Experimental study of WL-CSP reliability subjected to a four-point bend-test

This article deals with the reliability of WL-CSP subjected to a four-point bend-test according to the JEDEC standard and the repeatability of this test. The evaluation of the test repeatability shows a 5% variation on the characteristic Weibull parameter η. Two dedicated failure detection methods are used: with an event detector and with data acquisition and no difference are observed. Parameters considered are pre-load magnitude and loading frequency. PCB strain due to pre-load is measured and its effect on the product reliability is evaluated. Based on these measurements a pre-load value is defined. It is also shown that a frequency of 3 Hz modifies the studied package lifetime.