PCB Fabrication Expert

Do you want to venture in the PCB fabrication industry?

Or do you want to make PCB for personal use?

Well, this simple guide will walk you through the nitty-gritty of PCB fabrication process – from basic definition, techniques to simple step-by-step process.

It doesn’t matter whether you want to fabricate aluminum PCB, rigid PCB, flexible PCB, rigid flex PCB or high frequency PCB; you will learn the basics in this guide.

Let’s dive right in…

What is Printed Circuit Board (PCB) Fabrication?

A printed circuit board electrically connects and mechanically aids electrical parts or components.

It does this by using pads, conductive tracks, as well as additional features imprinted from single or extra sheet layers of copper. Normally, they are laminated onto or between these layers of non-conductive substrates.

Aluminum PCB

Parts of these boards are mostly soldered with a soldering iron onto the printed circuit board. This is done to electrically and mechanically connect fasten them strongly to it.

Printed circuit boards are utilized in every area and also the simplest electrical products like passive switch boxes or electronic products.

Alternatives of these boards include wire wrap and point-to-point construction. Both used to be very famous. However, they are not used these days.

These boards necessitate extra design efforts to have a circuit laid out. However, manufacturing and assembling can be well automated.

Unique PCB design software is readily accessible to ensure much of the layout work is done.

PCB design software

Parts of PCB

Here, you will know about the parts of printed circuit boards.

However, before that you need to understand that having to produce circuits with PCBs in bulk makes it cheaper.

It is also faster.

This is more so compared to other wiring methods. This is because all parts are mounted and wired in a single operation.

Large quantities of printed circuit boards can be made at one time. The good news is that, the layout needs to be done just one time.

PCBs can as well be manually made in smaller numbers. However, this comes with benefits that are limited.

Here are some parts of PCBs and how unique they are:

1.PCB Solder Mask

These solder masks are applied to protect the board from any accidents that can happen or occur from soldering.

Engineers when working on printed circuit boards use solders to connect components to the board.

Green solder mask on PCB – Photo courtesy: Wikipedia

There should be much caution when soldering. When any copper melts and touches another component, it can lead to the damage of the circuit board.

These masks are used to ensure nothing like this happens.

It helps to protect the engineer and the board. Used to protect the board from all elements of failures and makes it highly functional.

2. PCB Silk Screen

The silkscreen mostly has a schematic pattern and some numbers that are followed by engineers to ensure circuit boards are well designed.

 Silk screen PCB

Without these schematic patterns and numbers, their work will be very difficult. It also helps in enhancing the look of the board altogether.

Also, it helps to have all board elements marked out.

3.PCB Substrate

This is the base material upon which other components are adjoined to have the board well set. This helps to make creation of boards easier.

PCB Substrate

It helps to move electrical energy from one part of the board to the other.

4.PCB Copper Layer

It is laid in designing these boards.

Its coating is necessary to make other methods easier to be achieved. This makes them last longer for various electronic and electrical devices they are installed in.

PCB copper layer – Photo courtesy: PCB Manufacturing and Assembly

Each component of PCBs works ideally and act to favor users in the end.

This is why you must always look out for the unique qualities of these boards.

Some other components you need to know of that helps to make these boards work include:

• Battery – It provides circuits with the voltage it needs.
• Transistors – It amplifies charging.
• Capacitors – These components are able to harbor electrical charges.
• Resistors – They help in controlling electrical current as it goes through the circuit. They come with specific color codes. This helps to determine their worth or value.
• Switches – They either permit for current to go through or block current. This is mostly dependent on their position as closed or opened.
• Inductors – They store charge and stops as well as change current.

Fully assembled PCB

All the above components and more are attached to these boards in so many ways. Generally, engineers will decide to use either surface mount methods or through-hole methods.

This will be used to have these components attached.

Material for PCB Fabrication

There are three main material types where printed circuit board (PCB) fabrication is concerned. They are:

§  FR-4 Material for PCB Fabrication

This material is the most common material that is used in making or fabricating printed circuit boards.

It comes in a glass reinforced epoxy laminate sheet form. Epoxies that are used is retardant to flame and resistant to water.

 FR 4 Material

This material offers weight rations with the right level of strength. Also, its tensile strength provided is extremely high.

§  Metal for PCB Fabrication

The normal materials of aluminum, copper, iron, and others are still famous in making printed circuit boards.

Metal core PCB

These materials make it easy for using Surface Mount Technology to have components integrated.

They as well offer the right level of mechanical durability for all engineers and PCBs. Due to this its product life is very long.

§  PTFE (Teflon) Material for PCB

This material type is a unique plastic material. It doesn’t welcome any resistance.

Due to this it is used more for high frequency and high speed applications. This material is very flexible.

This makes it invaluable in apps with tolerances that are tight. It is very light in weight.

PTFE PCB

This allows it to be used across all industries. It is resistant to flame, shows high level of strength physically, offers stability in temperature, and is unique when used.

All these different and unique materials that are used in fabricating PCBs have something unique.

They both have their good and bad features.

The material that is used in making specific printed circuit boards are selected based on its application, the outcome required, environmental factors, and other limitations the board will encounter.

You need to select a PCB that has been made with a material you know will provide the results you require.

Design Considerations in PCB Fabrication Process

Before a print circuit board fabrication process is undergone, there are so many things that come to play.

Different sizes of PCB after fabrication

Most engineers do not like to make mistakes. So they try to be very particular with the decisions they make. Below are some considerations made:

1. Specific design to be made.
2. Specific PCB design software to use.
3. Communicate software to be used to the contract manufacturer.
4. Wait for design approval.
5. Have design exported into a format that the manufacturer supports.
6. Software is allowed to perform oversight algorithms on design. This is done to make sure there are no mistakes.
7. Designers have the plan examined again. Here, thorough examination is done.
8. PCB file is then sent to the manufacturer for manufacturing.

PCB Fabrication Process Flow

Knowing the PCB fabrication process flow is always exciting. It makes it easier for you to value the board more. Below is the process to follow:

Step 1: Design the Printed Circuit Board (PCB)

The first step in this flow is the designing PCB layout.

Without the design there is no way there can be a board.

So this is very important and much attention should be paid to it.

Printed circuit boards must be very compatible with what the designer designs via a printed circuit board layout.

This is created using unique design software for PCBs. Some of the commonly utilized design software includes OrCAD, KiCad, Altium designer, Pads, Eagle, and so on.

Before the fabrication of PCBs, a designer needs to make their contract manufacturer know the specific design software that will be used to have the circuit designed.

This helps to prevent problems that are caused by inconsistencies.

Immediately the design is approved to be produced, the designer will have to export the design into a format that the manufacturer is in support with.

Extended Gerber is a program that is mostly used.

It is also called IX274X. What makes this software unique is the fact that the PCB world has chosen it as the ideal format for output.

Ideal design software mostly calls for different file generation steps.

However, they all encode detailed and important information as well as drill drawing, copper tracking layers, apertures, component notations, and some other alternatives.

 PCB design and layout

All areas of this board’s design goes through checks at this time. The software has oversight algorithms performed on designs.

This is to prevent all mistakes or errors.

After that, you need to have the plan examined to check elements linked to track width, trace and hole space, board edge space, and hole sizes.

After a complete examination, the PCB file is forwarded to the manufacturer to produce. Thorough check is always recommended to make sure the design meets all requirements and minimum tolerances when manufacturing is underway.

Step 2: Print the PCB Design

Printed circuit board printing starts after designers put out the its schematic files to manufacturers and have them checked.

After checking these designs, manufacturers use a unique printer known as the plotter to print.

This printer makes photo films of printed circuit boards to actual print circuit boards.

They also make use of these films to obtain PCB image.

Even though it is laser printer type, it isn’t the normal laser jet printers you might be used to.

These plotters make use of unbelievably accurate printing features to offer totally detailed film of PCB designs.

Printed board circuit

The complete product ends up in a plastic sheet. This sheet mostly has a negative photo of PCB in black ink like in the figure 2 shown above.

Black ink stands for the conductive copper parts of these boards for its inner layers.

The clear part left of the image stands for areas that have non-conductive materials.

However, all outer layers have a pattern that is opposite which is clear for copper.

The black as well stands for specific areas that will be imprinted away.

A plotter develops films automatically.

After that, the film is stored securely to prevent wrong contacts.

Each PCB layer and solder mask gets its own black and clear film sheet. In the end, a two-layer PCB requires four main sheets.

This means, two for its layers and two for solder mask. More importantly, all films need to correspond well with one another.

When rightly used, PCB alignments are well mapped out.

 Ceramic PCB

To have an ideal alignment of all films, there should be a punch of registration holes through all films.

The precision of holes happen when tables on which the film sits is adjusted. The hole is punched when tiny table calibrations result to the best possible match.

These holes will directly fit into registration pins as the imaging process go on in the subsequent steps.

Step 3: Printing the Copper for the Inner Layers

Film creation in steps before helps in having a figure of copper path mapped out. Now, the time is right to have the film figure printed onto a copper foil.

Layers of PCB – Photo courtesy: PCB Way

This step in the printed circuit board making process prepares to have the actual PCB made.

The unique and basic form of printed circuit boards comprises of laminated boards whose main or core material is made from glass fiber and epoxy resin.

These materials are also known as substrate material.

Laminate ideally serves as the unique body to receive copper that has the PCB structured.

Substrate material offers a strong and dust-resistant beginning point for printed circuit board. Copper is pre-bonded on all sides.

The process actually involves having copper whittled away to show the actual film designs.

In the construction of PCBs, cleanliness is highly necessary.

Copper-sided laminate through the process of manufacturing is cleaned and moved into an environment where it will not be contaminated.

At this stage, there is the need that no particles of dust settle on laminate. The smallest dirt particle can lead to a circuit being damaged. This doesn’t help at all.

 Controlled impedance PCB

Subsequently, clean panels receive photo-sensitive film layers known as photo resist.

Photo resist entails layer of photo reactive chemical that become hard after it comes into contact with UV or ultra violet rays or light.

This makes certain that exact photo film matches to photo resist matches are made available. These films then fit onto pins to keep them held in place over laminate panels.

Film and board line up takes place and gets a UV light blast.

This light goes through clear film parts.

So, it hardens photo resist on copper below. Mainly, black ink from plotters prevents UV light from getting to areas that aren’t meant to harden and they are scheduled for removal.

After the board is done, alkaline solution is used to wash it.

This is done to remove any photo resist that is left that didn’t harden.

Final pressure wash takes off anything else that is left on its surface.

After that, the board is dried up.

The product comes out with resist well covering all copper areas designed to be in its final form. Technicians examine boards to make sure there are no problems occurring at this stage. All resist available at this time shows that the copper will show when PCB is finished.

This step is applied only to boards that have more than two layers. Simple two-layer boards move ahead to the drilling part. Also, boards with multi-layers necessitate more steps.

Step 4: Getting Rid of the Unwanted Copper

With the removal of photo resist and the hard resist covering copper elements that you want to keep, the board moves to its next level or stage.

This has to do with the removal of unwanted copper.

Simply as alkaline solution gets rid of resist, a stronger chemical preparation is applied to have excess copper eaten away.

Mostly, copper solution baths gets rid of all copper that is exposed. In the meantime, desired copper stays completely secured under hardened photo resist layer.

There is no way you will find two copper boards to be the same. They all come with their uniqueness and differences.

Some have heavier boards that necessitate large copper solvent amounts and different exposure lengths.

It is, however, important to note that copper boards necessitate extra attention to track spacing.

Majority of the PCBs depend on specifications that are similar.

When the solvent succeeds in removing all unwanted copper, hardened resists that protect preferred copper must be washed off.

There is another solvent that works to have this task accomplished.

Now, the board sparkles with just copper substrate that is needed for the printed circuit board.

Step 4: Layer Alignment and Optical Inspection for Inner Layers

With all layers well cleaned and prepared, these layers necessitate alignment punches to make sure they are all in line.

Registration holes make sure all inner layers are well aligned to outer ones. Technicians place layers into a device known as the optical punch.

PCB quality control

This device is what makes it possible or allows specific correspondence. This makes registration holes punched accurately.

Immediately layers are well placed together, it isn’t possible to have errors that occurred on inner layers corrected.
Another device works by performing automatic optical inspection of all panels. This is done to confirm total defect absence.

The actual design that is sent to manufacturers from Gerber is what is used as a model.

The machine has layers scanned using laser sensors and moves to have digital images with original Gerber files compared electronically.

If the device finds true worth and consistency, comparisons are showed on monitors for technicians to have access to.

Immediately the layer is able to pass inspection, it is pushed to the final PCB production stage.

Step 5: PCB Layers Lamination

The circuit board takes its shape in this final stage. All separate layers wait for their coming together.

With all layers prepared and confirmed, they just need to be adjoined together. Outer or external layers need to join with substrates.

The procedure takes place in two major steps which is the bonding and layer-up process.

Embeded resistor PCB

External layer materials mostly consist of fiber glass sheets and pre-impregnated with epoxy resin.

Pregpreg is the short name or shorthand for this. There is also a thin copper foil that takes over the up and bottom of original substrate.

This contains copper trace etchings.

Now, the time has come to have them sandwiched together.

The bonding process takes place on a table made of heavy steel with clamps made of metal. These layers fit into attached table pins securely.

Everything needs to fit closely to ensure shifting doesn’t happen during the alignment process.

Here, technicians start by having a pregreg layer placed over an alignment basin. The copper sheet is then placed after the substrate layer is made to fit securely over the pregpreg.

More pregpreg sheets are put on the top of copper layers. In the end, a copper press place and aluminum foil is used in having stacks completed. It is now time for it to be prepared for pressing.

The whole process goes through automatic routine run through bonding press computers.

The computer has the stack up heating process orchestrated, the time to have pressure applied, and when to permit stack to cool at rates that are controlled.

Subsequently, a specific amount of unpacking takes place.

With all layers well molded together in an extremely sandwich PCB elegance, these technicians just have multi-layer PCB product unpacked.

It is a very simple issue of having retraining pins removed and having the top pressure plates discarded.

PCB goodness ends up being victorious from inside its aluminum press plates shell. Its copper foil that is included in the process stays to compromise PCB outer layers.

Step 6: PCB Drilling Process

In conclusion, there are stack board holes bored.

All parts scheduled to come one after the other like copper-linking through holes and leaded areas, depend on the precision of holes drilled.

All holes are drilled to a specification which is a hairs-width. This drill attains 100 microns in diameter even as hair at an average of 150 microns.

Drilling PCB

To obtain drill target location, the use of an x-ray locator is needed. This identified the right drill target spots.

After that, the right registration holes are securely bored to ensure safe stack for different and more precise holes.

Before drilling is done, technicians place a board to have materials buffered under the drill target to make sure a bore that is clean enacted.

The exit-material ensures all unnecessary tearing upon the exit of the drill are prevented.

A PC is what is used to control every micro-movement of drills.

It is just natural that products that determine machine behavior would depend more on PCs.

Computer driven devices that are used in drilling files from its original design to have the right spots identified to bore.

The drills make use of air-driven spindles.

These spindles turn at 150,000 rpm or rate per minute. At such a rate or speed, you might have the thought that the drilling process happens with ease or immediately.

However, there are countless holes that must be bore. So it takes time to finish. An average PCB has more than 100 bore specific points.

Through the drilling process, each requires its unique time with the drill. This is what leads to the time it takes.

These holes thereafter take in the vias and mechanical mounting holes ideal for PCBs. The final affixation of such parts will happen later after the plating process is done.

Holes on PCB

After the process of drilling is done, the extra copper that has production panel edges lined goes through the use of a profiling tool to have it removed.

Step 7: PCB Panel Plating

When drilling is done, the panel is moved onto plating.

This process adjoins different layers together with the use of chemical depositions.

After cleaning is completely done, the panel goes through different chemical baths.

Through the bath, chemical deposition methods have thin layers deposited. This is mostly about 1 micron thick copper over the panel surface.

PCB with plated edges

This copper goes directly into the freshly drilled holes.

Before this step, the inner surface of these holes just shows the fiber glass material that entails the inside of panels.

All copper baths cover or plate completely all hole walls. In that case, the whole panel gets a new copper layer.

More necessarily, new holes are sealed. Computers generally have the entire dipping, removal, and procession methods controlled.

Step 8: Outer Layer Imaging and Pattern Plating

In the 3^rd step, photo resist was applied to the panel. It will be done again in this step.

However, this time, outer layers of panels are imaged with PCB design.

It starts with layers within the sterile room to have all contaminants prevented from sticking to the surface of the layer. Then, have a photo resist layer applied to its panel.

Flexible PCB

The panel that is pressed is made to pass through the yellow room. Ultra violet lights affect photo resist.

Also, the wavelengths of yellow light doesn’t carry enough UV levels to have photo resist affected.

The securing of black ink transparencies is done with pins to do away with panel misalignment.

With stencil and panel coming into contact, high ultra violet light is used via a generator to blast them. This when done, hardens photo resist.

The panel is then taken through or into a machine that has all unhardened resist removed. This is done with the panel safeguarded by black ink opacity.

This method stands out as a unique inversion to the inner layers of the board.

Lastly, the external plates go through inspections to make sure all photo resist that is undesired is removed in previous stages.

Step 9: PCB Etching

The plating room is visited again. As it was done in step 8, the panel is electroplated with thin copper layers.

All exposed sections of panels from external photo resist stages receive electro-plating of copper.

https://youtu.be/IXKwkcgimZI

The sections that are exposed of the panel from its exterior layer photo resist level are what received copper electro-plating.

After the original bath of copper plating, panels mostly receive tin plating.

This is what permits or allows the removal of excess copper that is left on boards slated for removals.

It is the tin that protects the section of panels designed to stay covered with copper for the next stage of etching. Etching gets rid of all unwanted foil from panels.

Unwanted copper that is exposed and copper under the remaining resist layer goes through removal.

Additionally, chemical solutions are well applied to get rid of additional copper. Also, the tin safeguards valued copper during such stages.

All conducting parts and connections become well established now.

Step 10: PCB Solder Mask Application

Before solder masks are applied to all board sides, panels are well cleaned and covered with ink known as an epoxy solder mask ink.

The board is given a blast of ultra violet light. It is this light that goes through solder mask photo films. All covered portions stay unhardened and go through removal too.

The board finally goes through an oven to have solder mask cured.

Step 11: PCB Surface Finish treatment

To include additional solder-ability to the printed circuit board, they are chemically plated with silver or gold.

There are some printed circuit boards that obtain hot air-leveled pads throughout this stage.

The leveling of hot air leads to uniform pads.

 PCB with different finishes

That methods result to surface finish generation.

Generally, the best makers of printed circuit boards can have multiple types of surface finishes processed based on the demand of clients.

Step 12:  Silk Screening

The almost completed board is given ink-jet writing on the surface.

This is done to show all needed information regarding to the printed circuit board.

The PCB ultimately goes onto the final coating and curing level or stage.

Step 13: Electrical Reliability Testing of PCB

As a concluding safety measure, a technician needs to perform tests electrically on the printed circuit board.

The automatic method has the functionality and conformity to the ideal design of the printed circuit board confirmed.

The best makers of these boards can provide you with an enhanced version of electrical tests known as the Flying Probe Testing.

This depends more on having probes moved to have electrical performance of every net on bare circuit boards tested.

Electrical testing PCB

Image of final caution performed by experienced technicians

Step 10: PCB Profiling and V-Scorin

So, this is the final step which is the cutting step.

Different printed circuit boards are cut out from the actual or original panel.

The process used either bases more on making use of a v-groove or a router.

Routers leave minute tabs along the edges of the board as v-groove has diagonal channels cut along all board sides. Either ways allow boards to pop out with ease from the panel.

 Printed board circuit

As shown clearly in all 10 stages, you can see there is so much work that goes into manufacturing printed circuit boards.

When the wrong methods are used, you will not have the quality printed circuit board that