In-situ Measurement Method for Warpage of Electronic Package Substrate Based on Speckle-free DIC and Carbon Coating

In recent years, speckle-free three-dimensional digital image correlation (3D-DIC) technology has been progressively applied in electronic packaging reliability evaluation, particularly for warpage measurement of substrate structures. However, the 3D-DIC measurement accuracy is often compromised by specular reflections from solder balls, especially when measuring substrates with solder balls attached. To address this issue, a carbon coating-based surface pretreatment method is proposed in this study, in which a nanoscale carbon film is deposited onto the specimen surface to suppress glare caused by solder ball reflections. This significantly enhances image clarity and improves the accuracy of DIC subset matching and warpage reconstruction. Experimental results demonstrate that the proposed approach practically reduces the interference of glare, improves the completeness and stability of warpage data, and is particularly suitable for non-contact measurement of complex or highly reflective electronic packaging substrates. This advancement highlights the potential value of the proposed approach in improving the accuracy of reliability assessment for electronic packaging structures.