The vertical integration of microelectronics is an appealing approach that offers significant performance advantages over conventional planar devices. However, one of the main challenges for implementing such technology is the limited volume for heat dissipation. Microfluidic interlayer cooling is a feasible solution for the thermal management of such devices, but several challenges remain to achieve a comprehensive solution that is compatible with electrical and structural parameters. In the present study, a Thermal Demonstration Vehicle (TDV) is numerically and experimentally investigated in an effort to provide a practical cooling solution for vertically integrated devices with heterogeneous heating. The flow boiling of the dielectric refrigerant HFE-7200 is investigated to provide insights regarding the two-phase flow regimes, heat transfer, and pressure drop characteristics in this type of microgaps. The physics of the flow boiling mechanisms are also explored through a mechanistic phase change model, which can be used with commercial computational fluid dynamics and heat transfer (CFD-HT) codes. The numerical modeling approach is validated with experimental results in representative layouts with variable density of pin fins and non-uniform power inputs, making this technique an attractive alternative for the design of practical two-phase micro-cooling layers operating in realistic conditions with hotspots. (C) 2019 Elsevier Ltd. All rights reserved.