Decrease of energy deposited during laser decapsulation attacks by dyeing and pigmenting the ECA: Application to the forensic micro-repair of wire bonding
Abstract
Polymeric adhesives are of interest in the digital forensics domain. They can be used to perform more or less complex repairs or even to realise advanced man-in-the-middle attacks in order to carry out reverse engineering of secure systems (Heckmann et al., 2017).
The main aim of this paper is to develop a technique that makes polymeric adhesives sensitive to laser decapsulation attacks while decreasing the laser power deposited during ablation. We will first introduce a theoretical part on the properties of laser radiation ablation and discuss the fundamental equations characterising laser-matter interactions.
In the practical part, we vary the absorbance of our target materials (Electrically Conductive Adhesive (ECA)) by adding either dyes or pigments at different concentrations, to evaluate the influence on sensitivity to laser decapping attacks. The addition of dyes or pigments will have an immediate and crucial impact on coefficients of the fundamental equation of heat that make the polymeric glues sensitive to laser decapping attacks.
Finally, to demonstrate the value of this work, a direct example of application is implemented for the micro-repair of broken bonding wires in areas where traditional techniques using the wire-bonder are not applicable or are likely to create additional damage to neighbouring bonding wires. This paper shows how to make conductive bonding, using ECA, with an accuracy of 15 μm.