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30 PCB007 MAGAZINE I APRIL 2018 To guarantee robust PCB substrates in auto- motive electronics, we simulate the local envi- ronmental conditions like temperature and hu- midity in the PCB in an electronic system. This will be compared with the load capability of the materials used, as well as designs. Derived lifetime models help to transfer the PCB qual- ification test results to real conditions in the electronic systems and to define the adequate distances in the design rules inside the PCB. This is already done for the CAF failure mode and is ongoing regarding other cracks in PCBs. Here, qualification tests and lifetime models are still under development. If no life- time model is applicable, the materials or fail- ure modes must be eliminated by material re- striction or strict process control (e.g., in case of hollow fibres). Figures 13 and 14 show an overview of this approach. High-Speed Requirements High-speed applications like radar (77 GHz) and signal processing for connectivity or image recognition (in future up to 10 GHz) need well- defined substrates and design rule elements. Impedance-controlled PCB stackups and con- trolled processes at PCB suppliers are stan- dard in the consumer industry and have to be used by the automotive industry to guarantee excellent signal and power integrity with good electromagnetic compatibility. The material choice needs special attention to guarantee Automotive Electronics | AE/EAI1 | 12/10/2017 Bosch GmbH 2017. All rights reserved, also regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights. Local humidity load in PCB: • Realistic prediction of local humidity in PCB by simulation models Load capability of design elements in PCB: CAF and Hollow Fibre • CAF Failure mode understood • Material qualification by established tests • Monitoring and improvement processes Cracks in PCB • Development of qualification methods • Selection of materials based on these methods Figure 13: Realistic prediction of local humidity in a PCB by simulation models. (Source: Bosch) Figure 14: Environmental load in a PCB and load capability of the materials used. (Source: Bosch)