Xref: utzoo rec.audio:31657 sci.electronics:20238 Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!rice!uw-beaver!fluke!frankw From: frankw@tc.fluke.COM (Frank Wang) Newsgroups: rec.audio,sci.electronics Subject: Re: Transitor deterioration Message-ID: <1991May16.194955.487@tc.fluke.COM> Date: 16 May 91 19:49:55 GMT References: <18030315@hpfcdj.HP.COM> <3961@polari.UUCP> Distribution: usa Organization: John Fluke Mfg. Co., Inc., Everett, WA Lines: 36 In article <3961@polari.UUCP> miker@polari.UUCP (Mike Ranta) writes: >In article <18030315@hpfcdj.HP.COM> myers@hpfcdj.HP.COM (Bob Myers) writes: >>>Can anyone tell me if the power transistors used in ampifiers degrade >>>over time? What I'm getting at is: will it be necessary, after x number >>>of years, to replace the transistors to get that "like new sound". I >>>know that with tube amps, you must eventually retube. >> >This is an interesting question. Supposedly, bipolar transistors are prone >to a phenomenon known as "secondary breakdown". This occures when they're >driven near the limits of their "safe operating area" as the output devices >in audio power amps often are if you like it loud. Secondary breakdown is >where the current flow becomes localized within the silicon "die" instead >of being uniform. Bipolar devices conduct "harder" as they get hotter and >hence you end up with local "hot spots" on the die. Supposedly each time >this happens it alters the gain and other key properties of the device. >This is one of the big "claims to fame" of MOSFETS--they're immune to >secondary breakdown and hence will not degrade. There is a so called "metalization" in all bipolars, MOSFETs, and ICs that has recently drawn much interests for QA guys in Intel and other big volume semiconductor manufacturers. The term "metalization" came from the fact that metal diffuse into contact regions and/or SiO2 regions under high temperature or long time duration. This is not a major problem in old days. But, it is becoming a problem now because the line width can go as thing as 0.35 um for those high density DRAMs. Frank Wang @ John Fluke Mfg. Co., Inc. frankw@tc.fluke.com frankw@milton.u.washington.edu -- Frank Wang @ John Fluke Mfg. Co., Inc. frankw@tc.fluke.com frankw@milton.u.washington.edu