What Is PCB Functional Testing?

What Is PCB Functional Testing?

Printed circuit boards (PCBs) are essential tools for many industries. PCBs allow you to connect electronic components using conductive pathways. Copper sheets are laminated onto circuit boards and facilitate the movement of electric currents. In turn, these tools become the building blocks for countless electronic devices in many industries.

PCB functional testing is a crucial aspect of their creation. Performed at the end of manufacturing, the tests ensure the PCBs will operate correctly. They serve as the last step between manufacturing and the market.

What is PCB functional testing, and how is functional testing done? Learn more information about PCB functional testing.

What Is PCB Functional Testing?

Common Functional Testing Techniques

Functional testing, also known as FCT testing, is the last manufacturing step of PCB creation. Essentially, functional testing makes sure the PCB works correctly. Functional tests examine the entire assembly rather than individual components. The tests simulate the final electrical environment where the PCB will reside. For example, if your PCB will rest in a computer slot, the functional test will recreate a similar slot to test its functionality. Then, you can uncover potential problems with the product before opening it to consumers.

Tools for functional tests often include:

  • Connective interface
  • Cables
  • Central processing unit
  • Monitors

Functional tests vary by product specifications. The length and type of the test depend on factors like:

  • How much of the PCB is being tested
  • The needed inputs and stimuli
  • Desired results
  • Testing parameters

During a functional test, you check each component to ensure it’s in working condition. If you’re wondering how FCT testing is done, you can use various techniques to test the board. Here are some common ways to functionally test PCBs:

What Is PCB Functional Testing?

Test Procedure List Creation

Deciding which tests you’ll perform is usually the first thing you do before starting the functional testing procedure. List the techniques you plan to use while testing the board.

For example, you might make a list of components and how you will test them during functional testing:

  • Resistors: Resistors transmit the electric current that powers a PCB. You can use a multimeter or other device to test resistors. Touch the multimeter’s probe to each resistor lead, then check the readings.
  • Sensors: These devices can sense alterations in the environment and create an electrical signal in response. You could also use a multimeter or similar device to test a sensor.
  • Capacitors: These components hold an electric charge on the board and release it when necessary. You could also add this component to your testing list.

As you progress through your functional tests, you can use your list to ensure you complete every option.

Voltage Meter Testing

The correct voltage is essential for a PCB to function correctly. The voltage reflects the power routed to the circuit. Whether a high-voltage or low-voltage unit, you must test the levels to ensure the board is safe to use.

A voltage meter test ensures the voltage levels of the PCB are at appropriate amounts. During this test, you place a voltage meter at every point on the board and ensure the reading is correct. Technicians then power on the board for the first time to ensure it powers properly.

Load Testing

These tests measure a board’s capability to withstand certain pressures and changes in other parameters. The test makes sure the board can handle its intended capacity. You could test the board’s operating capacity when these aspects change:

  • Temperature: Temperature maintenance is crucial for PCBs. If the board gets too hot, it could degrade the performance or cause it to break down. The maximum temperature a board can reach depends on its materials. During load testing, you could put the board into conditions that simulate heat and monitor how well it responds.
  • Current: You can determine a PCB’s current capacity by using a cross-sectional area of trace and monitoring the temperature rise. In load testing, technicians check the board’s current to ensure it’s at the right level.
  • Operating frequency: PCB functionality also depends on the operating frequency. The boards are classified as high-frequency or low-frequency. You can also ensure the operating frequency meets manufacturing requirements during functional testing.

QC Testing

Lastly, quality control (QC) testing ensures a PCB meets the specifications and regulations of the product. Because functional testing is the final step of PCB manufacturing, QC tests examine the finished product. During this test type, you check the PCB’s design and functionality. You then ensure these meet industry or federal standards. For example, you could measure if a board meets ISO 9001:2015 requirements.

Quality control testing might also involve a procedure like automated optical inspection (AOI). This thorough test examines your board’s components for potential defects. It magnifies all the components so you can inspect them more precisely. For instance, it checks for incorrect solder amounts and missing or damaged components.

Why Testing Is Crucial and How It Matters to You

No matter what type of electronics functional testing you use, it benefits your PCBs greatly. By using functional tests, you can guarantee a PCB is fit for sale. They also prevent costly replacements in the long term. You can maintain manufacturer quality and reputation with consistent tests. 

Functional tests can identify issues like:

  • Power issues: PCBs require stable power to function correctly. Functional PCB tests can examine power strength and point out issues with low frequency or rippling during operation.
  • Signal distortion: Tests can also display problems with signal distortion or failure during use.
  • Inaccurate voltage: Many factors could cause incorrect voltage, from incorrect component placement to missing a part entirely. A functional test can display these issues and let you get started on a solution.

By using functional tests for your PCBs, you can maintain the quality of your products. Your customers can save money and time by trusting their product is of the highest quality right when they buy it. Electrical functional testing is an essential step for PCB production.

What is PCB functional testing, and how is functional testing done? Learn more about the value of PCB functional testing, why some organizations skip it — and come to regret that call — and why it’s worth the investment.

What Is PCB Functional Testing?

Common Reasons for Not Pursuing Functional Testing 

Functional testing is essential to ensuring products perform as expected. However, many organizations shy away from pursuing functional testing due to the perceived obstacles. Let’s look at some of the core reasons people avoid functional circuit tests despite their many benefits.

1. More Expensive Than Other Techniques

Cost is one of the primary reasons people refrain from using functional testing. Functional testing can be more expensive when compared to other techniques — especially in terms of time and research. Establishing a comprehensive suite of test cases, setting up testing environments and employing skilled testers can all contribute to increased expenses. Higher costs are particularly significant concerns for small businesses or startups with limited budgets, making them hesitate to invest in such testing practices. 

2. The Finished Product Is Required for Testing

Functional testing simulates the environment your PCB will be working in. Functional testing does not allow you to test for bugs until you have the finished product — this method does not catch undetected bugs throughout the assembly process. However, functional testing is essential for ensuring the product you send out will perform as expected. Without functional testing to examine PCBs before they’re sent out, you can’t know how they will perform under natural conditions — you might see short circuits and other issues. 

While making continual changes throughout development is practical, functional testing offers a way to analyze the whole PCB in a way that incremental changes and tweaks cannot. Additionally, it can delay production if you have to wait until the product is complete to test. However, it is possible to continually test throughout development and then implement functional testing to perform the final checks your product needs before approval. 

3. Needs More Time and Coordination

Functional testing requires more time and coordination to complete, making it challenging to finish projects with tight deadlines. Teams may fear that dedicating valuable time to testing will hinder the overall development process, causing delays in delivering the final product.

While it is true that functional testing can be time-consuming, the benefits it offers are worth considering. By investing in thorough testing, developers will save time in the long run. Where skipping functional testing and rolling out a product with bugs can lead to expensive, time-consuming recalls or customer satisfaction issues, taking the time and effort to coordinate a functional test will improve your performance results and customer satisfaction. Additionally, the time you invest in functional testing contributes to a higher-quality end product and reduces post-launch support requirements. 

4. Complicated Testing Procedure

Another factor that deters individuals from pursuing functional testing is the complex, challenging nature of the testing procedures. Some developers may feel more comfortable with more straightforward testing techniques like visual inspection and hesitate to embrace functional testing due to a lack of familiarity with its intricacies. 

While functional testing can be more involved, automation and investing in quality testing services can help simplify the process for your company. Working with a skilled testing company can provide you with thorough, custom testing solutions without dealing with the testing process yourself. Professional testing services have the methods and skills to seamlessly carry out effective functional testing. 

What Is PCB Functional Testing?

Benefits of Functional Testing

Functional testing is a crucial evaluation methodology that ensures your PCBs perform as intended. Functional testing evaluates individual functions and features to verify that they meet the desired standard of functionality. If you’re looking to guarantee accuracy and reliability, functional testing is an excellent testing method to try. Here are a few benefits you can expect when using functional testing:

1. Reduces Failure Rate

One of the most significant advantages of functional testing is its ability to dramatically lower the probability of defects and failures in your PCBs. Our research shows the failure rate with functional testing is 100 times less probable than without it. When functional testing is used, the failure rate stands at an impressive 0.0003% — without functional testing, the failure rate surges to 0.03%. 

This substantial reduction in failure rate is attributed to functional testing’s comprehensive nature. Testers evaluate each feature, verifying adherence to specified requirements and noting any need for corrections. Functional testing helps prevent major problems and improve product satisfaction by identifying issues between design process completion and product rollout. With thorough functional testing, your PCBs are more likely to function as expected, reducing the risk of frustrating bugs or unexpected behavior. 

2. Provides the Most Foolproof Means of Circuit Board Testing

Functional testing thoroughly examines the circuit board’s behavior, testing individual functions and components. This in-depth evaluation helps verify that each element performs as intended. For example, in-circuit testing checks test points to look for faults. Without this evaluation, you leave your product open to undiagnosed issues. By focusing on the completed circuit board’s functionality, testers can identify potential issues before the product is sent out — this ensures everything operates flawlessly when it’s time for distribution. 

Since functional testing simulates real-world scenarios, testers can identify issues in a secure environment, long before the units are in customers’ hands. Functional testing acts as a last line of defense against malfunctions and bugs by offering comprehensive evaluations, ensuring your PCBs operate reliably and boosting user satisfaction and trust. With its extensive and effective testing procedures, functional testing is an indispensable aspect of the electronics manufacturing process. 

3. Diagnoses Other Product Issues

Functional testing can be a versatile tool for diagnosing product issues extending beyond the circuit board. While PCB functional testing is primarily focused on evaluating the circuit board’s performance, it can indirectly provide insight into broader product issues by simulating real-world scenarios for various functionalities. Here are some of the ways functional testing sheds light on other concerns:

  • Component integration: Functionality testing often tests the PCB with other connected components. Any issues arising from the interactions between the PCB and sensors, actuators or communication modules could indicate a potential integration issue in the overall product. 
  • Interoperability with software: Testing the PCB’s interactions with embedded software can reveal potential compatibility problems or communication gaps between the hardware and software components. 
  • Power management and consumption: Functional testing may also include evaluating the PCB’s power management features to ensure the proper functioning of power regulators and assess power consumption levels. This information can indirectly highlight potential power-related issues affecting the product’s overall performance and battery life. 
  • System stability: By validating the circuit board’s functionalities and connections, this testing contributes to overall system stability and reliability. A stable PCB design positively impacts the product’s overall performance and longevity. 
  • User interface and experience: If testing finds that the PCB performs correctly, it can lead to a smoother user experience. 
  • Safety and compliance: Properly functioning PCBs contribute to the product’s safety and compliance. Any issues detected during functionality testing may lead to further investigations to ensure the product meets safety standards and regulatory requirements. 

Other Functional Testing Techniques

Various functional tests can be applied to assess your PCB. Since a functional test validates your PCB’s behavior, the development process, procedures and criteria can differ significantly based on the PCB and its end application. Additional types of tests include:

  • PCB contamination testing: Identifies potential contaminants that could compromise the board’s integrity, leading to corrosion and related complications. 
  • Time-domain reflectometer (TDR): Detects issues in high-frequency boards.
  • Solderability test: Confirms the surface’s durability and enhances the probability of establishing a dependable solder connection.
  • Micro-sectioning analysis: Explores shorts, defects, openings and other malfunctions. 
  • Solder float test: Determines the PCB’s hole resistance to thermal stress. 
  • Peel test: Measures the force necessary to peel the laminate from the board. 
What Is PCB Functional Testing?

Learn More About EMSG PCB Testing Services Today

FCT testing is crucial for product quality. At Electronic Manufacturing Services Group, Inc., we understand the importance of PCB functionality testing and offer a wide range of full-service testing solutions. Our inspections magnify units and ensure they meet customer and manufacturer standards. We also provide product-specific tests for individual units, ensuring the highest quality for your product.

We never sacrifice quality for speed and guarantee thorough PCB tests. After a consultation with one of our experienced engineers, we can put together a detailed quote that explains our testing plan.

To get started with EMSG’s testing services, contact us today.