PCB Assembly Expert

PCB Assembly: The Ultimate Guide

Honestly, PCB assembly is one of the most challenging aspect in the electronics manufacturing process.

Whether in the smartphone, digital watches, medical equipment or industrial machines, you must do it right.

The best part?

Today’s guide covers all the critical aspects of printed circuit board assembly process.

It focuses on the following:

• PCB Assembly Definition
• PCB Assembly Applications.
• PCB Design Basics
• PCB step by step Assembly Process
• PCB Assembly Process flow
• PCB Assembly Techniques – Automated and Manual
• PCB Assembly Capabilities
• Hiring PCB Assembly Company

Now we dive into the detailed segments…

Chapter 1: What is PCB Assembly?

Now that you are already aware of what PCB is, I am going to introduce you to a fundamental process for the PCB.

Have you ever noticed that the boards had got several components firmly attached to them? What do you think they are?

Rigid flex PCB

Many would think they serve for decorations. Absolutely no.

PCB is not capable of independently functioning without those components.

Meaning every single one of them is vital and significant to the functioning of the board.

Technically speaking, detaching any single component would impair the operation of the PCB.

All these elements get embedded through a distinct manufacturing process.

Thus, it is this procedure that we refer to as the PCB assembly abbreviated PCBA process.

BGA Assembly

Therefore, a PCB that has undergone through this course is an assembled PCB.

If you have a close look at the board, then you should see various copper lines.

These are the traces.

They are very tiny yet serve an essential purpose.

Traces link all the components and connectors of the PCB amongst themselves electrically.

They do this by supplying signals throughout these constituents thereby achieving the operation of the board.

Essentially, PCBs serve from simple to complex functions.

Unlike other electronic devices, size doesn’t matter here, in fact, some are tiny and thin, yet they continue to function optimally and run complicated tasks.

So what are the exact areas applications of PCBs?

Chapter 2: PCB Assembly Applications

The PCB applications range from simple devices such as watches, smartphones to sophisticated areas, for example, CT scanners.

Digital watch

To date, the PCBs are in almost all sectors of the economy and industries. It also continues to grow into other unexplored segments.

Now that virtually all electronics have PCBs, it’s easier to pinpoint their uses.

With every development in advancement in technology, PCBs configurations as well improve and become better suited to sustain and tolerate even some of the hostile environment.

The flexibility and configurations of these circuits enable the PCBs to work in various segments and applications.

Remember, at the core of any electronic device is a PCB.

The modern technology significantly utilizes these circuits.

Now, let’s explore some of the typical applications where we got the PCBs incorporated:

1.Industrial applications

In any industry, PCBs play a significant role in running the machines.

The boards run seemingly high-powered machines primarily in the manufacturing or processing factories.

In these areas, the PCBs are fabricated to adapt to and sustain the harsh conditions in which they are getting exposed.

 PLC PCB

Such PCB assembly can withstand:

• Tremendous multitude vibrations
• Corrosive chemicals
• Extreme mechanical stress
• Fluctuating temperature, etc.

Due to such ever-increasing challenging conditions in the industrial setups, the PCBs technological advancement has been over time propelled to solve the problem.

For that reason very thick copper printed circuit board fits in situations where the average or standard PCBs aren’t favorites.

Note that thick copper PCBs serve a similar purpose to the ordinary ones.

However, the significant difference is that the former one is capable of sustaining a high amount of current output demand together with the battery charge.

Thick copper PCB

Have a look at some of the PCB driven electronics or machinery in this sector.

• PCBs are in the: Electric drills, presses, hydraulics, generators especially in the manufacturing and processing industries.
• Measuring instruments including Pressure pumps, thermometers, weighing scales, etc.
• Power generating equipment such as DC – AC converters, power generators

2.Common Consumer Electronics

Consumer electronic devices consist of the locally available devices which we commonly and daily use in running our activities.

They are available in different categories from household appliances such as refrigerators, microwaves to ordinary ones like smartphones.

All these appliances make use of PCBs.

 Consumer electronics

Manufacturing and fitting these kinds of PCBs require a high degree of precision and accuracy.

Take for example, in cases where the appliance involved is quite big and voluminous, then many PCBs must be fitted in it.

The only task would be quality control and homogeneity.

The good news is that all the manufacturers have to adapt and work within accurate, specific quality control measures set by regulatory bodies.

Thus, they will only have to manufacture good and efficient consumer appliances.

Because consumer electronics are so numerous we won’t discuss all of them.

But for the sake of our discussion, we shall focus on a few common case scenarios for PCBs applications.

• Handsets: mobile devices including smartphones, tablets, and telephones are fitted with PCBs to assist in running their process systems.
• Computer devices: desktops and laptops contain several PCBs at different parts especially in the CPUs, screens and secondary devices.
• Record keeping gadgets such as digital cameras, microphones and camcorders are all PCB fitted devices.
• Home and kitchen Appliances: microwaves, refrigerators, blenders, televisions sets, wall clocks, etc.
• All entertainment system in your living rooms e.g. DVD players, radios, etc.

3.Medical applications

Thanks to the advancement in technology, the pharmaceutical industry has witnessed tremendous technological achievement.

Besides, the PCBs have complemented this improvement.

They are ranging from flexible to rigid PCBs, which all work to enhance the operations of these machines.

In hospitals, there are modern machines practitioners use to diagnose patients.

 CT Scan

 Most of this equipment will not function without the critical PCBs.

In fact, due to the ever modification in the fabrication of PCBs, it is believed that this medical equipment in the laboratory would likely to be advanced.

That is to fit in the growing demand for medical machines.

Because of the strict adherence to rules and regulations that these machines have to abide by, the PCBs construction mechanism must comply with these regulations.

It is thus vital to note that this circuitry is of strict adherence to precision and quality.

Some of the most common and practical example include:

• Scanning machines such as CT Scanners and Ultrasound machines, X-Ray devices.
• Medical monitors – comprising of all healthcare and personal ones for monitoring heart rates, glucose level, measurement of blood pressure among others.
• Regulator systems- comprised of those for fluid infusion which are electrically precise in controlling the amount of fluid dispensation and degree of flow.
• Medical equipment such as those for the diagnosis of diseases, researching cure and infections.
• A variety of internal equipment which consists of the heart pacemaker among other internal devices.

4.Automotive sector

At the heart of any economy of a country, a viable automotive industry plays a vital role.

Indeed, with the incorporation of PCBs in this sector, the experience has been overwhelming.

Automated vehicle assembly plant

In this century, unlike the past years, motor vehicles heavily depend upon the robust importance of this circuitry.

You will find the PCBs in the car headlights among other parts in the car auxiliary devices.

Also, contemporary cars utilize the use of high-frequency PCBs such as RF together with the microwaves.

Openly speaking, this circuitry has come with many benefits in the automotive sector ranging from increased safety measures in the road to exciting driving experience.

https://youtu.be/5pn8qAKL0V4

These are the applications of the printed circuit boards in the autos:

• Regulator systems – regulator system is responsible for directly controlling the fuel consumption. Others as well serve in the management of the car engines together with the distribution of power and current from one segment of devices to another.
• It is applied in electronic monitors used for measuring the distances when driving, speed and timing the driven interval.
• Found in navigation gadgets especially the GPS and trackers.
• Set of the entertainment system in the vehicles mostly on the dashboards. They may include video and audio devices.

5.Lighting Applications

Lighting sector has seen tremendous improvement due to PCBs.

Nowadays the LED manufactures significantly make use of this PCB assembly to design and produce a variety of lighting systems.

Indeed the PCB assembly has been a success in lighting as they improve the working technique and versatility of the LEDs.

In fact, we have LED PCBs.

LED PCB

Due to this, new LEDs are famous for little power consumption, better lighting, and increased efficiency and functionality.

If you look at the street indicators and display signs, then you will surely be a witness for this revelation.

LED Lighting system

Below are the applications of the PCB assembly in lighting.

• Telecommunication production makes use of the circuitry in regulating the LED displays and indicators. The chip used here must be light in weight though durable.
• In Computing technology: here PCBs function in the desktop, laptop, and phone indicators. To sustain high thermal conditions, the aluminum backed PCBs are employed.
• The automotive industry found on the car dashboards, brake lighting, headlights, and even interior vehicle lighting system.
• Medical sector especially for the lighting purposes during surgery to enhance visibility for the practitioners. You can also trace them in other peripheral devices for the scanner, monitors among other functions.
• Also, they are applicable in Home, business premises and residential apartments where they serve for purposes of displays and local lighting.

6.Other Notable Applications

As earlier mentioned. The PCBs have numerous general applications, which we want to discuss all.

Flex PCB Assembly

For the sake of our discussion, it is prudent we focus on the following general applications.

• Marine and water applications such as submarines and sailing boats. Here, they play a role in the navigation control system, power supply, and engine supervision.
• Security monitoring applications primarily in the various equipment, which supervises and keep track of any intruder or suspicious activity in the premises. Also, it is used in the Fire, smoke and theft alarms to trigger sound in case of emergencies. The alarm is useful in enhancing prompt response to the situation.
• Weapon and firearm applications for which the manufacturers use PCB assembled testing devices to confirm the reliability and safety measures of the weapons. The manufacturers have to be sure of the functionality and consumer safety before introducing them into the market.
• Telecommunication and broadcasting applications are more on high frequency demanding equipment or amplifiers. Booster stations, receivers, safelights, microphones, frequency boards, and mixing decks are some of the areas you will undoubtedly get the PCB assembly.

Chapter 3: PCB Design Basics – Learn the Basic Steps in PCB Design

Here, I will take you through the basics that you need to master when dealing with PCBs.

There are the facts that are essential in making up the whole set of the manufacturing process for the circuitry.

So, if you have been thinking of indulging in the fabrication process, we are good to go.

LED PCB Assembly

Let’s begin.

What is a PCB Layout?

PCB layout is a precise schematic drawing done by a PCB designer.

It entails the whole set of practicability PCB that needs to be formatted and implemented to come up with an exact circuit.

PCB Layout

The layout and design is indeed a technical concept, which involves various auxiliary skills and techniques such as knowledge of relevant software.

A professional designer should be capable of implementing the layout into a real PCB production.

It is thus prudent for the designer to make use of excellent standards.

Now for the case of the PCB design software to use, you may opt for any of the following: Xpedition, PADs, Altium, and Cadence Allegro.

Interestingly the software varies depending on their suitability and the type of working environment. consequently, extra vigilance is essential when selecting a suitable one

The assembling of the PCB always begins with the base.

The base comprises of numerous alternating layers, which individually are vital in the overall functionality of the PCB.

The alternating layers are:

• Conducting material/copper- this is a thin layer of copper traces added to both sides of the PCB for a double-sided PCB while on one side for a single sided PCB.
• Substrate – this is the dominant material for the base of a PCB. It’s responsible for either the flexibility or rigidity of the PCB.

• Solder mask layer applied over the thin copper layer. It gives every PCB the characteristic color as well as insulating the copper traces from other conductive materials.

• Silkscreen – this is the final layer placed on the PCB board. It is on this layer that the characters, symbols, and writings appear which are essential in helping to identify the function of each board component.

Chapter 4: Types of PCB Designs

The following are the types of designs you may pick depending on the type of application you want.

· Flex PCB Design

Flex PCB is an easy to bend, thin, light in weight, and small kind of printed circuit.

It’s very popular among manufacturers due to its flexibility properties.

Due to these properties, you will find them incorporated in highly sophisticated devices, which makes use of extreme accuracy such as digital cameras, heart monitors, etc.

 Flex PCB design

Copper and flexible substrates including polyimides are the principal materials used in the fabrication of these flex circuits.

Others are insulators and adhesives.

Customizing flex designs into a various number of layers is possible.

·Rigid Flex PCB Design

Rigid Flex PCB is a harmonized flex, and rigid circuit blended to function.

Due to this technique, it is very versatile and efficient since it incorporates both the qualities of the two loops.

 Rigid flex PCB design

Usually, the rigid segments hold most components while the flexible regions act as connections. Cellular gadgets are one of the primary applications of this circuitry.

·Rigid PCB Design

Unlike the flex circuit, the strict circuit is not capable of any flexibility. It comprises solid, firm and sturdy substrates.

 Rigid PCB

The significant difference between flex and rigid circuits lies in the flexibility and testability.  The computer motherboard is a typical example of the rigid circuit.

·Multilayer PCB Design

Multilayer PCB is a unique design of the printed circuit board which comprises of three or layers.

Multi layer PCB

Insulating layers are bonded in between the conducting copper layers.

It is primarily applied in aerospace equipment, weather analysis, atomic, space and fire alarm system.

·High-Speed PCB Design

High speed printed circuit design is that kind of PCB which has got its equipment signals interrupted to produce high pitch.

By altering the packaging, layout, and interconnections, the signal is interrupted to that desired high speed.

High speed PCB

What’s more, the high-speed design is vital in:

• Identifying the precise location for creating the traces.
• Knowing the extent of closeness between the traces and signals.

·High Power PCB Design

These high power PCB designs are suitable for use in devices, which consume high power.

High power PCB

Because of the ever-increasing manufacture of smaller gadgets, production of these types of PCB is gaining momentum since they are capable of tolerating a large amount of power.

·HDI PCB Design

High –density interconnect PCB have got buried and blind vias, micro-vias which are less than a diameter thickness of about 0.006 micrometers.

HDI PCB

Significantly, it has got a higher circuitry density compared to other ordinary PCBs.

·LED PCB Design

Light emitting diode PCBs are the new type of PCBs, which got the connection of the LED to the circuit board together with another chip which produces light from the flow of current.

LED PCB

Due to the high amount of dispensed heat, this PCB is aluminum backed.

The LED PCB design find its application in automotive headlights, military and street lighting.

· RF PCB Design

The Radiofrequency PCB is any type that operates above 100MHz.

It’s thus used in complex and sophisticated designs especially those that utilize both the analog and digital signal transmission.

RF PCB

Some of the devices, which use RF PCBs, are smartphones, robots, and sensors.

·High Voltage PCB Design

This type of circuit suitable for use in the applications, which require extremely high voltages to operate.

 High voltage PCB

Therefore, several factors require consideration when constructing this type of PCBs such as creepage, clearance, insulation, and altitude.

·Amplifier PCB Design

For this one, you surely must have interacted with it in audio devices, which got an alternating output of low to high frequency.

Amplifier PCB

Power supply and signals are the major factors, which need attention in designing an amplifier PCB.

·Metal Core PCB Design

Metalcore PCBs abbreviated as MCPCB are the types of circuit boards, which uses a metallic material as the base material for dissipating heat.

These base metals are a good substitute for CEM3 or FR4 boards since they are exceptionally suitable for distributing heat.

Metal core PCB

Common metallic materials for use are aluminum, copper or other suitable alloys but which got a thickness of 30 mils to 125 mils.

Shall we proceed to the next essential segment of our discussion?

Chapter 5: Steps In PCB Assembly Process

Now, this is a very significant process in the PCB technology.

However, just like any other industrial equipment, PCB requires several pre-assembly steps and measures.

This procedure helps the manufacturers try to evaluate the functionality of the PCB design.

A primary pre-assembly assessment is the DFM Check.

You need to know that most manufacturers require a complete set of design file and documents before kick starting the manufacturing process.

All these assist the manufacturer to review the record for any inconsistencies, which might affect the functionality or even fabrication.

That is what we call the Design for Manufacturability Check (DFM).

The check focusses entirely on the specifications of the design.

Above all, it’s specifically aimed at pinpointing any inconsistencies in the design such as missing, surplus features or even faulty features.

All these issues may negatively affect the operation of the final PCB.

Sparing only a little spacing is one of the common faults that most people tend to make.

Short-circuiting and malfunctioning subsequently result from this flaw.

It is thus worth noting that the DFM check is a significant step that needs to be undertaken by the manufacturers?

Why?

The test identifies any impending fault before conducting the construction process.

Thus, it saves costs in the fabrication process by eliminating any unforeseen budgetary allocation.

PCB prototype assembly

We can now discuss the detailed steps of PCB Manufacturing Assembly, which result in a final finished product.

No complication whatsoever in the levels so read on.

Step 1: Preparing the Circuit Board Surface

Preparation of the circuit board is generally an open step that comes first.

Interestingly it involves various issues that you must do to make the board surface suitable for component fabrication.

Let’s discuss these issues:

• Choosing the board and panel size – ensure that you select the required size of the board. Also, the boards do come already assembled in a panel. A single panel may contain numerous boards. The material from which the boards get fabricated from is the panel.
• Dry the board to get rid of unnecessary moisture content.

Step 2:  Placing Parts on the PCB

After preparation, the board moves onto the next manufacturing process where placing of the components takes place.

The machine you use for this purpose is the Pick and Place machine.

Traditionally, this was a manually undertaken procedure where manufacturers would place the components on the boards by use of tweezers.

However, this was a faulty technique full of numerous human error.

Right now, thanks to the automated PNP machines everything, you can do things accurately.

Through hole assembly

This machine picks the active component right away from its packaging and places it at an already pre-programmed location on the rightly positioned PCB.

The PNP machine is an automated machine that would require programming before this step.

Programming is essential for it to place the components at their designated locations accurately.

Again, these machines do use either a vacuum or gripper nozzle for accurate picking.

You can purchase a suitable type of PNP machine depending on the kind of technology and your budget.

Importantly, there are two major types of mounting techniques commonly applied in the assembly.

Take for example, the surface mount and Thru-Hole technologies.

We shall analyze the technologies in the next step.

Turnkey assembly process

Step 3: Start the PCB Assembly Process

Some of the main processes include the following:

i. Soldering parts on the Printed Circuit Board

A solder paste is a homogenous mixture of solder and flux.

Remember, the solder refers to tiny pellets of metal while flux is a sticky chemical, which aids in melting the metal and subsequently bonding it to the surface.

The tiny balls of metals comprise of 96 % tin, 3% silver, and 0.5 % copper.

Since this is quite a technical process, you will need an automated solder paste-printing machine. It’s thus evident that this the first machine you will set up in PCB assembly.

The machine has a smooth sheet of metal drilled with holes called stencil and applicator.

Ensure that you hold the stencil firmly in position just above the board.

Switch on the applicator to introduce the solder paste in strictly measured quantities on the designated locations on the boards.

Usually, apply the solder paste to the sections where the components are to be attached to the final PCB.

The machine evenly spreads the solder paste across the stencil over the board.

Finally, you can remove the stencil, which subsequently leaves the paste on desired areas.

Make sure you keenly do this to avoid spilling of the solder paste.

 ii. Through Hole Parts Using Wave Soldering

Thru-Hole Tech (THT technology) works best if you specialize on components, which got either protruding wires or leads.

THT is especially suitable in forgeries dealing with sizeable components such as capacitors and coils.

Besides, it would be suitable if the exterior parts, i.e. the wires and leads would require you to mount them on the boards by plugging through holes on the circuit board.

You can now solder the extra lead section on the opposite side of the board.

Afterward, you should pass the board through the wave soldering process.

The board moves gradually over a wave of heated solder at a high temperature of about 227 degrees Celsius.

This process leaves the leads and wire connections successfully attached to the board.

 iii.Reflow soldering technique

For this procedure, you shall need to use the surface mount Technology.

SMT is advisable in case you are dealing with very delicate components, which could be tiny such as diodes and resistors, mostly in integrated circuits.

The technique involves spontaneously and correctly placing the components onto the board surface.

Reflow soldering

In fact with this kind of technology, you can easily mount a fragment as little as 0.01005 mm.

Elsewhere, the reflow technique can be incorporated.

Reflow technique involves placing the boards on conveyor belts and directing the strap to pass through a large reflow oven.

Inside the oven are heaters, which heat the boards to temperatures of above 250 degrees Celsius.

This kind of temperature is enough to melt the solder.

Apart from the heaters, the oven has coolers.

After liquefying, the flowing board goes through the coolers where the melted solder cools, solidifies and creates a permanent joint connecting the surface mount devices to the board.

The reflow is appropriate for firmly solidifying the solder while sticking the components onto the surface board.

You have to make a few reservations when working on the two-sided PCB assembly.

For the double sided PCB assembly you need to stencil and reflow each side distinctively.

To do this correctly, you need stencil, place, and reflow the flank, which got fewer and smaller parts then you turn to the other side.

The printed circuit board will be then ready after the solder has sufficiently solidified.

I know you’re probably asking:

Which type of mounting technology is the best?

All the techniques are suitable, and you are free to use any as long as the type of application is right for you.

Again, both the methods interchangeably as you prefer.

Step 4: Cleaning Fully Assembled Printed Circuit Board

The reflow process may leave behind some rugged and unwanted excess materials.

As a result, you can use a fiber brush to shake off these ‘dirt’ leaving the PCB clean and tidy ready for the next step.

Flexible PCB assembly

 Step 5: Inspection and Testing PCB

From the preceding steps, it’s likely that some errors will be evident on the PCB.

The errors are due to continuous movement in the reflow process.

The faults may manifest through improper or no connection, shorts, or misalignment.

For this reason, inspection is vital to detect and correct the mistakes.

This is to avert any unnecessary expenses.

Testing PCB

Elimination of these blunders involves the use of any different inspection techniques. The best inspection methods include:

· Automated Optical Inspection

This is a more appropriate technique undertaken by use of an automatic optical inspection machine otherwise known as AOI machine.

The AOI machine is fitted with numerous powerful cameras to scan and view the PCBs from different angles.

The machine works on the basis that PCB connections reflect light in varying degrees.

Thus, the weak associations would inappropriately reflect light and thus making them detected by the cameras.

Despite the use of this sophisticated technique, the AOI machine can inspect a vast number of PCBAs.

Figure 32 Optical inspection of PCB – Photo coutesy: AXIOMTEK

Most importantly, the process is undertaken at a quick speed without any unnecessary delays.

·X-Ray Inspection

Another technical method this is that incorporates the use of X- rays.

The inspectors utilize the scanning properties of the x –rays to see through layers of the PCBs and identify any hidden inconsistencies for rectification.

The x-ray inspection is good for multilayered or complex PCBs.

·Visual Inspection

Despite the accessibility of a more automated inspection method, a manual or visual inspection can’t be ruled out.

Visual inspection is indeed applicable when you want to inspect a small batch of PCBs after the reflow manually.

Visual inspection of PCB – Photo courtesy: SMTnet

A skilled designer can then identify the damaged areas to enable him to rectify those parts.

However, it’s prone to inaccuracy as it likely to fatigue and distractions especially when

Working with a massive batch of PCBs.

·Electrical Testing

Electrical testing is the final test for the PCBs. Regardless of the findings of the other inspection methods; the PCBs should pass electrical testing.

Electrical testing establishes the degree of functionality of the PCBs.

This procedure occurs by customizing the typical environment in which the PCB works.

Electrical testing of PCB – Photo courtesy: Pyro Electro

Electrical current and simulated signals are run through the PCB as various testers establish the workability of the circuit board.

The workability traits sought out are the voltage, current and signal transmission.

In case of any unacceptable trend then the PCB has failed the test.

The PCB should go through the entire assembly or possible design process.

Testing is the ultimatum step in the PCB assembly.

Manufacturers use this to assess the productivity of their process.

It’s thus vital for frequent inspection during the assembly process to limit any eventual test failures.

Keep reading.

Chapter 6: Printed Circuit Board Assembly Process Flow

Let’s flashback on an important concept we learned.

Printed circuit board assembly refers merely to the process by which components, electronics accessories are combined onto a PCB.

Having known that, in this segment, we shall discuss how the PCBA process occurs. Let’s begin.

• Single side surface mounting

Single side SMT process is quite simple and direct.

• Once you have already cleared and dusted off the printed circuit board, pass it onto the inspection chamber. You can use any suitable inspection method for you.
• Note that this is just a first-time inspection procedure at the beginning also called an incoming
• Having inspected the board, proceed to solder paste printing. Here, the solder paste is only applied to the designated locations but not entirely on the PCB.
• Surface mounting the components follows after which you may leave the whole combination to dry and solidify.
• Now you may proceed to do the reflow soldering process.
• Ensure to clean the assembled PCB afterward.
• Using any inspection method confirm the success of the process.
• Finally, conduct a test on the assembled PCB. The testing technique varies as earlier discussed.

For simplicity, observe the following chart.

• Single sided Plug-in mounting
• Basically pass the printed circuit board through the forming process. However, with this process, you need to be keen. Why? Because forming when done wrongly may prove to be very insufficient. Besides, it may result in electrostatic damage whereas may cause unexpected errors such as delay in delivery.
• By use of THT assemble the PCB.
• Afterward, pass the combined PCB through the wave soldering process.
• Finally, you have to inspect and test the assembled PCB.

• Double-Sided Surface Mounting

this is a bit unique type as opposed to the previous ones. Why?For the double-sided SMT, we are mainly dealing with two sides. So for our discussion let’s name the parts A and B. Additionally, we shall perform the technique in two consecutive stages.

Let’s begin with stage 1.

• First of all, undertake the incoming inspection.
• Print solder paste on the side A of the PCB.
• Again, solder paste print on the other side B of the PCB.
• Surface mount the components on the printed circuit board after that leave it to dry.
• Now pass the PCB onto the reflow solder preferably the side B.
• Do the cleanout.
• Finally, inspect and test the combination.

Stage 2:

• Perform the initial inspection.
• Now Solder paste print the side A.
• Surface mount the devices and leave the PCB to solidify.
• Do a reflow soldering PCB on the side A.
• Clean the PCB and turn over the board.
• Solder print the PCB side B.
• Surface mount the components and give time for solidification.
• Place the side B on the wave solder afterward clean the combination.
• Finally, inspect and test the assembled PCB.

Note that it’s advisable to perform reflow soldering on the side A of the PCB as well as wave soldering the side B as outlined.

• Single sided mix assembly
• Inspect the PCB.
• Solder paste print the PCB on one side.
• Surface mount the SMD.
• Reflow solder the PCBA.
• Clean out the worked PCB and DIP.
• Next is wave soldering the PCB combination.
• Clean it again, inspect and test the PCBA.

• Double-sided mix assembly

For this technique, we again follow a dual stage process while considering that we still working on two sides i.e. side A and B.

Stage 1.

• Initial inspection.
• Solder paste printing PCB on side B.
• Surface mount the components and solidify.
• Carefully turn over the plate.
• DIP on PCB side A.
• Wave soldering.
• Clean out the PCBA, inspect and test it.

In summary: SMT then DIP. This process is suitable for SMD components

Stage 2.

• Initial inspection
• DIP on PCB side A, ie. Bending the pin.
• Plate turnover
• Solder paste printer the PCB on side B
• Surface mount the devices and leave to solidify.
• Plate turnover
• Wave soldering
• Clean, inspect and perform the test.

In summary: DIP then SMT, very suitable for separating components.

Stage 3.

• Initial inspection
• Distribute surface mount adhesives(solder) on side A.
• Surface mounting the device and cooling to solidify.
• Reflow soldering
• DIP, ie. Bend pins
• Plate turnover
• Screen solder paste print on side B.
• Surface mounting and solidify.
• Plate turnover
• Wave soldering
• Clean, inspect and test the PCBA

Stage 4.

• Initial inspection
• Solder paste printing screen on side B.
• Surface mounting and solidify
• Plate turnover
• Solder paste printing screen on side A
• Surface mounting
• Reflow soldering on side A.
• DIP and wave soldering on side B.
• Clean, inspect and test the PCBA

In summary Stage 3 and 4 follows the following procedure.

Stage 5:

• Initial inspection
• Distribute solder paste on side B of the PCB.
• Surface mounting and leave to solidify.
• Reflow soldering
• Plate turnover
• Solder paste printing PCB on side A
• Surface mounting and drying
• Reflow soldering
• DIP
• Wave Soldering
• Clean, inspect and test the PCBA.

Now that’s the PCBA process flow.

I am moving on.

Chapter 7: Printed Circuit Board Assembly Techniques

There are only two common PCBA techniques available for use by a PCB designer. The methods are:

• Automated PCB Assembly Techniques
• Manual PCB Assembly Techniques
• Mixed technology

The PCBA technique for use depends on various variables and are susceptible to change depending on the steps needed during the assembly.

Are you wondering about the favorite technique for you?

Worry no more.

I am sure it’s a big decision to make. For that reason, I have compiled a couple of questions to help you get on with it.

Ways of assembling PCB

• Which technology will you be using?
• Is it Surface Mount Technology (SMT) or Through Hole Technology?
• Do you require any hand or physical involving assembly?
• Are there any components that require soldering at a separate point other than the rest of the elements?

Now to enable you to understand and pick the right technique genuinely, we should discuss each of them.

·Automated PCB Assembly Techniques

Generally, this technique employs the use of state of the art machines, which are fully automatic.

For example, the surface mount components are worth positioning with the aid of an automated pick and place machine.

Again, reflow soldering is commonly for surface mount components usually done in a reflow oven.

An automated solder stencil is also used to apply the solder paste on the PCB.

Finally, high tech inspection machines are used to confirm and check the quality of the PCBA. Some of which include: Automated optical inspection machine (AOI), X-ray inspection machines, etc.

Above all, due to the precise monitoring, control of soldering, no human input and versatile machines.

This technique ensures utmost efficiency, output consistencies, and limits defects.

·Manual PCB Assembly Techniques

This method is favorite for use with through-hole parts, which needs manual placement on the board.

Besides, with these through-hole parts, it’s advisable you use wave soldering.

Note that in the through- hole assembly process, you need to place the components and electronics on the PCB.

After that, you use wave soldering to solder the leads.

Typically, you will need an individual to insert a component into a marked PTH.

Once done, transfer the PCB to the next station where the next person will be on standby tasked with fixing another part.

Manual assembly of PCB – Photo courtesy: TI Electronic

Subsequently, the task cycle continues repeatedly till the last part is set and the PCBA becomes ready.

This method is very suitable if you are aiming at producing an only a limited number of PCBs.

Besides, it greatly relies upon human input especially during the placing of the components.

That is, a designer can physically pick and place the electronics by use of tweezers.

Again, the inspection procedure, in this case, is purely visual.

A designer inspector checks the board to identify the existence of any faults.

The careful inspection is done after reflow soldering.

Manual PCBA is good to use whenever you are running on a fixed budget because it doesn’t entail the purchase of expensive machines.

The downfalls of manual PCBA techniques can be attributed to inaccuracy.

This is because humans aren’t perfect, a small number of batches of PCB which can be done and largely inconsistencies in the output.

The manual process could also lead to longer cycles and delays during assembling if the PTHs to be fixed are numerous.

Despite these numerous challenges, this technique and PTH is still prevalent among PCB designers.

Chapter 8: PCB Assembly Capability

Every PCBA has to do whatever it takes to remain competitive in the market.

One of the measures that the printed circuit assembly should be first at accommodating is the RoHS compliance and lead-free electronic production and construction.

The traditional PCBA mostly involved the productions of leaded PCBs.

Thankfully, today there is wide-ranging lead –free PCB assembly which doesn’t present as many challenges as the latter years.

Therefore, the common PCBA capabilities are:

i.Flex PCB Assembly

A suitable assembly should be capable of designing several types of PCBs. One of the most competitive ones being Flex PCB.

Flexible PCB Assembly

The flex PCBs are famous for their ability to bend through different angles, elimination of manufacturing errors and their ability to assume different shapes and designs.

ii.PCB Stencil

To help you know what a stencil is, you need to flashback to the solder printing process.

During soldering in a solder paste printer, a clear template covers the board.

PCB Stencil

Now this template would make sure that the solder paste accurately remains on the desired right locations where the components or ICs are to be mounted.

This template is the PCB stencil also known as solder screen.

iii.Through Hole Assembly

THT assembly is suitable for use with THT components such as heads and larger electronics.

The difference with these components is that you have to attach them on the circuit board via the holes.

Through hole assembly

After that you can solder the protruding lead on the opposite side of the circuit board.

iv.Prototype PCB Assembly

A reliable PCB manufacturer should be capable of providing fast and budget-friendly prototype assembly.

Prototype assembly

Provision of these services in house is a plus as well to save on time together with availing a couple of benefits such as:

• Substantially lowering the R and D time thereby saving time to market.
• Avails freedom to create and experiment quickly at relatively lower costs.
• Maintainance of the designs confidential.
• Provides chance of reworking, adjusting, trimming and tuning the PCBs.

v.Component sourcing

With the growth of the PCB assembly services, most of the manufacturers have had to extend their network.

One of the services introduced is the across the board component sourcing. Indeed this addition has brought a broad range of benefits including line efficiency.

PCB Components

Additionally, it enables you to have more time and space for dealing distinctively on project engineering and designing.

Above all, components sourcing comprises of two existing options the manufacturer can choose. Either:

• Procurement of parts from prominent certified distributors of electronic components.
• Acquisition of parts from well known endorsed channels and dealers.

These two modes of purchases would subsequently make an assembly guarantee components and parts longer life, utmost quality, and optimum performance.

vi.Turnkey PCB Assembly

Naturally, the term “turnkey” refers to a product sold to a buyer in a configuration, which is ready for direct use.

Now, turnkey printed circuit board assembly means that the dealer takes care of all details involving:

• PCB solutions
• Components procurement
• Manufacturing
• Picking
• Placing of components

Turnkey PCB assembly

In principle, turnkey PCBA allows the buyer to concentrate upon designing while the rest of the other backload remains with the supplier. Therefore, turnkey has grown into a popular service in the PCB assembly.

• Using Turnkey PCB Assembly enables you to enjoy the following benefits:
  reduced lead time
• Reduction in costs
• Free and clear monitoring

vii. LED PCB Assembly

The light emitting diodes are popular in most electronics.

Fundamentally, it’s now possible to fix LED onto PCB. To make a LED PCB which produces light whenever you connect the whole circuit to a power supply.

LED PCB Assembly

During the assembly process, the LEDs are attached to a metal base PCB.

Why?

The LEDs potentially disseminate high quantity of heat. So the metal is responsible for quickly releasing away the heat providing a better option for this.

For that reason, an aluminum backed Printed circuit board is preferred when designing a LED PCB.

Also, the aluminum backed PCB ordinarily contains a fragile layer of dielectric which allows quicker thermal dissipation.

Why is there an increase in the production of LED PCBs?

• LED designs produce better quality and high-intensity
• LED designs are also available for infrared, ultraviolet and visible light.
• They are cost effective and are user-friendly.
• LEDs offer higher energy efficiency.

The applications of LED PCBs include street lighting, flashlights, vehicle headlights, surgery operating room lighting and much more.

viii.BGA Assembly

BGA (Ball Grid Array) Packaging contains lots of ball-shaped bumps at the bottom parts of the tube.

The bumps are responsible for providing an interconnection between the base and the packaging body.

BGA PCB Assembly

We can classify some of the BGA components broadly into:

• Plastic BGA (PBGA)
• Ceramic BGA (CBGA)
• Ceramic column BGA (CCBGA)
• Tape BGA (TBGA)

BGA SMT can be closely associated with solder paste, components, PCB, silkscreen, and soldering.

However, when performing BGA soldering, you should consider;

• Prebaking – plastic components should be baked at temperatures of 100 degrees Celsius for few hours to eliminate humidity.
• Oxidation – before indulging in the assembly, you need to inspect BGA components especially at the pins for cleaning to remove any oxidation layer.

Just like other types of assembly BGA defects and inspection methods are varied.

The most accurate and better technique is by use of Automated X-Ray Inspection (AXI) machine.

The optimal BGA soldering joints need to be smooth, clear, voidness.

The diameter, capacity, grayscale and contrast should be uniform among all the soldering joints with full alignment.

Chapter 9: SMT Assembly of Printed Circuit Boards

Unlike the Thru-hole technology, the surface mounting process is distinct about manufacturing efficiency.

The SMT features entirely automatic mounting process initially from solder paste printing, pick and place step, and finally reflow soldering.

Briefly, let’s have a look at the significant steps involved.

Step 1. – Solder  paste printing

Apply the solder paste uniformly on the circuit board via a solder paste printer.

To ensure accurate solder printing on the board where the components would be mounted, you can use a template.

This sheet is the stencil or solder screen.

Because most manufacturers deal with high-quality products, they have to inspect the products just after solder paste printing.

They do the regular inspection in the solder paste inspector.

Step 2. – Components mounting

After solder paste printing, PCB is auto sent to a pick and place machine.

Here the components or even the integrated circuits are mounted on pads with the effect of solder paste.

Expertly the components are installed on the PCB board using component reels in the machine.

Component reels play a vital role in this process.

They rotate to supply parts to the machines which will subsequently attach pieces to the circuit board.

Step 3. – Reflow soldering

After mounting all the parts on the boards, pass the PCB onto a furnace set at a temperature of 223 degrees Celsius.

The high heat causes the solder paste to melt and liquefy.

After the severe heat, the board is cooled town making the solder to solidify firmly binding the SMD components to the board.

Chapter 10: How to Hire Professional PCB Assembly Company

Having known all the details about PCB Assembly, am sure you have some burning questions. The basic one would be:

How can I hire a professional PCBA company?

Right?

It’s so much exciting that I have detailed information to help you with that. So read on.

First, I have to admit that this a sensitive issue that you need to get right.

I do trust you want that company which will do the assembly that fits your specifications, and that should be the fundamental objective of any PCBA company.

So then, the company needs to make you fully aware of the details of the design type you want.

For that reason, I have compiled these few steps.

Have a look.

PCB Manufacturer

Step 1. Set and follow a reasonable timeframe

It’s a common trend for customers to want to go over this critical step within a short period.

You probably might be trying to figure out how long it will take you to move on with your projects.

Most likely, you’re thinking of getting the products in time to the market and acquiring a sizeable profit.

Well, indeed time awaits no man.

However, rushing and picking any company may bring you a lot of losses than you may presume.

You may end up have wasted more time.

Take time to understand what the company offers before signing a deal with them.

Make detailed inquiries to the company.

I know some might delay in their response.

In case of that proceed and contact another company.

Consider the company that would result in a reasonable timeframe for you.

Unfortunately, you might not get an exact company that would precisely stick to your limits.

So take time to think of the right timeframe that is reasonable for your business.

Above all, you need to be patient in collecting information you require for deciding on the right company that would promptly fit your timelines.

Step 2. Consider the Company’s experience in the field

Exposure is quite essential. You will surely need a company, which has got adequate experience matching your job needs.

Venture Electronics

To do this source for this information on the company’s website.

• How long have they been doing SMT or THT or both?
• What batch sizes does the company prefer?
• What types of firms have they previously partnered?
• What kinds of products have they manufactured?
• What other after-sale services do they offer?
• How long has the company been operating?

If the answers to these questions aren’t available online, ask one of the company’s representatives.

Step 3. Assess quality

Before picking a company, you will surely want to partner with one which does a high-quality job.

Doing this evaluation before you have the actual might prove difficult.

To solve it, you may order a small run with a new company to check if indeed the quality matches your expectations.

If so then you may now make a more significant run of order.

Besides being on the watch for the following information:

• Type of equipment they use – if they have got a state of the art machinery then that’s a good indicator though it isn’t an automatic guarantee.
• Some certifications – a top class company, would have several certifications. These certificates are issued by independent parastatals, which look out for adherence to set standard rules and regulations. Most certifications begin with ISO followed by some numerical.
• Customers’ feedbacks and reviews – the kinds of reviews and customers feedback is a direct indicator of the type of quality you would expect. You may also physically want to reach out to the company’s former clients to get detailed information.

Step 4: Inquire about the Testing and inspection options

To assess the quality and achievement of objectives, proper inspection, and testing options are crucial.

Failure to do comprehensive tests or inspections may bring enormous losses to the clients.

The losses depict when the products suddenly fail during operations.

So, to avoid all these failures and short life span, a comprehensive test is the answer.

Some of the tests carried out are automatic optical inspections, component level checks, internal circuit verification, etc.

Step 5: Look out for customer support services

A little issue but vital one often forgotten by many is the customer care.

The level of seriousness of a support system would tell you about the kind of company you’re partnering.

The customer support answers your questions promptly about inquiries and problems you face.

An outstanding company will have customer support that works ethically to solve customers’ issues.

Again, you only need to speak to one customer care agent to assess the quality of the support system.

Ask about the customer services offered by a company.

Do they work with the clients to come up with a custom assembly?

Do they work with customers to fix any technical problem experienced?

Are they flexible enough to accommodate your timeline?

Step 6: Compare and contrast costs

Finance is crucial. You would want to get value for your money and again at the lowest affordable price while providing quality products to your customers.

Should we look at the factors that affect the costs of a PCB?

• Type and number of services requested – surface mount technology and through-hole manufacturing all may incur different expenses. Additionally, additional multiple testing, component sourcing, help with designs may all attract more costs.
• Size of your orders – extra large orders would cost more. Interestingly, many companies offer a discount on large units.
• Resources supplied – if the company provide you with all the resources such as components, the price will On the contrary, if you issue your parts, then you’re likely to save costs.
• Transport and shipping costs – the expenses for your shipping vary entirely on how far you are from the assembler, the order size and the kind of shipment offered.

 Importantly, don’t shy from spending if you’re going to get high-quality work.

Step 7: Warning signs

You may want to consider this other information when dealing with companies.

If you experience any of them, then you have no chance but to dismiss the assembler.

• Poor communication strategies such as unresponsiveness.
• Rigidity and inflexibility on the part of the company to accommodate or source out for solutions for your problems.
• Exaggerated pricing
• Longer lead time in completing a project.

Conclusion

There you are.

That’s all the information you need about the printed circuit board assembly.

You’re now capable of venturing into PCB Assembly.

Keep this guide for reference at all time.