Along with the demand for miniaturization of electronic products, we are faced with the serious challenge of producing products with hundreds of parts that are not visible under normal conditions. The surface mount manufacturing industry faces the following major challenges:
We are trying to assemble sand-sized components onto hundreds or even millions of PCBs with extremely high component density. During the assembly process, the equipment we use may cause occasional or frequent systematic positioning deviations due to a number of factors. These factors include: aging problems; the ability to mount 0402 or 0201 components; the problem of maintaining accurate placement and positioning; the time before the 0402 slabs are produced due to the accumulated debris nozzles; The number of components installed; the ability of the operator to flip the reel. In addition to this, there are quality problems with standard solders. These are enough to make people understand why the cost of poor product quality is huge. Wait until the error is discovered, it is too late, some errors are found during online testing, and online testing can find up to 60% of errors. Many products cannot be tested online due to high assembly density or design characteristics. Some errors are Found during functional testing (if such testing is performed on the product). Most of the defects are discovered by consumers. Most of us have either suffered from inferior products or have read reports of bad quality records and large returns in newspapers, which is much more expensive than the cost of rework.
These errors are caused by the lack of automatic optical inspection equipment during the production process. Many of these errors are not detected by the naked eye. Even if there is time to test a board for several hours, it will not help. However, the only test method used in many countries, including China, is visual inspection. Even more surprising is the fact that each tester detects a board with more than 400 small components for an average of 10 minutes. For the same inspector, even if he was given 40 minutes to check the simpler board of the larger component, he could not see 90% of the problem. And this problem is not only related to medium-high capacity SMT. I have noticed similar problems with high-mixing-low-capacity surface mount products. In many cases, rapid switching often causes serious problems in the SMT process.
Ultimately, without the use of AOI, there is no reliable way to guarantee the inherent quality of surface mount products. Although the image-based automatic optical inspection device has defects and does not support medium-high-capacity surface mount, the parametric automatic optical inspection device can fill this gap. Whether you choose image comparison for low volume placement or parametric type for medium to high volume placement, manufacturers have the ability to perform 100% AOI support testing. Efforts by manufacturers to implement reliable automated optical inspections will not only reduce their own production costs, but also ensure the quality of most consumer products. This is the most basic expectation for advanced SMT manufacturers in the 21st century.