Re: Tim May's Passing Confirmed

On Sat, Dec 15, 2018 at 07:47:42PM +0000, jim bell wrote:

Tim May was very well-known in the 1979-era for his discovery that alpha particles (helium nuclei) caused data-read errors in then-current technology DRAMs.   (An article from the last year or two incorrectly stated that we met; I think that was simply a misinterpretation of the fact that I also worked for Intel during 1980-82. But, I worked in Oregon, Aloha-3 specifically; I believe May worked in Santa Clara. I never visited any Intel locations outside Oregon; I do not recall that Tim May ever visited Oregon.)  One of the very minor things I did while working at Intel involved Kapton (polyimide) 'shims' that were being experimented with to protect against such errors caused by alpha particles.  A rectangular sheet of very thin plastic was attached over the DRAM chip.  Due to the very-low penetration characteristic of alphas, this was plenty to stop them from striking the surface of the chip.  As part of the development and evaluation process, it was occasionally necessary to remove those shims from assembled devices. Peeling them off frequently destroyed the chip:  I used a tiny part of my Chemistry knowledge to recommend the use of the solvent, DMF (dimethyl formamide) to assist in this removal process, in a way which did not risk damage to the chip itself.   The reason Intel had the problem of alpha particles was its heavy use of "cerdip" packages. http://eesemi.com/cerdip.htm    (short for "ceramic dual inline package")   Cerdip looks vaguely like an Oreo cookie, with two ceramic plates attached with a glass 'glue'.  That ceramic had tiny amounts of radioactive elements in it; not a lot, but it didn't take much to produce a significant amount of alphas.  Cerdip was used because it achieved a hermetic seal, but it was cheaper than a different kind of ceramic packaging.   http://www.globalchipmaterials.com/visitors/products_visitors.htm  Had they packaged their DRAMs in plastic, that would have been a vast improvement, actually virtually eliminating the problem:  Production of plastics go through chemical processes where their components (monomers) are distilled, and so they contain virtually no radioactive atoms.  But they couldn't immediately shift to using plastic packaging, because such packages were not hermetically sealed:  Packaged in plastic, water from the environment eventually found its way to the chip itself.  The problem with that is that this water slowly reacted with one component of the glass, phosphorus-containing 'pyroglass'.  (a related material was 'pyrox')   These phosphorus glasses slowly reacted with that moisture to generate phosphoric acid, and in turn that slowly corroded the very thin aluminum conductors making up interconnects in that chip.  Fixing the problem caused by alpha particles eventually required changing the chip process so that it didn't require hermetic packaging, making plastic packaging workable.             Jim Bell

Fascinating. I enjoy reading the TUHS (The Unix Heritage Society) list, for posts similar to this - except they tend to be about software, specifically old versions of UNIX :P RIP Tim May.

               

On Saturday, December 15, 2018, 10:44:21 AM PST, John Young wrote:

This confirms Tim May's passing, by long-time cpunk, Lucky Green

Dear Friends, It is with sadness that news reaches me of the passing of my dear friend Tim May - Cypherpunks co-Founder, Discoverer of Radiation-Induced Single Even Upsets in Integrated Circuits, and Uncompromising Firearms Proponent: Tweet: https://twitter.com/luckygreen/status/1073925779304693760 Obit: https://www.facebook.com/lucky.green.73/posts/10155498914786706 Ad Astra, Tim! --Lucky

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