GROWTH – DEDICATED CALL – 10/00
TOPIC IV.8
Thermal specifications and properties of electronic components and
materials
1. CONFORMITY WITH THE WORK PROGRAMME
This topic falls under the Competitive and Sustainable Growth Programme, generic
activity Measurement and Testing. Specifically, it is related to Objective GROW-20006.2.1 Methodologies to Support Standardisation and Community Policies for which
expressions of interest have been called.
2. KEYWORDS
Thermal specification, thermal design, electronic component, modelling, thermal
interface, properties of materials, design rule, test method, standardisation.
3. SUMMARY OF OBJECTIVES AND JUSTIFICATION
Controlled thermal design of electronic equipment is currently a very important area of
electronic design. This is because the dissipated power densities of modern electronic
chips have now reached such a high level that advanced heat transfer systems are
needed. However there currently exists very little standardised information about the
thermal properties of various electronic components and materials, or the test methods
for verifying these thermal properties.
With the new standardised specifications, models and test methods the users and
designers of electronic equipment could get better, compatible and more realistic
description of the thermal behavior of electronic equipment. Design time reduction and
better accuracy can be achieved by using more effective and harmonized thermal
models and specifications of electronic components and of heat conducting materials.
4. BACKGROUND
Controlled thermal design of electronic equipment is currently a very important area of
electronic design. This is because the dissipated power densities of modern electronic
chips have now reached such a high level that advanced heat transfer systems are
needed.
However, there currently exists very little standardised information about the thermal
properties of various electronic components and materials, or the test methods for
verifying these thermal properties. In CENELEC there are no standards for the thermal
design of electronic equipment and components.
With regard to standardisation, the technical development of thermal models for components, and thermal simulation methods are advanced enough, to be used for better
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thermal specifications for electronic components. Recent studies performed in Europe
by DELPHI and SEED projects (DELPHI = Development of Libraries of Physical
models for an Integrated design environment, SEED = Supplier Evaluation and
Exploitation of DELPHI, SEED is European ESPRIT project) and the published
documents by JEDEC and SEMI will help when starting specification work at
CENELEC. In the International Electrotechnical Commission (IEC) there are not any
activities on this area yet.
The information sources of thermal data for the manufacturer of electronic equipment
are material suppliers and component suppliers. Using both of these channels the
equipment designer should get reasonable thermal data. To improve this data flow from
supplier to equipment manufacturer, some standardised specification system is needed.
CENELEC is the most suitable organisation to co-ordinate this task.
Information routes for thermal data
Materials supplier
Flow of thermal data
Components Manufacturer
Equipment manufacturer
(thermal designer)
CENELEC will develop
guidelines for specifications
used in thermal design
processes
On the following page there is a key figure illustrating ideas on how to manage the basic
thermal specification parameters which should be addressed when specifying an electronic component. In these specifications it is very important, to cover all the applicable
heat transfer mechanisms: thermal conduction, convection and radiation.
It is also important to describe every component type by the actual feasible method
(which is also measurable) to be used in verification of given parameter values in
various models.
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How to manage thermal properties of electronic components?
Thermal specification objects of electronic component
- component itself (inside structure e.g. DELPHI, mostly thermal
conduction and capacitance)
- contact properties (bottom side and conduction to PWB, mostly thermal
conduction)
- surface properties (sides and top, thermal conduction if heatsink,
convection and radiation)
Heat sink area (possible)
Surface properties of the
component, outer properties
Inner properties of
component
Printed wiring board
Contact areas
Modelling inner properties of component serve
mostly the management of component itself
Modelling outer/surface properties of component
serve mostly the management of interface between
component and neighbouring environment
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/capacitor networks for example the DELPHI-project. Both of these methods should be
possible in component level specifications.
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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 subsystems 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 integrated 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 characterization 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
5. ECONOMIC AND SOCIAL BENEFITS
A good thermal design of electronics is crucial on the reliable and safe operation of
equipment. 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.
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6. 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.
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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.