{"id":233,"date":"2012-06-04T20:34:12","date_gmt":"2012-06-05T01:34:12","guid":{"rendered":"http:\/\/tonykordyban.com\/?page_id=233"},"modified":"2014-04-13T20:21:52","modified_gmt":"2014-04-14T01:21:52","slug":"everything-you-know-is-wrong-may-2001","status":"publish","type":"page","link":"http:\/\/tonykordyban.com\/?page_id=233","title":{"rendered":"Everything You Know Is Wrong May 2001"},"content":{"rendered":"

Answers to those Doggone Thermal Design Questions<\/strong><\/p>\n

By Tony Kordyban<\/strong><\/p>\n

Copyright by Tony Kordyban 2001<\/p>\n

Dear Thermal Pessimist,\u00a0<\/em><\/p>\n

Isn’t your job actually getting easier day by day?\u00a0 It seems like every year the voltage level of digital logic devices goes down another notch.\u00a0 Years ago everything ran on 12V and 5V.\u00a0 Now you got your 3.3V logic family, your 1.8V stuff, and 0.5V is just around the corner.\u00a0 Isn’t the heat generated proportional to the square of the voltage drop?\u00a0 Pretty soon the power you deal with will be only 1\/100th as much as your grandpappy handled back in the good ol’ days of TTL (Twentieth Thentury Logic).\u00a0 Why be so pessimistic, except about your job security? <\/em>
\nPollyanna,Cape of Good Hope\u00a0<\/em><\/p>\n

\n
\n<\/div>\n

Dear Polly,<\/p>\n

I am pessimistic about everything, including job security for electronics cooling specialists.\u00a0 But not for the reason you give.<\/p>\n

You are right that power (heat generation) is related to the square of the voltage drop.\u00a0 Power per gate has gone down dramatically, and thermal issues for run-of-the-mill logic devices like flip-flops, buffers, and inverters have been eradicated like smallpox.\u00a0 But gate sizes have shrunk at an even faster rate.\u00a0 In the time that power per gate has been divided by a factor of 100, the number of gates on a single die has gone up by a factor of something like 1 million.\u00a0 There have been lots of other changes that have prevented the average processor power from being 10,000 watts.\u00a0 The point is that power per area is still going up faster than power per gate is going down.<\/p>\n

Thermal challenges continue to get worse with time.\u00a0 Power per chip is growing exponentially.\u00a0 There are plans to continue shrinking die features, and clock speed appears to be able to increase without limit.\u00a0 Power is directly proportional to clock speed for technologies like CMOS.<\/p>\n

One of these days they will figure out how to make integrated circuits in three dimensions.\u00a0 That will increase gates per volume, while reducing the surface area.\u00a0 And surface area is the only tool we thermal engineers have to pull out the heat.<\/p>\n

Optical computing and optical communications have just entered the game.\u00a0 Lasers produce much more heat than they do light, AND are very sensitive to temperature.\u00a0 Lasers with tight wavelength specs actually work best when cooled below normal room temperatures.\u00a0 They are some of my biggest headaches (opportunities!).<\/p>\n

And in case you think our jobs are much easier today because of all the advances in computer analysis tools, like desktop CFD, I\u00a0 agree, up to a point.\u00a0 Ever try to find flash memory that is rated to 125 degrees C ambient?\u00a0 If my “grandpappy” couldn’t cool his 8 kHz micro by slapping on a heat sink, he’d just bump up the device temperature rating from commercial to industrial grade, or even military grade if he had to, for a few extra bucks. Thanks to the end of the Cold War, nobody makes military grade components anymore.<\/p>\n

All that should point to better thermal job security, right?\u00a0 Not when you take a closer look at this minimally researched timeline of electronics cooling history:<\/p>\n

\n\n\n\n\n\n\n\n\n
\n

1940’s<\/p>\n<\/td>\n

Vacuum tube computers<\/td>\nThermal engineers are created to add heat sinks, fans, and water cooling to keep tubes from burning out every five minutes<\/td>\n<\/tr>\n
\n

1960’s<\/p>\n<\/td>\n

Transistors replace tubes<\/td>\nThermal guys become TV repairmen<\/td>\n<\/tr>\n
\n

1970’s<\/p>\n<\/td>\n

TTL integrated circuits<\/td>\nRe-hire thermal guys<\/td>\n<\/tr>\n
\n

1980’s<\/p>\n<\/td>\n

CMOS replaces TTL<\/td>\nThermal specialists re-trained to write C code<\/td>\n<\/tr>\n
\n

1990’s<\/p>\n<\/td>\n

high frequency CMOS, introduction of the 100W microprocessor<\/td>\nMechanical designers and analog circuit gurus take 3-day courses in CFD<\/td>\n<\/tr>\n
\n

2000<\/p>\n<\/td>\n

Worst thermal problems ever<\/td>\nElectronics cooling viewed as a legitimate engineering discipline<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

It is pretty obvious, at least to me, that we are overdue for a huge, unforeseen breakthrough in technology which will wipe out all our thermal problems for the next 5 to 10 years.\u00a0 What will it be?\u00a0 I haven’t got a clue.<\/p>\n

Could the person plumbing cold water into ENIAC have foreseen the invention of the transistor?<\/p>\n

I saw a paper presented at SemiTHERM a few years ago that may provide a hint.\u00a0 (V. Guruprasad, Synchronous Coherent Extraction of Heat<\/em>, Proceedings of IEEE Semiconductor Thermal Measurement and Management Symposium, 1998)\u00a0 I couldn’t tell if the guy was a genius or a fruitcake, or both.\u00a0 His idea was that CMOS devices all generate heat synchronously — all gate transitions occur on a clock signal.\u00a0 That makes them predictable.\u00a0 So you could add some other device (exactly what it was, he was somewhat vague about), acting out of phase with the clock, that could either cancel out the heat, or recapture the energy back into electricity, or laser light.\u00a0 Maybe it was perpetual motion.\u00a0 But some outlandish notion like that is bound to put me out of a job soon.<\/p>\n

That is my kind of pessimism.<\/p>\n

\n
\n<\/div>\n

Dear Mr. Temperature,\u00a0<\/em><\/p>\n

My grandpappy always told me that the electronics cooling business was cyclical.\u00a0 Do you have a favorite anecdote about it from the world of TV, or maybe science fiction?\u00a0<\/em><\/p>\n

Z. Cochrane, Talos IV\u00a0<\/em><\/p>\n

\n
\n<\/div>\n

Dear Zeph,<\/p>\n

I’ll do you one better — a true story about electronics cooling from sci-fi AND TV.<\/p>\n

In 1966 they were filming the original Star Trek<\/em> series.\u00a0 The show was set a few hundred years in the future — when thermal problems were so important that an engineer was a major character.\u00a0 Scotty was always warning the captain, I forget his name, that his engines were about to overheat, or that the dilithium crystals were on the verge of cracking from channeling too much energy.<\/p>\n

The show’s writers must have become familiar with these kinds of problems by just hanging around the Enterprise<\/em> bridge set.\u00a0 Robert Justman, the Associate Producer of the series, described the situation in Inside Star Trek, the Real Story<\/a><\/em>, (Herbert F. Solow and Robert H. Justman, Simon and Schuster, 1996.)<\/p>\n

\n\n\n\n
“It was the equipment, specifically that which powered all the console read-outs and light displays in the Bridge set.\u00a0 This was 1966.\u00a0 There were no computer chips or integrated circuits yet.\u00a0 Left on for any length of time, all the old-fashioned vacuum tubes, flickering lights, and wiring built up heat inside the cramped consoles until the overheated circuits blew out.We shut down the displays during rehearsal, but that didn’t solve the overheating problem.\u00a0 Heat built up continuously, and by afternoon the circuits overloaded within minutes of being activated.\u00a0 Our only solution was to rent portable air conditioning units.\u00a0 Large flexible ducts snaked across the stage floor and pumped cold air into special effects boss Jim Rugg’s complicated electronics.”<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

So cooling electronics was critical in 1966, and will be again when the Star Date is 4213.8.\u00a0 The trouble is convincing the bosses how important it is in between.<\/p>\n

 <\/p>\n

\u00a0<\/strong><\/p>\n

Isn\u2019t Everything He Knows Wrong, Too?<\/strong><\/p>\n

\"\"<\/a>\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014\u2014<\/strong><\/p>\n

The straight dope on Tony Kordyban<\/strong><\/p>\n

 <\/p>\n

Tony Kordyban has been an engineer in the field of electronics cooling for different telecom and power supply companies (who can keep track when they change names so frequently?) for the last twenty years.\u00a0 Maybe that doesn\u2019t make him an expert in heat transfer theory, but it has certainly gained him a lot of experience in the ways NOT to cool electronics.\u00a0 He does have some book-learnin\u2019, with a BS in Mechanical Engineering from the University of Detroit (motto:Detroit\u2014 no place for wimps) and a Masters in Mechanical Engineering from Stanford (motto: shouldn\u2019t Nobels count more than Rose Bowls?)<\/p>\n

In those twenty years Tony has come to the conclusion that a lot of the common practices of electronics cooling are full of baloney.\u00a0 He has run into so much nonsense in the field that he has found it easier to just assume \u201ceverything you know is wrong\u201d (from the comedy album by Firesign Theatre), and to question everything against the basic principles of heat transfer theory.<\/p>\n

Tony has been collecting case studies of the wrong way to cool electronics, using them to educate the cooling masses, applying humor as the sugar to help the medicine go down.\u00a0 These have been published recently by the ASME Press in a book called, \u201cHot Air Rises and Heat Sinks:\u00a0 Everything You Know About Cooling Electronics Is Wrong.\u201d\u00a0 It is available direct from ASME Press at 1-800-843-2763 or at their web site at http:\/\/www.asme.org\/pubs\/asmepress<\/a>,\u00a0\u00a0<\/em><\/strong>Order Number 800741.<\/p>\n","protected":false},"excerpt":{"rendered":"

Answers to those Doggone Thermal Design Questions By Tony Kordyban Copyright by Tony Kordyban 2001 Dear Thermal Pessimist,\u00a0 Isn’t your job actually getting easier day by day?\u00a0 It seems like every year the voltage level of digital logic devices goes down another notch.\u00a0 Years ago everything ran on 12V and 5V.\u00a0 Now you got your […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-233","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages\/233","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=233"}],"version-history":[{"count":3,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages\/233\/revisions"}],"predecessor-version":[{"id":236,"href":"http:\/\/tonykordyban.com\/index.php?rest_route=\/wp\/v2\/pages\/233\/revisions\/236"}],"wp:attachment":[{"href":"http:\/\/tonykordyban.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=233"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}