Estimate PCB component temperatures by solving a thermal resistance network (thermal↔electrical analogy) with the built-in MNA solver. Each component gets a junction node (package θjb from a typical-datasheet table), a local board node coupled to its neighbours through in-plane FR4/copper conduction, and convection to ambient. Computes per-component junction and case temperatures, board extremes, and flags max-junction violations. Runs instantly in-worker; mesh-level CFD via container backend is planned.