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QA: More than Meets the Eye
December 31, 1969 |Estimated reading time: 5 minutes
By Jacob Rubin, Proventus Technologies Ltd.
To the main challenges that the electronics manufacturing industry is facing today belongs the question: how can the industry's conversion-cost roadmap be reduced in the cost per I/O of each assembly over time? An important factor in minimizing this conversion cost is assuring higher quality, thereby delivering higher utilization, shorter product cycle times and reduced cost of test, and lowered instances of repair and scrap.
Achieving higher quality levels is a constant and familiar goal in the electronics industry. Manufacturers know that, if they fail to improve quality performance, they will not be able to reduce manufacturing costs. Thus, every PCB assembly line includes some kind of quality assurance (QA) mechanism. In recent years, a significant number of manufacturers understood the importance of such mechanisms and began seriously investing in QA technologies such as in-circuit test (ICT), automated optical inspection (AOI), boundary scanners, and others. These technologies, combined with visual/manual inspections, enable QA at various stages of production, such as paste print, soldering/reflow, touch-up, functional test (FT), and final quality control (QC).
The SMT industry has managed to address several of the mentioned challenges. It is proven that the SMT method of electronics assembly works well in productions with a high degree of automation, reducing labor costs and increasing the production rates. However, the question remains whether a faster and highly automated assembling process is able to guarantee high-quality product. The importance of QA to the future of a given product and its market value, to the credibility of the manufacturer, and finally to the confidence of the customers cannot be neglected and constantly has to be addressed.
QA often is carried out by planning the production carefully and trying to prevent defects. However, this is hardly achieved, due to the difficult analysis process. Many defects are caused by fixable failures in planning (i.e. wrong shape) and technology (i.e. bad mask or placement). In most operations, PCB manufacturers can only manually and retroactively fix the planning and technology failures using traditional methods such as ICT or more advanced ones such as AOI or automated x-ray inspection (AXI). To ably identify and prevent possible defects at an early stage, these operations require assistance from additional technological tools. Most companies use reports and charts to analyze the data, but these methods are too simplistic and limited to unravel many defects' causes.
The complicity of such examination processes can result in collected defect information being used solely for repair purposes, like manually fixing particular defects on specific PCBs or rejecting the PCBs altogether, depending on the defect. Locating failures retrospectively presents a problematic situation for the manufacturer and is inefficient and costly in labor and materials. With early identification, some harm can be eliminated and defects prevented. Manufacturers with a long-term perspective will have to look out for other methods and technologies that can tackle and solve the mentioned problems.
One such method is the defects per million opportunities (DPMO) process, an active alternative to the measured yield metric. Its benefits to electronics businesses include creating an environment where the delivered quality of manufacturing processes is constantly improved and the PCB assembly costs can be estimated as early as possible, which will help reducing costs of assembly, test, rework, and scrap. However, effective results from DPMO measurements that would influence cost reduction activities and assist in strategic decision making can be only achieved through implementing other tools capable of interpreting the information collected.
In the electronics manufacturing industry, there is a demand for tools that consider yield increase together with DPMO compatibility, while not compromising on quality assurance. Several companies have begun developing solutions to meet these demands, but their effectiveness is measured by user-friendliness and whether the QA specialists at any given factory are able to apply them without any specific knowledge and training. Furthermore, it is preferred that such a technology would not be connected with additional expenses for its deployment.
Software applications that don't require extra infrastructure or hardware, other than a regular PC station, are effective and simple solutions. A dynamic visual analysis software solution can detect and prevent defects on PCB topography, while calculating DPMO. One such product* maps several defect data sources AOI, ICT, visual manual inspection (VMI), and others as well as PCB design data as input data to the PCB components, creating a color-coded map of defects on the PCB's geography (Figure 1). This is designed to make it easier to find the damaged area or root cause of a defect. This form of presentation unravels patterns in the defect spread that are otherwise invisible, since defects can be concentrated in certain geographic areas due to a damaged mask, temperature-spread problems, or other causes. This process helps the inspector to find solutions for preventing the same defects in the future. Another benefit of visual analysis software tools is that they are applicable for OEMs with either in-house or outsourced production and can be used by small and large operations for small batches through mass production.
It cannot be neglected that the common use of automatic advanced technologies such as AOI, ICT, boundary scan, and others that assure quality of the PCB, companies could not have yet fully replaced VMI, which includes examination and correction of faults in production lines. In many companies, manually locating the faulty diodes on PCBs still takes place. This takes up a lot of time and doesn't always guarantee accurate data. A software tool that can locate the faulty component and to point it out for the inspector can be of great assistance. One program** uses CAD data to provide the PCB layout on the QC inspector's computer, for easier and faster identification of faulty components (Figure 2). Through this method, faulty boards can be traced back to inspectors who failed to identify or fix the defect, which can be significant to managers that supervise and interpret productions.
ConclusionIn the long term, the level of quality assurance a product receives will remain a leading factor to determine a company's value and its status on the market. Companies that wish to sustain competition and save unnecessary costs for inspection and correction will have to put the acquisition of enabling QA tools high on their agenda.
* TopoQC** DCollector
Jacob Rubin, CEO, Proventus Technologies Ltd., may be contacted at jacobr@proventustech.com, www.proventustech.com.