What Is PCBA? A Guide To Printed Circuit Board Assembly Process

By Bester PCBA

Last Updated: 2023-08-11

What Is Pcba

What Is PCBA

Printed circuit board assembly (PCBA) is the process of assembling electronic components onto a printed circuit board (PCB) to create a fully functional circuit board. A PCB on its own is incomplete as it does not have the electronic components mounted on it. The PCBA process involves mounting both passive and active components, such as resistors, capacitors, transformers, diodes, ICs, and transmitters, onto the PCB.

There are two types of electronic components used in PCBA: surface mount devices (SMD) and through-hole components. SMD components are mounted directly onto the surface of the PCB using surface mount technology, while through-hole components have leads that are inserted through holes drilled on the PCB surface.

The assembly of the PCB can be done using various soldering techniques. Wave soldering is commonly used for through-hole components, while reflow soldering is often used for SMD components. Mixed soldering technology can also be employed, and in some cases, hand soldering may be used by skilled professionals.

Once the electronic components are soldered or assembled onto the PCB, it becomes the PCBA or Printed Circuit Board Assembly. The PCBA is the fully assembled circuit board that is ready for use in different devices and applications. Without the PCBA, the PCB itself is not ready for any application.

PCBA is a critical process in the manufacturing of electronic devices. It brings a PCB to life by adding the necessary components to make it functional. PCBA is used in various industries and applications, including consumer electronics, automotive, aerospace, medical devices, telecommunications, and industrial equipment. From smartphones and computers to automotive control systems and medical devices, PCBA plays a crucial role in the production of electronic devices that we rely on in our daily lives.

The Complete PCBA Manufacturing Process

The complete PCBA manufacturing process involves several steps to transform a PCB into a fully assembled and functional PCBA. Here is an overview of the process:

Solder Paste Stenciling

The first step in the PCBA manufacturing process is applying solder paste to the PCB. Solder paste, which is a mixture of tiny metal balls (mainly tin), is applied to specific portions of the board where components will be placed. The solder paste is mixed with a flux, which helps in melting and bonding the solder to the board surface.

Component Placement

After applying the solder paste, electronic components and surface mount devices (SMDs) are placed on the PCB. This step can be done using either traditional manual methods or automated pick-and-place machines. In the traditional method, manufacturers use tweezers to place components, while machines are used in the automated method.

Reflow Soldering

Once the components are placed on the PCB, the solder paste is solidified through a process called reflow soldering. The PCBs are sent through a conveyor belt, passing through a reflow oven. The oven heats the boards at different temperatures, melting the solder paste and creating a strong bond between the components and the PCB. The boards then pass through a series of coolers to solidify the solder paste.

Through-Hole Assembly

In some cases, through-hole components may need to be inserted into the PCB after the surface mount components are soldered. This step involves manually inserting the components into pre-drilled holes on the PCB and soldering them in place.

Inspection and Quality Control

After the reflow or through-hole assembly (optional) process, the PCBAs get inspection and quality control to ensure they meet the required standards. Various methods are used for inspection, including manual checks, automatic optical inspection (AOI), and X-ray inspection. These methods help identify any misalignments, errors, or connection problems. If any issues are found, the boards may be sent back for reworking or scrapped. If the inspection is successful, the next step is to test the functionality of the board.

Testing and Calibration

PCBAs are tested to ensure they function properly according to the requirements. Testers check if the board works as intended and may perform calibration if necessary to ensure its functionalities are accurate.

Final Inspection and Packaging

After all the necessary components are assembled and tested, the PCBAs get a final inspection to ensure they meet the desired quality standards. Once they pass the inspection, the PCBAs are packaged and prepared for shipping or further assembly, such as box-build assembly.

The complete PCBA manufacturing process ensures that the components are properly assembled and soldered onto the PCB, resulting in a functional and reliable printed circuit board assembly.

PCB Assembly Technologies

The most common assembly technologies used in PCBA include surface mount technology (SMT) and through-hole technology (THT). These technologies are used to mount electronic components onto a PCB and create a functional circuit.

Surface Mount Technology (SMT)

SMT is the most widely used assembly technology in the PCBA industry. It involves mounting electronic components directly onto the surface of the PCB. The components used in SMT are smaller and lighter compared to through-hole components, making it possible to create smaller and more compact PCBs. SMT components are typically soldered onto the PCB using solder paste, which is applied to the PCB pads before the components are placed. The PCB is then heated to melt the solder paste and create a strong electrical connection between the components and the PCB.

Through-Hole Technology (THT)

THT is an older assembly technology that involves mounting electronic components through holes drilled in the PCB. Through-hole components have leads that are inserted into the holes and soldered on the opposite side of the PCB. This technology provides a stronger mechanical connection between the components and the PCB, making it suitable for applications that require high durability and reliability. THT components are typically larger and bulkier compared to SMT components, which can limit the size and compactness of the PCB.

Mixed Technology

In some cases, a combination of SMT and THT is used, known as mixed technology assembly. This allows for the use of both SMT and THT components on the same PCB, taking advantage of the strengths of each technology. For example, SMT components may be used for smaller and more densely packed components, while THT components may be used for larger and more robust components.

Other Assembly Technologies

There are also other assembly technologies used in PCBA, such as Ball Grid Array (BGA), Chip-on-Board (COB), and Flip Chip. BGA is a type of SMT where the electronic components have solder balls on the bottom instead of leads. COB involves directly mounting bare semiconductor chips onto the PCB without using a separate package. Flip chip technology involves mounting the bare semiconductor chip face-down onto the PCB. Each of these technologies has its own advantages and applications.

You should consider the specific requirements of your project when selecting the appropriate assembly technology. Factors such as component size, space constraints, durability, and electrical performance should be taken into account. Consulting with an experienced PCB assembler can help you determine the best assembly technology for your needs.

Files You Need for PCBA Manufacturing

In order to ensure a successful PCBA manufacturing process, there are several files that you need to provide to the manufacturer. These files include the Bill of Materials (BOM), Gerber files, and the First Article Test (FAT) report.

Bill of Materials (BOM)

The BOM is an Excel sheet that lists all the necessary components for the PCBA. It is essential to choose a reliable manufacturer who thoroughly inspects the BOM to ensure that the correct components are used during assembly. 

Gerber Files

The Gerber files, on the other hand, contain the information needed to fabricate the PCB and the necessary SMT stencils for assembly. These files provide the manufacturer with a detailed representation of the PCB layout, including the copper traces, pads, and other features.

First Article Test (FAT) Report

In addition to the BOM and Gerber files, the FAT report is also crucial for the PCBA manufacturing process. The FAT is a test that helps identify any potential glitches or issues before mass production. During the test, a technician uses a probe to measure parameters such as resistance and voltages on every device of the PCBA. The test results are then analyzed, and a test report is created for the client to review. Once the client approves the batch manufacturing based on the test report, production of the PCBAs begins.

Select the Electronic Components for Your PCBA

When selecting electronic components for your PCBA, there are several important parameters to consider for optimization. Here’s an enhanced guide to help you make informed decisions:

Through-Hole or SMDs

Choose between through-hole or Surface Mount Devices (SMDs) based on the mounting process and the complexity of the assembly steps. This decision can impact the completion process and overall efficiency.

Component Availability

Verify the availability of components before making your selection. Choosing components that are readily available can streamline the manufacturing process and prevent delays.

Moisture Resistance

Avoid selecting components that are susceptible to moisture damage. Improper soldering of moisture-sensitive components can lead to circuit failures or component explosions.

Temperature Tolerance

Opt for components that can withstand high temperatures, ideally up to 80 degrees Celsius. Choosing temperature-sensitive components can result in circuit connection failures or damage.

X-Ray Sensitivity

Consider the sensitivity of components to X-ray radiation. Some PCBA manufacturers use X-ray testing for quality control purposes. Components that are sensitive to X-ray radiation may be damaged during the testing process.

Analyze the Cost of PCBA

Collaborating with your PCBA manufacturer and design team to identify cost-saving opportunities and optimize your budget while ensuring the quality and functionality of the final product is critical for every PCBA project.

Analyzing the cost of PCBA involves considering various factors that contribute to the overall cost. These factors include labor costs, tooling and setup charges, turnaround time, quantity, technology, and packaging. Let’s take a closer look at each of these factors:

Labor Costs

The cost of labor plays a significant role in determining the overall cost of PCBA. This includes both human labor and automated factory labor. Labor costs can vary depending on the country where the manufacturing takes place. Some countries may offer cheaper labor, but it’s important to consider the quality expectations associated with those labor costs.

Tooling and Setup Charges

Custom shapes and builds may require additional tooling and setup, which can add to the overall cost of PCBA. In contrast, standard PCB designs can help avoid these setup charges, resulting in cost savings.

Turnaround Time

The time required to complete the PCBA process can impact the cost. Factors such as the time of the year, country of manufacturing, customer expectations, and more can influence the turnaround time. Expedited shipping or extra work time may incur additional costs.


The quantity of PCBA units required can affect the cost. Higher volumes often lead to economies of scale, resulting in lower unit costs. Customers usually need to decide and balance between quantity and cost-effectiveness.


The technology used in PCBA, such as Surface Mount Technology (SMT) or Through-Hole Technology, can impact the cost. SMT, for instance, is a highly automated process that can save costs compared to other technologies.


Packaging requirements should also be considered when analyzing the cost of PCBA. Different packaging options may have varying costs, and it’s important to choose packaging that meets your specific needs while considering the associated costs.

PCBA Inspection Methods

PCBA inspection involves examining and testing the assembled printed circuit boards to ensure their quality, functionality, and adherence to specifications. It is a crucial step in the manufacturing process of PCBA. The primary goal of PCBA inspection is to identify any defects, faults, or errors that may have occurred during the assembly process.

By identifying and rectifying any issues early in the manufacturing process, it helps prevent costly rework, repairs, or product failures. It also helps manufacturers meet industry standards and regulatory requirements.

There are various types of PCBA inspections that are commonly conducted to ensure the integrity of the PCBAs. These inspections include:

Solder Paste Inspection (SPI)

This inspection is performed after the solder paste is applied to the PCBs. Infrared cameras are used to scan the solder paste and ensure that its size, thickness, and position meet the required specifications.

X-Ray Inspection for BGA

If the PCBA includes ball grid arrays (BGA), an X-ray inspection is conducted before reflow soldering. This inspection checks the integrity and adequacy of the solder balls on the BGA.

Visual Inspection

Before reflow soldering, a visual inspection is carried out to examine the surface of the PCBA and ensure its quality. Trained technicians visually examine the PCBAs for any visible defects, such as soldering defects, misalignment of components, or physical damage.

Automated Optical Inspection (AOI)

After reflow soldering, the PCBA undergoes AOI to detect any soldering mistakes, such as solder bridges, component offsets, solder voids, or tombstones. AOI machines use cameras and image processing algorithms to automatically inspect the PCBAs for defects and anomalies.

Functional Testing

This type of inspection involves testing the PCBAs to ensure their proper functionality. It can include testing the electrical connectivity of the circuit, verifying the performance of specific components or features, and conducting environmental tests to assess the PCBAs’ reliability under different conditions.

In-Circuit Testing (ICT)

In-circuit testing is a method of testing the electrical characteristics of PCBAs using specialized test equipment. It helps to ensure that the PCBAs meet the required electrical specifications and perform as intended.

What Is a PCB Box Build Assembly

A box build, also known as system integration, is the final stage of the PCBA manufacturing process. It involves assembling and integrating all the electronic components, PCBs, and other necessary elements into a complete system or product. In simple terms, it is the process of putting all the pieces together to create a functional electronic device.

During the box build process, various components such as PCBs, connectors, cables, displays, sensors, and mechanical parts are assembled and integrated into a housing or enclosure. This enclosure not only protects the internal components but also provides a user-friendly interface for the end-user.

The box build process includes several steps, such as:

Mechanical Assembly

This involves mounting the PCBs and other components onto the enclosure or chassis. It may also include attaching brackets, heatsinks, or other mechanical parts necessary for the proper functioning of the device.

Wiring and Cable Assembly

The box build process also includes the installation of wiring harnesses and cables to connect various components within the system. This ensures proper communication and power distribution between different parts of the device.

Testing and Quality Control

Once the assembly is complete, the box build undergoes testing to ensure that all the components are functioning correctly. This may involve functional testing, electrical testing, and environmental testing to ensure the device meets the required specifications and standards.

Final Packaging

After passing the testing phase, the completed box build is packaged and prepared for shipment. This may involve adding labels, user manuals, and any necessary accessories to the packaging.

Why is Box Build Important in PCBA Process

A box build is an essential part of the PCBA manufacturing process as it transforms individual electronic components into a fully functional product. It requires expertise in mechanical assembly, wiring, and testing to ensure the final product meets the desired specifications and quality standards.

Box build can vary in complexity depending on the specific requirements of the product or device being manufactured. It can range from simple enclosures with basic interfaces and displays to more complex assemblies that involve the installation of additional components, routing of wire harnesses, and the construction of custom-made enclosures.

When looking for a PCBA manufacturer, it’s always good to inquire about their box build services. This ensures that the manufacturer has the capabilities and expertise to handle the complete assembly and integration of the PCBA into a finished product. By partnering with a manufacturer that offers box build services, you can streamline the manufacturing process and ensure the delivery of a fully functional and ready-to-use electronic device.

How to Order and Get a Custom PCBA

Getting a custom PCBA involves careful planning, collaboration with experts, and attention to detail. By following these steps, you can ensure your custom PCBA meets your specific requirements and performs reliably.

Define Your Requirements

Start by clearly defining your project requirements, including the purpose, desired functionality, and specific features or components needed. Consider factors such as size, power requirements, and environmental conditions.

Design the PCB

Work with a skilled PCB designer to create a custom PCB layout that meets your specifications. Provide detailed information about the components, connections, and any specific design constraints. The designer will use specialized software to create the layout and generate the necessary files for manufacturing.

Generate Gerber Files

Once the PCB design is complete, generate Gerber files, which contain all the necessary information for PCB fabrication. These files include PCB layers, component placement, and trace routing. Gerber files are used by PCB manufacturers to produce the physical PCB.

Source Components

Identify the electronic components required for your custom PCBA. Research reputable suppliers and source components that meet your specifications. Consider factors such as quality, availability, and cost. Ensure the selected components are compatible with the PCB design and meet any specific requirements.

Choose a PCBA Manufacturer

Select a reliable PCBA manufacturer that can handle your custom requirements. Look for experience in producing PCBAs similar to your project. Consider manufacturing capabilities, quality control processes, lead times, and pricing. Request quotes from multiple manufacturers to compare offerings.

Provide Documentation

Once you’ve chosen a PCBA manufacturer, provide them with the necessary documentation, including Gerber files, a bill of materials (BOM), and any specific assembly instructions. Clear and detailed documentation ensures accurate production of your custom PCBA.

Prototype and Testing

Before full-scale production, request a prototype of your custom PCBA to verify functionality and performance. Thoroughly test the prototype to ensure it meets your requirements. Make any necessary adjustments or refinements before proceeding with mass production.

Mass Production

Once the prototype is approved, proceed with mass production. The PCBA manufacturer will use provided documentation to assemble the PCBs, solder components, and perform any required testing or inspection. Follow industry standards and quality control processes to ensure the final product meets your specifications.

Quality Assurance

Conduct thorough quality assurance checks on the finished PCBA, including visual inspection and functional testing. Ensure the PCBA meets the required standards and performs as expected.

Delivery and Support

The PCBA manufacturer will package and deliver the finished PCBAs to your specified location. Maintain clear communication channels for any post-production support or warranty issues.

Common PCBA Applications

Printed circuit board assembly finds its applications in a wide range of industries and electronic devices. Its versatility and reliability make it an essential component in many everyday goods and critical systems. Here are some of the common applications for PCBA.

Consumer Electronics

PCBA is extensively used in consumer electronics such as smartphones, computers, TVs, printers, calculators, and home appliances. These devices require complex circuitry to function properly, and PCBA provides the necessary platform for integrating and connecting electronic components.

Automotive Industry

In the automotive industry, PCBA is widely used in engine control units (ECUs), infotainment systems, navigation systems, sensors, and lighting systems. The ruggedness and durability of PCBA make it suitable for the demanding conditions of the automotive environment.

Medical Devices

PCBA is widely used in medical devices and equipment, ranging from diagnostic instruments to life-saving devices. It is used in devices such as patient monitors, defibrillators, infusion pumps, medical imaging equipment, and laboratory instruments. PCBA ensures the accurate and reliable functioning of these critical healthcare devices.

Industrial Automation

PCBA is an integral part of industrial automation systems, including programmable logic controllers (PLCs), motor control systems, robotics, and control panels. These systems require precise control and communication between various components, and PCBA enables the seamless integration of these components.


PCBA is used in telecommunications equipment such as routers, switches, modems, and base stations. These devices require high-speed data processing, signal routing, and communication capabilities, which are facilitated by PCBA.

Aerospace and Defense

PCBA is extensively used in the aerospace and defense industry for applications such as avionics systems, navigation systems, communication systems, radar systems, and missile guidance systems. The high reliability and performance of PCBA are crucial in these mission-critical applications.

Energy and Power Systems

PCBA is utilized in energy and power systems, including smart meters, power distribution systems, solar inverters, and energy storage systems. PCBA enables efficient power management, monitoring, and control in these applications.

Internet of Things (IoT)

With the rise of IoT, PCBA has become an integral part of connected devices. IoT devices such as smart home devices, wearables, and industrial sensors rely on PCBA for data processing, connectivity, and control.

These are just a few examples of the wide-ranging applications for PCBA. Its versatility and adaptability make it an indispensable component in modern electronic devices and systems across various industries.

How To Select a PCBA Manufacturer for Your Project

When it comes to selecting a PCBA manufacturer, there are several important considerations to keep in mind. Here are some key factors to help you make an informed decision:

Capacity and Capability

Before reaching out to a manufacturer, it’s necessary to determine if they have the capacity to handle your specific order. If you require a large quantity of PCBAs, ensure that the manufacturer can fulfill your order without compromising on quality or delivery time. Additionally, consider their overhead costs and manufacturing time to ensure they align with your project requirements.

Thorough Testing and Design

Partner with a PCBA manufacturer that prioritizes thorough testing and design. Inquire if the manufacturer has built a working prototype and if they have tested the PCBA design extensively. This helps identify any potential design issues early on and ensures the quality of the final product. Testing is time-consuming but crucial for a successful project.

Consider the Complexity

The complexity of your PCBA design can impact the manufacturing process. Boards with multiple layers may require more time and resources to build, test, produce, and assemble. 

Work with a manufacturer who considers factors such as size, weight, design, and function. Transparency about costs, technology, and design is key in selecting the right partner.

Collaboration and Design for Manufacturing

Involve your PCBA manufacturer early in the product design stage to ensure their capacity and technology align with your design requirements. This collaborative approach, known as Design for Manufacturing (DFM), helps optimize the manufacturability of your design and reduces potential manufacturing issues and costs.

Lead Time and Delivery

Timely delivery is crucial to avoid disruptions in your production schedules or product launches. Choose a manufacturer that guarantees prompt delivery of the assembled boards. Additionally, ask for a detailed DFM report, which provides recommendations to enhance the manufacturability of your design and avoid future issues.

Pricing and Negotiation

Consider the pricing structure offered by the manufacturer. Competitive pricing, in line with market rates, allows you to maximize the value of your investment. Look for a manufacturer that is open to negotiation and willing to work with you to achieve the best possible pricing while maintaining high-quality standards.

Remember, selecting a PCBA manufacturer is a critical decision that can impact the success of your project. Consider these factors and choose a manufacturer that aligns with your specific requirements, offers reliable communication, and demonstrates expertise in the industry.

What Is the Difference Between PCB and PCBA

The difference between PCB (Printed Circuit Board) and PCBA (Printed Circuit Board Assembly) lies in their functionality and stage of production. 

A PCB refers to the bare board itself, which serves as a carrier for electronic components and facilitates the conduction of electrical signals between them. It is made of non-conductive substrate materials with layers of copper circuitry placed internally or on the external surface. PCBs can vary in terms of material, flexibility, and layers. They can be made from materials like metal, ceramic, or FR4, and can be flexible or rigid, with different numbers of layers.

PCBA refers to the PCB that has undergone the assembly process. It is the finished circuit board with all the electronic components mounted and soldered onto the PCB. The PCBA is created by soldering or inserting various components, such as resistors, capacitors, ICs, and transformers, onto the PCB. It includes processes like reflow furnace heating to establish a mechanical connection between the components and the PCB. Once the components are mounted and soldered, the PCBA gets its quality inspection and testing to ensure its complete circuit connection performance.

To put it simply, a PCB is the bare board without any components, while PCBA is the PCB with all the components mounted and soldered. PCBs are the starting point of the manufacturing process, and PCBA is the end result after the assembly of components. 

Note that while the terms PCB and PCBA are often used interchangeably in casual conversations, they have distinct meanings in the context of the manufacturing process. Understanding this difference is crucial when discussing the various stages of electronics manufacturing and when communicating with manufacturers and suppliers in the industry.