Experimental determination of strain distribution on Printed Circuit Boards using Digital image correlation

Abstract

The paper investigates the use of digital image correlation (DIC) for strain measurement on Printed Board Circuits (PCBs). Digital Image Correlation (DIC) is a full-field contactless optical method for measuring displacements and strain in experimental testing, based on the correlation of the digital images taken during test. This method is used to measure strain of the surfaces of materials and structures subjected to various stresses (such as mechanical stresses or thermal stresses).So, this method is used according to the documentation for a variety of applications such as: large deformation measurements, crack analysis, stress strain curves (σ-ε) for new materials, constructions - to evaluate certain displacements and cracks, measurement of strain caused by temperature variations.Circuit boards (PCBs) are designed to mechanically support and electrically connect an electronic component assembly. Due to screw assemblies, the surface level differences on which the PCB is placed, the process of assembling the electronic components induces a certain state of stress and deformation in the PCB. The main components affected are microprocessors due to the way they are glued to PCBs with BGA - Ball grid arrays (BGA).To determine the strain on PCBs, the actual measurement method uses strain gages. This method allows determining the strain only at certain points. The Digital Image Correlation method provides full field strain field. The experimental setup is realized with Dantec Q-400 system used for image capture and Istra 4D software for image correlations and data analyses. The maximum level of the obtained strain is compared with the allowable limit.