Nas =h ike Ofb3 Electronic Components and Circuits Electronic Systems Physical Sciences Fa>rication Technology Mathematics and li.t0. mation Sciences TOOOOOFYDU! : Life Sciences 02-03 POCA EAS FS © Gul Cc March 2002 INTRODUCTION ‘Tech Briefs are short announcements of innovations originating from research and development activ- ties of the National Aeronautics and Space Administration. They emphasize information considered Say tob o Cenaterebte exrons Huhete, eaponel, orC acyuly Snes Gnd ae Neues t encowage con. nercial application. 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NASA Field Centers and Program Offices Ames Research Center John F KennSpeaced Cyent er NASA Program Offices Carotna Biake Jim Alibert At NASA Headquarters there are seven major program offices that (650) 604-1754 or (321) 867-6224 or Gevelop and oversee technology projects of potential interest to i~t.stry: [email protected]. gov Jim Alibert- [email protected] Cari Rey Glen Muckiow Dryden Flight Research Lan‘e y R h Conter ys ae aedeeny Office of Space Sciences Baer-Riechart 757) 050-4005 or Small Business Technology (202) 358-2235 or = (661) 276-3689o r GSA. GOv 202) : ny -fiednart@dirc nasa.gov [email protected] Roger Crouch Glenn Research Center Office of Microgravity Scence Godderd Space Flight Center ~~ , Dr. Robert Norwood Appecatons (Code U) (301) 286-5810o r nasa.gov — tll gov (202) 358-2320 or ya — [email protected]. 1asa.gov Grenville Paules + ~ ccc + hy y Office of Mission toP lanet Earth (818) 354-2577 or (256) 544-2- 615 or O‘fofhince oMafn Skpiancee Pligit (Code MP) (202) 358-0706 or or Johneca Spece Center John C. Stennis Spece Center aa 281) 483-0476 or (228)6 80°1 829 oe or henry. davis1 @jsc.nesa.gov gov — (202) 358-4636 or thertr@mai_.hq.nasa.gov NASA Tech Briefs, March 2002 & TechBriefs National Aeronautics and Space Administration Electronic Components and Circuits 11 Electronic Systems 19 Physical Sciences 31 Materials 41 47 51 2||O'#B0/ 0 0/6 9|0 61 ir This document was prepared under the sponsorship of the National Aeronautics and Space Administration. Neither the United Government nor any person acting on behalf of the United States Goverment assumes any lability resulting from the use of the contained in this document, or warrants thet such use wil be free from privately owned rights. {BILAN PAGE Electronic Components and Circuits Hardware, Techniques, and Processes 7 Mounting Flip Chips on Heat-Dissipating, Matched-CTE Boards 8 Lightweight, Dimensionally Stable Printed-Wiring Boards 8 Nanoelectronic Devices With Precise Atomic-Scale Structures Books and Reports 10 PCI Bridge to Instrandu Tmeleecomnmunticastio n Systems b BLAN PAGE Mounting Flip Chips on Heat-Dissipating, Matched-CTE Boards John H. Glenn ResearCecnther , solder joints are less likely to fail. Cleveland, Ohio “Fip chip on board (COB) with high thermal conduacnd ttaiilorved icoetffiycie nt of thermal expansion (CTE)” denotes a Gevelocopncempt eforn reltativaelyl in ex- pensive, ightweight packaging of electron- ic croults to accommohgdh adetnsieti es of compaond nof eintnercotnnecstion s. The cor.cept addresses several issues thal pertain to fp-chip performaandn rcekaet¥ - ity and to the integration of fip chips with other compoTnhesee nisstuess in:clu de munsrof iundzesiared tmiismaotchnes of CTEs between fip chips and printec-winng boards (PWBs), removal of heat from high- power fip chips, and the need to madmize Usually, a conventPiWBo insa mlad e of an epoxy-matro/giass-lfarimnbienarte , Called “FR-4," with copper surface lay- ers that can be etched to form signal and power conducAt PoWBr sof. th e present developtmypee nintcluadels a core layer that contains a carbon cloth, sandbewtweien cFR-h4 oueter dlaye rs. Typically, the thickness of the carbon- Cloth layer is about one-third the overall thicokf nthee lasminsaie . Carbon doth is used in the core ayer because ft has several properties that ae Gesirable with respect to the issues men- tioned above. There properties include the high thermal conductivity of carbon fibers (up to 1,100 Wim), low CTE |<<10°* (Cy" in some cases], low mass density |=0.07 bin? (1.9 kg/m) for carbon versus =0.1 bin? (28 kg/m) for av minum], and high stifiness jup to =42 Mpsi (=290 GPa) for carbon versus =10 Mos (~69 GPa) for atminum]. The uss < 3 carbon-cofrie blayeerr t o increase the therma conductance of a PWS and thus the ability of the PWB to dis- sipate haat offers two benefits. One benefit is higher refabity: t has been estimated that in many cases, lowering the ternpera- These Temperature Maps were computed in a finite-element simutation of thermal conditions on ture of operation of electronic components a PWB on which four heat-generating fip chips are mounted. For each of the two cases shown by 10 °C approddnouablets ethle myea n here, the peak temperature mentioned in the text was caicuéated as an average over all nodal values within the “ootprints” of the flip chips. fi chp was estimated to be «277 F PWB was found to be «2.1 x 10°5 °C)’. (=136 °C) on a conventiFRo-n4 aPlWB Thus, the carbonc-oref eixhibbiets rle ss but only «129 °F (<54 °C) on a carbon- CTE mismatch with the chip substrate fiber-core PWB. material — silicon — for which the CTE in one example in the CTE-mismatch ranges from 3 x 10° to 5 x 10°6 ¢Cy"’. fiber-core FCOBs have shown the poter- analysis, the effective CTE of the region Ultrasonic imaofg caribon-nfibegr-co re tial for matchingo f CTEs and lowenng of a carbon-fibweherre- cfiop rcheip s FCOB specafiter mtheermaln tescts of Operating temperoaf ctomupornenetss. in would be mounted was foutnod b e the specreveraledn theat tnhe tsher mal one @arnple m the temperataunarlyesi s = 1.0 x 10°° (C}"; in contrast, the cor- tests dij not result in any detectable (see figure), the peak temperatuundreer a respCToE ofn a dconvientinonagl F R-4 increase in the incidence of faiures of NASA Tech Bnefs, March 2002 7 fip-Chip-mosuolndteri jnomgt s inquines concneghitms fiortnheg co m- Altn: Steve Fedor Mai Slo4p-8 21000 Ths work was done by Gan Lee ax meraal use of ths nverton should be Brookpark Road Cevela Oho 44135 Willan E Devs of Anpled Maternal Tech addrto eNAS‘s Glsenne Redsea rch fete to LEW-16890 nologres, inc., for Glenn Research Cx:er Center, Commercaal Technology Office, Lightweight, Dimensionally Stable Printed-Wiring Boards in comparison with traditional PWBs, these offer John H. Glenn Research Center, better heat dissiapnd aCTtE imaotchning . Cleveland, Ohio ad te comporets feo. badess Cm Camers) mounted on them. Prevous sobp tons to the heat-cisasndp aCTtE oprno t lens fheve moiced Te use of copper inver/co(OpOp ecorre s. WhCIeC co res contribute to reduced CTEs and noreased thera conducttheuy tasio econstri,bu te to Incr¢me wagaitss aend scos ts. Carbon cloth is used in the core layers of the present PWBs because @ affords a Comboif prnopeartiets filow oCTEn. h igh and hgh stifiness) that help io satisfy the requirements mentioned above. [The use of carbon cloth in the core layers of PWBs for this reason is reported in the preceding article, “Mounting Fip Chips on Heat- Dissipating, Matched-CTE Boards” (LEW- 16890).| The present carbon-coPrWBes Offer the advantbuta nogt ethes d,isa d- vantages, of PWBs with CIC cores: that is, unlike those with CIC cores, these are This PWB Contains a Carbon-Cioth Core and a total of engi copper layers. The overall dimen- sions of the board are approxim3.a25 tbey 4l2y5 in. (ab8.3o byu 10t.8 c m) Printed-vwiing boards PWBs) tet ae plus inner cores thal cortan carbon Goth especialy sudable as substrates for hghy rel- These PW2Ss are intended to accornmno- abe, ightwagt d@ectonc croutts fo aca date wh densities of d@ectrornc compo- and spacheavec berena defveltope d. Like nents and of interconneacmotnig otnhsan vaditona PVs, these PVs are laminated The designs of these PWSs can be opb- compthat oinclsude ciialatctnc einnesr la yers mized to satsly sevea requreme;nts., ps copper oute ayers that can be etched including removal of heal generated nm elec: to form signal and power conductorGsa.ng tronic components, ma@enization of stiffness Center, Commercial Technology Office, beyoy! the desgns of taditiond PVWGs, with minwnof wwazg, aantd omrwnriz a- Attn: Steve Fedor, Mail Stop 4-8, 21000 these PWSs node muffpie copper ayers ton of mismbeatweetn tche hcoefsicen ts Brookpark Road, Cleveland, Ohio 44135 separated by Gielectnc (e.g... polyrride) layers, of thermal epangon (CTEs) of the PWBs Retto LeEW-r166 48 Nanoelectronic Devices With Precise Atomic-Scale Structures Field-effect transistors with nanometer dimensions are Ames Research Center, under development. MofFfielde, Ctalitforn ia Since its invention in 1948. the transistor hon of integratechidps- hcavre osiuzets o f below 0.1 umn — a thousandth of the wadih has revolutionzed everyday life. The elec- «18 umn, and the eiectroncs industry has of a hurnahna r However, studies ncicate trorecs revolution is based on mwatunza- completed development of O.13-urn tran- that the mwwaturof vsoaont tiranoasntor s ton of transistors; snaler transistors ae sistors, woh wil enter productwointh n wil soon reach its knw faster, and Genser crouitry has more func the next few yeas. ndusty researchers For further progress in microelectronics, tonality Transn tihe sprteseont rgesner a- are now wortdng to reduce transistor sizes iti S Necessary to turn to nanotechnology NASA Tech Bnets. March 2002 Rate flan cor@rury to rewire ra seis © @ port wee fey becore urvelabie, nanctactrOffoeris oheg yne w approach of buliding devices on the aforn- ic scale. One wsion for the ned generation of mwwhre dectok Gosty & ta of @tomic-chan @lectorics, according to fs vigion, each devic:s is composed of alors aged on top of a .istate astace na regula pattem. The Atomic Chain Gec- tonics Project (ACEP) — part of a nan Cecnology goup @ Ames Reseach Carter .— has been developing the theory fo understanding alormic-chan devces. ad 8 patert to aomc-chain e@actorics has been Sed and is now pending. The use of Goparts 6 clicd lo fe tirctonaity of tarestors. Doparts we mpuries merntadodedn tao tlhe ysar e contadnsisiuo: Ccharreti to; rais e or lower the device swic+-on voltage Typically, @ macroscopic varsisio’ fore wih a size of the order of 10° m contains severa fousand dopant alors fal, on the scale of the over device, apped to be sneered ouf as a dopart “jelly,” as @us- vated in the top part of Figure 1. Because of the large nurrbe of dopart ators, the Source precise location of each dopart atom is not very enportart to the tunctioning of the vangistor. Howewhevn tehe rsiz,e of a vanaistor is reduced to the range of 10°* to 10°” m, as Gustated in the middie part of gure 1, the nunibe of dopart atoms s less fran about 100, n which case fe Ato<m10°i mc (ta:p) (c) of the few dopant atoms precisely, and as Figure | Transistors Heve Been Mintsartesd. startny form fhe macroscop scale. where Mou a ream, ond vemos fm irctowg sands of dopat storns can be regarded as being © a encom deeingon Pet deternmes fhe switt-on voRtage Al the mesoscope scate, anemstors hove Giterert sxitt+on volagss, depend ocoy among tranaistors. Such variaiions ig on precisaly where fhe dopart storms ave located To prevert such u-to-w veriafors, fhe ae tata’ when miiors o blions of tarais- Next step © murusturizeton w8 not be ecoomplished by matung comentora/ vansist-ys safer tors we megated m a commuter Cw, retesd. vaneiwish Gtreonsrorss <1 rym wi be made turn chams of preciesly posiiioned strns. because the variations can cascade fom one device to the next. evertualy gg not) appied — field effect. Metals aways atoms in air iti s necessary to place them fee tf a marci A sohdioof nfi s conduct cvrert. A feki-eflect ranistor on top of a substrate. Surface atoms of aspect of te minetvization protien, uses @ semicontodr tuhe cChtannoa ran d tte s.israte attract ators in the chan devised by the ACEP és to cuate di te @ meta to d@ectanod dfse 6s h,ow & and hokd then at ted positions. The sur- device structures wih aor Cwis ed actweves large gan. Thus, @ is necessary face of a substrate can be made to have oul na reguéer precise pattern by anchor- to devee Chains wih semiconductasr d atc" *cale Corrugaatndu thnesse ,ca n rg atoms to a sierate, as stated n meta properties. Fret, fe ACEP tean be used to creste ¢ precise pattern for the botptarto ofr Fignure 1. tackéed @ senple protien theoretically ff @omic-chan d@ecturics. However, te A second oftical aspect of the function one can arrange siicon atoms dong a re atractve toro, between the sisrate ng Of a vanesto 6 gan te ag of te foating in a, is tis Chan sericoncact- and chain ators that ae srnply placed n vangistor shouid be a magiied version of rng? The weve 6 superg Shag the corruigs iaco tweiak oton ssecv e & rout. ACEP rosheasa iecd bh t e buk or twin silicon is sericoni.ctry, atorne reliably, ACE reseahars ctehd t o condusion that n desigwng atomic-chain @n isolated chain of silicon atorns is aways the concthlat ua Chsemiicalo bonndi ng vansitos ptrodoucre sga n, ore sou metalic. FortunACaEP treeselarcyh ,as o scheme is neede:! to secure Chain atorns egicot te tek ofect, wih 6 Te ov letaf fde sfixi ng Tal 2 magnesium rehably, and to the turther conclusion that mechveriiaed nepeiimenstalyn ©) tr Chain iss emiconduevcent tiounghg ,bu k the properties of a C.ain are strongy inf a@t the atorric scale. Serra ochuctors o> magnesisi muetamli c enced by the substrate material and au- @uct current only when a ode voRage is és Of course, @ is not possittoi feoa t face orienwhetn cahetmicial obonndi ng