How to control Populated PCB Quality?

Understanding the diversity of PCBs is very important as an engineer. PCB population is an important aspect of the PCB industry. Without it, a PCB is just a bare board. This aspect is carried out by professionals to avoid any mistakes.

The performance and the functionality of a circuit board depend on the PCB population. It is crucial to understand what PCB population entails. In this article, we will discuss important details about the PCB population.

What is a Populated PCB?

A populated PCB is a circuit board with electronic components. A board without electronic components mounted on it is a bare board. This means a PCB can either be bare or populated. PCBs can be populated through surface mount technology or through hole technology.

A populated circuit board is the same as a printed circuit board assembly. The components mounted on this board are surface mount devices. A populated PCB is electrical equipment that connects electronic components. This PCB features pads, conductive tracks, and more.

Manufacturers solder the electronic components on the PCB to achieve a populated PCB. The populated circuit board comprises components such as IC, capacitors, and diodes. While a populated PCB features electronic components, a bare board doesn’t.

It is important to understand that a populated PCB is different from PCB manufacturing. The process of PCB manufacturing entails the production of a bare board. The manufacturing process involves creating a PCB prototype. The method of populating a PCB depends on the purpose of the circuit board.

PCB population

PCB population involves several processes. It is important manufacturers carry out each of these processes carefully. To carry out PCB population, you will need the following;

Each of these equipment is very important during PCB population. The bare board serves as the foundation of the populated PCB. It is a core material in PCB population. Manufacturers either use SMT or THT to mount components on a bare board.

Tips for PCB Population

populated circuit board
populated circuit board

PCB population is an aspect that entails some processes. When populating a board, planning, organizing and sorting are very vital.

Clean your bare PCB

This is the first step in populating a circuit board. Therefore, to achieve a functional populated circuit board, clean your board. Cleaning is what you do before and after populating a PCB. Cleaning your PCB helps you perform soldering well.

Populate from the lowest to the highest

PCBs can become overpopulated if you aren’t careful enough. An overpopulated PCB makes things more difficult for you. It leaves you with little or no space to get your components mounted where necessary. The best way to prevent overpopulation from occurring is to plan beforehand. Solder your components across the bare board. Start populating the board with the lowest component. This will prevent big components from getting in your way.

Use tweezers

For THT mounting, you need a pair of tweezers. Tweezers help you to mount through-hole components on the circuit board.

Use a component lead tool

The component lead tool measures spacing in the hole and bends all shapes and sizes of lead components. This tool helps you keep your circuits firm. Bending your component leads to the appropriate lead width is helpful.

Incorporate poster putty as helping hands

A poster putty is an underutilized tool in PCB population. This tool can help to hold small objects while you are working on them. Poster putty can replace conventional helping hands tools. This tool won’t leave any residue on your PCB when used.

Use hot glue as insulation

When mounting components on PCBs, hot glue can serve as an insulator. However, you should avoid the use of hot glue on thermally sensitive components. Hot glue can help you secure wires in the right place.

Plan the enclosure

This is very important when populating a PCB board. Enclosures put boundaries on the shape and size of a circuit board. Select an enclosure that meets the requirements of the intended application.

Reduce handling and repositioning

Several repositioning of circuit boards increases the required time to populate a board. Repositioning happens when a board is two-sided and components are on the two sides of the rigid flex PCB. It is advisable to use all SMT components on a single side of a board.

Techniques for PCB Population

Manufacturers carry out PCB population using two major techniques. These techniques are surface mount technology and through hole technology. SMT and THT are common ways to populate a printed circuit board.


This is a common way of populating a circuit board. Manufacturers use SMT for mounting sensitive components.  In Surface mount technology, the components feature short leads. Furthermore, this technique uses automated machines to populate components on circuit boards. SMT involves mounting SMD s directly on the PCB. Manufacturers populate this circuit board with the use of pick and place machine.


The through hole technology involves inserting the pins of the components into the holes of the board. Here, the placement of components must conform to the standards of the THT process. Manufacturers make use of tweezers to place a component on the circuit board in this technique.

However, in THT, manufacturers place components with leads via plated through holes. This was a common technique for populating boards before the advent of SMT.

Factors that Affect PCB Population

Manufacturers should pay attention to certain factors while populating a bare board. Some factors directly affect the PCB population process.

Part size

The electronic components of a circuit board vary in size. The manufacturer must consider the components’ sizes to determine the speed of the process. The pick and place tool will change according to the part size.

Placement speed

PCB population involves the placement of components on bare boards. This aspect involves a lot of processes. Manufacturers can increase the speed of placement by decreasing the number of steps. For instance, you don’t need to rotate components during placement if they are in a similar direction.

Types of board

There are different types of PCBs. The board type will determine how to populate it. The population of a multilayer board will differ from that of a single layer board.

Benefits of Populated Printed Circuit Board

A populated PCB offers a lot of advantages. Therefore, it is important to note that a populated PCB is the one used in electronics manufacturing. A bare PCB won’t be functional without electronic components. Populated printed circuit boards play a significant role in today’s electronics.

Compact design

Mounting electronic components on a board gives a compact design. Therefore, while populating a PCB, a PCB designer can experiment to achieve a great design. Populated circuit boards interconnect the components and enable both output and input connections.

A reliable option

A populated circuit board is a reliable option for several companies. It is a reliable option that can function in a wide range of products. These boards can last long. Manufacturers adhere to a specific pattern when populating a board. This helps to ensure the reliability of these boards.

Low electronic noise

There is a tendency for electronic noise in a circuit. The PCB manufacturer mounts the components in a way to reduce electronic noise produced by the circuit. Populated PCBs can decrease path lengths to reduce electromagnetic radiation.

No loose connections

You will likely deal with loose connections when you make connections in a PCB via copy tracks. However, you won’t have to deal with this if the connections are done properly.

Ease of repair

This is one of the benefits of a populated PCB. It is easy to test and detect any defect on the board. Therefore, manufacturers can easily identify a faulty component and replace it. You can do this without disturbing other electronic components on the board.

Applications of a Populated Circuit Board

A populated circuit board is commonly used in a wide range of applications. This board is available on most electronic devices. The electronic industry incorporates this board for designing electronic products.

Military Industry

Populated circuit boards are commonly used in military devices. These boards are designed to meet the increasing demands of the military industry. Populated circuit boards are present in military devices like missile detection machines. However, manufacturers fabricate high-frequency populated PCBs for military purposes.

Consumer Electronics

Consumer electronics such as TVs, remotes, and more feature populated PCBs. These circuit boards are the foundation of these devices. They offer electrical and mechanical support to these devices. Populated boards with connections help to design laptops and smartphones.

Industrial System

High-end machines used in industries feature populated circuit boards. Populated PCBs are available in surveillance systems, vending machines, and printers among others. Boards used for industrial purposes must be electrically and mechanically stable.

Medical Sector

This is another application of populated boards. The medical industry is using increasing numbers of populated PCBs. These boards are ideal for use in tracking treatment, diagnostics, and more. You will also find these boards in CAT, ultrasound scanners, and other medical devices.


The aerospace industry also uses populated circuit boards. The boards used in this application are high-speed and high-frequency. This is because they are more likely to be exposed to harsh conditions.  Aerospace devices like satellites, radio communication systems, and aircraft feature this PCB.

The aerospace industry uses monitoring devices like pressure sensors and accelerometers. These devices help to track an aircraft’s operation. Populated PCBs are available in these devices.

Populated PCBs are ideal for use in several applications. These boards have great properties which make them suitable for most applications.

How to Populate a PCB

PCB population involves several steps. When populating a PCB, manufacturers need to carry out these steps carefully.

Prepare your components

Before you create a populated PCB is to prepare your electronic components. Asides from the electronic components, you also need ground and power signals. You will need to connect the board to external devices like potentiometers.

Check the board layout view

After preparing the components, ensure you run an electric rule check. There might be breaks in connection or wires. You must check the board layout view once the schematic is ready.

Apply solder paste

The next step is to apply solder paste to the circuit board. Here you will place a stencil over the board. This will help you apply the solder paste to a specific part of the PCB. This is where you will mount components on the board.

Pick and place the component

This is a crucial step in PCB population. In fact, this is what gives birth to a populated PCB. The SMT technique uses a pick and place machine to place components on the bare board. Before the advent of SMT, manufacturers place components on the board manually. They use a pair of tweezers to mount components on boards.

However, humans are likely to make mistakes. The manual process of placing components is slower. Therefore, the use of pick and place technology has helped a lot.

Reflow soldering

After placing the components on the boards, you need to solidify the solder paste. This will help the components to stay firm on the board. Here, the PCB moves to a conveyor belt. Then the belt heats up the board at a high temperature. This process is very important as it helps to keep the components in the right location.

Frequently Asked Questions

What is an unpopulated PCB?

An unpopulated circuit board is usually found in a hardware device. This circuit board features empty sockets for firmware updates.

What is the function of a breadboard in a populated board?

A breadboard helps you to hold pins firmly when soldering then onto the circuit board. You put the header pins in the breadboard. Then, you align the circuit on top. You can slot the pins via the holes on the PCB and solder it.


A populated PCB is of great importance in the electronic industry. This board is widely used in several applications. They serve as the backbone of most electronic devices. PCB population is an important aspect that produces a populated PCB. This process must be carefully carried out. With the advancement in technology, PCB population has become easier.

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