The printed circuit board (PCB) is a crucial component of the electronics sector and helps in various applications. Therefore, it is essential to test the PCBs to ensure the design complies with the specifications and that the final product is of excellent quality. This article will cover the crucial procedures involved in testing a PCB, the various testing techniques, the equipment, and the advantages of the PCB testing.
PCB testing is a fundamental requirement in the PCB manufacturing sector. It focuses on looking at particular specific board standards. The PCB testing will show whether the design satisfies the requirements to meet its standard. Therefore, this assures end customers of the product’s integrity.
The Primary PCB components tested
The PCB lifeline relies on the lamination quality – the final functionality of a given board may expereince issues due to a peeling laminate. Generally, when you perfrom tests on the lamination, you check out the laminate’s resistance to peeling whenever there is application of heat or force.
- Copper plating:
We laminate the PCB with copper foil to provide or enhance conductivity. Still, we need to test the copper quality with the use of tensile strength and analyze the elongation for more details.
- Hole wall quality:
This ensures the hole walls have no signs of cracking or delaminating once the PCB is released to the field. We expose the hole walls in regions experiencing cycling and quickly adjusting temperatures to check the reaction to thermal intensity.
One must test the material’s solderability to ensure proper functioning of the PCB. This ensures firmness when attaching components to the Board and also prevents the final product developing soldering defects. Wetting is among the most factor to analyze and it refers to a surface’s capability in accepting liquid solder.
You must test the PCB’s electrical conductivity and ensure it can pass electric currents with less to no leakages.
Since most PCBs are suited for humid environment operations, the standard test is water absorption. As the designer, you weigh the board before setting in humid environment and also do so after. If there is significant change in weight, it could indicate a failing grade for the PCB.
The cleanliness of PCBs means they are resistant to environmental factors like humidity and corrosion. You undertake the tests by doing an analysis before and after exposure to different ecological conditions.
Tools for testing PCB
- Analog/Digital Multimeter:
A multimeter is an essential tool for testing PCBs. It measures AC and DC voltage, current, resistance, and other parameters. This tool helps test whether a circuit is functioning correctly and diagnose problems. Additionally, it helps to measure the voltage and current of components such as resistors, capacitors, and inductors. Furthermore, the tool measures the quality of connections between components and the PCB.
- Soldering Gun:
A soldering gun joins two pieces of metal or electronic components. For example, this tool connects two pieces of metal or attaches components to a PCB. Using a gun with a temperature suitable for the material the manufacturer is soldering is essential. This action will help to prevent damage to components.
- Desoldering Station:
A desoldering station removes components from a PCB. This tool also removes components the designer soldered incorrectly or replaces damaged ones. Using the correct station type when desoldering materials is essential to prevent damage to the components or the PCB.
- Magnifying Glass:
A magnifying glass inspects the PCB for any visual defects or damage. Examining the components and their connections to the PCB is essential to ensure everything functions correctly. Additionally, magnifying glass detects any signs of corrosion, burnt components, or broken connections. This can help you diagnose problems and fix them before they worsen.
PCB Testing Methods
PCB testing methods have evolved, and different testing methods are available today. This section will discuss four of them and their advantages and limitations.
1. The In-Circuit Test (ICT) Method
One famous PCB testing technique is the in-circuit test (ICT). Engineers examine the electrical connections of the components on the PCB using this non-destructive testing technique. ICT uses a customized test fixture with several probes that come into contact with the test spots on the PCB. The ICT then checks the PCB for any component flaws once the investigations have sent an electrical charge through it. ICT is a quick and effective testing technique that can immediately identify component defects in the PCB. It can reduce testing time and expenses and is appropriate for high-volume production. It does have some restrictions, though. Components not connected to the test sites cannot have problems detected in them. Moreover, it cannot test parts not mounted on the Board.
2. Fixtureless In-Circuit Test (FICT)or the Flying Probe Test
A specialized test fixture is unnecessary for the FICT, also called Flying Probe Test, a PCB testing technique. Instead, it uses a collection of roving probes to check the component electrical connections on the Board. The probes can reach all of test spots on the PCB because they may move in any direction. PCBs with intricate designs can be tested using the adaptable FICT approach. Due to the lack of a specialized test fixture, it is also a cost-effective testing technique. However, because it operates more slowly than ICT, it might not be appropriate for high-volume production. The FICT is suitable for prototype and low-volume production.
3. Burn-in Testing
The burn-in testing type helps in testing the PCB. Acute circumstances arise as a result that exceeds the design criteria. The test demonstrates the flaws and confirms the PCB’s load strength in adverse conditions. The power source operates primarily at its best efficiency, running at a high temperature. The PCB might be in danger from this.
4. Functional Circuit Test
A PCB testing technique that examines the functionality of the PCB is the functional circuit test. Designers can subject the PCB to a series of test signals, and the output signals are then measured. The test signals mimic how the PCB in an electronic gadget operates. The Functional Circuit Test determines whether or not the PCB’s components are functioning correctly and generating the desired output signals. The Functional Circuit Test is a reliable technique to find PCB component flaws that other testing techniques might miss. It is appropriate for prototype and low-volume production. Unfortunately, it is a labor-intensive testing technique that needs specific test tools.
5. In-Circuit Functional Test
A thorough testing technique that combines the ICT and the Functional Circuit Test is called the In-Circuit Functional Test. Using a dedicated test fixture, it applies a series of test signals to the PCB while also examining the electrical connections of the PCB’s components. The In-Circuit Functional Test determines whether the PCB’s components are operating correctly and generating the desired output signals by simulating the fundamental operation of the PCB in an electronic device using test signals. It takes specific testing tools to perform the In-Circuit Functional Test, which is a challenging testing technique. Nonetheless, a particular testing technique can find problems with the PCB’s parts and guarantee that the PCB is operating correctly. It can reduce testing time and expenses and is appropriate for high-volume production.
6. Automated Optical Inspection (AOI):
AOI performs a mechanical visual examination of the PCB. Throughout the test, the designer examines the PCB with a high-focus camera to spot frequent issues and catastrophic failures. The manufacturing industry typically utilizes this type of testing since it is contactless. It helps the production process in numerous phases as well.
How to test a PCB includes:
1. Visual Inspection:
Doing a visual examination is the initial stage of checking a PCB. Visualization entails inspecting the Board for any glaring flaws or potential problems. This process involves looking for any damage to the Board’s components or traces and any damage to the Board itself. During a visual check, there are a few specific items to look for, including:
- Physical Damage:
Inspect the Board for any physical damage, such as cracks, scratches, or other flaws. The Board’s edges should receive special care because it is where damage is most likely to happen.
- Solder Joints:
Verify the Board’s solder joints to ensure they are correctly made and joined. Look for any chilly joints or separate areas.
- Component Placement:
Make sure that every component is positioned and aligned correctly on the Board. Check to see if any parts are missing or misplaced.
Inspect the Board’s traces to ensure no breaks or shorts. Additionally, Verify whether you have linked each trace securely to the appropriate component.
2. Power Module Testing:
Testing entails ensuring the power supply is operating correctly and that the voltage and current levels are within acceptable bounds. Do the following actions to test the power module:
- Power On:
Connect the Board to the power source and turn it on. Verify that the power supply’s voltage and current settings are correct.
- Voltage check:
Measure the voltage levels all around the Board using a multimeter. Check whether the voltage levels fall within the parameters listed in the Board’s documentation as acceptable.
- Current Check:
Check the current levels everywhere over the building with a multimeter. Check to see if the stories are acceptable within the parameters listed in the Board’s datasheet.
Examine the power module’s heat output. Use a temperature sensor or a thermal camera to ensure the temperature is within acceptable bounds.
3. Check the Input/Output Ports:
The third stage in inspecting a PCB is to check the input/output ports. I/O ports are the interfaces that allow the PCB and other devices to communicate. While checking the I/O ports, you should follow the procedure below:
- Check for connection:
Verify that each I/O port is wired correctly and communicates with the Board using the appropriate signals. Analyzing the signals with an oscilloscope will ensure the integrity of the I/O ports. The signal ought to be undistorted and noise-free.
- Check for signal integrity:
Use an oscilloscope to check the signal integrity of the I/O ports. The signal should be clean and free from any noise or distortion.
- Check for short circuits:
A multimeter checks the I/O ports for short circuits or other issues. Short circuits could cause damage to the PCB and other components.
4. Check Communication Ports
This step involves examining the communication ports. The communication ports are the points of interaction between the PCB and external components, such as computers or microcontrollers. Do the following actions to inspect the communication ports:
- Check the connection:
Verify that each communication port is wired correctly and sending the right signals to the Board.
- Check the integrity of the signal:
Check the communication ports’ signal integrity using an oscilloscope. The signal must be clear and devoid of distortion or noise.
- Test the communication protocol:
Use the proper testing tools or software to assess the communication protocol. Check that the data is transmitted and received without interruption and that the communication is effective.
- Check for short circuits:
Use a multimeter to look for any short circuits or other issues in the communication ports. Short circuits could cause damage to the PCB and other components.
Benefits of PCB Testing
PCB testing has the following benefits:
- Bug identification:
The main advantage of PCB testing is that it aids in the detection of PCB issues. PCB tests find issues in a PCB design so that designers can make the necessary adjustments, whether the fault is with functionality, manufacturability, or somewhere else.
- Time savings:
PCB testing early on can help designers save time later on by allowing them to spot important problems during the prototyping stage. In addition, comprehensive testing allows designers to swiftly and readily identify the underlying cause of each problem presented, making improvements so they can forward with manufacturing more quickly and shorten product lead time.
- Cost reduction:
By evaluating the products using prototypes and small-scale assemblies, PCB testing avoids the wasteful creation of defective products. Designers can avoid costly full-scale assemblies of defective PCBs by doing comprehensive testing early in the design phase, ensuring the design is as error-free as possible before it is put into production. Significant production cost reduction is made possible by this process.
- Less returned goods:
When businesses test their PCBs, they reduce the likelihood that they will sell goods that are flawed or fall short of expectations. As a result, they experience a decrease in product returns, which lowers expenses related to processing defective products and refunding clients. Having fewer returned goods can also boost customer satisfaction and enhance a company’s reputation.
- Greater safety:
Due to PCBs’ importance in fundamental electrical technologies, their failure can seriously affect a company’s productivity or capacity to deliver crucial services. A faulty PCB could start a fire, thereby endangering people around. Testing before to manufacturing can help prevent equipment damage or worker injuries brought on by a defective design.
In conclusion, PCB testing is crucial in manufacturing PCBs and offers several advantages. It assists in locating problems with a PCB design, saving time and resources and lowering the likelihood of defective goods. Furthermore, it safeguards users from any harm from a faulty PCB and maintains worker safety. A product’s compliance with performance requirements and customer expectations is further ensured by testing.