Re: ASIC DESIGNER: case temperature OR ambient temperature...?

ronald de smedt vh41 4650 ([email protected])
Thu, 1 Aug 1996 11:27:50 +0200

Dear all,

I have put forward the question of Mr. Y. Yizreali concerning the
thermal modelling of ASICs to my collegue Dr. Willem Temmerman, who
has provided the following answer.

Best regards,

Dr. Ronald De Smedt
Alcatel Bell Telephone, Research Division - EMC
Francis Wellesplein 1, B-2018 Antwerpen, Belgium
Tel.: +32/3/240-4650, Fax: +32/3/240-9932
e-mail: [email protected]


Dear Ronald and Yehudin,

In my view, neither value is satisfactory :

TETA_Junction_case is really not a well-defined value, because the case
is typically not iso-thermal, so the temperature difference to be
divided by the power is not a constant.

TETA_Junction_air is well-defined in a specific application. However, it
is certainly not a unique value for a specific component: it depends
heavily upon the application (e.g. air flow, use of heat sink, ...).

Our conclusion is that no single number suffises: even a simple model,
if it is to be valid for a wide range of environments will contain
several parameters. Unfortunately, such general models to characterise
the thermal behaviour are still missing for most of the electronic

This is one of the reasons why we are involved in the EC project DELPHI
(ESPRIT III), which should be finished at the end of this year. One of
its objectives is to have a standardized thermal model /
characterization, suitable for all relevant system environments. Already
some US-based and European component manufacturers have shown an

It is to be envisaged that as a consequence of the DELPHI approach we
are going to ask the component manufacturers in a foreseeable future to
provide us with thermal data that are more suited to predict the
critical temperatures within our application.

More information on DELPHI can be found in the literature (recent
conferences: I-therm, Semi-therm, Eurotherm, IEPS, ECTC, ...) and/or it
could be obtained from H.I. Rosten and/or J.D. Parry from Flomerics, the
project coordinator. They should have brochures and copies of overview
papers readily available. This company also has a WWW-site with some
DELPHI information :

We ourselves are managing the experimental validation workpackage in the

Best regards.

V Willem Temmerman
------------------- Alcatel Telecom - Research Division
| A L C A T E L | Fr. Wellesplein 1 - 2018 Antwerpen - Belgium
------------------- Phone: +32 3 240 9462 - Fax: +32 3 240 9932
TELECOM Email: temm[email protected]



Dear ASIC designer,

Back in the past, we were used to see all thermal data for packages in
TETA_Junction_air. Nowadays, when all parts consume more heat due to
size and operating frequency, more and more companies are using

My question to the ASIC designer and/or ASIC manufacturer is how do u
find this change common to the ASIC world. Does this trend acceptable or
not for u as a designer or u as an ASIC manufacturer..?

I will very much appreciate answering the list AND directly to me too.

best regards, yehuda


_/_/_/ _/_/_/_/ _/ Yehuda D. Yizraeli
_/ _/ _/
_/ _/_/_/ _/ Chip Express (Israel) Ltd.
_/ _/ _/ P.O.Box 2401
_/_/_/ _/_/_/_/ _/_/_/_/ Advanced Technology Center
Haifa , Israel 31024
Chip Express Israel Tel: +972-4855-0011 Ext. 245
-------------------------------- Fax: +972-4855-1122
The ASIC Time-to-Market Solution E-Mail: [email protected]