Digital Speckle Correlation with HDI PCB Failure Mode
Authors: Thilo Sack, Hua Lu, Laurence Schultz Company: Celestica International Inc., Ryerson University, High Density Packaging User Group International Date Published: 9/17/2017
Abstract: Stacked microvias connecting multiple HDI layers are key structural elements enabling HDI circuit boards. The main reliability challenges have been microvia separation, interfacial delamination and copper fatigue failure. Experimental evidence suggests that HDI structures experience different stresses and exhibit different failure modes during thermal operation, and the challenges become tougher under leadfree processing. This paper presents the results from an HDP User Group project, which made use of a unique but mature Digital Image/Speckle Correlation method for the measurement of thermal strains in microvias and surrounding areas in HDI PWBs of different structure designs. By comparing the strain measurements directly with the failure results obtained from the traditional reliability testing (IST), the project aimed to find correlation between the experimental physics predicted failure and the failure statistic obtained actual failure data. The results todate look promising.
Digital speckle correlation, HDI, microvia, stackup, failure, thermal reliability