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 > <[email protected]> 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 > > > -- GPG fingerprint: 17FD 615A D20D AFE8 B3E4 C9D2 E324 20BE D47A 78C7
signature.asc
Description: PGP signature
