Oak Ridge National Laboratory Oak Ridge, Tennessee, United States
A conductive tamper mesh, a common feature of verification systems, is designed to detect tampering and allow the system to respond (e.g., erase encryption keys). The real-time detection of tampering is particularly important for unattended and remote monitoring systems that may experience extended periods between direct observation by an inspector. Typically, a tamper mesh is formed by one or more traditional printed circuit boards, often using either a flex substrate or combination rigid-flex substrates to allow the mesh to enclose the monitoring system. Additive electronics manufacturing techniques present a unique opportunity for a new approach to conductive tamper meshes and other monitoring features. The additive nature of these processes places limits on high-volume manufacturing, but it facilitates the creation of tamper meshes with part-to-part unique features, including unique identifiers. Furthermore, some additive electronics technologies enable the tamper mesh to be fabricated directly onto the surface of an enclosure after the electronics package is complete, allowing a mesh to be formed with no folds or seems. The conductive mesh can be monitored from the inside with minimal additional circuitry and extremely low power requirements. This work involved investigating the additive manufacturing of conductive tamper meshes and other monitoring features using commercially available aerosol jet, inkjet, and extrusion-based printers with commercially available conductive and insulating inks. This presentation evaluates the application of the different additive electronics technologies to conductive tamper mesh printing, addressing the differences in capabilities and the technical challenges in applying these differing technologies. Examples of such challenges include multilayer alignment, thermal constraints on substrate and monitoring electronics, and size constraints.
