The problem of electronic cooling

Quote:

— THE RATIONAL USE OF ENERGY ————————————————————————————

The problem of electronic cooling,
and solutions


Microprocessor with improved performance,
covered by its system of heat evacuation.
Evergreen Technologies

Heat control is a key point in the design of electronic equipment, as the quality and reliability of equipment components are highly reliant upon the temperature. Miniaturization only serves to increase the sensitivity of heat dissipation. This is why the CEA, in coordination with the Grenoble polytechnic institute, is studying solutions to different problems posed by the rational use of energy in this field. Just limiting the temperature of an electronic chip below a critical level reduces heat movement in the semiconductor network. The component's connector temperature, which represents the average nominal heat level of the chip, is around 125° C for silicon. Homogeneity of temperature in the volume of the component also limits thermo-mechanical stress.
The architecture of a conventional component (figure) shows the heat path and the way that calories are dissipated from the base unit. This unit is the chip made of semi-conductor material and housing the electrical function toward the card or toward the printed circuit via the substrate. The substrate, made up of numerous levels of different materials, assures the mechanical hold, or the electrical insulation between the chip and the casing and the transmission of electrical signals outward. The chip/substrate combination, constituting the casing, is generally coated with a protective resin. In power electronics (see Toward low-tension, energy saving and low cost power electronics), there is no card, and the casing is threaded together with other elements.


An increasingly tricky problem

Electronic applications are everywhere and have seized the public's interest. In all fields – military, space, industrial, household – an increase in response speed is called for, as are size reduction, more complex operating methods, and greater reliability. Moore's Law, that predicts that semi-conductor performance will double every eighteen months, continues to hold out since the start of the 1970s for all components – microprocessors, memories, logic circuits, power components.
The problem of heat evacuation is present today at the very level of the component, because of the strong increase in flow density, owing to miniaturization and the increase in operating frequencies. Heat flux densities of 50 W/cm2 are the rule for the new generations of microprocessors. As for electronic power converters used for electric traction on rails and future hybrid vehicles, their volume is impressively reduced (by several grades). The IGBT (Insulated Gate Bipolar Transistor), with a surface area of around cm2, transfers high voltage and current, works at high frequencies and with flow densities up to 400 W/cm2. Laser diodes dissipate 500 W/cm2 and more.

New technologies to be implemented

There is thus a real need for innovation in mounting, connecting and cooling of components. In recent years, studies on micro-exchangers in copper integrated in the substrate of the power components, and functioning in forced convection with a cooling fluid in a laminar flow regimen or in diphase form (liquid and vapor phases) have been carried out. The studies showed the usefulness of such methods of cooling when the densities of evacuated flows reach 400 W/cm2 with water. However, these systems have several flaws, in particular the lack of electric insulation when water is used, and the overall thermo-mechanical ageing when an insulating ceramic is inserted between the chip and the exchanger.

Infra-red photograph showing the network
of the microchannel, the two collectors and
the two fluid power supply holes of
a silicon-etched micro-exchanger.
CEA

Another solution is to design micro-coolers in the silicon, using deep etching techniques (rectangular and hexagonal channels with internal hydraulic diameter of around 250 mm) and automatic soldering of silicon wafers, techniques with which the CEA's electronics and information technology laboratory (Leti) are highly familiar. In this type of structure, which serves both as support and casing, the cooling is carried out in forced laminar convection, with a single-phase fluid. It is pertinent for applications in which the component dissipates power greater than 100 W. The electrical insulation is facilitated through the insertion of a thin layer of silicon oxide, which reduces to two the number of interfaces between the neighboring expansibility materials (silicon and silicon oxide). Its small volume also allows for a more compact and lighter micro-cooler. The flow densities measured range from 200 to 400 W/cm2 (depending upon the shape of the channel) with a variation of 40°C between the extraction fluid and the channel wall. Coolers with hexagonal channels are less efficient but more flexible and less expensive.
For lower-power applications, i.e. less than one hundred watts, it would not be appropriate to implement a structure in silicon with powerful heat evacuation capacity, but rather to put into place a structure with strong diffusion capabilities. The concept of a passive, silicon with integrated heat pipe type exchanger, functioning in dual phase, and with a flow density potential of 100 W/cm2, is very promising. Numerous research laboratories are now investigating this, among them the CEA laboratories.

Alain Bricard
Research Group on Heat Exchangers
(GRETh)
Technological Research Division
CEA/Grenoble

and Christian Schaeffer
Grenoble electrotechnical laboratory
ENSIEG (Grenoble national college of
electrical engineers)
Grenoble Polytechnic Institute

http://www.cea.fr/gb/institutions/Clefs44/an-clefs44/clefs4485a.html

<i>if you know you don't know, the way could be more easy ...</i>
13 answers Last reply
More about problem electronic cooling
  1. Quote:
    Heat control is a key point in the design of electronic equipment, as the quality and reliability of equipment components are highly reliant upon the temperature.


    Quality and reliability(stability) not performance.

    :wink: The Cash Left In My Pocket,The BEST Benchmark :wink:
  2. yes, i know it now.


    <i>if you know you don't know, the way could be more easy ...</i>
  3. BUT DO YOU KNOW WHAT'S <b>ELECTRO-MIGRATION</b>? :lol: hehe

    i've plugged my home blower to my case ... dunno what happen ... that works?!?
  4. Oh, Oh, Oh, I know! I know!

    <font color=blue>At least half of all problems are caused by an insufficient power supply!</font color=blue>
  5. i have always the last word. hehe

    i've plugged my home blower to my case ... dunno what happen ... that works?!?
  6. What?

    <font color=blue>At least half of all problems are caused by an insufficient power supply!</font color=blue>
  7. Quote:
    Overclocking - Le Rodage


    Tension, température et ... électro-migration

    Au cœur de votre processeur, il y a quelques millions de transistors qui travaillent, et le passage d’un courant dans un transistor crée de la chaleur. Multipliez ça par le nombre de transistors et par la fréquence de fonctionnement (quelques centaines de millions de commutations par seconde), et vous obtenez la puissance que votre processeur dégage, qui est exprimée en Watts. Intel et AMD donnent des indications précises sur le dégagement maxi de leurs processeurs, qui est de 18,6 W pour un Celeron 300a, mais qui peut atteindre le double sur un PIII 600 ou un Athlon.

    Il y a une formule assez efficace pour déterminer la chaleur que dégage un processeur OC’é, qui à été proposée par un ingénieur en électronique de Singapour travaillant chez Lucent Technologies (anciens labos d’ATT), où il s’occupe de la conception des circuits intégrés : Matrix. Son principe de calcul est basé sur le fonctionnement des circuits CMOS (les processeurs de nos PC sont des circuits CMOS) et peut être résumé par la formule suivante :

    Puissance dégagée = fréquence (Mhz) x tension (v) x tension (v) x constante.

    La constante est ce qui est le plus dur à déterminer, mais par comparaison des processeurs Intel de la gamme Celeron, Matrix à pu l’estimer à 0,0155. Ce qui nous donne pour un Celeron 366 OC’é à 550 Mhz à une tension de 2.0 v le résultat suivant : 550 x 2.0 x 2.0 x 0,0155 = 34,1 W. Cette constante doit être ajustée selon le type de processeur (architecture, finesse de gravure, etc…) et on peut constater que les progrès réalisés dans la qualité de fabrication peuvent la réduire. Chez les plus récents processeurs de Intel, il semble qu’elle doive être ajustée à la baisse.

    Cette méthode empirique est assez intéressante, car elle montre bien l’impact de la fréquence de fonctionnement et surtout celui de la tension de fonctionnement du processeur : passer d’une tension de 2.0 v à 2.5 v augmente de 50% la chaleur dégagée par votre processeur ! Et la chaleur, c’est l’ennemi du processeur. Bien entendu, parce que la chaleur augmente l’instabilité de ce dernier (c’est bien pour ça qu’on vous parle des meilleurs radiateurs sur ce site), mais aussi parce avec le temps, elle peut détériorer celui-ci.

    Ce phénomène est bien connu en électronique et s’appelle " électro-migration ". Pour simplifier les choses, quand vous faites passer un courant dans un conducteur, donc à travers les microscopiques pistes métalliques gravées sur circuit intégré, des électrons se déplacent dans le métal et peuvent " arracher " des atomes quand ils rentrent en collision avec eux. Vous imaginez que cela n’est pas très bon pour un processeur, dont les pistes sont actuellement gravées en 0.25 microns. Et puis, ces atomes ne disparaissent pas dans la nature, ils peuvent naviguer et se retrouver sur une autre piste, où ils créeront un joli court circuit !

    Voici quelques belles images du genre de dégâts que peut engendrer l’électro-migration (détérioration ou rupture du métal, accumulation d’atomes), que j’ai copiées sur le site de Matrix. Cette galerie des horreurs, ça fait froid dans le dos ...


    <b>Mais la bonne nouvelle, c’est que grâce aux progrès réalisés par l’industrie de l’électronique, l’électro-migration est aujourd’hui bien maîtrisée, pour les processeurs utilisants l’aluminium comme composant. Elle met des années avant de se manifester, et la vie d’un processeur peut être estimée à environ 25 ans. SEULEMENT, soumis à une forte chaleur, le processus s’accélère, et la durée de vie de votre beau Celeron va être raccourcie. J’entends des cris : " raccourcie de combien ? ? ? " Suffisamment de temps pour que votre processeur fasse figure d’antiquité quand il finira par lâcher.</b>

    Mais, dites, je vous ai indiqué les risques, donc n’essayer pas de rôder votre processeur à 3,0 v, ou il vous claquera rapidement entre les doigts.


    << Page précédente
    Méthode pour roder son processeur
    Page suivante >>
    Le Rodage expliqué


    from <A HREF="http://www.hardware.fr/art/lire/165/3/" target="_new">Hardware</A>
    well it's in French, pick up a dictionary to translate that part. nevertheless i don't think it is really needed... :smile:


    i've plugged my home blower to my case ... dunno what happen ... that works?!?
  8. LIke I said, I already know about electo-migration. And I also know some French.

    <font color=blue>By now you're probably wishing you had ask more questions first!</font color=blue>
  9. Looks like this might be an interesting read. Could you please highlight the interesting areas, so I don't have to read all of it. ;-)

    <b><font color=red>I'm a bomb technician. If you see me running, try to keep up.</font color=red></b>
  10. LoL. the point is the first paragraph.

    Quote:
    — THE RATIONAL USE OF ENERGY ————————————————————————————

    The problem of electronic cooling,
    and solutions


    Microprocessor with improved performance,
    covered by its system of heat evacuation.
    Evergreen Technologies

    Heat control is a key point in the design of electronic equipment, as the quality and reliability of equipment components are highly reliant upon the temperature. Miniaturization only serves to increase the sensitivity of heat dissipation. This is why the CEA, in coordination with the Grenoble polytechnic institute, is studying solutions to different problems posed by the rational use of energy in this field. Just limiting the temperature of an electronic chip below a critical level reduces heat movement in the semiconductor network. The component's connector temperature, which represents the average nominal heat level of the chip, is around 125° C for silicon. Homogeneity of temperature in the volume of the component also limits thermo-mechanical stress.
    The architecture of a conventional component (figure) shows the heat path and the way that calories are dissipated from the base unit. This unit is the chip made of semi-conductor material and housing the electrical function toward the card or toward the printed circuit via the substrate. The substrate, made up of numerous levels of different materials, assures the mechanical hold, or the electrical insulation between the chip and the casing and the transmission of electrical signals outward. The chip/substrate combination, constituting the casing, is generally coated with a protective resin. In power electronics (see Toward low-tension, energy saving and low cost power electronics), there is no card, and the casing is threaded together with other elements.

    i've plugged my home blower to my case ... dunno what happen ... that works?!?
  11. OK, ok, enough!

    <font color=blue>By now you're probably wishing you had ask more questions first!</font color=blue>
  12. huh?!?


    i've plugged my home blower to my case ... dunno what happen ... that works?!?
  13. Good!

    <font color=blue>By now you're probably wishing you had ask more questions first!</font color=blue>
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