Vapor chambers are passive devices that are used to spread heat from localized hotspots to larger surface areas. Their passive operation utilizes the latent heat of a working fluid that is pumped by capillary action through an internal wick structure. A localized heat source evaporates working fluid, which spreads throughout a vapor core and condenses over a larger area via heat rejection to the ambient or surrounding media. This mechanism of transport offers highly effective heat spreading for thermal management in both low- and high-power applications. Due to their complex operation and strong coupling between the wick and vapor core, modeling and predicting the steady-state and transient thermal response of a vapor chamber is non-trivial compared to heat spreading by conduction in a solid. A common approach for predicting the thermal response is direct numerical or analytical simulation of vapor chamber transport by solving the governing mass, momentum, and energy equations for the wick and vapor core. This approach typically requires coupling of a standalone vapor chamber model with a separate system-level conduction solver and is computationally expensive. An alternative approach is to represent a vapor chamber in system-level models as a solid conduction block having some effective physical properties that mimic the correct thermal response. Here, an effective anisotropic properties-based representation of the vapor chamber is presented. These effective anisotropic properties are intrinsic to the vapor chamber and enable prediction of steady-state and transient thermal response using conduction physics. The effective properties method is compared against a validated vapor chamber transport model, and shows an excellent match for a number of cases spanning a range of form factors and heat inputs. Closed-form expressions are derived for estimating error in predicted thermal response due to the assumptions involved in formulating the effective properties.


Compact Modeling of Vapor Chambers Using Effective Anisotropic Properties

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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