Date: Tue, 29 Aug 1995 20:57:00 -0700 (PDT) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: msmith@atrad.adelaide.edu.au (Michael Smith) Cc: hardware@freebsd.org Subject: Re: S.O.S -2.1Stable and ASUSP54TP4 Message-ID: <199508300357.UAA05821@gndrsh.aac.dev.com> In-Reply-To: <199508300318.MAA27585@genesis.atrad.adelaide.edu.au> from "Michael Smith" at Aug 30, 95 12:48:44 pm
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> > Rodney W. Grimes stands accused of saying: > > I would have agreed with this 3 years ago, but I suggest you go study > > some of the current technology in use. > > I'd love to - you try getting that sort of data on this side of the planet 8) :-(. > > First alpha particle disturbance in DRAM is gone, it was pretty much killed > > 4 years ago with the advent of certain epoxy materials used to coat the > > die with before plastic encapsolation. At todays DRAM scales a single > > Neat - I knew they were using plastic because they could control the > isotope content more closely, I wasn't aware they'd gone to those > lengths. Once the charge on a cell dropped to about 2 alpha particles it become rather important to solve. > > Static memories are suspetable to alpha particule disturbance, it just > > takes a heck of a lot more to do it, and given ceramic is out of the > > picture it won't occur anyway. In a cmos static memory you have to have > > enough disturbance to perturb the gate voltage of one side of the latch > > to cause a bit flip, about 10 micro rinkens will do it, but it usually > > sends the device into latchup at the same time :-). > > Exactly; and to get that sort of flux, unless you're direct-beaming the > device, you're going to poach anyone standing nearby 8) Nah, just acid etch the plastic down to the die cavity and point a good UV light at it similulate similiar failure modes due to photon disturbances. > > The more prevelent cause today in single bit errors in both DRAM and SRAM > > is cause by VCC noise and or ION contamination caused by moisture > > absorbition into plastic packages before surface mount vapor phase soldering. > > Is that what the bother about mositure absorption is? I thought it had to > do with sweating during soldering - we get lots of SMD parts coming through > in moisture-proof packaging, but never got an answer out of the > manufacturers as to why... Yes, that is why you see all the mosture proofing. The problem is if the plastic obsorbos mosture prior to soldering, that mosture boils and expands quite rapidly when it hits the vapor phase, this causes micro cracks in the plastic, that then allow mosture to easily pentrate the package and cause ion contamination, which causes corrossion, which is very nasty/ugly for the chip. Answer can be obtained from any good pacakgeing engineer :-). And a few papers on the subject. > > Current FIT per bit are in the 0.0002 to 0.0004 range, that is measure in > > billions of power on hours. Today MTBF in a 2MB x 16 bit DRAM subsystem > > is 30 to 35 years... I'd say I can live with that given that my disk > > is going to go belly up in 57 years anyway :-) :-) :-) > > *chuckle* You're not taking vibration into account there - I'd love to > see some numbers on accelerated failure due to bond wire stress from > fan and disk spindle vibration Especially given the MTBBF > (mean time between bearing failure 8) for modern taiwanese CPU fans is > about, oh, six weeks ... Your back in the 80's again, bond wire stress does not exist in plastic packages, the bond wires are either a) totally gone due to TAB bonding between the die and the lead frame, or b) supported by the plastic used in encapsolation (ie, there is _no_ die cavity to speak of any more). That does not hold true of PGA or other cavity type packageing, but I haven't seen any of that stuff on disk drives lately! By American Enhance power supplies, the are made in Taiwan, but they use a ball bearing fan, and American Enhance long ago learned all about fan failures and how to fix them :-). Remeber, those low dollar clone manufactures are targeting the home PC market, where the MTPO (Mean Time Powered On) is only about 3 weeks a year :-). > > Sources of information for this and more details are in many vendors > > data books, Mircon's 1995 has a few good tech notes about it, as does > > Intels memory products books. > > Almost impossible to get over here 8( The agents for either of those two > want to talk MOQ 1000+ before they'll even think about giving you data. Hummm.. never had that problem here, simply explain that I am a contracting consultant by trade, drop a few client names, and boom.. I have all the data books I want. But then, these are all true things and I have a very lagitimate reason for needing there data books. > > > Rod Grimes rgrimes@gndrsh.aac.dev.com > > (note the new cc:) :-) Thanks... -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Reliable computers for FreeBSD
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