Outward radiator and bridge candidate
Dimensioned engineering view. This is an isolated candidate for review, with the current112×105.6×47.1mm assembly envelope preserved. It replaces a defined roof region; it is not an extra plate glued onto the current closed lid.
The radiator is a1.5mm6061 aluminum insert: main rectangleX8..100,Y−2..62, plus tongueX84..98,Y62..74.5, atZ44..45.5. The6061 bridge is machined as one U-shaped saddle:12×10×1.2mm foot with lowerfaceZ34.5; two1.2×10×5.3mm webs;14×10×3mm uppercap atZ41..44. TwoM2×5 countersunk screws on(87,67)/(93,67) join the cap to the insert. The screw/pilot/countersink and gasketed perimeter capture remain detailing work; full holes are not represented as manufactured geometry.
The foot bears through a compliant dielectric thermal interface onto the MCU's metal shield. Reserve12×10mm contact and actual installed thickness0.55..1.3mm. ParkerTHERM-A-GAP PAD60, without foil carrier, is a concrete material candidate with typical6W/(m·K). Its standard thickness starts1mm; its typical5–40% deflection range and±10% thickness tolerance do not guarantee a safe force at every current gap. Measure shield height and pad thickness, set bridge standoff accordingly, and prove an acceptable shield/solder load before manufacturing this assembly. A large unverified preload is not accepted. The datasheet's1mm thermal-impedance example is1.8°C·cm²/W at10psi; over1.2cm² that is1.5K/W, including the test interfaces. Pad selection and contact pressure require a supplier/assembly acceptance, rather than a nominal conductivity-only pass.
Hydro's primary6061 data gives typical167W/(m·K) forT6. The screening budget uses150W/(m·K) as an engineering acceptance target. The bridge bulk path is≈1.65K/W; pad bulk0.69–1.81K/W; allocated insert spreading0.6K/W and joints0.4K/W produce3.34–4.45K/W. Target measured shield-to-insert≤5K/W. Insert/joint/pad figures are qualification targets, not guaranteed source-to-air performance. Manufacturer thermal impedance and preload measurements supersede this simple bulk estimate.
heatpath-candidate.json records exact Boolean envelope checks. The bridge intersects none of561 components or42 manufactured solids. The insert intersects only7,884.6mm³ of the current rigid lid, which is explicitly replaced. Both stay outside the current RF exclusion; minimum rear gap is5.5mm. The existing button/window are clear. RF performance still needs testing with the new conductor near the module. The proposal adds about26.5g of aluminum before holes and removes about8g ofPA12: approximately18.5g net, plus pad/gasket/fasteners. It provides no size reduction.
Battery isolation is geometric: the bridge remains above the PCB and has no connection to battery wrap, base or existing fasteners. Retain the pack-to-PCB air separation and bottom foam. No new insulating-film or body-cooling credit is assumed. Independently bond the pack readout NTC, chargeNTC and baseNTC. Their shutdown paths remain necessary because the bridge extracts mainly module/shield heat; charger/main-converter/package-to-shield heat partitioning is unresolved.
The whole-case model's0.2W/K electronics-to-entire-outer-shell sensitivity is a separate target. This candidate may achieve0.2W/K from the MCUshield to its metalinsert; that does not turn remainingPA12 walls into one isothermal radiator. A spatial or partitioned measured model must distinguish insert, nylon sides, PCB, cells and base. The insert area is only6,063mm²; by itself, at50°C against35°C ambient, it rejects roughly0.76–1.34W under the earlier h/emissivity assumptions. Actual surface finish/emissivity needs specification, and remaining heat must leave through other real paths.
Thermal shutdown establishes a protective stop, not six-hour availability. The prior sensitivity still exceeds the40°C contact target at some25°C corners and throughout the35/40°C improved-path ranges. First-article fixtures must measure contact/base temperature, both cells, shield/insert, other power hot spots, thermal lag and continuous workload runtime before authorizing an ambient/workload envelope. Current geometry and fabrication quote files remain unchanged.