PCB Testing Methods: A Complete Guide

Introduction

Lab testing of a PCB
Lab testing of a PCB

PCB testing is a crucial step in the production of PCB. It focuses on using diverse techniques and instruments to check the performance of each element, thus ensuring the best PCB assembly. The PCB testing ensures the manufacturing of high-quality boards leading to enhanced efficiency and reduced costs. This article will cover all the important techniques, protocols, and criteria for testing PCBs.

What is PCB Testing?

PCB testing is the process of checking subtle errors or flaws in the circuit board to ensure the proper functioning of the PCB. It helps the manufacturers in confirming the circuit’s correct operation. Manufacturers perform PCB testing when the entire assembly is complete. After the end of the designing phase, multiple factors can lead to various defects in solder and component connections.

What does PCB Testing Check?

The main aim of PCB testing is to confirm whether the PCB is functioning according to the standard performance expected from a circuit board. These PCB testing methods include the following:

Copper Plating

Manufacturers check the fault in the copper foil that is attached to the board for conductivity in the PCB. Designers usually check the copper’s quality. They deeply analyze its elongation and tensile strength. The manufacturers and operators are professional in these checkups.

Lamination

The designers also check the feature of lamination. The quality of a PCB is dependent on the standard of its lamination. The fault in laminates is very dangerous for the board’s functionality. The lamination test evaluates the resistance level of laminates to heat or external force.

Solderability

The designers check all the solders on the circuit board to prevent flaws in the soldering process. Solderability tests examine PCBs to ensure that all the components are stable on the board. It prevents soldering issues later on. It tackles the issues beforehand to avoid the issues that may disappoint the customers due to faults in electronic devices.

Electrical Testing

The manufacturers also check the electrical systems of the newly manufactured PCBs. They analyze if the current is passing through the circuit board or not. Conductivity is a major concern in any PCB. Therefore, it is necessary to check current leakage in PCBs to ensure proper functionality.

Environmental Testing

Manufacturers analyze electronic devices from the perspective of environment friendliness for the best functioning. This includes a performance test to check the ability of a PCB to operate properly in harsh conditions. The PCB is subjected to a wet environment and then the changes are evaluated. PCBs with prominent weight changes are rejected.

 

Popular PCB Testing Methods

Visual Inspection

Visual inspection of PCB
Visual inspection of PCB

The experienced individuals visually check the PCBs for defects in welding and other noticeable irregularities by just using their eyes and magnifying glasses. It is a well-suited test for visual inspection of PCBs. It is also helpful in analyzing the place of components and understanding the solder mask application. This method is considered as one of the most convenient, important, and professional means of PCB inspection.

Advantages

  • It has a quick setup and is cost-effective.
  • This process is effective in identifying major solder defects.

Disadvantages

  • This process is time-consuming and demands a significant amount of labor.
  • This test is vulnerable to human errors and is heavily dependent on the skills of the technician.
  • This test is limited to the inspection of visible solder joints only.

Application

This approach is mostly suitable for simple designs with larger components.

Flying Probe Testing

Flying probe testing of PCB
Flying probe testing of PCB

 

Flying Probe Testing is a very cost-effective alternative to in-circuit testing that is a type of in-circuit testing. In this method, a small probe is used to make contact with test points, such as SMD pins. During flying probe testing, electrical and power test signals are received from the test location which ensures the proper functioning of the PCB. The outcome of this test decides whether the circuit board has any faults or not.

Advantage

  • It is low-cost and flexible to implement this type of test.
  • It offers a complete test by utilizing component pads used as test points.
  • It is space-saving and there is no need for additional testing points.

Disadvantage

  • It is less effective for tests at a large scale.
  • This test is unable to evaluate defects like improper solder ratios and voids.

Application

The flying probe test is suitable for small to medium-sized boards having a higher component density.

Automated Optical Inspection (AOI)

Automated optical inspection of PCB
Automated optical inspection of PCB

Automated Optical Inspection utilizes either one or two cameras for capturing high-resolution images of the PCB. Then the images are compared with templates of the tested design. AOI testing machines can make real-time adjustments for production and it operates directly. As long as components are available for testing, AOI can identify error and provides a precise evaluation.

Advantages

  • It is effective in identifying the significant defects in the solder.
  • It offers greater accuracy as compared to automatic testing methods.
  • It can be integrated directly during the production stage for early identification of defects.

Disadvantage

  • It is limited to the detection of surface defects only.
  • The template matching requires reconsideration with each change in design.
  • This test gives accurate database matching but it depends on the quality of the database.

Application

AOI is suitable for testing large essential products in large amounts.

Automated X-ray Inspection (AXI)

Automated X-ray inspection of PCB
Automated X-ray inspection of PCB

 

Automated X-ray inspection differentiates itself by employing X-rays. By penetrating the X-ray on the PCB and component body, AXI visualizes the solder joints in either 2D or 3D. This capability is beneficial for hidden joints in ball grid arrays (BGAs) and underside pads that are also hidden. AXI has the unique ability to detect solder faults.

Advantages

  • This test has the highest defect detection rates.
  • This test places a strong emphasis on solder joint quality rather than just connections.

Disadvantages

  • This test is time-consuming and very costly.
  • It demands professional and experienced operators.

Application

AXI testing is used in high-volume production of boards having chip components.

In-circuit testing (ICT)

In-circuit testing of PCB
In-circuit testing of PCB

 

In-circuit testing is a highly recommended circuit examination technique that is capable of examining each circuit in a PCB. It assesses the PCBs and all its components. This automatic fault detection system effectively addresses almost 90% of defects. It is also known as a “bed of nails” test because it activates every circuit on the PCB.

Advantages

  • Approximately, it can find 98% of faults in the circuit board.
  • It ranks among the efficient and swift testing methods suitable for mass-produced boards.

Disadvantages

  • It is unsuitable for small circuit boards.
  • This test is incapable of detecting defects like excessive solder.

Application

In-circuit testing is used for examining well-established products that are produced in large quantities.

Burn-In Testing

Burn-in testing of PCB
Burn-in testing of PCB

 

The PCB burn-in test is a procedure where circuit boards are exposed to elevated temperature and voltage stress to check the aging process and uncover the flaws. This process is typically used for newly manufactured boards. Its aim is to detect defects before they reach the customer. It points out the components or solders joints that can be premature.

Advantage

  • Enhanced Reliability: Burn-in testing checks the weak and faulty components and connections that can lead to product failure. It can impact the quality and longevity of PCB.
  • Cost Reduction: Identifying and replacing the defective components, reduces the issues of cost related to product returns and warranty claims.
  • Improved Quality: This test of all components enhances product results and quality. So, it increases customer satisfaction and loyalty.

Disadvantage

●        Expense: Burn-in testing is a costly process that requires extra resources and time.

●        Potential Damage: This testing can damage the components and connections leading to reduced quality.

●        Stress: Burn-in testing is stressful for the components and connections leading to their premature wear and tear.

Application

This testing is very valuable for checking the functioning of PCB in extreme environments where failure is not tolerated at all, like, medical devices.

Functional Testing

Functional testing of PCB
Functional testing of PCB

Functional testing is beneficial in checking the functionality of PCB components. This test checks whether the device under test is functional or not. The complex design demands the on-off power test to check a simple power cycle. Functional testing is a cost-effective alternative to costly testing methods.

Advantages

  • It is highly flexible and suitable for testing nearly all types of PCBs.
  • It is a cost-effective and convenient option as compared to specialized device testing methods.

Disadvantages

  • It requires skilled personnel to point out the causes of defects in PCB.
  • Boards can fail even after passing the test under stressful conditions.

Application

This testing method is suitable for the manufacturing of small-quantity boards.

Time Domain Reflectometry Test (TDR)

Time domain reflectometry test of PCB
Time domain reflectometry test of PCB

Time Domain Reflectometry test is a technique used to check the electrical properties of a printed circuit board (PCB). Its purpose is to check the capacitance, and inductance of the PCB components. TDR test operates by sending an electrical pulse through a PCB trace. In this analysis, one can test the electrical characteristics of both the trace and the PCB components.

Aging Test

Aging test of PCB
Aging test of PCB

An age test is performed to check the product aging in relation to environmental conditions that the real-world users of the products have to face. The aim of subjecting a product to a controlled environment for testing is to check its quality and stability. In order to perform an aging test, the product is exposed to controlled temperature and humidity settings from 72 hours to 7 days. The received data is recorded and adjustments are made to improve the performance of the product.

GM/LTS

GM/LTS of PCB
GM/LTS of PCB

The GM/LTS PCB testing approach has many procedures for examinations. It is specially designed to address best internal CCA (Circuit Card Assembly) issues. The terminal computers are programmed to undergo comprehensive loopback tests and self-assessments. Both tests are helpful in the early detection of faulty components that can be replaced with new components.

Laser Detection

Laser testing of PCB
Laser testing of PCB

PCB testing methods represent the latest advancements in the field of technology. It utilizes laser beams to collect measurement data. In the initial stages, this technology was used on bare boards before being adopted for assembly board testing. This testing method offers rapid output results without defects and with clear visibility.

The Benefits of PCB Testing

Ensuring Product Reliability and Safety

PCB testing ensures the reliability and security of electronic goods. Defective PCBs can lead to malfunctions, financial losses, and harm to the image of the brand. PCB testing aims at detecting and eliminating these flaws before the product is launched in the market.  Thus, it assures the safety and reliability of the final product.

Reducing Production Costs

PCB testing in the early stages of production helps save money by lowering the quantity of defective PCBs manufactured. Flawed PCBs can only result in product recalls and revenue losses. Detection of defects at an early level enables the manufacturers to avoid the production of defective PCBs. In this way, it results in cost reductions.

Improving Product Quality

The early identification of faults in the production process through PCB testing leads to an increase in the quality of the product. Manufacturers can find and resolve these issues at an early stage. It can refine the procedures of production that lead to superior-quality products. PCB testing is very helpful in enhancing the overall quality of the product.

Meeting Regulatory Requirements

Organizations like the International Electro-technical Commission (IEC) and the International Organization for Standardization (ISO) have defined specific criteria for electronics. Electronic products must follow these regulations for increased quality. PCB testing ensures that the end product aligns with these regulations. It helps in the high sales of the product in global regions.

Identifying Design Flaws

The PCB testing is performed in the early stages of development.  It helps in the early detection of design weaknesses. Manufacturers can recognize these design flaws to implement the required alterations. It helps in improving the overall design and functionality of the product. This results in the production of electronics that are more efficient and reliable.

Ensuring Consistency in Production

PCB testing ensures uniformity throughout the production process. Manufacturers verify that each manufactured unit follows the same standards and criteria. This increases the overall quality of production and results in a higher-quality end product. PCB testing ensures the production quality of electronic products.

Enhancing Customer Satisfaction

PCB testing enhances customer satisfaction by ensuring the quality of the electronic products. PCB testing identifies the faults before the product is supplied to the market. Through PCB testing, manufacturers can prevent complaints in an efficient way.  The process of PCB testing can improve the overall customer experience and feedback as well.

Saves time

Identification of PCB defects at an early stage can reduce the time required for system updating. During the manufacturing process, designers have the opportunity to point out the problems. The PCB testing helps in the identification of the root causes that are responsible for malfunctioning. This can save time for the production of PCB products.

Common Defects in Circuit Board Testing

Opens and Shorts

An open circuit is created when the PCB’s conductive pathway is disrupted. It results in a lack of connection between the two points of the circuit board. A short circuit might happen due to an unintentional connection between two conductive paths. It causes the current to flow between them.

Soldering defects

PCB testing is done to check the defects in the soldering of the circuit board. Soldering plays an important role in the PCB assembly. Soldering faults occur when the solder fails to make a proper connection between the component and the PCB. Such faults can lead to a complete disruption of connectivity between the components of the board.

Component Defects

During PCB testing there are some defects that are left in the components of the circuit board. Flaws in components arise due to wrong handling procedures. These wrong handling procedures include electrostatic discharge and improper storage conditions. These faults can cause malfunction in the components leading to device malfunctions and even failures.

Inaccurate Component Positioning

Inaccurate Component Positioning is another defect that arises during the PCB testing process. It is caused by to attachment of components in inappropriate places on the circuit board. It can also lead to short circuits or disruptions. This defect is very dangerous if it is not tackled properly.

Conclusion

PCB manufacturing demands testing to ensure that the quality of the product is maintained. The industry uses a variety of testing methods and protocols to ensure the proper functioning of PCBs. The testing procedures discussed in this article explained the importance of PCB testing for the production of high-quality circuit boards. This guide will prove to be very beneficial for all professionals and manufacturers alike.

Frequently Asked Questions (FAQs)

What are PCB standards?

PCB standards a criteria that ensure the quality parameters for PCB design, production, and testing are followed.

Can PCB be any size?

PCBs are produced in various sizes according to the specific demand of the electronic device in which it would be used.

What is the importance of PCB testing?

The importance of PCB testing is due to its role in ensuring the safety, quality, and excellent working standards of electronic products.

What is PCB test equipment?

PCB testing equipment includes special tools that are used for checking the PCB.  This testing equipment includes multi-meters, oscilloscopes, function generators, and dedicated testing fixtures.

Is PCB mechanical or electrical?

PCBs are technically electrical in nature. They maintain electrical connections among components.

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