The thermal analysis is becoming an important and crucial need in the design of electronic devices and systems because of the increasing of the electrical power handled by the electronic and optoelectronic devices in automotive systems and lighting applications. However the common tools used to perform the thermal analyses, which is the finite element based programs such as ANSYS, FLOWTHERM, are generally very expensive, time consuming and overall they require a certain cultural background by the operator on the finite-element calculation technique. All these features makes these program unsuitable for the use in a medium and small industries.
Just to overcome all these problems, a novel thermal simulation tool, called DJOSER, was created by increasing the complexity of the mathematical implementation but in the same time by making the user interface and model construction more friendly and fast, by decreasing the number of the input parameters and avoiding a deep knowledge of the mathematical background by the operator.
More precisely, the DJOSER simulation system is a steady state thermal solver based on the direct analytical resolution of the heat transfer equations by means of the Green's functions and for this reason is intrinsically fast. It was purposely developed for multi layered assembling structures for the electronic industry similar to stepped pyramids with any number of layers and any degree of asymmetry.
It was designed just to replace the use of expensive, time-consuming and more complex thermal solvers based on the finite-elements method while maintaining the same accuracy in the evaluation of the temperature and thermal flux maps at all the structure interfaces. Its limitations (it works on structures with homogeneous layers and on rectangular geometries) are largely compensated by the possibility to insert many details (as the thermal contact resistances between two layers, two types of power sources) and boundary conditions (convective heat exchange at all the surfaces exposed to ambient) which make the model absolutely realistic and the thermal analyses very reliable.
Moreover, while the finite-element based programs need complex not uniform 3-D meshes composed by solid elements, the DJOSER system require 2-D uniform meshes at the layer interfaces which can be easily automatically generated. Especially thanks to these properties and to the friendly pre-processor, this simulation system has powerful didactical properties since it allow an immediate verification of the effect on the temperature distributions of many physical and geometrical details, such as the number and nature of the stack of layers composing the assembling structure, their asymmetrical positions, the presence of interposed soldering or attaching layers, the presence of convective boundary conditions and the capability of an external dissipator in reducing the device junction temperature.
The didactical activity on the thermal effects on electronic system mountings is carried out not only within the university courses but also within the industrial environment. A close collaboration between the University and the EFFEI of Florence (Italian industry involved in the design and production of substrates for electronic systems) recently started in order to train persons in thermal analysis and to offer design helps and services to other industrial partners.