Printed Circuit Boards are the most used and basic assembly unit applied by all types of electronic devices. All functions and performance of devices are implemented mainly by PCBs. PCB is the heart of electronic devices and both their quality and reliability is directly correlated with quality and reliability of electronic equipment. Nowadays, intelligence and miniature of electronic devices leads to increasingly smaller size and complicated structures of PCBs.
In terms of PCB performance, it can be testified that even if schematic is correctly designed, subsequent assembly and debugging will still be influenced if PCB design and manufacturing receive low-qualified processing while undemanding quality inspection is carried out on PCBs. Therefore, it's especially important to implement quality control in the process from PCB design to PCB manufacturing.
The task in quality control of PCBs comes primarily in effective administration, monitoring and measurement on PCB design, circuit board manufacturing and PCB inspection.
Quality Control in PCB Design
In order to ensure quality in PCB design, your task should cover the following three aspects.
• Validity of PCB design file has to be ensured.
Project leader should be responsible for checking PCB design file and corresponding approval procedures have to be implemented so that validity of PCB design files has to be ensured.
• Manufacturability of PCBs has to be ensured.
Project leader and technologist should strictly conform to technological requirement in order to ensure manufacturability of PCBs. Technological requirement can be directly listed on design drawings if it is relatively simple. Otherwise, it has to be summarized into a text that is saved in additional file. No matter what is the simplicity of technological requirement, it has to be explained ACCURATELY, CLEARLY and REASONABLY. Technological requirement after checking should not only meet the present production craft level with high cost effectiveness but also leave much convenience to implementation of subsequent assembly, debugging and checking.
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• Testability and Normalization has to be ensured.
Standardiser implements normalization checking in terms of test points, structural style, dimensions, routing, through-hole via and characters so as to ensure testability and manufacturability of PCBs which should conform to requirement of national and industrial standardization.
Quality Control in Production of PCB
In order to ensure quality in PCB design, your task should cover the following three aspects.
• Capability of manufacturers has to be ensured.
Quality department, together with sourcing department should investigate and approve aptitudes and manufacturing capability of PCB manufacturers in order to ensure their sufficient manufacturing capability on your design project.
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• Checking and confirmation have to be constantly done prior to manufacturing.
PCB designers have to check and confirm the design drawings that will be applied by manufacturer for many times prior to manufacturing. Since PCB design can't be successful just after one trial and modifications have to be made time and time again, PCB manufacturers will hold multiple versions of design drawings. So it's necessary to carefully check and confirm the final design drawing provided by manufacturer prior to practical manufacturing so that manufactured PCBs conform to requirement of the last version.
• Much attention should be paid to the key procedures of PCB manufacturing.
The quality of key procedures of PCB manufacturing influences a lot on performance and reliability of PCBs and quality control on that has to be strengthened. The key technological procedures formulated by PCB manufacturer have to be monitored and checked including etching, via mentalization etc. so as to ensure absence of burr, gap, bridge defect and void. Furthermore, quality control has to be overtaken on stacking of multi-layer PCBs in order to ensure the thickness, adhesive intensity and positional accuracy. Since gold plating is usually required by high-frequency PCBs and micro-strip boards, specific gold plating operation instructions have to be made in order to ensure the thickness and purity of plating plane.
Quality Control in PCB Inspection
Quality control in PCB inspection refers to monitoring and measurement of PCBs in strict accordance with inspection through visual inspection or the application of professional equipment. The inspection result has to be stored. If special requirement needs obtaining, specific acceptance rules have to be made additionally. Specific PCB inspection items will be introduced in subsequent articles.