Evaluation of very low bending radius of flexible circuits beyond the standard design rules
The Flexible Printed Circuits (FPC) used in high-end applications have some specific characteristics. It has a more complex build-up and must be compatible with repair processes. Moreover, they are used in harsh environment and long mission profile. Current FPC design are based on industrial standards, which propose design rules, such as minimum bending radius calculated from the maximum accepted copper elongation. This work is part of a large study focused on the development of a new generation of digital board solutions for electronic interconnection. In this paper, a finite element simulation study will be applied to FPC bending analysis beyond industrial standard limits. As a conclusion, we propose to consider the maximum copper strain and the bending shape for the minimum bending radius definition.
Experimental and numerical analyses of flexible PCBs under various loading conditions
This work will present case studiesof three types of Flexible Printable Circuits subjected to different loading conditions in order to evaluate their tecnologies regarding mechanical reliability. Typical causes of failure in electronic devices are associated with mechanical stress, moisture, heat from transportation and field use. Typically manufacturers carry out tests to evaluate the reliability of electronic components regarding these environmental loads. Common tools used for this evaluation, in early stages of design, are FEA (Finite Element Analysis) and experimental laboratory tests. In this work simulation models were generated aiming at developing tools for early stages of design, and mechanical tests were performed to assess actual reliability of parts and also to provide information to evaluate the simulation models. The different types of failure in the flexible printed embeded circuits, such as delamination, will be presented. Failures due to high shear stresses in flex- rigid joints will also be evaluated. Experimental tests and computational simulation will also be applied in order to perform these evaluations.
Cracking Phenomena on Flexible-Rigid Interfaces in PWBs under Thermo Cycling Loading
Flexible printed circuit boards (fPCBs) have an important role in electronic product miniaturization due to their reduced thickness and ability to bend and adapt to various shapes. As with any new technology reliability should be assessed to guarantee quality of products that benefit from the additional features. Typical causes of cracking failure in electronic devices are related to mechanical stress, moisture, and heat from transportation and field use. Typically manufacturers carry out tests to evaluate the reliability of electronic components regarding these types of loads. Common tools used for this evaluation in early stages of design are finite element analysis and experimental laboratory tests. In this present work simulation models were proposed in order to develop tools for early stages of design. Thermomechanical tests were performed experimentally to assess reliability of parts and also provide information to evaluate the simulation models. The objective of this work is to develop simulation models for flexible printed circuit boards (fPCB) flex-rigid interfaces and to perform experimental tests in laboratory in order to evaluate the cracking phenomena when this device is submitted to thermal cycling.