Connectors, electronic drives, and sensors can be scaled to smaller dimensions than ever before due to increasingly sophisticated development and production methods in electronical engineering, electronics, and precision engineering. Nevertheless, there remains a sticking point: Complex wiring needs space, which is often not available. The solution has arrived: Rigid-flex PCBs. They are the result of a creative interdisciplinary collaboration between the drive manufacturer WITTENSTEIN in Igersheim and Würth Elektronik in Niedernhall (both in Baden Württemberg).
High-precision servo motors are used in different industries and need to comply to the specifications of their respective industries, in particular in the aerospace, medical, or automotive sector. In many applications, the predictable reliability of the components used is important.
For motor-transmission units, both the mechanics and the control electronics must be optimized or intelligent sensors need to be integrated. Yet the question of precision and robustness ultimately decides on the interplay between control electronics and mechanical components. Especially in vibrating mechatronic units, there is a particular weak point: The cable connections. Contact failure and loss of function or even weaknesses due to long-time use can occur.
“At a connector where two electronic modules are joined with a cable, impurities may be deposited or the contact springs of the connectors produce insufficient connections,” explains Michael Matthes, an expert on new electronic technologies at WITTENSTEIN electronics GmbH, a subsidiary of WITTENSTEIN. “Such impurities and temporary contact problems can, for example, lead to changes in the contact resistance between the modules and subsequently change the electrical characteristics of the tracks in the long-term or even lead to control and measurement errors.”
For this reason, WITTENSTEIN started early exchanges with PCB manufacturers to find better solutions. This resulted in an innovative combination of employees from WITTENSTEIN and Würth Elektronik, who dealt with the question of how connections in confined spaces can be successfully achieved. The solution: A rigid-flex PCB to replace the conventional cable and connectors.
“We had the progressive miniaturization of electronic components in mind during the development,” explains Andreas Schilpp, product manager at Würth Elektronik. “This requires considerations for the efficient use of the housing volume in all three dimensions. Whether and how this idea can be implemented, of course, was a creative challenge, but we were happy with our solution.”
The result is a combination of a stable rigid PCB with a flexible film of polyimide and liquid crystal polymer (LCP); the so-called rigid-flex printed circuit boards.
