Although strict process management is implemented in the production of PCB circuit boards, in the actual production process, some unfavorable conditions that do not meet the process requirements often occur. According to the standards and requirements of total quality management, these defective products need to be sorted out. , and analyze and deal with these defects.
Cognitive quality control in PCB production
(1) Cognition of quality inspection in PCB production
① Cognition of the purpose of quality inspection in PCB production. Find and eliminate errors during the SMT assembly process to achieve good process control and improve product yield.
② Cognition of the role of quality inspection in PCB production. Early detection of defects prevents defective products from flowing to the next process and reduces repair costs; timely detection of defects and timely processing avoids the generation of scrapped products and reduces production costs.
③ Cognition of quality inspection methods in PCB production. When it comes to means, there are mainly the following methods for PCB quality inspection:
Visual inspection: that is, to directly observe and check the quality of PCB products with human eyes. In the actual production process of PCB, there are visual inspection processes after printing paste printing, chip placement, reflow soldering, wave soldering and online inspection, which are pcb printing visual inspection, post-furnace comparison visual inspection, assembly visual inspection, and quality inspection.
Its characteristics are: the cost is low, and the inspection effect is related to the PCB mounting density. In the case of low-density mounting, the reliability, accuracy, and continuity of inspection vary from person to person. In the case of high-density mounting, the reliability, accuracy, and continuity of inspection are generally reduced, and the inspection time is correspondingly longer. long.
PCB mounting density
AOI inspection: Automated Optical Inspection (AOI), which uses automatic optical equipment for inspection, is an alternative to visual inspection. Usually there is an AOI inspection process after printing paste printing and reflow soldering.
Its characteristics are: the detection system has nothing to do with PCBA mounting density, fast detection speed, high precision, and high reproducibility. Bad detection results are directly marked on the PCB with ink or marked with graphic errors on the operation display.
ICT detection: line test (In-circuit Tester, ICT), that is, use a line tester to diagnose line faults. Usually there is an ICT inspection process after the PCB is assembled.
Its characteristics are: the fault diagnosis ability is extremely strong. For welding defects such as bridging, empty welding, virtual welding, and broken wires, the solder joint position can be directly displayed; welding defects caused by component defects can also be detected, as shown in Table 1.
(2) Quality control in PCB production
1. Build a document system for quality control in PCB production.
1. Establish PCB quality inspection system;
2. Formulate PCB quality inspection standards;
3. Formulate visual inspection, AOT inspection, ICT inspection and FCT inspection operation specifications;
4. Guidance on the use of standardized testing equipment (AOI detectors, ICT detectors and FCT detectors);
5. Develop inspection record forms or labels;
6. Precautions for standardizing equipment operation.
2. On-site management of quality inspection in PCB production
Full-time, trained quality management and inspection personnel strictly implement the PCB quality inspection system inspection process. Set up visual inspection or AOI inspection after solder paste printing, set up visual inspection after placement, set up visual inspection or AOI inspection after reflow soldering, set up ICT and FCT inspection after wave soldering, and then set up assembly visual inspection and quality inspection ; All tests are based on inspection standards to judge whether the quality of PCB products is good or not, and record the test results for future reference or affix corresponding labels on the products; the use of all equipment is correctly operated according to the instructions for use; all testing processes are carried out according to standard procedures, all Record accordingly, etc. For example, the requirements (notes) for ICT testing: the machine is operated by a dedicated person, non-designated personnel are not allowed to operate or modify the program without permission, and unrelated personnel are prohibited from using the machine; operators must wear qualified electrostatic rings or electrostatic gloves, and are not allowed to wear metal ornaments ; It is forbidden to do functional testing; when placing the board, handle it with care so as not to damage the components; if the machine breaks down or the same bad situation occurs three times in a row, immediately notify the corresponding engineering and management personnel to deal with it. process.
Operation steps during ICT testing: Check the material number, scan the operator code, take the board to be tested, open the socket cover, visually inspect, install the pcb board, close the cover, scan according to the main screen, get the test result, open the cover, Take out the test board.
The above are the quality control requirements in the pcb production process, and pcb manufacturers can do better by strictly implementing this standard.
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Business manager：Jack lee