The modelling technics currently used have at least two different methods for creating real models for thermal design. One method uses direct geometrical/material analyses to make thermal model for components and the other method uses thermal resistor/capa-citor networks for example the DELPHI-project. Both of these methods should be possible in component level specifications.
The European co-operative project DELPHI /Rosten et al/ is an example of an activity where the responsibility of the thermal design has been attempted to be shared between the supplier of component and the end user.
The specification system for thermal specifications of electronic components and sub-systems and the applicable tests/measurement methods should cover following areas:
- Component specifications
- Interface specimens and materials (heat conducting specimens, thermally conductive insulators) and their specifications and models
- Subsystems (Printed circuit boards, units, rails)
- Heat sinks and fans.
- Material specifications (materials of components and other parts of electronics)
Some guidelines are needed for the thermal specification of PCB and subsystem level. It should be kept in mind that all relevant heat transfer mechanisms are treated, conduction, convection and radiation, when components are positioned on PCB. Monitoring the work of existing groups generating thermal models - DELPHI, SEED, JEDEC; SEMI, and standardising these different methods will be an important task for this research project and CENELEC.
REFERENCE
1. Rosten, H.I. et al. Final report to SEMITHERM XIII on the European-funded project DELPHI - the Development of libraries and physical models for an inte-grated design environment.
Thirteenth Annual IEEE Semiconductor Thermal Measurement and Management Symposium, Austin, TX, USA, 1997. Pp. 73 - 91.
2. Vinke, H. & Lasance, C.J.M. Recent achievements in the thermal characteriza¬tion of electronic devices by means of boundary condition independent compact models.
Thirteenth Annual IEEE Semiconductor-Thermal Measurement and Management Symposium, Austin, TX, USA, 1997. s. 32 - 39
1. ECONOMIC AND SOCIAL BENEFITS
A good thermal design of electronics is crucial on the reliable and safe operation of equip¬ment. The current situation makes it difficult to design electronics effectively because of the lack of standardised thermal specifications of electronic components and heat conducting materials. The ever increasing power density of electronics causes large difficulties for the designers who need more accurate and reliable information of thermal properties. The existence of standards could make it much more economical to make good thermal design.
2. SCIENTIFIC AND TECHNOLOGICAL OBJECTIVES
The RTD work-programme should contain the following tasks:
1. Definition of specifications of the thermal properties of electronic components
1.1 Parameters
Definition of the specific thermal parameters concerning thermal design of components, assembled printed wiring boards, materials and test methods.
1.2 Units
Units (and symbols) of the thermal parameters concerning thermal behavior and also design of components, assembled printed wiring boards and various materials shall be defined.
2. Thermal specifications of electronic components and interface parts
2.1 Evaluation of various package types of electronic components
Evaluation of package types used in electronic components shall cover such packages which probably have use also in the future. Evaluation concentrates on finding possibilities to use some simplified geometric thermal model for these package types. Therefore the project has to find and develop some principles how such simpilification should be done.
2.2. PBGA-package evaluation of simplification of detailed geometric models
The objective is to develop methodology for deciding what level of geometric simplification is practical in modelling thermal properties of Plastic ball grid array packages (PBGA). The project includes comparing the simplified models to accurate geometric model of this package type by using simulations and testing.
2.3 Resistor package geometric model
The effect of mounting method of resistors on temperature of the component itself. Developing description of some standardised mounting methods.
2.4 Description of heat sink thermal properties
Develop a method for describing thermal behaviour of heat sinks by using effective heat transfer surface area for the component instead of using the thermal model of heat sink. This kind of scaling factor reduces the size of accurate thermal model considerably.
3. Thermal specifications of materials used in electronic components
3.1 Material types
Selection of basic material types, how to manage specification for
- construction materials
- interface materials, glues, adhesives, plates
Metals, plastics, ceramics, adhesives, glues, printed wiring board materials, other conductive materials, powder metals, composites
3.2 Basic properties of various materials
- Standard definition of various properties (use of other standards)
- Description of specification for various basic material types
- Effect of surface contact resistance on thermal properties
Thermal conductivity, thermal resistance, contact resistance at surface, thermal capacitance, specific heat, emissivity, density, coefficient of thermal expansion, surface properties (roughness), etc.
3.3. Test methods of thermal properties of materials
- Comparison and further development of test methods
- Selection of test methods to measure various material types
7. TIME SCALE
Although no rigid time scale requirements apply to this project, based on the described objectives, the whole project should be completed within three years maximum.
8. IMPORTANT ADDITIONAL INFORMATION
To get a reasonable amount of progress in this area, a minimum of three intrested parties is necessary.
Close connections with CENELEC should be demonstrated in the proposal, and ensured during the proposed workplan, in order to properly match the requirements of industry and the evolution of technology.
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