PCB board, also known as a printed circuit board. The quality of PCB determines the quality of electronic components to a large extent. Therefore, in the process of producing PCB boards, inspection is a very important part. Through PCB inspection methods, it is usually possible to find out poorly assembled circuit boards, such as open circuits and short circuits and other defects affecting functionality. Printed circuit board testing can minimize major problems, find minor errors, avoid defects found after PCB assembly, dismantle and reorganize, save working time and reduce overall cost.
Visual Testing is the simplest and basic PCB testing method that utilizes operator visual inspection to determine whether a board fits or fails.
However, PCB visual inspection is downside should not be overlooked for its ease: it is susceptible to human error, has high long-term costs, data collection difficulties, and the inability to detect small and invisible defects.
Due to the increasingly stringent requirements for PCB production, increasing competition in the market, and the continuous and precise reduction of components, manual visual PCB inspection is no longer feasible.
ICT testing, by touching the pins of each component on the PCB assembly and measuring whether its value is consistent with the nominal value, Including some pre-installed electronic probes that align under the PCB board with preset access points is an important PCB testing means to check the value of resistors, capacitors, inductors and other components.
(1) ICT testing can check for shorts or opens, solder mask defects, misplaced or missing components, etc;
(2) The method includes test jigs to properly hold the board with probes, and test jigs to inspect multiple components;
(3) PCB ICT testing is used in high-volume PCB production, accurate and free from human error.
(1) It is not suitable for small-batch production;
(2) Requires test fixtures, programming and debugging time;
(3) The cost of making fixtures is high, and it is difficult to use. Technologies such as test fixtures will increase costs;
(4) Unable to detect voids or insufficient solder mask.
PCB board Functional system testing is to use special testing equipment in the middle and final stages of the production line to conduct a comprehensive test on the functional modules of the circuit board to confirm the quality of the circuit board.
FCT testing often involves simple switching tests, sometimes it requires complex software and precise protocols. Functional testing directly checks the functionality of the board under real environmental conditions.
The Advantages of FCT Testing:
(1)Through functional testing, errors, defects or damage in the PCB manufacturing process can be found to ensure the quality and reliability of PCB boards and improve production efficiency
(2)Through functional testing, the number of defective PCBA manufactured can be reduced, the cost can be reduced, and repair and warranty costs caused by product failure can be avoided.
(3)Functional testing can help identify fault points on the PCB board without affecting the life of the board
The Disadvantages of FCT Testing:
(1)PCB Functional testing requires specialized test equipment and requires experienced technicians, thereby increasing manufacturing costs
(2)Functional testing usually only verifies the basic functions of the PCB board and cannot cover all possible usage situations. Some specific PCB problems may require other testing methods and PCB board testing equipment to discover.
Flying probe testing has been proven by the PCB Assembly industry to be a particularly cost-effective test method for raising board standards.
Flying probe testing uses two or more independent probes that operate without fixed test points. These probes are electromechanically controlled and move according to specific software instructions. Flying probe testing is used to check:
Resistors, capacitors, inductors, no-hole vias or terminations of components, etc.
Advantages of Flying Probe Test:
(1) The initial cost of flying probe testing is low, and it will be cheaper than in-circuit testing
(2) No fixtures are required
(3)Greater pcb test coverage
Disadvantages of Flying Probe Testing:
(1)The efficiency of PCB testing is not high. After all, the flying probe test is a point-by-point test of moving the probe, so it is very time-consuming.
(2)Difficult to set up if the board does not include any test points, test vias, or masked vias
Also known as automatic visual inspection, it is based on the principle of optics and PCB inspection machine uses various technologies such as image analysis, computer and automatic control to detect and process defects encountered in the process of PCB processing. It is a newer method for confirming manufacturing defects.
AOI testing is used in the PCB production process before and after reflow and before electrical testing. After the copper foil on the PCB is etched out of the circuit pattern, the AOI test is performed. The graphics on the equipment scanning board are compared with the design documents to distinguish the graphics status of the PCB board surface, and then compared with the PCB board surface graphics data stored by AOI itself. If there are pcb testing meets questions, the defect will be reported, and finally confirmed by the inspector processing to complete the entire detection process. The cost of correcting defects at this time is far lower than the cost of the final test, often reaching ten times.
Advantages of AOI Testing:
(1)AOI testing can find all visible errors very accurately.
(2)AOI testing can be included directly on the production line to prevent any premature board failures.
X-ray Inspection Detect errors in hidden components, solder connections, BGA packages, internal traces, and gun barrels with X-ray imaging.
Advantages of X-ray Inspection:
(1) No need to inspect every layer of the PCB
(2) X-ray machines can easily inspect internal layers from the top of the circuit
Disadvantages of X-ray Detection:
(1)This requires experienced and skilled technicians
(2)The process requires more labor and cost
PCB testing and inspection is a key component of the quality control process during manufacturing. These PCB testing standards help find defects early in the production cycle, allowing PCB manufacturers to take corrective action quickly and efficiently. This improves PCB board quality and reliability, increases efficiency, and reduces costs associated with scrap and rework.
But don't rely on only one PCB detection method, choose the PCB reliability test, you should use a variety of PCB inspection checklists
· AOI test and flying probe test
· AOI test and in-circuit test (ICT)
· Functional testing and X-ray testing
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