Investigation on the optimum sampling rate of strain measurement during printed circuit board (PCB) system assembly

This paper discusses the Min. sampling rate of strain measurement during the system assembly process. The test boards including the server, desktop computer and laptop boards with different board thickness. A 1% variation in the diagonal strain and principle strain are used as the threshold for determining the Min. sampling rate. The test results show that the absolute values of diagonal strain and principle strain reduce with the decreasing sampling rate, this trend is really apparent when the sampling rates is lower than 100Hz. In addition, the principle strain metric is more conservative than diagonal strain metric. Min. sampling rates for strain gages at different locations of boards vary widely, this is due to they have different strain rate, i.e. change in strain divided by the time interval during which this change is measured. The higher strain rate of the strain gage, the larger Min. sampling rate should be chosen. The Min. sampling rate of the server, desktop computer and laptop boards is 250 Hz, 667 Hz and 200 Hz respective. If the strain measurement equipment doesn´t have the selfsame option, a higher sampling rate should be chosen.