Effect of shield-can for drop/shock behavior of board level assembly

Abstract

In order to protect electronic components on a Printed Circuit Board (PCB) against electromagnetic radiation/wave, a shielding in the form of an electrically conductive shield-can or box is normally attached on the PCB covering the electronic components. The attached shield-can could provide an additional mechanical strength and minimize the out-of-plane deformation especially where the electronic package is located. In this study, both the dynamic responses of PCB and the characteristic life of solder joints with respect to different shield-can designs were investigated. Board level drop tests were conducted. A non-contact full field optical measurement technique, 3-D Digital Image Correlation (DIC) with images taken by high-speed cameras was used to quantify full-field dynamic responses of PCB during the drop test. Effect of different shield-can types varying in shape and size on the dynamic responses of PCB was analyzed. In addition, number of drop to failure for each shield-can was also recorded by event detector which connects with daisy chain of the package. Using ANSYS/LS-DYNATM, 3D FEA modeling was conducted and it is validated by experimental results. In modeling, defining the connection boundary condition between shield-can and PCB was a challenge. In this work, the connection was modeled with a fictitious bonding material between shield-can and PCB. The stress analysis were performed to study failure mechanism and location in solder joints after drop impact and correlate the stress results with characteristic life of solder joint. In addition, using this calibrated model, the parametric study was also performed to optimize the size and shape of shield-can yielding lower PCB deflection.