Two-dimensional (2D) in-plane strain mapping using a laser scanning technique on the cross-section of a microelectronics package

Strain distribution exists in all microelectronic devices, including emerging flexible[1] and foldable[2] electronics. When a device is subject to bending or elevated temperature, the mechanical and electrical properties change. In some cases induced or applied strain can cause the device to fail[3-5]. For this reason, accurate strain mapping techniques are of great interest[6] to the electronics industry and could provide a detailed understanding of the strain distribution across a device. This understanding will help improve the structure or layout design of mechanical and electronic devices. The laser scanning technique demonstrated in this work could potentially provide a solution to map the two dimensional (2D) strain distribution within an electronic package. We have validated the strain sensitivity and spatial resolution of features for the device in a previous report[7, 8] and are now applying the technique to a practical microelectronic package sample. Here, we demonstrate 2D strain mapping capability by preforming 2D scans across the composite solder bump region at room temperature and an elevated temperature.