Rigid PCB

Your Premier Rigid PCB Supplier

Ever since the first PCB created in 1920’s, rigid PCB has no doubt, is one of the most influential inventions of the electronics world, and even till now, although Flex PCB and Rigid-Flex PCB have become more popular and affordable, Rigid PCB still cannot be replaced in all applications.

Rigid PCB in manufacturing

Venture manufactures rigid PCB (printed circuit board) using the latest materials and technology, that has worked with thousands of electronic engineers to get their products into market, we have full technical knowledge and rigid PCB manufacturing experience in rigid PCB fabrication (also called rigid printed circuit board manufacturing or rigid printed circuit board fabrication).

Rigid PCB Waiting for Routing

From single layer board to 32 layer board, from flex PCB to rigid flex PCB, Venture can offer the complete PCB solution. Our two production plants are fully equipped with state-of-the-art machines that can support you from rigid pcb prototype to volume production.

Rigid PCB: The Ultimate Guide

Did you know that all most all the general circuitry applications incorporate the use of PCBs?

And that the most used type of PCB in these cases is the rigid PCB.

Well, in this guide, I will take you through all the detailed information you need to have about Rigid PCB.

Whether you are a manufacturer or a buyer, you surely will find this piece worthy.

From the benefits of rigid PCBs, rigid vs flexible PCBs, choosing PCBs, classification of rigid PCBs, to the Manufacturing process of PCBs are some of the vital aspects widely discussed.

Let’s begin.

Rigid PCB

What is a Rigid PCB?

First, a Printed Circuit Board is a device in the form of a board which is specially manufactured to form a stable base for most electrical applications.

It’s on this platform that wiring connections are intertwined to connect mechanical components besides from providing a support base.

Rigid printed board circuit with components

Most importantly, the PCBs were initially developed to replace the conventionally built hand wire connections and connectivity boards.

Now rigid PCB is one of the types of the PCBs made of solid substrates that makes the board untwistable but firm or inflexible as the name suggests.

The direct converse application for rigid PCB is the flexible PCB.

Flexible PCB

The significant difference between the two solely reduces to the twisting and flexibility. Therefore, flex PCBs can turn and twist into different shapes as opposed to Rigid PCB.

However, these two types of PCBs can be used together in a single device.

This combination provides an outstanding result achieved from the unique capabilities of the two models. For this is known as Rigid-Flex PCB.

 Rigid flex PCB

Primarily, both the rigid and flex circuits serve the same function which is the interconnection of electrical components.

Interestingly, rigid PCB is the most commonly manufactured PCB and widely used in electronics.

So the rigid PCBs are used in applications if there is a need for the board to maintain its initial designed shape permanently.

A typical example of the rigid circuit board is the computer motherboard.

 Computer motherboard

The motherboard serves various vital functions amongst them is the reliable power supply to different components from the power supply.

At the same time, it effectively initiates data communication among the computer elements such as the central processing unit (CPU), GPU and the RAM.

You need to take into account that rigid PCBs aren’t similar to circuit boards. The usual manufacturing process here for the rigid PCBs involves printing the boards.

Printing can be done mechanically or by use of an advanced technological technique which involves the use of photo or laser imaging.

Having discussed the brief overview, let’s move into another segment.

Benefits of The Rigid Printed Circuit Boards in Electrical Circuits.

These PCBs have got several pros as compared to other types of connection.

https://youtu.be/X1ptGA1JSTc

• Some of the notable advantages include:
  elimination of any hand-built wiring faults
• It facilitates complete replacement of mechanical cable connections.
• Supply of reliable and robust
• They are available in varied sizes.
• Reliable
• Relatively to mass produce

We shall now comprehensively discuss the benefits of rigid PCBs which makes them dear and highly regarded by users worldwide.

1.A wide range of sizes

Availability in different formats is undoubtedly one of the outstanding features of rigid PCBs. You indeed might have noticed that all your various electronic equipment has got a wide range of PCB sizes.

 Different sizes of PCB

From smaller to larger ones, the sizes vary depending on the general scope of the electronic device.

So large devices will use bigger rigid PCBs conversely to small appliances.

This feature makes it possible to produce up to tiny PCBs.

2.They are Relatively Inexpensive due to the Simple Manufacturing Process

The manufacturing technique here isn’t much sophisticated.

The whole designing and fabrication process is relatively inexpensive as opposed to the complex wired interconnections.

3.They are Compact

Have you ever noticed the ever evolution of bigger electronic devices into smaller effective ones?

Besides, there is an ever-increasing demand for smaller electronic devices.

All these factors are made possible as a result of the unique compatibility of rigid PCBs.

Compact rigid PCB

 For the smaller gadgets, the rigid PCBs can be made into tiny sizes to sufficiently fit and connect these components in them.

It ensures that a variety of applications is buildable upon it.

Furthermore, the rigid boards only consume little space within the gadgets.

4.Stability and Doesn’t Move

Keenly observing the rigid PCBs, you shall notice that all the components are attached to the board. To connect them you need to solder with flux.

Rigid PCB with components

Now, this makes all the wiring connections to be stable.

Therefore, in cases whereby the applications are vulnerable to harsh conditions, the components won’t tangle.

Also, this reduces any chances of damage to the electrical connections in such circumstances.

Thus this feature makes rigid PCB the final option to use in applications that are vulnerable to such movements or disturbances during the usage.

5.Limited chances of manufacturing errors

The production of these gadgets makes use of technologically versatile machines which makes the fabrication process to be efficient and reducing any unintended errors.

PCB design and layout

Regretting, these errors are prone in the manually built wires and cable connections. However, there may occur some machine-related errors in the rigid PCBs.

6.Easy Maintenance and Repair

To diagnose a rigid PCB is such an easy technique due to their design.

Why?

Their components markings are clear and conspicuous. As a result, the assembly and disassembly are made more accessible and faster.

Welding components on rigid PCB

Besides, the organisation of the signal paths of the rigid PCB is highly efficient as well as adequately designated.

All these features will enable a skilled technician to trace these signal channels during repair and maintenance effectively.

The minimisation of the Errors and unintended damages occur in the course of the procedure.

You can easily see these on the surface of the PCB.

Above all, the rigid PCB is easy to handle and not so much fragile.

7.Reduced Electrical Associated Noise

This PCB is specially designed to minimise such noise in an application by the following mechanism.

Remember that all the circuit components are intertwined together.

Additionally, this technique ensures that it limits the electrical currents among them radically reducing the radiation emissions.

Rigid printed circuit board

Consequently, the reduced radiation emission and currents also contribute to the minimised chances of the PCB not picking up any unnecessary electromagnetic waves.

Eventually, this results in a much-reduced cross-talking among the components.

Now that’s just a simple way in which these PCBs limits noise production.

8.Highly Reliable and Durable

One significant failure commonly experienced in most traditional circuits especially cable wiring is the failure in the interconnection parts.

Thumbs up to rigid circuits, we shall no longer experience these failures.

Why?

 Durable rigid PCB

Because the interconnection points are very few thereby enhancing the reliability of the loop.

It’s also notable that the circuit connections on the boards are protected with the insulated coating thus increasing the lifespan of the PCB.

9.Sufficient thermal regulation

Since these PCBs are compact and tiny, a small heat path is generated ensuring that the heat dissipated is limited.

PCB with thermal insulation

10.Easy to replicate

Replication of the circuit is also another simple procedure. Once one design is ready, then the others can be subsequently made in a similar design.

PCB design software

Replication is a simple process which requires zero effort since its computer generated from a similar schematic layout plan.

11.Portable

These circuits are never bulky nor heavy thus can be moved from place to another without any mechanical damage.

Portable rigid PCB

The wired connections are much complicated to run especially when large.

With that, you now have the numerous benefits associated with this kind on of connection as opposed to other.

Reflect upon them before proceeding.

Rigid PCBs vs Flexible PCBs – An Ultimate Comparison

Even though these connectivity devices serve similar purposes, they have some distinct differences regarding structural and mechanical composition.

Many people commonly differentiate the two by flexibility and the ability to bend.

Well, that’s very right, but for a manufacturer or a designer, more detailed information is vital to avoid any unnecessary mistakes that may result in failures.

Rigid flex PCB

So we shall kickstart this segment with the pretty obvious differences.

§Bending and Flexibility

Direct and straightforward, a flex circuit can bend, twist and fold to assume different shapes as required by the designer or application whereas rigid one cannot.

Rigid vs. Flexible PCB

This significant difference comes as a result of the different materials and rules used in the manufacturing process of the PCBs.

§  Materials used in the fabrication

The most significant differences between the two PCBs lie in the materials used. Take for instance a single side circuit, the base construction includes:

• Dielectric layer
• Adhesive base layer
• Conductive material layer
• Protective overlay material

Now, let’s discuss the different material layers

Sample PCB Layers

§ Base layers

For a rigid PCB, this layer is usually stiff and firm. The primary constituents incorporated here are the FR4 and glass reinforcement.

Well, these materials are necessary and essential in providing firm support and stability to the circuit.

Also, they are good for thermal regulation besides providing mechanical strength. However, they are rigid and doesn’t easily allow the board to bend or twist.

Polyimide is the principal material base of the flexible circuit.

This material is perfectly flexible although it doesn’t provide any stability or mechanical support. Above all, it’s dimensionally unstable as compared to the FR4.

§ Type of adhesives

The kinds of resins used in rigid PCBs are only limited to chemical and thermal properties since they neither bend nor twist.

Thus a resin for rigid PCB would crack or produce a pitiable result when employed in flex circuits.

Elsewhere, adhesives for the flex circuits take into account the bending or twisting ability. It, therefore, needs to stretch to some degree.

In a nutshell, the adhesives for the flex circuit would have distinct thermal, mechanical and chemical properties unlike the ones in the rigid PCBs.

§  The conducting material (copper)

There are two basic and common types of copper film materials including Electro Deposited (ED) and Rolled Annealed (RA).

The ultimate difference between the two is that RA copper is more flexible compared to ED copper.

Due to this, it becomes suitable for use in dynamic applications.

However, it doesn’t mean that ED is entirely rigid.

It has got some flexibility properties and may be used in some circumstances even though you shall commonly find it in the fabrication of rigid PCBs.

Other types of copper film materials are also available for selection.

This includes HDED copper which is a high ductility material which is electrodeposited with treatment materials to enhance its flexibility.

Quite good but not to the level of RA  copper.

Rigid Circuit Board

Note that for the rigid PCBs, you need to make little considerations when selecting the copper material since it doesn’t need flexibility.

But to flex PCB, copper choice and selection is critical and significant because it has got huge impacts on the general performance, ie. Flexing and flexibility in installation of the applications.

§Cost of the individual PCB

Looking at the ‘specific’ value of each category, then it would be easier to say that rigid PCB costs less compared to Flex PCB.

Now here, I used the word ‘specifically’ with an intention.

In some situations, it’s likely to be that the total cost for fully installing a rigid PCB in an application is much higher compared to that of the Flex PCB.

Flexible PCB

Importantly, when focusing on the initial cost for purchases, then rigid PCB is pocket-friendly.

This so due to the low costs incurred in designing and the manufacturing procedure, unlike flex PCB.

To fully understand this, we shall later on comprehensively discuss the fabrication process in this guide.

§ Type of Applications

Remember, rigid PCBs are older generation equipment.

Therefore, most general and straightforward electronic devices that were initially mainly invented form the usability for them.

They may include audio keyboards, desktop computer devices among other many electronic gadgets.

Computer keyboard with flex PCB

On the contrary, Flex circuits are made use of in more sophisticated and complex electronic devices.

Why?

They eliminate any need for connectors. Besides, they are ultra-thin than flex PCB so then they can be used in digital cameras, smartphones, tablets, GPS, etc.

Main Applications of Rigid Printed Circuit Boards

The compactness, existence in a whole set and simpler maintenance makes the rigid PCBs be a

‘darling’ for use in many applications.

One major feature of rigid PCBs that needs consideration is that once it’s designed and installed in a device, then you can’t alter it whatsoever. Seemingly they last over the whole lifespan of the application.

Industries that require complete fixing of components and need to deal with solutions to mobility stress are particular beneficiaries of this technology.

Below are some areas for consideration of their uses.

i.Mechanical and Automation Industry

This category involves the use of light and heavy-duty machines to ease work. They involve robots, hydraulics, gas pressure levers, trolleys among others.

For that reason, multilayered PCB is employed to provide impedance.

PLC circuit board

Heavy duty PCBs similarly are used to provide support to applications that consume large voltages and current.

ii.Automotive Industry

All sorts of vehicles utilise the rigid PCBs. The only way to ensure they serve optimum is by adding more copper or aluminium substrates.

High-temperature laminates should also make it a perfect combination.

All these critical modifications are necessary to take for instance the high-temperature lamination.

Lamination helps to shield the PCB from the excess harmful temperature in the engines or environment.

Temperature cycling test board

Automotive PCBs are made from plated copper to increase their durability.

The AC/DC power converters, transmission sensors, electronic communication sensors all make use of rigid PCBs.

iii.Medical and Laboratory Sector

Though this one of the fields widely dominated by flex circuits, rigid ones also play a significant role.

For example, small but ultra performing machines in this sector are some of the applications which utilise the flex circuits.

On the other hand, large and bulky devices are some of the devices fitted with rigid PCBs.

Some of them are Magnetic Resonance Imaging (MRI) systems, X-Ray radiation machines, Electromyography machines (EMG), Tomography system.

MRI Machine

iv.Aerospace Industry

Without contradiction, this is one of the most challenging industrial sectors.

Unfavourable temperatures, high rates of humidity are just a few difficulties that hit this sector.

Some of the applications in this field include; temperature sensors, auxiliary power units, power converters, control tower systems, aeroplane cockpit machinery, etc.

Boeing cockpit

Consequently, rigid PCBs are preferred for use here since they can be modified to suit the conditions.

For invariant temperatures, the rigid PCBs gets designed with a copper and aluminium substrates coating together with high-temperature substrates.

Now, these are just a few applications of the rigid PCBs.

They can be incorporated in several sectors as long as better and improved instrumentation is applied.

For that reason, both the manufacturers and clients need to work together to ensure that they have a deep understanding of the application needs.

The client needs to provide detailed information to ensure correct designing of the circuits that suit their needs.

Comprehensive designs, industrial grade components, manufacturing procedure, are some of the vital information useful in the fabrication of suitable PCBs.

With that information, you should have enough ideas about this circuit.

The next section we cover the steps that should assist you to select a suitable one for your needs and preferences.

How to Choose Rigid PCB Material

Selection of a rigid PCB is a massive technique that needs to be well understood by both the manufacturers and clients.

Luckily, we shall discuss all the ideas that you need to know.

Shall we begin?

I.Pricing Factors

Any manufacturing process should aim at providing a quality product but at minimum costs.

For that reason, we begin by considering the factors that may increase the values of the PCB.

Mostly the final costs are affected by the type of material and component.

However, there costs continuously varies according to the market trends.

Most importantly don’t be shy from high costs. You only need to assess if the product meets your expectations.

Therefore some factors that affect the PCB manufacturing and costs are:

• Size of the boards – standard boards are of 50 by 50 mm, a smaller board size lowers cost while a larger one costs more. But those less than the optimum size (50 by 50mm) are even more complicated to fabricate.

PCB Dimension

• Many layers – many layers costs more.
• Quality of laminate material – Tg 140 materials which are low quality would certainly cost little while high-quality ones like those of Tg 180 are relatively expensive.
• The copper weight – more massive copper, costs more.
• The thickness of the board – the costs increase with an increase in board breathe. Standard width is 0.063 inches.
• Via in pads slightly increases costs of fabrication.
• The type of surface finishing for example solid gold and gold plating also affects the costs.

These are just a few factors. Other parameters also do affect the overall costs. To be sure contact your nearest dealer for a quote.

II.Consider the Material Properties

The critical component material for fabrication of rigid PCB is the substrates.

Above all, you need to know that different substrates have got different characteristics, performance, and associated costs.

PCB material

So it’s essential that we have a look at these substrates and make some general comparison and contrasts amongst them.

Our core objective here is a selection of appropriate substrate concurrently minimising the production costs.

The financial aspects form the basis of setting up a fabrication plant and the substrate costs impact mainly on it.

The critical factors in selecting an appropriate laminate material for the PCB are the costs, quality and the lead time.

Size of the PCBs is also a complementary aspect to check.

The PCBs consumes a lot of material during fabrication meaning that their sizes are directly proportional to the costs involved.

It therefore, means that you need to put into greater considerations the size of the PCBs you are planning on manufacturing.

A slight difference in the dimensions may have a considerable impact on the general costs of the PCBs.

As evident, different materials have got different costs in addition to different characteristics.

When comparing the properties of laminates for use, we first of all need to consider some associated traits below.

• Glass Transition Temperature (Tg) – this is the temperature at which the physical properties of the materials transform. The transformation here for the laminates could be from hard, glass material to a softer and smooth material.
• Decomposition Temperature (Td) – it is the temperature at which the laminates chemically decompose.
• Dielectric constant (Dk) – this is a numerical value that helps in showing the relative permittivity amongst a set of insulator materials. Generally, it refers to the ability of the materials to store or keep electrical energy when placed in a specific electrical field.

It’s possible to compare the dielectric constants in two scales. That is in insulation scale and RF applications scale

In the insulation scale- then, you shall realise that those of lower values are better and preferred compared to those of higher costs. Meaning, they have got little insulation properties.

For RF Applications – a larger dielectric constant is picked ahead of the rest.

• Dissipation Factor (Df) – this a parameter that is used to measure the rate of efficiency of an insulator.

The leading indicator of this is the percentage energy lost when under a type of oscillation such as electrical, electromechanical, or mechanical oscillation.

PCB Structure

With that, we now venture into the types of laminate substrates.

For the case of our discussion, we shall limit ourselves to eight main types of laminates classified under four groups of glass transition Temperature (Tg).

1. Shengyi S1140 (Tg 130) – it is of the lowest quality among the group. However, the good news is that it hugely saves the project costs.

Many manufacturers tips this type to be suitable for use in joint projects.

2. Isola FR 406 (Tg 130)- comparable to S1140
3. Shengyi S1000-H (Tg 150) – commonly used by most manufacturers for optimum projects.
4. Isola FR 406 (Tg 150) – Similar to S1000-H.
5. Shengyi S 1000-2M (Tg 170) – recommended by some.
6. Isola FR 406 (Tg 170) – closely similar in quality to S 1000-2M.
7. Iteq IT180A ( TG 180) – High-quality one
8. Isola 370 HR (Tg 180) – comparable to IT 180A(Tg 180)

For in-depth coverage of the laminates against their associated characteristics have a look at the table below.

So which is the appropriate laminate material to use?

You may pick one of the higher quality laminate materials in cases whereby:

• You are designing PCB of 8 or more layers.
• The copper weight in use exceeds 3 oz.
• The PCB board thickness is of less than 0.5 mm.

III.Laminate Material Thickness

Note that the core material thickness varies according to the needs of the client and applications for most applications the thickness range from 0.145mm to 3.0 mm.

PCB laminate material

IV.Prepreg Description and Width

Prepreg is a material component used in the manufacturing process of multilayer PCBs. However, after curing, it assumes the properties of the core layer materials.

Prepregs have various series of glass styles that can be used by fabricators.

Below is a table that shows the respective thickness and the resin contents of the glass styles.

V.The Weight of the Copper Material

Mass and weight is also another right parameter to consider.

The weight of Copper FR- 4 laminate materials is measurable in an ounce (oz). This weight per square foot.

PCB Material

Most forgeries prefer working with the copper weight of up to 10 oz. also copper weights of 4 oz or higher do affect the manufacturing process as well as increasing the lead time.

VI.Multilayer Properties

To ensure quality construction, both the designer and the manufacturer need to deeply consider some little but vital features of the multilayer boards.

First, the multilayer boards should have an even set of layers.

Second, select the dielectric thickness of each layer from the two previous tables in this guide, i.e. table showing prepreg thickness and type of cores.

But if you not sure about this please you need to consult a reputable manufacturer.

Third, ensure that the multilayer designs balance with the layup relative to the Z-axis median.

It is essential for reducing the bow and twist.

Fourth, in case you working with thicker copper weights, you may balance the back and front circuitry distribution of the board.

In summary, the copper and dielectric thickness, Z- axis, number of layers need to be optimally balanced.

For the thickness tolerance, pick one with ± 10 % for the general thickness greater than 1 mm.

Therefore, when selecting a suitable PCB then look out for the multilayer properties.

VII.Material Alternatives

You might be living in different parts of the world. For that reason, it’s only fair to discuss substitutes for the materials that you may easily find at lower costs.

Apart from the material quality type, we bring in other important variables into account. That is the cost and the lead time.

For a manufacturing plant located in China, then we advise using China laminate materials.

Why?

Because it would be costly importing North American materials as well as increasing the lead time which may be unfavourable for your needs.

This vice versa for the case of North American manufacturing plants.

There you have it folks, the tips on how to choose a suitable PCB for your needs. It’s paramount to internalise them before making a quote.

Let’s move onto the next chapter.

Classification of Rigid Printed Circuit Boards

A wide range of circuitry is available in the market depending on the functionality, size difference, and structural configuration.

Since rigid PCBs are unique, then you only have access to selection from a small group.

They have similar functions; the only difference lies in their manufacturing procedures and structural design.

The following are the major available types:

• Single sided rigid PCB
• Double-sided rigid PCB
• Multi-layer rigid PCB
• Aluminium backed rigid PCB
• Copper embedded rigid PCB

We shall now constructively discuss each.

§  Single Sided Rigid PCB

Just as the name suggests, this circuit only has got one layer of conductive material on the dielectric film.

Single Sided Rigid PCB

As a result, it, therefore, means that they are the purest form of Printed circuit boards.

One-sided rigid PCB indeed is the earliest type of circuit initially used in olden PCBs.

Commonly they are adaptable for simple designs. Also, they have non-plated through holes on their boards.

Having a single side implies that the parts are laid out on one side while the circuit exists on the other one.

The only limitation of this circuit is that it’s got restricted use due to one conductor layer.

Thus it’s not cross permitted, and each line has to have its path.

Screen printing or network printing is used to design these circuits. This process entails printing resist on the bare copper, etch and solder mask.

Finally, the board should be punched to finish plated holes.

The principal raw materials for fabricating single layer PCB are FR4 Fiberglass laminates, aluminium, copper base.

§ Double-sided Rigid PCB

Unlike the single-sided PCB, this circuit has got double layers of conducting materials. For this one, it has got copper on both sides of the laminate materials.

Mostly, there must be fixed an insulator material in between the conducting layers for separation.

Uniquely this circuit has got plated through holes.

So what is the need for the holes?

Double Sided Rigid PCB

They are responsible for providing a connection between the two conductors.

Optionally though not conventional, the holes may be left out.

For such a case the features of the printed circuit may be accessed via the single side.

Additionally, a designer may choose to fabricate an outer covering layer on either both sides, one or none.

However, for most designers, this not an optional design and therefore they cover both the sides.

Remember, these are just little customisations which manufacturers incorporate according to the customer’s preferences.

Usually, the board thickness ranges from 0.1 mm to 5.6 mm with a maximum length of 1.2 m.

Above all, double-sided rigid PCBs are cherished by most users since they are suitable for designing interconnections.

§ Multi-layer Rigid PCB

This circuit especially has got more than three layers of conducting materials with insulating sheets placed in between the copper layers.

Optionally, the outer covering layers aren’t mandatory.

Assembling of a simple multilayer rigid PCB is done by combining single and double-sided printed circuits into a single shielded unit.

The several layers are attached firmly and fitted with plated through holes. During the manufacturing process, the circuit may be laminated.

Multi layer PCB – Image Source: The Engineering Projects

Benefits of using multilayer rigid PCB

By using multilayer rigid PCB, your options are endless such as limiting crossovers, eliminating crosstalk and controlling shielding.

§Aluminium Backed Rigid PCB

When operating a circuit with high heat energy dissipation, then aluminium PCB is the solution to your needs.

It is composed of aluminium material, an excellent heat conducting dielectric layer besides a standard circuit layer.

Aluminum Backed Rigid PCB

This circuit layer is a thin printed circuit board bonded to the aluminium backed layer.

For that matter, the circuit layer can as well be complicated as the case of a typical fibreglass backed layer.

It’s very good at driving away the thermal energy from your application thereby controlling the device’s temperature. It’s about ten times efficient at controlling heat compared to FR4 fibreglass backed PCB.

Therefore this superior high thermal regulation provides room for high power consumption and high thermal dissipating applications to be implemented.

Just like it’s common to have single and double sided designs, it’s also possible to have an aluminium backed design with a second side.

Additionally, designers attach the circuit layer through a highly thermally active dielectric layer on both sides of the aluminium coat.

Afterwards, the two sides can be connected by plated through holes.

Laptop rigid PCB

Fundamentally, the aluminium backed printed circuit has got three main layers which are:

• Circuit layer that consists of copper of varied thickness.
• Insulation layer which has got a thermally insulating material layer but with a high thermal dissipation factor.
• A base layer – comprises of the aluminium metal substrate.

Advantages of aluminium backed rigid PCB.

• High Heat dissipation – did you know that excessive heat is harmful to most electronics? It’s therefore wise to use a material that would swiftly dissipate heat don’t you think so? One of such material is aluminium. It has got superior ability to transfer heat away from the essential components thereby securing your circuit board from thermal damage.
• Long lasting – aluminium is a mechanically stable material with exceptional strength more than fibreglass or ceramics. It is thus useful for use in applications that need high mechanical stability or is likely to be exposed to much mechanical stress. Additionally, it reduces any chances of accidental breakage during handling or manufacturing.
• Low cost – aluminium is a standard metal easily found in most places, besides it’s easier to mine and refine. The expenses related to aluminium use is thus lower compared to other metals. Subsequently, it would then translate to the reduced costs of aluminium applications such as aluminium backed rigid circuits.
• Light in weight – to add onto its excellent thermal dissipation and stability, aluminium is equally an extremely light metal. It would therefore not add any extra weight to the printed circuits.
• Environmentally friendly/suitable – aluminium is toxic free and recyclable. The whole process of using aluminium is thus ideal for conserving energy around the globe. It’s a good indicator thus for using aluminium backed PCBs to care for our environment.

Applications of Aluminum backed PCBs

PCB with LED – Photo courtesy Smart Prototyping

• Power converters
• LED applications such as traffic lights, automotive and general lighting.
• large current circuitry
• power supplies
• motor controllers

In general, aluminium backed PCBs are perfect heat dissipation solution for any high power consuming device.

Hence any device that can be optimised by thermal conduction and temperature regulation is an application for aluminium backed PCB.

§Copper Backed Rigid PCB

Copper rigid PCB is an ordinary and usual type of printed circuit.

They are very similar to their aluminium backed counterpart except instead of using aluminium for the board fabrication; they use copper substrates.

Copper backed rigid PCB

Usually, it’s constructed in a manner that the copper metal binds onto one or both sides of the fibreglass epoxy resin.

Sometimes it’s possible to combine them with paper reinforced phenolic resin.

Whatever the combination, these circuits are less expensive as a result they are applied in household electrical appliances.

During the fabrication process, the printed circuits made of copper is either etched or plated on the surface of the substrate.

Afterwards, the desired pattern remains embedded on the surface.

However extra measures need to be taken when working with copper.

Since it’s highly oxidised, the copper surface is coated with a thin layer of tin-lead to prevent oxidation of the metal.

Distinctively, the contact fingers are also coated three times separately with different materials.  The first coating is of tin-lead, then nickel and afterwards gold.

This kind of surface is done to make the copper metal achieve a higher conductivity rate.

Manufacturing Process of the Rigid Printed Circuit Board

The whole manufacturing process takes place in a forgery industry that is entirely clean and free from contamination.

Most manufacturers have a slightly different propriety process. Nevertheless, the following procedure and steps may be used to make a rigid PCB.

Step 1: Design and Make Relevant Files in a Correct Format

Various Printed circuit design files together with documentation are essential before the start of the manufacturing process.

The primary two design files needed for manufacturing are: ODB ++ and Gerber Version RS – 274X.

§ ODB ++

For this format, the TGZ compressed file format contains all relevant data required for fabrication.

After that, the compressed file format get sent to a fabrication company where it gets implemented for use during manufacturing.

ODB ++ implies ‘Open Data Base’ while the suffix ++ added later on in 1997.

To create the layouts for the printed circuit boards, you should use a computer-aided software (CAD).

It later transfers it to a photolithographic computer aided manufacturing (CAM) system.

Since several distinct companies develop this layout information, an intermediary file format has to be incorporated, and that’s where the ODB ++ comes in.

The ODB ++ is responsible for efficient data exchange between the two software.

However, the database has got two versions that are: The original version owned by Mentor and XML version also termed ODB ++ (X).

§  Gerber Version RS – 274 X

The Gerber file has got three versions. One of the common and standard one being RS-274 X also referred to as Extended Gerber or X Gerber.

RS 274 X is a vector format used for designing 2D binary images.

The other ones being RS 274-D and Gerber X2.

Also, the Gerber files are all Computer Numerical control (CNC) files.

It means that they can be used to drive PCB fabricators since they are also CNC operated machines.

Interestingly Gerber files describe various board images including copper layers, solder masks, paste mask, and silkscreen.

The data captured in the files are traces, vias, planes, pads, and component footprints.

Now the RS 274-D is the olden obsolete version that has now been overtaken by RS 274 X which has got high tech kind of commands and controls.

You shall notice that the RS 274 X produces a precise machine plotting.

Again the latter one preferred since it has got a more comprehensive file system while the RS 274 D keeps the critical information separate from the primary data file.

Gerber X2 released in 2014 is compatible with RS 274 X, but it’s incorporated with some extra data though it has failed to gain industrial popularity.

It’s, therefore, the sure thing to say RS 274 X is the dominant force in the market.

The computer-aided design (CAD) system software is used to create PCB layouts.

Afterwards, the information directly gets saved in the RS 274 X format in which the Gerber set entails the entire description of every single layer of the PCB.

The CAD system is crucial for outputting a single Gerber file for each relevant layer.

These Gerber files can then be stacked onto the Computer Aided Manufacturing (CAM) system to offer data for every step of the fabrication process.

The Gerber files is a set of the following documents.

• Drill/ Route file – specifies the design and measurements of the holes that get drilled in a PCB design.
• Netlist file – entails the full connectivity information for a circuit.
• Solder mask file – reveals the information on the areas not covered for example holes, pads,
• Board outline file – elaborates on the board shape and size.
• Silkscreen – this another platform that contains the board surface markings info.

Step 2: Choose The Right Rigid PCB Material

As earlier on discussed, the material for the PCB is very significant to achieving an efficient result.

Laminates are the primary materials involved in the fabrication process. Remember the laminates have got varied properties, functions and costs.

Earlier on we discussed a whole set of information on the selection basis of the laminates; please refer.

Rigid flex PCB layers – Photo courtesy: EPEC

However, the list below shows the laminate materials and their properties in order of their quality. (From the highest to the lowest class)

1. ITEQ IT180A (TG 180) – for use when there is a need to achieve high-quality
2. Isola 370HR (TG 180)
3. Shengyi S1000-2M (TG 170)
4. Isola FR406 (Tg 170)
5. Shengyi S1000-H (Tg 150)
6. Isola FR406 (Tg 150)
7. Shengyi S1141 (TG 130) – Recommended for regular projects.
8. Isola FR406 (TG 130)

Having made the right decision for your material then proceed to the next stage.

Step 3: Consider Rigid PCB Manufacturing Capability

The manufacturing capability, in this case, is the facilities reliance on the delivery of suitable options and limits of the circuit board produced.

It’s paramount for you to be aware of the manufacturer’s capabilities as it will assist you in making the right choices for the suitable design.

Armed With the following guidelines, you will exactly have complete knowledge.

§ The technological ability of the PCB

Different manufacturers have got different set of proficiency in producing the right PCBs.

The specifications that are inclined to reveal this information are minimum trace widths, minimum hole size, minimum clearance, board thickness limits, number of layers, the board size among others.

Note that other vital factors affect each other that is an increase in one aspect concurrently leads to a decrease in the other. These factors include:

• Trace width against clearance.
• The minimum hole size and the board thickness compared against the aspect ratio.
• Hole sizes against the annular ring and the space between hole to other structures.
• Copper weights against impedance.

§  Pricing

Remember, the mode of pricing solely depends on the type of manufacturing process in place together with the different structural designs.

§  Lead time

It is an estimate of the amount of time necessary for completion of a single process. Such lead time includes delivery of material, manufacturing process, etc.

The prices most likely increases due to the following factors.

• Many numbers of layers increase the lead time.
• Making boards bigger or conversely making them tiny.
• Substantially increasing the copper weight above 3oz.
• Black solder mask.

Step 4: Manufacturing and Assembling Rigid Printed Circuit Board

Before we kick off the manufacturing process, it’s good to note that the process prominently requires a keen and strict balancing strategy.

PCB Assembly

The procedure is entirely procedural. However, we can simplify the process into some segments.

§  Building the Substrate

1. Treat the glass fibre with epoxy resin either by spraying or dipping after that pass the glass fibre through rollers to roll it into desired thickness and also to remove the excessive gum.
2. Pass the substrate into an oven for securing. Ones it’s secured, you can now cut the material into larger panels.
3. Stack the panels in layers alternating with layers of adhesive backed copper foil. Afterwards, place them in a press tuned to a temperature of 170 ⁰ C and pressure of 1500 psi. These condition cures the resin and firmly bonds the copper foil onto the substrate.

§  Drilling the Holes

Drilling holes on PCB

4. Stack together several panels of substrates that are enough to make many Place them in a CNC machine and drill the holes according to the predetermined patterns during laying of the boards.
5. Now deburr the holes to remove unwanted materials on the edges of the holes.

§  Plating the holes

6. Plate with copper the inside parts of the holes. Strictly the plated holes are the ones that should provide a conductive Conversely, the other nonconductive holes aren’t plated but plugged or drilled just after cutting each board from the panel.

§  Designing the PCB pattern on the substrate.

7. Degrease the foil surfaces of the substrate. Do this by passing the panels via a vacuum chamber in which a layer of positively charged photoresist material is pressed tightly onto the surface of the foil.
8. Lay the PCB pattern mask over the photoresist and expose the patterns to a server ultraviolet light.
9. Now it’s time to remove the mask. Spray the patterns with an alkaline developer to dissolve the irradiated photoresist on the PCB leaving the copper foil exposed on the substrate
10. Electroplate the panels with copper. The cathode in this process is the substrate surface, so you need to plate the copper on the exposed parts of the foil to a thickness of about 0.001 inches – 0.002 inches. To prevent oxidisation reaction, electroplate the copper metal with tin-lead or a more protective layer.
11. It’s now time to remove the photoresist using a suitable solvent to uncover the substrate copper foil in between the printed circuit board. After that spray the boards with an acid solution to eating away the copper foil. It isn’t possible for the plated copper to get dissolved by the acids due to the protective tin-lead

§  Fixing the Contact Fingers

9. Attach the contact fingers to the ends of the substrate.soon after mask the contact fingers from the board and plate it under three sequential stages with tin-lead, nickel and gold.

§  Fusing the Tin-lead Cover

10. Pass the panels through an oven to make the tin-lead outer cover meltdown. The tin-lead covering on the surface of the copper is also highly oxidised, and this is done to protect it.

§  Sealing

11. Seal each panel with epoxy to prevent any mechanical damage to the circuit when fixing the components.

§  Stencilling

12. Now you need to stencils the instructions and other markings on the boards.

§  Cutting

13. Finally, cut the panels into individual boards and smooth their edges.

§  Installing the components

14. Installation of the components is the final step in the manufacturing process. Pass each board in several machines to attach the electronic components in their correct spots in the circuit.

Rigid PCB with components

Step 5: Rigid PCB Surface Finish Options

Indeed surface finishing is one of the critical areas that is usually neglected by most manufacturers not to mention done improperly.

PCB surface finishes play an essential role in protecting the underlying parts of the board. It shields the copper surfaces not covered by solder mask.

The fundamental way to do surface finishing is by dipping, immersion or even electroplating.

Different types of surface finishes are available. We shall briefly discuss some of the major ones.

Rigid PCB

• Hot Air Solder Leveling (HASL) – This is the technique that produces the tin-lead coating and most common in the industry. It comprises of solder of about 63% tin and 37% lead or 60 / 40 split.

This kind of finishes is popular due to the low costs and excellent shelf life associated with it. However, it produces uneven surfaces.

• Organic Surface Protectant (OSP) – it is a watery natural type of surface finishing applied to copper pads on a printed circuit board.

not really a standard surface finish technique also attracts more expenses when selected.

• Electroless Nickel / Immersion Gold (ENIG) – this is a two-layer metallic surface finish comprising of a fine layer of gold applied over a thin layer of nickel.

Here nickel is first plated on PCB copper pads then afterwards layer of gold added on top.

Since the introduction of the ROHS regulation, this finishing technique has become the most used.

It brings along excellent and long shelf life together with a very level surface. Unfortunately, it’s complicated and susceptible to apply thus needs to be properly undertaken.

• Immersion tin – involves a chemical process used to apply a thin layer of tin over the copper layer.
• Other surface finishing techniques include:
• Immersion silver
• Electroless Nickel /Electroless Palladium / Immersion Gold (ENEPIG)
• Wire Bonding
• Full body Hard God
• Selective Gold
• Double gold
• Edge Connector Plating

Step 6: Solder Mask Rigid PCB

Another technical detail assumed by most. Let’s begin with the basics.

A solder mask is a strong permanent covering bonded over the copper traces of a printed circuit board.

The two vital functions of a solder mask are:

• It prevents the formation of solder bridges during an automatic mass assembly.
• It also prevents the copper traces from oxidation.

The thickness of the solder mask may vary even though the standard one is 5 micrometre on the corners, and 10 micrometres on the conductor surface.

Solder Mask PCB – Photo courtesy: Robot Room

You may opt for one of the following types of solder masks

• Liquid Photo-Imageable Solder Mask (LPI) – comprises of an ink compound sprayed on the board. Used together with HASL. After application of this solder mask then curing need to follow.
• Peelable Solder Mask – temporary solder mask applied on the boards to shield the gold plated parts from being coated with solder before the HASL process. Afterwards, it can be manually peeled

Another aspect is the smouldering colours.

No matter the chosen tone, it hasn’t any effect on the electrical properties and functionality of the PCB.

The only importance come in during the troubleshooting process of the board.

The standard PCB colours available are green, red, blue, yellow, black, white. Purple and orange are some of the few custom colours.

Step 7: Silkscreen Rigid PCB

What is a silkscreen?

A straightforward question. It is a set of all the readable texts printed on the PCB.

This information includes company logo, component reference designators, warning indicators, part numbers etc.

Now ones your PCB is ready, you only need to print beneficial information on the board since the space is always little.

Furthermore before beginning to do this ensure that the design you want to put adheres to the equipment you use.

The marginal printing error, line widths, text height, are some of the parameters you need to consider before starting the process keenly.

Apart from the aesthetical value associated with silkscreen, it also makes it easier to troubleshoot or rework the PCB.

Step 8: Electrical Testing Rigid PCB.

Finally, you need to conduct a PCB electrical test.

To do this use the electrical probes to test every unpopulated printed circuit boards for shorts opens, resistance, capacitance, and others.

To verify the adherence of the net continuity of the PCB to that of the NETLIST file of the PCB, you shall need advanced equipment.

Quality testing laboratory

Conducting the net continuity test is essential in the detection of problems in the fabricated boards after assembling.

If you are dealing with multilayer PCB, then you need to check and verify the inner layers. Ensure you also check for any short circuits in the plated through holes and all the SMD pads.

There you go. That marks the end of the manufacturing steps.

Top Ten Rigid PCB Design Software

To produce quality PCBs require additional measures. One of them is the design software, such include:

• eSim
• Kicad
• Geda
• Free PCB
• Osmond PCB
• ExprsssPCB
• PCBWeb Designer
• DesignSpark PCB
• Fritzing
• Eagle

Let’s have a look at each

PCB Software design

1. Esim

This an open source EDA tool used for PCB design, simulation, circuit design, and analysis.

Suitable since it offers all these services at a lower cost especially in the procurement of licenses.

Easy to use software and can be run on Linux and Windows operating system.

2.Kicad

This a large open suite design platform. It avails any aspects of electronic designs including the 3D viewer, schematic capture and PCB layout.

For easier inspection with Kicad, you can modify the aesthetical aspects of the PCBs according to your taste.

3.Geda

It is another all-inclusive software. With it, you have access to rats nest feature, schematic import, design rule checking and Gerber files, photorealistic design images and much more.

4. Free PCB

This is a free, open-source PCB editor for Microsoft Windows operating system.

It is indeed easy to use and learn software that gives you the desired results you can’t undermine.

Some of the features you shall find interesting in  this software are:

• Imports and export PADS – PCB netlist
• Exports extended Gerber files.
• Design rule checker
• Autosave among others

5.Osmond PCB

Another free software but for a small design.

With this, you can design through holes, surface mount PCBs, and multiple layers.

Apart from that, it also brings design rule checker with it.

6 .Express PCB

This is an easy to use software especially recommended for starters. It gives all the necessary documentation needed to get you going.

7. PCB Web Designer

Also free CAD design software for electronics hardware. With this, you shall get complete service design and manufacturing features.

Suitable for doing schematic capture and creating multilayer boards.

8.Design spark PCB

Are you working on intricate designs? Then this software will ease your workload with minimum configurations.

The additional huge library system, videos, and tutorials also incorporated.

9. Fritzing

This an open source hardware forum which offers a software tool, a community website that enables the users to keep track of their prototypes, enhance sharing amongst them.

It also makes it possible to learn to teach electronics in a classroom session, layout and manufacture PCBs.

10.Eagle

This is another suitable software for intricate designs. It’s robust but easy to use the software. You can access its free version and even paid one.

Its schematic editor is easier to use, together with efficient PCB layout and ready to use libraries.

Indeed these are the best software available.

We now switch our focus to another concept.

Frequently Asked Questions on Rigid PCB

Many people often have a lot of questions still unanswered about the rigid printed circuit boards. For that matter, we have sampled some of them and their best answers.

1)What information should you indicate in a drill file?

You need to provide data on the finished hole diameters.

2) What is the purpose for electrically testing standard PCB?

This vital in ensuring that the board is free of short circuits or opens.electrical test is thus a sure way to ensure that all hard to see errors are detected and corrected.

3)Are there other different colours of the solder mask?

Though green is the dominant colour for the solder mask, yes there’re other standard colours. They include, red, blue, yellow etc.

4)Can PCB be manufactured from a picture file?

Not at all, no picture file format, i.e. JPG, TIFF and others aren’t allowed for the manufacturing process. Luckily, you may use them for a quotation.

5)How can one reduce the general costs of the circuit boards?

The costs would depend on some parameters such as quantity of the layers, raw material, thickness, minimum trace widths, copper thickness etc.

So to cut down your expenses, you may want to construct a simple PCB.

6)What is the quality compliance of the rigid PCB?

The PCBs designs adhere to the quality standards of various institutions. Some of the standardisations are:

• UL (Underwriters Laboratories)
• ISO-9001 (International Organization for Standardization)
• AS 9100 (Aerospace Certification)
• IPC-6012/6013 (Institute of Printed Circuit Boards)
• MIL-PRF-31032 (Military Performance)
• MIL-PRF-50884 (Military Performance)

Conclusion

Congratulations for reaching the end of this educative guide.

I am pretty sure you now are aware of comprehensive information about the rigid PCBs.

The benefits of the rigid PCBs, the comparison between stiff and flex PCBs, types of the rigid PCBs and manufacturing procedures are just a few techniques that you indeed you should have a good mastery of by now.

Welcome to the new world of circuitry design and in case you have any problems, feel free to contact us.

Thanks for reading.