Use of a 1-dimensional heat flow model to calculate circuit board thermal resistance for use in the MQUAD(R) package thermal model

An analytical 1D heat flow model for the area of a circuit board outside the package footprint is described. The model is capable of dealing with infinite and finite boards. Thermal profiles predicted by this agree well with measured values for a range of circuit boards. The thermal resistance calculated by the 1D model also agrees well with values resulting from finite element models of the circuit boards. The 1D thermal resistance is used in the lumped parameter thermal model for the MQUAD(R)* package. θ_ja predictions from this model are close to observed values for packages mounted on a range of circuit boards