The PCB is the fundamental element of any electronic circuit. Regardless of the application, all PCB assemblies must meet the common requirement to function correctly to project specifications and be free from defects. In addition, the latest generation electronic circuits include hundreds of components and thousands of welds and interconnect. Therefore, it is essential to define rigorous control and testing procedures to ensure the quality of the final product. Let’s look at some of the most superior PCB assembly testing methods.
The situation in which the elements in the package prepared for serial assembly were defective copy is not something unusual. Detecting it at this stage means a slight loss in the form of a specific element, which, even in an advanced integrated circuit, is only a tiny fraction of the value of the final device. However, if the damaged component goes to assembly, it will only become noticeable when starting the finished board. At this point, the losses become pretty annoying. Recognizing the module as unrepairable and placing it in the trash can, we bear the cost of the board, assembly, a set of soldered elements, and finally wasted time of the commissioning person. Reliable PCB assembly suppliers know that testing is simply essential.
Purpose of PCB testing
PCB assembly is a process by which a company assembles various electronic components onto a printed circuit board. Many people confuse this process with PCB manufacturing, but these are entirely different processes. PCB manufacturing involves many sub-processes such as prototyping and design. However, the assembly process involves attaching components to the printed circuit boards. PCB assembly process begins after the manufacture of printed circuit boards. First, the assembly is performed under the supervision of experienced engineers. Then, the PCB must undergo appropriate tests so that the manufacturer can be sure of its quality.
Without carrying out, you cannot count on the highest quality of the finished product. Only through the testing process can you identify errors and various faults such as short circuits. Testing components before starting the assembly process saves time and money. Because if you have any problems after assembling the whole circuit board, you will have to repeat the assembly process repeatedly.
A professional PCB assembly supplier knows the value of testing, so his internal team is responsible for carrying them out. Each PCB undergoes a comprehensive testing mechanism. By outsourcing the assembly service to such a company, you can count on the final product to be of the highest quality and fully functional. Vendors offer a wide variety of tests with both in-circuit testing and 100% functional testing. Let’s take a look at the most popular PCB assembly Inspection and Testing Methods.
Functional tests (FCT)
Functional testing is arguably the most critical part of the test cycle. Functional testing (FCT) checks partially PCB assembled devices or final devices to operate a specific functionality and comply with the parameters specified in the product specification. It is a form of verification carried out on the finished product to check whether the product works – it will turn on, whether it complies with the requirements and specifications of the customer, and whether all elements work together consistently. PCB assembly suppliers should test the product with cooperation with the OEM. The OEM decides what is to be checked during the test. Functional tests are essential because they allow you to guarantee the highest quality of the product before it is released to the market.
In-circuit (ICT) test
In-circuit testing (ICT / FICT) is about checking connections and components on the PCB, analyzing the electrical parameters of the entire circuit or its sections. In other words, the ICT test aims to identify manufacturing defects and check the PCB assembly functions according to the specifications. In-circuit testing (ICT) is the consolidation of various test tools into one. It often requires the use of complex equipment and appropriate technological preparation. The test system connects to the PCB with test leads that relate to the test points on the PCB. Thus, it is an electrical check of circuits and components for critical values. In some cases, high-frequency plates require characteristic impedance monitoring.
Automatic Optical Inspection (AOI)
Today’s Automatic Optical Inspection System (AOI) methods in PCB assembly testing guarantees an excellent product. AOI is made at a very early stage of PCB production. As a result, faults can be detected early and corrected. As these defects are seen earlier in the production process rather than late, the time and money savings are significant. A notable advantage of optical testing is its high efficiency (several tens of seconds per plate) and the ability to locate undetectable defects. The main disadvantage of visual methods is that they are unfortunately not able to verify the invisible areas.
3D Automated X-Ray (AXI)
A visual inspection is often insufficient to check the solder joints of standard components. Therefore, X-ray inspection is required as an alternative verification method. X-ray radiation automatically scans the plate and detects errors that are invisible during visual inspection. 3D CT X-ray inspection is necessary to detect voids, hidden defects, or even defects related to the correct distribution of solder paste under the components. X-ray testing is costly, so it is not always profitable to perform a complete product inspection. However, no doubt carrying out an X-ray inspection of the printed circuit boards guarantees the highest quality of assembly work.
Such tests check the compliance of the constructed product with the relevant standards of functionality, safety, and durability within the product specification declared by the manufacturer. Thanks to this, they guarantee the reliability and high quality of its products. To carry out environmental tests, it is often necessary to use an appropriate temperature and humidity chamber or thermal shock chamber, which enables verification of the correct operation of the developed circuits in an extensive range of temperatures and relative humidity. In addition, appropriate conditions allow you to accelerate the aging process of the product. Thanks to this, it is possible to predict its life cycle and analyze the failures before implementing the product.
It is a well-known principle that the weakest component determines the reliability of a device. The second rule says that the sooner it is detected and eliminated, the fewer losses it causes. Whichever method you choose, PCB assembly testing is a fundamental step in the electronics manufacturing that saves a notable amount of time and money by identifying any faults affecting the circuit. Overall, an appropriate combination of the inspection and testing methods listed above will detect all possible failures at varying costs depending on the specific application and complexity of the circuit under test.