app

AI Flow

Public Made by Adom

by adom

Adom's AI Flow: a tool to help the AI follow all of the steps it takes to build a board.

kicadpcbedaroutingplacementcopper poursablationcurrent densitythermalkelvincomparison
Overview Files Skills Discover Packages Releases Dependencies Issues10 Breadcrumbs Pull Requests Activity
Closed general

analyze thermal / finish: no way to model board-bottom heat-sink (pedestal) cooling for tabless parts

John Lauer · ·closed by John Lauer

finish refuses a board whose hot parts are cooled through the board's bottom copper into an external heat sink (a pedestal through a gap pad), not through a tab or free air.

What happens:

  • The tab/copper-area thermal heuristic in analyze thermal assumes free-air or tab-net cooling.
  • Tabless packages (QFN/SON exposed pads) that dump heat through thermal vias into bottom copper pressed onto an external sink fail the heuristic, even when a numerical solve (Adom Fields) of the same board with the sink boundary passes with margin.
  • packageCooling models case-mounted sinks. Using it for a board-bottom path would misstate the physics, so it isn't a valid workaround.

Request: a spec-level way to declare a board-bottom sink, for example a boardSink region with its K/W (or h and area) and an interface resistance. analyze thermal would then include it, or accept a referenced numerical-solve evidence file in its place, with the assumption recorded in the run summary.

Current workaround: none without misrepresenting the cooling path. The run stays held at finish.

1 Reply

John Lauer ·

Added in adom-aiflow 0.2.3: spec.boardSink (name, region polygon or "outline", layer, kPerW or hWm2K, optional interfaceKPerW and maskOpen, and the parts it cools, plus a required note). analyze thermal judges the named tabless parts on a conservative series path: tab-net vias within 1 mm of the pads inside the region, then mask, interface and sink, with no board-spreading or air credit. Alternatively, fieldsHeatsink names a Fields conducting block, and the run's same-input solve judges those parts. The assumption goes into the run summary and finish. Parts not on a sink keep the still-air check, and a part cannot be on a sink and use packageCooling too. Read docs/board-sink.md. Note that the mask, via-reach and patch numbers are documented engineering choices, not vendor data, and Fields models the block as air-cooled, so kPerW is not part of the solve. Upgrade: adom-wiki pkg install adom/adom-aiflow, then adom-aiflow --version says 0.2.3.

John Lauer closed this ·

Log in to reply.