Low-Cost Laser Decapsulation of Wire-Bonded Memory Packages with Dual Thermal Gating for Forensic Data Preservation

Le résumé fourni par la source

Chip-off examination remains the method of last resort in digital forensics, applied when a device is locked, damaged or non-responsive, and it is the only route to data on many embedded targets such as vehicle event recorders and dashcams. The dominant removal technique is thermal reflow at approximately 360°C, and this is destructive to the evidence it recovers: charge leakage from flash memory is Arrhenius in temperature, so two minutes at 250°C consumes retention equivalent to centuries of room-temperature storage. This work develops a lower-temperature alternative using a consumer-grade 455 nm diode laser costing a small fraction of industrial equipment, together with an open-source browser-based tool that predicts thermal behaviour and gates recipes against two independent safety limits: wire-bond intermetallic damage and charge-retention loss. A finite element campaign in COMSOL Multiphysics characterised an eMMC package under a six-pass recipe. Two structural findings emerged. The bond-plane bulk temperature proved independent of remaining encapsulant thickness, because in quasi-steady state all absorbed power crosses the bond plane at fixed loop height regardless of the cap above it, which places the entire pass-to-pass risk in the per-pulse transient. Resolving finite spot size rather than assuming a one-dimensional heat source changed the predicted bond temperature from 181 to 272°C, which would condemn the process, to 94 to 139°C, which clears it. The campaign also identified two compensating errors in the tool's own analytical gate, which was corrected against the simulation. A single bench measurement, of laser spot size, returned 0.08 mm and satisfied a criterion recorded in advance. The wider bench validation programme is specified in full but was not executed, so the thermal model retains unverified status and all thermal figures reported are predictions rather than measurements. The claim advanced is one of data preservation, which is independent of encryption because charge leakage flips physical cells regardless of their contents.

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