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38 The PCB Design Magazine • July 2017 many design teams adding a mechanical analy- sis step to the product development process in order to better validate reliability. While this added step improves the process, it still has lim- itations, including: • Extensive library/model development • Lengthy setup and simulation cycles • Simulation results that are not tuned to the specific printed circuit board All of this means that, even with a special- ist, mechanical analysis is still unable to achieve 100% test coverage. Improving Validation by Simulating During Design To optimize the process and minimize time between finding and correcting issues, simula- tion of vibration and acceleration should be added into the design stage (Figure 2). To be clear, this does not eliminate the need for phys- ical HALT, however by eliminating early failures through simulation in the layout domain de- sign teams can reduce HALT expenses and en- sure that reliability specialists have more time to focus on hidden issues. To predict which parts will fail due to vi- bration, engineers need to identify the failure frequency or natural modes in the design. En- gineers and designers should also be able to de- termine the safety factor of components due to stress. During vibration and acceleration simu- lation (Figure 3), an acceleration load should be applied in all directions, thereby defining where the board will have stress during commercial use. For efficiency, the analysis must be tightly integrated and easy to use in order for tests to be performed concurrent with component place- ment. The simulation should allow the user to directly view the harmonic frequency and ap- plied stress on all components that could po- tentially result in a failure. As a best case, two options for quick design simulation should be available: 1. Vibration that calculates relative stress and deformation values to pinpoint weak links in contact areas of leads and pins of compo- nents. The results could later be translated to probability of potential component failure. 2. Constant acceleration that provides for a linear static analysis which allows constant ac- USING VIBRATION AND ACCELERATION ANALYSIS TO IMPROVE RELIABILITY Figure 1: Virtual HALT simulation. Figure 3: Vibration and acceleration simulation. Figure 2: In the optimal process, analysis is integrated within the design stage. Schematic Design Component Placement Vibration & Acceleration Analysis Routing Mechanical Analysis Physical Prototype Physical HALT / Acceleration