The DELPHI methodology was defined by the DELPHI Research Consortium, partially funded by European Community.
DELPHI Compact Thermal Model (CTM) is a thermal resistance network which is comprised of a limited number of nodes connected to each other by thermal resistors.
Each of these nodes can be internal or on the surface and each of these nodes correspond to a single temperature only.
Check the following link for more information on DELPHI Methodology.
http://www.simu-cad.com/images/UpFile/20085815411410742.pdf
Lattice provides DELPHI models for all FPGA devices. Each die-package combinations has its own DELPHI model. In the thermal simulation software, these models can be placed directly against the PCB, as they include balls (pins) conductivity.
You can download the DELPHI models for Lattice devices at:
www.latticesemi.com -> Products-> FPGA and CPLD devices -> Select the device -> Navigate to "Downloads" tab -> Delphi Models
DELPHI Models for the Lattice devices are derived using Ansys Icepak tools (http://www.ansys.com); so these can be directly imported.
These models have also been tested to work with Mentor Graphics' Flotherm (http://www.mentor.com/products/mechanical/products/flotherm).
The scope of the DELPHI CTM is to provide the mechanical thermal simulation model to be used in the tools mentioned above to perform thermal analysis.