科研之友
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摘要
Portable electronic products such as mobile phones experience various loadings in their use environments but accidental drops are encountered most frequently. Over the past few years the drop reliability of electronic assemblies has been studied by means of the travelling table test apparatuses described in the JESD22-B111 drop test standard. There are, however, a few essential shortcomings related to this approach: for example, (1) testing can be time-consuming as a result of the low impact repetition frequency (0.1 Hz) characteristic of the approach: (2) the peak deceleration amplitude varies from one pulse to another: (3) packages placed at different locations on the printed wiring board experience highly dissimilar loading conditions, and (4) the lifetime of a particular location varies significantly from one board to another. In order to overcome these shortcomings an alternative impact test method is presented in this paper. The new method is based on the use of a pneumatic cylinder to produce the desired shock pulses, for example those defined in the JESD22-B110A and JESD22-B111 standards. The measurements showed that the pneumatic test system is capable of producing peak deceleration well above the maximum (2900 G) stated in the JESD22-B110A. More importantly, a testing time an order of magnitude shorter was achieved by increasing the drop impact repetition frequency; an impact repetition frequency of 1.6 Hz was achieved with the pneumatic shock impact tester. Two improved component board attachments based on the support of the full board width were designed in order to simplify the bending motion of component boards. Both the finite element calculations and the experimental results showed that under the full board width support conditions the bending of the component board is more uniform and different component locations experience more equal strains as compared to bending under the conventional 4-point support conditions. The reliability tests that were performed verified that the full board width support produces the same failure modes and that the lifetimes of packages at different locations on the printed wiring board are more comparable with each other with the full board width support than they are with the conventional 4-point support. The benefits of the pneumatic tester that was developed are related to the time needed for testing, the stability of the impact pulse over long periods of time, and the more consistent lifetime statistics achieved by the simplified bending of the component board during testing.
- 出版日期2010-8
