Augmented Reality Case Study
The Design Challenge
Osterhout Design Group (ODG) out of California has paved the way forwearable technology in America. Recently ODG has developed theworld’s most advanced head worn computing system: augmented realitysmart glasses. The wearable device involves an array of PCB andelectronics with multiple antennas which were initially sealed into aplastic housing.
Thermal testing of the device revealed high temperature issues on theinternal components and the exterior surfaces that touch the body. ODG had initially designed a small heat sink for the CPU but its effectivenessin solving thermal issues was unclear.
The challenges of creating a safe and comfortable exterior temperature,facilitating signals to the antennas, and keeping the inside devices coolwere presented to the team of Aavid, Thermal division of BoydCorporation. Within a stipulated time, we were to predict and improvethe thermal performance of the glasses in a natural convectionenvironment with plastic casing material over the antenna area.
The Aavid Solution
Aavid created a CFD model of the existing device and fine-tuned themodel parameters to match thermal testing data that was provided. Thetop aluminum spreader was modified to enhance radiative andconvective heat transfer by increasing its effective surface area. Nextthe conductive heat transfer throughout the device was optimized toreduce temperature gradients between the hot spots and exteriorsurfaces. Strategically placed graphite sheets were added to spread theheat while insulating material was used to isolate heat from surfacesthat will be in contact with the skin of the user.
To improve the aesthetics of the device, the aluminum spreader wasmounted to the PCB suing bosses and numerous locations. The PCB itselfwas used as a part of the thermal system which enhanced performance.Additionally, the gap between aluminum spreader and critical devices onthe PCB were filled using thermal interface material.
The baseline simulation results closely met the prototypes thermal testdata. The top aluminum spreader was effective in removing heat fromthe systems. There was significant improvement to the aesthetics andusability by introducing other conductive and insulating materials suchas pourable thermal interface material, graphite, foam, and the PCBitself.