PWB Vs PCB: The Ultimate FAQ Guide

I know comparing PWB vs PCB can be confusing even to experts in the PCB fabrication industry.

That’s why today’s guide will answer all questions you have been asking about PWB and PCB.

So, if you want to be an expert PWB and PCB, keep reading.

What is the difference between a PWB and a PCB?

PWB is short for a printed wiring board whereas PCB is a contraction of a printed circuit board.

A printed wiring board typically encompasses the creation of an electrical network over a substrate.

The electrical connection is usually furnished on an etched conductive plate.

Electronic components are typically attached to it to make a functional circuit.

A printed circuit board provides physical support to electronic components while electronically connecting them.

The electrical paths commonly known as traces are created via etching and run across a board surface.

They can also be furnished over multiple layers which are connected through vias.

You find that a printed circuit board is essentially a populated wiring board.

A PCB makes a given function possible by the component composition.

You can alter the use or performance of your PCB by connecting different electronic components.

PCB

PCB

How is a PWB made?

You find the printed wiring board is made from a sequence of different fabrication processes.

These processes involve other material and equipment which you find imperative for the success of the process.

The making of a PWB will involve the following steps:

Lamination

The lamination process is one where layers of substrate and prepregs are combined under heat and pressure to form laminates.

The substrate is usually a dielectric material such as FR-4 or ceramic, which provides electrical isolation for the conductive layers.

 Ceramic PCB

 Ceramic PCB

On the other hand, prepregs are resin-based formations used to hold together the laminated parts.

During the lamination process, you find the substrate and prepreg layers are arranged as a sandwich.

They are then held together in a press and placed in a regulated oven where the heat melts the prepreg.

The temperature is just enough to make the prepreg soft without running. You find this allows it to securely adhere to the substrate surfaces when it sets.

Drilling

The drilling process seeks to bore the holes for component fixing and vias.

You find drilling is carried out to individual laminate layers and where multiple layers are involved another lamination procedure will follow.

Drilling can be conducted both manually and automatically by employing different machines and equipment.

The laminate or conductive plate is typically marked out for the drill-holes.

You can use Gerber files to generate the drill files, which will indicate the location of the drill-holes.

Manual drilling can be carried out by the use of a human-operated milling machine.

In this process, you find drill bits of the required drill-hole sizes are employed.

Automatic drilling procedures can take various forms.

You find the use of programmable machines that rely on the drill files to make the hole sizes to the required parameters.

Laser drilling can also be employed where laser beams are utilized in the drill-holes formation.

You find laser drilling to be an expensive but much faster process, especially when using multiple beams.

Conductive Track Formation

The conductive track is a vital feature of the printed wiring board. You find this track provides the desired electrical signal path.

The standard material employed for the conductive trace is copper due to its signal transfer qualities and availability.

There are two approaches to creating the conductive trace: additive and subtractive methods.

The additive method involves the deposition of copper on the substrate surface in the desired pattern.

Contrarily, you find the subtractive approach to apply a copper film which is etched to rid out unwanted material.

A pattern in the shape of the desired conductive path is then obtained.

What Materials are used in the Fabrication of PWBs and PCBs?

The printed wiring board and printed circuit boards are composed of different parts that require different materials.

Furthermore, similar material can be used for both the PWB and PCB due to their design similarity.

You find the materials used in a PWB and PCB are dependent on the application of the board.

You have conductive and non-conductive layers in these board types.

The conductive layer is usually used for signal transfer, whereas the non-conductive layer is employed for electrical isolation purposes.

Some of the common PCB materials used for the conductive layer include copper, silver, and gold.

 FR 4 PCB Material

 FR 4 PCB Material

While gold has the highest conductivity with the least resistance, it has a high-cost factor that makes its use limited.

Copper is preferred for most PWB and PCB applications because of its low cost and good conductivity among other qualities.

The conductive layer is used to furnish the path of signal transfer for PWBs and PCBs.

The non-conductive layer is composed of a material with low electrical transference capability.

The material used for this layer includes FR-4, Composite Epoxy Material and Ceramic.

These materials have different insulation properties and thermal conductance capability.

You find FR-4 to be commonly employed with multiple variations to augment its dielectric properties.

Ceramic PCB Material

 Ceramic PCB material

Another common material you will find employed in PWBs and PCBs is the prepreg material.

The prepreg is used to hold layers together, such as the board core.

It is composed of fiberglass material pre-impregnated with resin.

When subjected to elevated temperature, it softens and adheres to the layer surfaces before setting to form a bond when cooled.

You will also find other material such as solder used on these boards.

The solder material is commonly used in component attachment and is composed of elements of tin and lead.

Furthermore, the conductive traces can be coated to prevent corrosion with materials such as gold, nickel, silver and tin.

 CEM PCB Material

CEM PCB Material

Can you use Conformal Coatings on PWBs?

A conformal coating is a resin-based layer applied over a populated board to protect it from unwanted external elements.

These elements include dust, moisture, and other conditions that could lead to board deterioration such as spillage.

Conformal coatings adhere to the board surface such that it takes up the board’s form.

You find that printed wiring boards are typically unpopulated with bare copper traces.

Using conformal coatings on such boards is prohibitive to the board development process.

Furthermore, the lack of features on the PWB board surface presents an absence of aspects requiring protection from the external elements.

What Surface Finishes can be Employed on PWBs as well as PCBs?

Surface finishes are protective coatings applied over the trace pattern of a printed wiring board.

For copper traces, you find using a surface finish prevents corrosion while also improving the solderability of the board.

You have different options for use as surface finishes such as immersion tin and silver, HASL and ENIG.

Your choice of surface finish will depend on various factors, such as:

  • The cost of applying the surface finish.
  • The size of the board and the overall board count.
  • The board populates and features with their related properties.
  • The level of durability of a particular surface finish.
  • The impact on the environment of using a particular surface finish.

Can PWBs be Furnished in Multilayer Configurations like PCBs?

Yes, they can.

Printed circuit boards are essentially populated printed wiring boards.

Therefore, you find that for you to have a printed circuit board, you first have to create a printed wiring board.

You can consequently furnish, printed wiring boards in multilayer configurations through the typical fabrication process of lamination.

PWBs can be furnished in different layer counts depending on the application type.

The number of layers is provided in even counts such as four, six, eight, ten and so forth.

The layers in a PWB are separated by dielectric layers such as FR-4 or ceramic.

Alternately, the interconnection between the several layers is provided by a network of vias.

What Component Types can be used on PWBs and PCBs?

PWBs are typically unpopulated, and when they are, they are referred to as PCBs.

Electronic PCB components are used to populate the printed wiring boards to convert them for practical usage as PCBs.

Two types of components are attached to a PWB: through-hole components and surface mounted components.

Through-hole components are leaded components whose attachment requires drilled holes for fastening the leads.

Leads are wire extensions that help to provide board attachment to the component through a soldering process.

You find the leads on through-hole components to be either axial leads or radial leads.

Axial leads constitute a single lead protruding from either end of a component.

The leads are such that they seem to be a single wire extension cutting through the component body.

Conversely, radial leads are a pair of leads stretching out from a single component surface typically the bottom.

You also find surface mounted components used on the circuit boards.

Surface-mounted components lack leads but have modifications that allow their attachment to the board.

The bottom surface or edges of the surface-mounted components are metalized to attach to mating parts on the board.

The attachments of surface mounted components are usually pinned formations or ball grids.

SMTs do not require drilled holes but instead landing pads for onboard attachment.

The pads are applied with solder paste during component placing, which is attached during a reflow process.

You find these component types to be much easier to use, allowing a higher density.

Is Copper the only Metal used for Traces in PWBs?

PWB traces are configured to facilitate electrical signal transfer across the board.

Consequently, metal elements with good electrical conductivity and low resistance are desired for trace formation.

Copper is commonly used as the conductive material for the traces in printed wiring boards.

However, you will also find other metal elements such as silver and gold employed in printed wiring boards.

Both silver and gold have higher conductive abilities with lower resistance levels.

Gold exhibits the least resistance to the electrical charge movement and consequently offers the best conductivity.

What makes the use of Copper Popular in PWBs and PCBs?

You realize that copper is not the only element that can be employed as the conductive material in PWBs and PCBs.

Silver and gold are alternative elements available for use with even better electrical conductivity and resistance qualities.

However, the use of copper is attributed to the following properties.

Copper is widely available, making its cost comparatively low to silver and gold, for instance.

Using copper in PWB and PCB construction, therefore makes the cost of fabrication economical.

The electrical conductivity of copper is admirable with a relatively low level of signal loss during transfer.

Thus, you find its electrical signal transfer performance to be dependable.

PCBs during operation generate heat that needs to be dissipated to prevent thermal board stain upon accumulation.

Thermal strain can result to board failure and/or damage.

Copper has good thermal conduction qualities that contribute to the dissipation of onboard heat.

When manufacturing printed wiring boards and circuit boards, there are various fabrication processes involved such as lamination.

These processes typically involve the use of other materials such as substrates and prepregs.

Copper is highly compatible with these materials allowing faultless fabrication.

What Copper Weights can be used in PWBs?

Copper is employed in PWBs to make the conductive tracks for electrical signal transfer.

Copper as a metal element is measured in ounces, which is a weight measure.

However, in the electronics industry, you find the ounce is used as a length parameter.

In this case, it describes the thickness of copper when uniformly laid over a square foot.

You find various copper weights employed on PWBs, leading to a triple classification of PWBs.

These categories encompass standard copper, thick copper and extreme copper.

Standard copper is described as copper measuring half an oz, one oz or two oz.

Such copper weights are employed in basic PWB boards with no significant application demands.

Thick copper is used to describe copper ranging from three oz to eight oz.

You find multiple copper sheets with different weights can be used to achieve the overall PWB copper weight.

For instance, to build a four oz copper PWB, four sheets of 1 oz copper can be used.

Thick copper PWBs are fabricated for intermediate power needs.

You find extreme copper weights useful in applications requiring large current transfers.

Their large copper imprint allows them a large cross-sectional area of conductance.

These printed wiring boards have copper weights from ten oz up to twenty oz.

Consequently, you are bound to stumble on PWBs with several layers to realize the designated weight.

What Influences the Current Carrying Capacity of a PWB?

A printed wiring board is furnished to provide a path for electrical signal transfer when employed as a PCB.

You find PWBs with different current-carrying capacities that are influenced by various factors.

Some of the significant factors include:

The Area of Application

Printed wiring boards are employed in many areas such as electronics, heavy industry use, automotive, and space applications.

The current-carrying demands vary from one application to another.

For instance, a heavy industrial application such as power converters will require large currents compared to radios.

The Copper Thickness

The thickness of copper in PWBs is provided by the weight of copper used in the fabrication.

The copper weight (ounce) describes the copper thickness when evenly laid out on a flat surface, a foot square.

The larger the copper thickness used, the larger the current-carrying ability of a PWB.

How are the Conductive Traces made in PWBs and PCBs?

PCB trace width

PCB Trace width

Conductive traces in printed boards are furnished from materials with good electrical conductivity such as copper.

The layers on which these traces are fabricated are referred to as conductive layers.

There are two approaches you can use to make the conductive traces on printed wiring boards:

Subtractive method

In the subtractive method, a copper film is stripped off to leave the required trace pattern.

Usually, the process begins with a copper film or sheet of the desired weight.

The desired trace pattern is then stenciled and placed over the copper film.

Thereafter, you employ a process such as etching to remove the unwanted copper.

Additive method

With the additive method, the desired copper pattern is furnished onto the substrate.

You find this method is less wasteful as only copper in the required pattern is used.

The electroplating process actualizes the additive process.

You can use either a full additive approach or semi-additive method with the latter being more common.

The full additive approach involves imaging of the substrate with a photosensitive mask followed by a chemical bath that precedes plating.

In the semi-additive method, a thin film of copper is first laid over the substrate.

You find a reverse mask used instead, allowing copper to be plated over the unmasked zones.

The extra-thin copper is then removed through etching.

Is Etching a Fabrication Process in PWBs?

Yes, it is.

Etching is a subtractive method of making conductive traces on printed wiring boards.

In the etching process, you selectively remove material from the conductive film to reveal the desired pattern.

Etching is a popular method that you can carry out via two approaches: dry or wet etching.

Wet etching involves the use of chemical solutions to induce reactions that strip off unwanted material from the conductive surfaces.

Usually, the material to be etched is submerged in the etching solution.

The process is isotropic and finds the most common use.

The wet etching process will be affected by the concentration of the solution and the temperature.

Dry etching to be based on plasma effect where impact whittles are employed.

You can also initiate a volatile reaction between the base and surface molecules of the materials by plasma.

The dry etching process is anisotropic and can be used for very thin films in the range of sub-microns.

Can the Application Affect the choice of PWB and PCB materials?

Printed wiring and circuit boards are employed across various industries.

You find these boards useful in-home electronic appliances, industrial machinery, automotive applications and space equipment to mention a few.

While these boards follow a similar design approach, different materials can be employed for each according to use.

PWBs and PCBs include a conductive and insulating layer in their design.

Copper is commonly used as the conductive material due to its availability, cost, and good electrical properties.

Otherwise, gold and silver can also be used but are limited due to their high costs.

However, you find gold suitable for sensitive high-frequency PCB applications.

There are many options for the substrate material, including FR-4, CEM (Composite Epoxy Materials) and ceramic.

Use of FR-4 is more prevalent in standard PWBs and PCBs due to impressive dielectric features.

You find FR-4 material with high glass transition temperature, low coefficient of temperature expansion and wide operating temperature range.

However, you find PWBs and PCBs with ceramic substrates are much desired for high power applications.

Ceramic material has a higher thermal conductivity rate than FR-4 materials.

Consequently, when used in applications with large thermal dissipations, ceramic PWBs deliver better performance than other substrate materials.

What Factors Determine the Design of PWB?

Designing a printed wiring board is dependent on several factors that include:

Area of application

PWBs are employed across different industries for various unique functions.

You need to identify the needs of your application and incorporate them into your design.

One primary consideration for a PWB based on the area of application is the current demands.

You will need the information to determine your copper thickness.

Cost

For any design project, it is critical to evaluate its cost, especially where there are budgeting concerns.

The cost of a printed wiring board will increase with the complexity.

For instance, a multilayer board configuration will cost more than a single-sided board.

Configuration

The configuration of a board is a design element that defines how the board will be structured.

There are several different board configurations to choose from.

You will find, single-sided boards, double-sided boards, and multilayer boards.

The overall board thickness will influence the board configuration as well as the area of use.

Component Density

Printed wiring boards are made to provide electrical connections for connected components in a circuit to execute a given function.

When designing the board, you have to know the number and types of components to be attached.

Having this information can help you establish the appropriate layer structure.

Thermal Requirements

Printed wiring boards can be employed in applications with large thermal dissipations.

It is vital to incorporate thermal design elements in your board design to ensure there is no thermal build-up.

You find thermal accumulation, if not addressed, can damage the board through inducing strain.

Why are Dielectrics used with PWBs and PCBs?

Dielectric materials in their fundamental formation are incapable of conducting electricity.

However, these materials can exhibit conductivity when manipulated through doping.

In printed wiring and circuit boards, dielectrics are employed to offer electrical isolation to the conductive layers.

Common dielectric materials used in these boards are aluminum oxide, plastic materials, porcelain, paper and glass.

These materials affect board performance, especially when under conditions such as high-frequency levels and temperature.

You need to evaluate the electrical, mechanical, thermal and chemical properties of dielectrics before using them.

Is Panelization Employed in PWBs?

Panelization is an approach to manufacturing that allows convenient and efficient production of large board volumes.

A panel consists of many PWBs which allows for simultaneous execution of processes.

You extract individual boards from the panel by cutting through serrations marking out the borders.

You find panelization to reduce the fabrication costs of large volumes of production significantly.

Furthermore, the production cycle of a large order is much shorter when you implement panelization.

You will find two common approaches of panelization: V-grove panelization and breakaway tab panelization.

What are the Advantages of Employing PWBs and PCBs?

PWBs and PCBs find use in many day to day applications such as communication gadgets, motor vehicles and entertainment devices.

Consequently, the role of these boards in our lives is indisputable.

Some of the benefits derived from using these boards are:

  • You find PWBs and PCBs simplify the connection process of components in devices saving on space and material.

The design of these boards eliminates the need for wire connections while also accommodating many components.

  • You can efficiently execute repairs and rework on PWBs and PCBs. These boards have simple layouts with clear labelling through the use of silkscreen.
  • When compared to breadboards, you find the process of making printed wiring and circuit boards is faster and simpler.

Furthermore, the manufacturing process of these boards is heavily automated, allowing shorter cycles and fewer errors.

  • The printed circuit board has fixed components which prevent their movement.

Both through-hole and surface mounted components are secured to the board through soldering.

  • Printed wiring and circuit boards use conductive traces as their signal paths.

You find the methods used to develop these traces reduce chances of short circuits through cutting as observed in wire connections.

  • The presentation of PWBs and PCBs is such that you will find reduced instances of electric noise generation.

Fabrication of these boards is done according to defined design rules to ensure their apt performance.

  • You find using PWBs, and PCBs greatly reduces costs for large scale electronics production.

You can build these boards simultaneously with the implementation of computer-aided design and manufacturing.

  • The reliability of PWBs and PCBs is one you can depend on.

These boards are subjected to different tests and inspections to identify any inherent flaws or failings.

It is only after successful testing that these boards are allowed to market.

Can you Employ Vias on a PWB?

Vias are board through-holes made conductive to allow the conduction of electrical signals or heat energy.

Printed wiring boards of various configurations feature vias.

Vias on PWBs can be through-hole vias, blind vias and/or buried vias.

The through-hole vias provide a connection between the outermost layers.

You can find this via type on double-sided boards and multilayer boards.

The blind vias offer a connection between an external layer and an internal layer.

Contrarily, buried vias connect the inner layers of a PWB only.

Where are PWBs and PCBs Employed?

PCB in electronics

 PCB in electronics

Many electrical controlled devices employ PWBs and PCBs.

These applications cut across various industries, increasing reliability and performance.

Some major areas where these boards are used are:

  • You find these boards in all electrical household appliances such as TVs, radios, microwaves, and washing machines to mention a few.
  • Communication devices such as satellites, receivers, mobile phones and receivers are all furnished from the heart of the PWB and PCB.
  • The automotive industry also employs PWBs and PCBs in its electrical systems.
  • You will find PWBs and PCBs in industrial power application equipment including, power transistors, power diodes and DC/AC modules.
  • Intricate lighting applications such as runway lights and those used in advertising employ PWBs and PCBs.
  • Another area of the application you will find for PWBs and PCBs is in optical devices of variable design and solar cells.

In short, that’s all you need to know about PWB vs PCB.

However, if you have any question about PWB and PCB, feel free to contact Venture Electronics experts.

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