Measurable mechanical accuracy

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Increasing mechanical demands on printed circuit boards

At Becker & Mueller, the processes are constantly being optimized and further developed. Technology and quality have always been the focus. For example, through investments in new milling and drilling systems, the introduction of direct exposure and the development of special customer tools, the portfolio has been expanded over time and production further optimized. The results are documented by integrating a video measuring microscope from Garant and corresponding measurement protocols for the customer – measurable mechanical accuracy.

However, improvements were not only due to new CNC machines. In addition to special parameters for the wet-chemical processes, the entire process has also been optimized. All improvement measures have a positive influence on the quality of the printed circuit boards. In addition, the PCB are at precise mechanical requirements are not only measured manually, but compliance with the specifications also ensured with a video measuring microscope.

Measurements are taken with a video measuring microscope from Garant. Garant is part of the Hoffmann Group and this, with its development teams, focuses on areas of application such as machining, clamping technology, hand tools, factory equipment and more. The microscope measures on the Z axis with a probe and on the X and Y axes with optics and a probe (e.g. for contours) in a measuring range for up to X=300 mm and Y and Z=200 mm.

The video measuring microscope is used at Becker & Mueller for precise measurements in the process and in the final inspection. In this way, tolerances in the μm range are achieved with a high-resolution color camera in conjunction with a telecentric lens. For each circuit board a special measuring program is created. This can then be used as often as you like with a high repeatability – a user-friendly method in which measurement, evaluation and documentation are automated.

The output measurement logs are electronically transferred to a customer report in a standardized manner. A traffic light system is used to visually show employees and customers how to classify the measurement result. The individual printed circuit boards can be assigned exactly to the respective measurement result by means of numbering. Depending on the customer’s requirements, the data can be transmitted electronically via the cloud or in paper form.

The circuit board-specific measurement programs are carried out by the Becker & Mueller team itself developed from technical drawings. A program is once for a specific board created and executed, then it can be automated and repeated as often as you like. The reference points on the PCB are approached manually. It doesn’t matter how the circuit board is positioned on the measuring table, the program is adapted to the position accordingly.

The base material also plays a major role in mechanical accuracy. Since the physical properties of the PCB substrate must not be compared with those of e.g. metals – where it would be easier to hold tight tolerances – were at Becker & Mueller developed special drilling parameters for the materials used.

For example, a customer in the field of measuring devices for ICs has very high requirements. Test devices are manufactured, non-compliance with the tolerances on the circuit boards would then result in either no or poor contact in his measuring system and are therefore unacceptable. The PCB produced are later assembled at the customer’s site using dowel pins, which is why the bores must also be positioned exactly and precisely. In the customer application, test tips are run onto the contact pads. The conductive pattern must therefore match to the holes exactly. NDK drilling (not plated-through holes) is one of the last steps before milling out the finished PCB. Through the high mechanical accuracy and compliance with specified tolerances an increased failure rate and the associated high costs becomes counteracted.

The requirements in this customer project therefore push the limits of the mechanical feasibility. The tolerances were in the special customer project e.g. with a drilling diameter +-10 μm and a positional accuracy of +-20 μm for the conductive pattern to the drilling. By using the video measuring microscope, the manufacturing process is controlled, the highest quality is assured and this is fully documented for each individual circuit board.

The product area with very high demands on mechanical accuracy is growing Becker & Mueller. With the trend in the market that the printed circuit board is becoming more and more common as a carrier plate for mechanical components used is the optimization and further development of processes are constantly necessary.

Mechanical properties also gain in importance when, for example, components in the subsequent end product screwed directly onto the PCB or should be exactly aligned with dowel pins. The influence of PCB quality on customers’ products is increasing also from this direction.

“We continuously invest in our prototype production and are constantly developing it further. Among other things, it is such project requirements that push ourselves in terms of quality forward.” For Janik Becker, one of the managing directors of Becker & Mueller, the choice of high-precision equipment and the further development of the processes are spot on for the production of Becker & Mueller. That means, also for the future, not to stand still.

Video Messmikroskop Garant
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