holes are away from surface pads compared to SMT.
  • If you observe a hobbyist application of the THT circuit board, you will see the ICs with the 8 or 14-pin having centers up to 0.100”xp.300”. Sometimes even the DIP processors have such spacing between the holes that helps in manual soldering, making the PC Board assembly easier.
  • After assembly, the troubleshooting or revision reduces in THT because it does not involve bridges between the pins, be it single or multiple components.
  • THT has better professional assembly, especially when a project is at a prototype stage. You can apply the through holes in a prototype layout to assemble the board faster.
  • After evaluating the board function, you can swap in the SMT having the same value, revising the circuit board’s layout. The new layout has small footprints to be inspected before final production. Such techniques reduce the front cost of a project which can benefit a subcontractor.

Remember that small products demand more pricing from outside vendors as they prefer high-volume production for continuous machine work.

Benefits Of Through-Hole Technology

  • When it comes to PCB design revision, a through-hole technology doesn’t need to create an additional solder stencil. So, manufacturers can save a huge amount of money on a PCB design having 2 to 3 revisions before it is ready to use. Besides, you don’t have to arrange the equipment for the pick and place function.
  • The manual inspection of a small lot of printed circuit boards reduces the fixture expenses or any other cost regarding linked setups.
  • Soldering is also cheap in THT, such as the tin-lead solder. Besides the issue of HASL or hot air solder leveling does not occur in through-hole technology, unlike SMT where the HASL makes it hard to place the components having a precise pitch.
  • You can easily assess the mechanical faults, including twists, and warps, and can deal with them while redesigning without affecting the assembly as what happens in SMT. Issues like twist and warp are not as problematic in manual assembly as in SMT.
  • The hand assembly of a PCB helps fit hard components by changing the wrist angle. Whereas the automated assembly needs an extremely flat circuit board for proper functioning.
  • THT can help pinpoint mechanical faults before it gets hard to resolve them. Otherwise, the inspection becomes costly when it has to go into the hands of three persons, including you, the contract assembler, and the PCB Manufacturer.
  • The components for THT are easily accessible that keep the job going without interruption. Moreover, you don’t need a third-party assembly in the case of small production.
  • With THT, the project timeline is predictable and easy to manage with minimum issues without causing any production delays.
  • Even if you don’t want to prefer a through-hole assembly, you must consider it as a temporary solution at early stages like validation and development. So, it can benefit anyone, including a hobbyist, any established company, or a beginner in this industry.

Surface Mount Technology-Surface Mount Chip

Surface mount assembly and SMT is other popular PCB assembly technology. It is an advanced method involving automation. Besides, it is ideal for smart PCBs that today’s smart devices need.
As the name shows, PCB components are directly installed on its top surface, whereas the device having a surface mount technology is called SMD. You can say that traditional through-hole technology is being replaced by surface mount assembly.
However, through-hole technology is still in practice for big transformers or power semiconductors as their components are not compatible with SMT. Likewise, many other heavy electronic devices with heat sinks need through-hole PCBs.
Surface mount technology has more positive aspects than negative pros, so let’s discuss them in detail.

Positive Aspects Of Surface-Mount Technology

SMT Involves Minimal Surface: The component area, volume, and size in an SMT are 70% less than the component area in through-hole technology. Even the component area can become 90% less than its volume in a traditional PCB having a through-hole technology. Likewise, the overall weight of the PCB reduces, as the components’ weight reduces by 70 to 90%.
It Enhances The Signal Speed: a PCB assembled with SMT has a fast signal transmission due to a short circuit. The assembly density in such technology can go up to 5.5~20 solder joints in one square centimeter, like when there is paste on both sides of the PCB. Similarly, a PCB with SMT has a high impact and vibration resistance that helps create high-speed electronic devices.
Excellent Frequency: In SMT, the board has either no lead or it is very small which reduces its parameters, decreasing the interference in terms of RF. It means that the PCB gets high-frequency signals, and the device having it works faster.
Minimum Packaging Cost: when it comes to an SMT packaging price, you will see it much lower than THT. Since surface-mount technology involves effective production tools, the usage of packaging material reduces thus cutting down its cost. However, the decrease in the cost does not affect the quality of an SMT circuit board.
You don’t have to bend or cut the component leads in the SMT boards which reduce the assembly time, making production faster than THT. So, the production cost also reduces by 50% as the manufacturing process of SMT is quite simple.

Additional Info

In SMT, the solder paste is applied with a stencil printer that helps finish a raw board better and faster than a traditional method. In other words, you get fineness in an automated assembly.
The installation of the components becomes easier, as solder paste makes everything clear due to printing. Each SMT process is well-inspected that helps have accuracy.
In SMT, the process of reflow soldering also makes a circuit board highly durable. In reflow soldering, the technician places the circuit board under high temperature to melt and reshape the paste, making it permanent. You can use both reflow soldering and automation or can switch from one to another, depending on your needs.
The important thing is to design and assemble a PC Board considering all the dos and don’ts and have a flawless end product.

Some Negative Aspects Of SMT Assembly

Surface-mount technology is not full of benefits, instead, it has some drawbacks, such as:

  • It has less power
  • It is vulnerable to damage
  • SMT requires high-quality soldering because poor soldering can lead to leakage, tombstoning, bridging, and several other risks.
  • It involves delicate installation, resulting in dropped components.
  • Its inspection is hard, especially, the visual test as it has multiple types of solder joints.
  • The equipment cost is high.
  • It involves well-trained technicians that increase the learning expenses.
  • It needs consistent updates of assembly equipment due to fast development.

Final Thoughts

Printed circuit boards involve different assembly techniques, including a through-hole technology, and a surface-mount technology. The component area, volume, and size in an SMT are 70% less than the component area in through-hole technology.
When it comes to PCB design revision, a through-hole technology doesn’t need to create an additional solder stencil. So, manufacturers can save a huge amount of money on a PCB design having 2 to 3 revisions before it is ready to use.
Would like to know more about Surface Mount PCBs or PCB Assembly Services? Email us at sales@pnconline.com

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

What is Printed Circuit Board Copper Clad Laminate?

What is Printed Circuit Board Copper Clad Laminate?

Printed circuit boards come in different materials known as substrate, including copper-clad laminate or CCL. PCB substrates are either organic or inorganic, depending on their properties. The organic substrates come up in different materials known as the reinforced board, such as glass felt, fiberglass, fiber paper, fiber cloth, and so on.
PCB fabricators impregnate there in forcing materials with an adhesive called resin, making it dry, and then cover it with copper foil at high pressure and temperature. Such a substrate is CCL or copper-clad laminate that resides on either one or both sides of the board. So, CCL is either single-sided or double-sided.
Rigid PCB has a rigid CCL with a substrate, such as

  • Resin epoxy FR4
  • PTFE
  • Aluminum or copper
  • Ceramic

These materials help make different types of PCBs, including single, double, and multilayer PCBs.

CCL Standards

Engineers define the CCL standard specification with ASTM D1867 and develop their circuit boards according to these standards. To cover twelve grades of CCL, ASTM needs the laminates to meet certain factors for peel strength, like

  • High temperatures
  • Volume resistivity
  • Water absorption
  • Flammability ratings
  • Dissipation
  • Dielectric breakdown
  • Permittivity
  • Lengthwise and crosswise strength

The PCB Manufacturer should also check the CCL for twist, warp, or blistering. CCL manufacturers often follow the IPC-410IC as a standard. Moreover, they use IPC-IM650 to test the fabricated CCL.

CCL Materials

FF4 CCL: As discussed above FR4 is a popular material for copper-clad laminate. The material is resin epoxy, and it is ideal for rigid circuit boards. You will see it on both sides and only one side of the board. The material is a combination of epoxy resin and fiberglass cloth. Resin makes the board fire resistant that’s why we abbreviate it as FR or flame retardant. However, it has to pass through testing to see if it is according to the UL94V-0 standards.

Copper base: like aluminum CCL, copper core CCL has a copper plate, copper foil, and dielectric layer for bonding. PCB’s thermal dissipation and dielectric bonding determine the overall thermal conductivity.
PCB with copper substrate has three types, depending on its design, such as copper without PTH, COB, or chip-on-board copper circuit board which is without the thermal pad insulation.
Aluminum CCL: Copper-clad laminate also has aluminum as a base material combined with a dielectric layer and copper foil. These materials are bonded through hot pressing and very high temperatures. The dielectric bonding determines the thermal conductivity of the aluminum core laminate. However, both copper foil and dielectric have high conductivity, and manufacturers often use ceramic to fill the dielectric layer.

What Is RF, Radio Frequency CCL?

The RF CCL is also known as the Microwave PC Board CCL as the board has microwave frequencies. Such a circuit board has certain characteristics to consider, such as

  • DK, dielectric constant
  • DF, dissipation factor
  • CTE, coefficient of thermal expansion
  • TCDR thermal coefficient of dielectric constant
  • Thermal conductivity

It involves high-frequency materials of which PTFE is a common practice. It is a synthetic material having great dielectric properties at high frequencies which are also known as microwave frequencies. A few companies develop the high-frequency PCB CCL, including Isola, Rogers, Taconic, and Panasonic.

What is Prepreg in CCL?

Prepreg or pre-impregnated CCL is a kind of fiberglass that is impregnated with a bonding material such as resin. The resin is not hard, however, it is dry and gets sticky when heated. In other words, the fiberglass is made strong through an adhesive just like FR4.
Prepreg materials come up in different thicknesses that determine their quality, such as standard resin, SR, medium resin, MR, or, high resin, HR. The PC Board manufacturer use the resin thickness according to the type of PCB they require.

What is Printed Circuit Board Copper Clad Laminate?
Printed Circuit Board Copper Clad Laminate

CCL PCB Applications

PCB with copper clad laminate is ideal for:

  • Electronics PCBs
  • Radars
  • High-speed communication devices, like 4G,5G, and LTE
  • Automotive products, such as ADAS radar
  • Avionics Radar
  • Automobiles
  • Welded tanks
  • Offshore platform shearing
  • Steam condenses
  • Pressure vessels
  • Heat exchangers
  • Missile components
  • Hydraulic bushings

The above applications related to communications are essential to communicate faster, such as 4G helps you download anything within seconds. Whereas 5G is much faster, in this case, and you can see it by comparing it with the old and low-speed communication devices.

How To Identify The Best CCL PCB

A few parameters help you find if the copper-clad PCB is the best or not, such as size, neatness or appearance, chemical properties, performance according to the environment, as well as a physical performance.

PCB Design Parameters Including Size: The size of the CCL matters a lot in PCB design as it’s the base material. The quality of the end product also depends on the thickness of the core material. At the same time, you have to consider other parameters, including length, width, wattage, and diagonal deviation. Each design parameter should meet the necessary standards to have an ideal product that performs well.

CCL Appearance: several issues happen during Printed Circuit Board manufacturing that can affect the appearance of the copper foil. Such as dents, pinholes, scratches, resin points, bubbles, wrinkles, etc. These issues also slow down the PCB CCL performance.

Environmental Compatible: Copper-clad laminate PCB should be compatible with the environment. Like, it should resist water and corrosion or its production will get slow, resulting in serious issues.

Chemical Function: The chemical properties of copper-clad laminate are also vital and should be according to the standards in terms of flammability. The Z-CTE or, Z-axis coefficient of thermal expansion, Tag, chemical resistance, and dimensional stability has to be considered.

Physical Function: Copper-clad laminate has to meet certain physical requirements, including the PS or peel strength, bending strength, dimensional balance, heat resistance, as well as punching. It should resist thermal stress.

Electric Property: Copper-clad laminate should electrically perform high, as it’s very important. As described above, copper-clad laminate PCB should strictly meet certain requirements, such as DF, DK, insulation resistance, CTI or comparative tracking index electric strength, arc resistance, and volume resistance.

How Many Types Of Copper Clad Laminate Are There?

You can classify the copper-clad laminate according to different factors, such as size, thickness, mechanical material, structure, insulation material, types of reinforcement, resin type, and CCL performance.
Copper-clad laminate is either rigid or flexible of which rigid CCL is further divided, depending on its combination materials. It is either single or double-sided, besides there are also special rigid CCL PCBs with a high-flame resistance and other properties.
Flexible CCL: It includes,

  • Non-flame retardant polyester
  • Flame retardant polyester
  • Polyimides with and without flame retardant
  • Fiberglass cloth of small thickness

Benefits of Flexible Copper Clad Laminate

  • The FCCL has many benefits, such as
  • It has great flexing power
  • It is ECO friendly
  • It is free from halogen
  • Better heat resistance
  • Great adhesive properties
  • it is a blend of different copper clad thickness

Special copper-clad laminate has ceramic and it’s also called ceramic CCL. It has different materials, such as aluminum oxide, aluminium it ride, silicon carbide, boron nitride, and beryllium oxide.

FAQs

What is the manufacturing process of CCL?
Copper-clad laminate has complex manufacturing, including rolled copper foil that acts as a conductive material. PCB fabricators impregnate the reinforcing materials with an adhesive called resin, making it dry, and then cover it with copper foil at high pressure and temperature.

What Are The Uses Of CCL PCB?
Copper-clad laminate is fiberglass mixed with resin and glass and it is on either one or both sides of the glass fabric. Engineers use it to develop radios, mobile devices, televisions, computers, digital devices, and other multiple electronics.

What Is Copper Foil In CCL?
Copper foil in CCL is a cathodic electrolytic material that lies on the metal foil in a PCB. The material is easy to bond with the insulating layer to provide a protective covering. It is also easy to corrode to make a circuit protector.

What are CCL Standards?
Copper-clad laminate standard specifications are defined with ASTM D1867 and engineers develop their circuit boards according to these standards. To cover twelve grades of CCL, ASTM needs the laminates to meet certain factors for peel strength.
The fabricators should also check the CCL for twist, warp, or blistering. Copper-clad laminate manufacturers often follow the IPC-410IC as a standard. Moreover, they have to use IPC-IM650 to test the fabricated CCL.

Final Thoughts

PCB different materials known as substrate, including copper clad laminate or CCL. PCB substrates are either organic or inorganic, depending on their properties. The organic substrates come up in different materials known as reinforced boards, such as glass felt, fiberglass, fiber paper, fiber cloth, and so on.
PCB fabricators impregnate the reinforcing materials with an adhesive called resin, making it dry, and then cover it with copper foil at high pressure and temperature. Such a substrate is CCL or copper-clad laminate that resides on either one or both sides of the board.
Would like to know more about Copper Clad Laminate or prototype pcb manufacturer? Email us at sales@pnconline.com

Six Basic PCB Design Principles

Six Basic PCB Design Principles

Printed circuit boards are vital parts of smart devices and several equipments as they provide current or electrical signals to run them. You need different elements to construct a PCB, such as:

  • Schematic design
  • Database login
  • Electronic component configuration
  • Design preparation
  • Wiring
  • Block division
  • Testing

If any issue happens during a process, you have to go back to the previous process to correct it. The layout of PCB components is a complex thin as it determines a board\s appearance and neatness. Moreover, it also affects the function of the end product or device. We will discuss below the six basic PCB design principles in terms of its components and other factors.

1-Components Layout and Clearance

You have to place the components evenly on the board, leaving some space on the edges. The components around the edge should be 3mm away from PCB edges. In general, designers leave 5 to 10 mm space around the edges.

The components should be only on a board’s one side. There should be a separate pad for each lead pin.

Don’t cross up and down the components’ layout and keep a certain distance between the nearby components on the board. However, this distance should not be too small as it can hinder PCB maintenance.

Components should be installed at a low height and its lead should not be more than 5mm away from the PCB, as it can affect its quality to bear vibration.

Printed Circuit Board components that reside on a pad’s both ends must be a bit larger than their axial dimensions. The pads should be located where the coordinate grid intersects. The central distance of the pad has to be more than the board thickness to have a neat layout.

According to IEC or International Electrotechnical Commission, the standard spacing of the coordinate grid should be 2.54mm, whereas the axillary spacing should be 1.27mm.

However, these standards practically impact a few processes, including automatic drilling, computer automated design, components welding, and automatic assembly. But, such a grid spacing is not restricted in the case of manual drilling.

2-Defined Solder Mask

Solder mask expansion should be well-defined as it can cause issues if you over-define or under-define it. Tombstoning may happen if you don’t define the solder mask properly. Like, one side cools down faster than another side, affecting the board. So, by following the right parameters, you won’t have to revise your design.

The solder mask opening should be larger than the pad. In general, it expands 4 mils or 0.1mm. However, both can also have the same size, depending on the Printed Circuit board Fabrication.

3- Via Type& Routing Width

You must use the right via for routing as it won’t work if its diameter or ratio is not precise. The current won’t pass correctly due to fused vias. So, via styles should be considered while routing the entire PCB.

The routs should have enough width to carry the current that your device requires. You must have an impedance-controlled routing that needs various impedance profiles. You have to apply these profiles to routing widths to ensure a functional layout. Don’t have routing at an acute angle even if the signals have a low speed as acute angle hinders manufacturing. Like, an acute angle can increase the corrosion, leading to an open circuit.

Whereas it is vital to avoid the acute angle in the case of high-frequency circuits because it fully changes the track width at the corners and results in poor signals and discontinued impedance.

Six Basic PCB Design Principles
Six Basic PCB Design Principles

4-Components Installation

Different PC Board components are installed either vertically or horizontally. The horizontal components are parallel to the surface of the circuit board. Whereas in vertical installation, components are perpendicular to the PCB surface.

Vertical components allow you to have more quantity on a board’s surface. It is ideal for hearing aids, semiconductor radios, portable instruments, or devices that need a dense placement of components. For vertical installation, components have to be lightweight. Don’t install heavy components in a vertical direction as it can affect a PCB’s mechanical strength. Moreover, it causes vibration, and components can collapse, making a circuit less reliable.

On the other hand, the horizontal installation provides mechanical stability, and the circuit board also looks neat. It also helps lay down the printed wires because it enhances the elements’ span.

You can use any installation method, depending on your needs but make sure to arrange components evenly and the circuit should be anti-vibration.

5-Considering The PCB Layout Type

PCB layout has either a regular arrangement of components or is irregular. In an irregular format, the axis of the components are not aligned with each other, so it seems messy. However, it helps lay down the printed wires easily as there is no restriction of direction. Such a layout is ideal for high-frequency circuits and involves a vertical installation.

Whereas in a regular format, the component axis is aligned and either parallel or perpendicular to the sides of a PCB. It provides a neat board and makes certain processes easier, like PCB assembly, debugging, welding, maintenance, and production.

Moreover, a regular format is ideal for low-frequency circuits where the board has a few component types and its surface is loose. However, the number of components is high and such an arrangement also suits electronic instruments. But, due to the direction restrictions, such a PCB has a complex layout of wires, increasing the overall length of the wires.

6-Factors That Affect the PCB Layout

You also have to consider the factors that affect a PCB layout, like the direction of the signals, device position electromagnetic interference, thermal interference, mechanical strength, etc.

  • Generally, the direction of the signal flow is from left to right of which left is the input and right is the output. It is also from top to bottom of which the top is the input and the bottom is the output. Connectors which are in direct connection to the input and output should be close to the input and output connectors. Integrated circuits or transistors should be the core components. Whereas other components should be located according to their electrodes’ location. You should also consider the size, a number of pins, shape, and polarity of components.
  • You should adopt certain ways to prevent electromagnetic interference that occurs due to different external factors, like spatial electromagnetic ways, poor wiring, poor installation of components, etc. You can avoid these issues during the layout design. But, interference will happen if the PCB design is not right
  • You should shield the components that interfere with each other. High-frequency components should have small wiring. Similarly, the components of weak and strong currents should be separated. Wires with high potential should be at a great distance to avoid 50Hz interference. Likewise, the metal components should not be adjacent or they should be well-insulated to avoid a short circuit.
  • While designing a PCB, you must know which components are temperature sensitive and which are heat components. The heating components like resistors should be located near the shell or near vent holes to dissipate heat. Don’t place many heating components near each other. Also, use fans or radiators to prevent the rise in temperature beyond its limit.
  • Whereas the temperature-sensitive components should be away from the heat source. In general, integrated circuits, transistors, electrolytic capacitors, and thermal components are temperature sensitive. These components get affected due to the rise in temperature, especially in a circuit’s long-term operation.
  • The board should also be mechanically strong and its center of gravity should be stable. Don’t install heavy or heating components directly on the board, instead, they should be under the chassis to have a stable board. If the board size is above 200mm it will cause mechanical stress, so it should be strengthened with a mechanical frame.

Finally, many PCB design software uses the power layer to have a fast design process. You can connect more wires to ensure the current has a minimum impedance or voltage drop down, thus giving enough ground return paths.

FAQs

1.How To Layout A Printed Circuit Board?
You have to follow certain steps to create a PCB layout. Such as making the schematic drawings, developing a blank PCB layout, creating a PCB stack-up, schematic capture, defining design principles, defining DFM, linking to PCB, placement of components, inserting drill holes, and the route traces.

2.Is It Hard To Design A PCB?
It is not hard to design your PCB if the electrical schematic is right. Besides, following the design parameters also makes the design process easy.

3.Why Is My PCB Green?
The color of the solder mask determines the PCB color. So, if the solder mask is green, you say that PCB is green. The solder mask shields a copper circuit to avoid shorts circuit or soldering issues.

4.What Is The Purpose Of Following PCB Design Rules?
PCB design rules or principles help you to develop a system to automate the testing of design requirements. You get an interface between the physical and logical sides to create a circuit board. So, you can automate the DFM tests by following the rules to ensure that you can build a PCB.
Would like to know more about Design Principles or PC Board assembly? Write us at sales@pnconline.com

Printed Circuit Board Copper Thickness Vs Current

The right function of PCB depends on the copper thickness, trace width, and weight. Printed circuit boards have traces made of copper, and we also call them conductors. Copper traces have a specific thickness, width, length, and weight that affect the flow of current.

PCB has copper layers for the flow of electric current. The wrong copper thickness can affect the PCB assembly process. But, if you understand the relationship between copper thickness and signal transmission, as well as the cost of PCB fabrication, it would help you choose the right copper weight or thickness for PCB design.

So, you must know what is copper thickness or weight and why is it important. You should also know the heavy copper’s application, and PCB construction cost.

Sometimes you can’t change the trace width due to certain spacing requirements or PCB density. But, you can change the copper thickness to have maximum current flow. You have to consider signal integrity while designing a PCB. The signal integrity and current loss rely on the amount of impedance that happens on copper traces.

Printed circuit boards with heavy copper are used in high-power electronic devices which are vulnerable to tough environments. Thick traces ensure durability and can carry more current without increasing the trace width or length. However, lighter copper traces are also used to have a certain trace impedance without having a highly small trace width or length.

You must understand the relationship between the current flow and copper thickness while designing your PCB. So, you have to know the copper trace fabrication, in this case, and its effect on signal integrity.

PC Board Fabrication

PCB fabrication involves different steps, including etching which is done on the inner layers and the top surface of the board. You need a laminate sheet finished in copper. In etching, you have to remove additional copper from traces and several other parts of the PCB, like pads and angular rings. Fabricators use an ammonia-based liquid to complete the process of etching.

Generally, the copper sheet thickness is 1oz, like 0.5 oz. on each side of the sheet. You can etch it down to decrease the thickness or can increase the thickness by plating it up to have the desired sheet.

The sheets are done rough during fabrication to bond them to the dielectric material. However, the roughness can also affect the signal integrity in the case of high-frequency boards. The frequency above 100MHz can result in trace resistance that opposes the flow of current.

In the case of plated vias, you should add traces after drilling the holes and it often involves the process of electrodeposition. For example, the PC Board manufacturer places the circuit board in an electrolytic solution having copper ions. Then, he applies a direct current to create a potential around the hole, distributing the ions in the entire via, which is also known as filling. Such a distribution helps you to find the quality of the signal flow that occurs along traces. So, it is very useful to understand PCB fabrication to have a functional design.

Relationship Between Copper Thickness And Signal Flow

In general, fabricators buy copper sheets with specific weight and thickness as they want fixed numbers. But, engineers say that the copper parameters are changeable after having a set trace width and length to enhance the signal flow or integrity.

The current carrying capacity of a PCB is determined by a specific standard known as IPC-2152. It shows the trace parameters, including the thickness and weight of the copper, and trace length and width. These parameters are interconnected, depending on a material’s thermal and electrical properties.

Role of the PCB Copper Thickness to Enhance the Current

Engineers use some calculations and equations during PCB design as discussed below. These calculations are 99% correct in many PCB designs, so let’s understand them.

1-Finding the Signal Power, P (W) and Voltage, or V (Volts)
You must know these quantities from PCB operation design.
2- Finding Trace Impedance, R (Ω).
You have to set it and you can manage it during the fabrication of the PCB.
3-Finding The Maximum Flow Of Current For The Trace I (A).
You can find the current by using the below equations.
I = V2/R or I = P/V or I = √ (P/R)

4- Finding an Increased Temperature T (°C).

You must know the increased temperatures, or you can evaluate it from the PCB operation design.

5- Finding the Cross-Sectional Area of the Trace A (Mils2).

It involves constants of curve fitting, such as k, b, and c that approximate the
IPC-2152 curve. This curve links the area to its current carrying ability.

K for internal layers= = 0.024, b = 0.44, c = 0.725
K for external layers== 0.048, b = 0.44, c = 0.725

A = (I/ (k ×Tb)) 1/c

6- Finding Trace Width or W, Mils

You should also set the trace width as required.

7- Finding PCB Copper Thickness? (Mils).

= A / w

You can use the PCB design software to set the thickness of copper, or you can use values of the copper weight, as most contract manufacturers use it. Such parameters are proportional to each other. Here is how to find the copper weight.

Copper weight (oz.) = (copper thickness (mils) / 1.37
According to the thumb rule, the weight of one square foot of copper is one ounce. If you follow the right equations, you can create a well-designed PC Board even for the first time.
What Is Heavy Copper And Why Do You Need It?
If the copper weight is over 4oz, you can consider it heavy because a standard weight or thickness ranges from 1 to 3oz. You can use heavy copper to have

  • More current carrying capacity
  • High capacity to bear thermal stresses and have good thermal management.
  • Better heat dissipation
  • Great mechanical strength to have large through-hole components and heavy connectors.
  • Power converters and planar transformers

Sometimes the PCB fabricators use 1 oz. copper for internal layers and 4 oz. for external layers of a multi-layer PCB. Certain issues can be controlled by using the same copper thickness in stack-ups of opposing layers, as it can eliminate the PCB bending due to heat generated during its function.

Like, if you have a PCB with 8 layers, you can group the opposing layers as 1 & 8, 2 & 7, 3 & 6, 4 & 5. That means layers 1 and 8 should have a similar thickness or weight, and the same goes for layers 2 and 7 and other groups.

FAQs
What Is Copper Thickness And Weight In Printed Circuit Boards?

Copper is used in a PCB having a thickness of 1 oz., however, some engineers measure it in ounces. The thickness of copper determines the copper weight. Like, when the weight of copper covers one square foot of sheet, it makes copper thickness. Hence, 1 oz. of copper covering 1 square foot will result in 1.37 mils or 0.0348 mm foil thickness.
Why You Have To Consider the Copper Weight In PCB?

You can determine the current carrying ability of a PCB with the help of the thickness of its copper traces or copper layer. For PCBs with well-controlled impedance, the trace width helps determine the essential copper thickness. Besides, some other factors are also essential, such as a circuit board’s weight, compatibility of PCB components, and the type of connectors on a PCB.

Does Copper Weight Affect The Cost Of PCB Construction?

A printed circuit board with heavy copper involves expensive manufacturing, besides, it needs more time to make it. In other words, thicker copper is always more costly than standard copper. The manufacturing time of heavy copper is also high that also increases the total cost of PCB manufacturing.

What Is Etching In PCB?

In etching, you have to remove additional copper from traces and several other parts of the PCB, like pads and angular rings. Fabricators use an ammonia-based liquid to complete the process of etching.

How To Determine The Current Capacity Of A Printed Circuit Board?

The current carrying capacity of a PCB is determined by a specific standard known as IPC-2152. It shows the trace parameters, including the thickness and weight of the copper, and trace length and width. These parameters are interconnected, depending on a material’s thermal and electrical properties.

Final Thoughts

PCB involves different materials, including copper that have certain parameters, including thickness and weight. The copper thickness has a direct link to the current flow and the signal integrity, so its knowledge is essential for PCB designers, engineers, and fabricators. PCBs with heavy copper help create more reliable devices with increased current flow and better performance.

However, many smart devices have thin copper layers, depending on their requirements. You can develop a flawless circuit board by considering copper weight, thickness, as well as trace width and length, and several other features as described above. Besides, you must hire a good fabricator in this case.

Would like to know more about PCB Copper thickness and current or PC Board assembly? Email us at sales@pnconline.com