An important part of PCB assembly is the testing part of the process. It is never enough to just settle for creating the right number of PCB for any given time with the use of all the given instructions – the quality of the product matters just as much as following the guidelines in making them. The process of PCB assembly is never complete without inspection and testing, and we always try to do our best to diagnose and correct any problems early on in the process in order to avoid damaged products from getting in the hands of customers.
Nothing frustrates a customer more than the experience of having a product with a defect which could have been avoided entirely with more quality regulations.
Luckily, we never have had to experience any sort of discontent from customers due to the fact that rigorous quality analysis through testing and diagnoses are done during the PCB assembly process. The process of detecting errors and reworking on them in order to make sure that no problems ever get out from production is integral in the Quality Management Principles which guide us in PCB assembly.
High yield and quality are maintained thanks to multiple tests done on SMT equipment and on the produced PCBs, since we realize that only a couple of tests would only be so successful in getting all the problems out of the way of effective production.
One of the most common quality inspection processes that we do is visual inspection.
The mere observation of the products during the course of production can actually allow for the detection of many problems on the products before they go any further in being finished. A visual inspection allows us to see and correct problems as early in the production process as possible. This in turn greatly reduces costs in reworking of products and in the wastage of unusable, defective materials.
The visual inspection part of the quality process involves the use of a microscope to visually check each nook and cranny of every PCB. This process begins at the solder stencil printer level, with visual control systems being used in order to align stencils. After the printing of the screens, inspection checks are done to make sure that the components correctly reflow. Screen printing in itself is a complex and error prone process because of how delicate the work is, which is why it is very important to test each product first before it goes any further.
Another important part of quality control is the pre and post reflow inspection. The pre-reflow inspection is the part of the process which checks if there are any placement errors made during PCB assembly. At this point, errors are relatively easy to correct, which is why this part is more rigorous than the post-reflow inspection. This process is even more important for automotive boards where the compliance standards are really high, and require that the PCBs can no longer be reworked. The destruction of the boards can also be prevented during this stage since the components are sensitive to heat.
On the other hand, a post reflow inspection, unlike the pre reflow process, involves the use of more equipment, since the products are already considered as ready for release, and any corrections to damaged products are not as easy to fix at this point. Certain devices are used in order to check the PCBs, including computed tomography (CT) scanning, endoscopes, microscopes, and X-ray machines. Probably the most effective method of detecting errors is with the use of a 3D X-Ray machines, which easily detects misalignment and other mistakes that will otherwise go unnoticed with any other methods of inspection.
In addition to these, post reflow inspection also includes bed of nails, custom test boards, and flying probes. These options have their pros and cons, and how we select the one to be used for the products would depend on the product specifics and requirements.
Flying probe testing is a good testing method to use for high complexity boards. The setup of this kind of testing procedure does not require as big of a cost as any other testing method, and it can be both installed and used within the same day. What happens in this process is PCBs produced are compared to a golden board’s measurements through electricity. This process will help determine if the produced PCBs are able to do their job of circulating electricity correctly, and helps in determining if the correct alignment and placement have been made on the PCBs.