Browse Topic: Printed circuit board assemblies
Reliability states the degree to which the result of a measurement, calculation, or specification can be depended on to be accurate. And, tests according to GM specifications represents a minimum of 15 years of vehicle life time with defined Reliability and Confidence level. In this work, actual number of thermal cycles for Thermal Fatigue tests (Thermal Shock and Power Temperature Cycle) are calculated for Copper Wire whose Coffin Manson exponent is 5. Overstressing the PEPS Antenna under thermal fatigue requirement (defined number of thermal cycles based on Reliability and Confidence requirements) will lead to broken Copper wire which will result in component’s functional failure and thus impossible to continue reliability testing. The objective of this paper is to determine thermal fatigue requirements for Antenna’s Copper wire whose Coffin Manson exponent is 5. Testing with exact number of thermal cycles will reduce the validation failures owing to broken Copper wire and thus save incurred revalidation cost. The current study is limited to only adjusting the thermal fatigue requirements (Number of Thermal Cycles) for only specific E/E components having Copper wire soldered directly on to the PCBA. The limitation of validation experiment is to choose the correct Coffin Manson exponent for achieving desired number of thermal cycles for all specific E/E components having Copper wire soldered directly on to the PCBA. Conclusion- Derived appropriate thermal fatigue cycles (22% of actual total number of 100% cycles) for Copper material with Coffin Manson exponent of 5 will reduce the failure associated with the broken Copper wire and thus will save the revalidation cost.
Most modern automotive electronic systems are composed of two major mechanical elements: an equipment chassis or enclosure, and a PCB (Printed Circuit Board) assembly. The PCB is composed of laminated copper and FR-4 glass epoxy. Very small and delicate electronic components are populated on both sides of it. As the amount of electronics on vehicles increases, the electronic control units (ECU) are becoming larger, increasing the size and mass of the board as well. The vibration often plays the key cause of invalidation and component failures. In the design of PCB assemblies, it is preferable to increase their fundamental natural frequency for improving the fatigue life because the PCB displacements are reduced very quickly. PCBs carrying electronic components are typically fastened with screws to the enclosure. The locations of the supporting screws and the large component placements can be optimized to achieve a maximum fundamental natural frequency for the loaded PCB. With this objective, a fully automated optimization tool based on dynamic structural optimization is developed using the commercially available software. This tool is driven by a user-friendly Excel spreadsheet which takes various geometric, material property and optimization parameters as user inputs and generates the HTML report containing detailed information about various configurations with improved dynamic performance. This tool enables the user to optimize the PCB assembly very early in the design phase without an extensive knowledge of dynamics, finite element or optimization required and thus, addressing the vibration issue proactively.
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