nations in Thick-Film and LTCC Technologies. Andrzej DZIEDZIC. Absrrucl - The miin d this papcr is to present and discuss some nondandard diagnostic ...
PROC. 22nd INTERNATIONAL CONFERENCE ON MICROELECTRONICS (MIEL ZOOO), VOL 2, NIS, SERBIA, 14-1 7 MAY, 2000
Non-Standard Physicochemical and Electrical Exami-
nations in Thick-Film and LTCC Technologies Andrzej DZIEDZIC Absrrucl - The m i i n d this papcr is to present and discuss some nondandard diagnostic mcthods used for physlcochcmical and electrical investigations of raw materials, inks, films and devices necesamy for or fahricatcd by polymer ur cermet thick-film techndogy as well as Law Temperature Cofircd Ceramics (LTCC) one. Uoth manufacturer’s and usor’s point or view are proscnted. Bcsides description of particular methods, their results and conclusions a t k t e d improvement of thick-film dcvlce faabdcation and reliability Increase is discumed.
I. INTRODUCTION Modem thick-film malerials are cvolving into passive elements of ititegratetl componcnts. On the other hand, the progress of photovoltaics, high-rcmperaturc supcrconductors as well as sensors a r d actuators is connected sigtdficantly with su-called lion-conventional applications of thick-film technulogy. At present, it is possible to distinguish thrcc basic modifications of this tcchnology: polymer thick~film-teci~nology, cermet thick-film tcchnology, Low Teinperaiure Cofued Ccramics (LTCC) technology.
In all cases thick-film dcvices are complicated, nonequilibr i m systems with physical and electrical properties dependent on microstruCture, which in lurn is dcrermined by proper arrangcmcnt of raw matcrials properties and canditiom of fabrication process. Ttie aim of this paper is tu present and discuss some non-standard diagnostic methods used for physicochemical and electrical investigations of raw materials, inks, films and devices. Thc so-wide range of described mcthods, useful 011 subsequent stages of fabrication of thick film, causes that both manufacturer’s as well as user’s point o f vicw will be presented. Moreover, besides description of particular methods, thcir results and conclusions affected improvement of thick-film device fabrication and reliability incrcase will bc presented. Andrzej Dziedzic Is with h e Institute of Microsystem Technology, Wroclaw University of Technology, Wybrzetc Wyspianskicgo 27,50-370Wroclaw, Poland, E-mail: adziedziclpwr.wroc.pI
The following physicochemical investigations (plicnomena) will be considered: 4 requirements for raw materials; methods of (heir fabri-
cation, application of scanning and transmission electran microscopy for analysis of subsequent stages of microsuucturc crcation, analysis of micmiructurc as well as interactions into and/or among different films with the aid of X-ray diffraction and chosen surface analytical tcchniques, influence of firing (crrringl conditions (e.g. tcmpcrature, firing atmosphere) OII film properties, influence oE ion and laser beam 011 film behaviour. The measurcnients from DC through low, medium and high frequcncies as well as microwaves up to optical rarigc can bc helpful in electrical characterization of thick-film dcviccs. The ineasurcments of resist“ during firindcuring process, low-frequency noise, voltage nonlinearity, high-voltage pulse durability and impedance spectroscopy will bc discussed from among tens of twstandard methods rcported in the litcrature. Moreover some methods used for acceleratcd srability and relinbiliiy examinations of thick-film cornponcnts and circuits will hc prcsented too. One should notc that tnost of information is based on papers prcsentcd during recent 10 years. Moreover, author used many of described methods in his own wscarch. Those readers, who me iiitcrcstcd in physicochemical and non-standnrd clcctrical measurements described bernrc 1990, are kindly asked to bccotiic familiar with hibliogrnphies [ 1,2].
TI. ANALYSIS OF SUBSEQUENT STAGES OF THICK-FILM FORMATION Thc mcasurctnent of film thickness at each produclion step secnis to be vcry uschl method to control the lhickfilm fabrication process. Especially noncontact inspection, performed using either optical microscopes or laser-based profiling systems. is preferrcd method far evaluating sam plcs because the same system can be used for wet, dricd and fired samples [3]. Thc above method contributes to increase the yield of well-characterized, commonly used ink system but does no! bring near to thorough understanding of processingc-tstructureoproperties relationships.
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On the other hand the commercially available thick-film dcviccs are too complicated, nonequilibrium systems. Therefore, the analysis of subsequent stages of particular thick-film formation is possible in the case of model ttiickfilm with well-known initial composition. For examplc some conclusions, available irl the literature connected with thick-film carbon hlacWpolymer systcm haw becn incompatilk with tach uttlcr. This is one of the reasons why during recent eight years the nulhor together with a group of co-workers have been involved slrongly in investigotions of plymer thick film-resistors [4-71. These investigations, tending among others towards creation of materials science principles for these dcviccs, started with morphology characterization of raw ink components (mean diamctcr as well ils shape and distribution of carbon black, graphitc and/or inorganic filler, physicochcmiml prnpcrties of applied polymer resin). Similar procedure has beea applicd earlier in invcstigations of cermet thick-film resistors [8,9j. Novcl technologies h a w been applied in preparation of raw materials and novel materials have been introduced into the inks. For example, very small (0.3to 1 pm), tightiy distributed splicricul gold particles have been cambined with a ncw vchiclc systcm which allows to printing and firing to a very smooth surface with no agglotncration of particlcs. Excctlcflt line dcfinition has been pallcrned by proper photoresist followcd by ctch process [lo]. This solution perrnit to overcome many of difficulties connected wilh application fur high petformancc packaging. Application uf sol-gel technology for resistor conducrive phssc fabrication [I I ] (this permits tu usc much smaller amount OF functional phasc in comparison with commcrcially available systems), application of functionally gradient Ag-cu potvdcr in cermet as well as polymer thick-film conductors [12], fabrication of new photosensitive conductivc psstcs (based on copper, silvcr-palladium, and tungstcn) for ccrmet, LTCC and IWCC (high temperature cofircd ceramics) circuits [13] and propcr dielectric matcrials [10,14] as well as eIaboratioii of novel capacitor materids with very high dielectric permittivity [15,16] can sewc as an examples of technological novclty innovations in thick-films. Such matcrial as diamond, thanks to its high thermal conductivity and high hiudness, can be applied no1 only as a new substrate for thick-film techno[ogy [I 71 but also as promoter oF abrasion resislanco, important c.g. for lifetime entarging of the thick-film thermal printheads [IS]. Thick-film technology has many features common with ceramic one. However, lack of compacity of the films causcs that in many applications thc electrjca1 propertics of corresponding ceramics is superior to thick-film cuunterparts. The inkresting, original solution of this problcm has been proposed in [I91 - the mechanical pressure, cithcr uniaxial or isostatic, has bccn Rpplicd on unfired screenprinted samplCS to producc densification level spproachlng that of ceramics.
There is no doubt that except of initial composition the firindcuring process affects microstructure and electrical propcr!ios of thick-films in a predominant way. Therefarc, it is important to analyse the subsequent stages of microstructure formation and rclatcd electrical propertics. Typical firing profiles are shown in Pig. 1.
v.:
I
Fig. 1, Firing (curing) profiles Tor polymcr, cermet and LTCC technologies.
The significant differences of firing (curing) profiles are visiblc. 'The LTCC technology is much more l h c consuming process than thc otbcr two. Therefore the possible interactions within the film and hetwccn film and substrate (LTCC tapc) should manirest itself hero much stronger. It is worth to mention that sometimes IR Rring/curing is used for productivity increasc of cermet [20) or polymer [21,22] thick-films. But up to now such a method has not been rcported for LTCC circuits. The resistance measurements in the course of standard firing (curing) cycle is very interesting method for chwacterization of thick-film resistor microstructure formation. It has bccn reported for ccrmet [8,9,23-261 and polymer 14.61 resistors as well as for analysis of curing kinetics of isotropically conductivc adhesives [27,28]. Time-temperalure supcrposjtion kinctics has been employed to mcasure activation cncrgy of cure of dielectric and conducting pdymer thick films, gcncraro master cure curves, and to analyse 1K cure profiles to give equivalent cure times at R sclected reference tcmperatures 1291. Moreover it has becn found that AC impedance memrement techniques can provide a mcans of monitoring thc microscopic changcs occurring within polymer thick-film rcsistor matcrials during the curing proc~ss[30]. The characteristic rcsistance changes during in-sim resistance measurement of ccrmct resistors rcsultcd from thc pyrolysis of organic vchiclc, sintcring of glass, pcnctration of glass into aggrcgatos of functional phase and bubblc formtion. I-Iowcver the in-siru resistancc is not seen to be a goad predictor of as-fired propetties.
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Thrcc basic stages of morphology development have becn distinguished in t l ~ ccase of polymer thick film rcsistors (carbon blacklpolyesterimidc systcm) independently on kisd and amount of active ptiaee. Bclow 20O’C they are connected with solvent cvoporation, thc pulycandcnsation process of CB-filled polyestccrlmide takes placc between 200 and 35OUC,and decomposition of polymer matrix connected with gra{luol film dcstruction occurs abovc 350°C. One should note that the X-ray diffraction, thcrmal P T A ) and thermogravimctric (TG) analyses, SEM and TEM observations of rilw inatcrials and cross-seclioiis OF surfaces of firedcured films, adhesion test as wcll as film thickncss measureincnt after sequential step of firinglcuring HISOshould be used for control and analysis of microstructurc development.
111. PHYSICOCHEMICAL ANALYSTS OF FIREDKURED TI-IXCK-FILMSTRUCTURES, COMPONENTS AND CIRCUITS Aluminium nitridc (AIN) is currently a real alternative aiumina as a substratc tnatcrial for microcircuit applications, in particular whcre high thermal conductivity is required. Howevcr, Ru02 used in resistor pastes can be rcduced by AIN [31]. The usc of crystallizing glass inten,sively impedes the ahovc reaction and enables the escape of gaseous reaction products. The lithium boratc gIass has been successfully uscd as ail adhesion promoter in a PdAg thick-film metallization on A!N [32,331. The nbove acbievcments arc not only B resuIt of thermodynamic considerations but have becn dctcymined by use of hut-stagc microscopy, SEM, DTA and TG measurements carried out in air or in nitrogen and X-ray diffraction. But still c o m mcrcially availnblc resistw pastcs for A1N substrates do not girdrantee such excellent properties as those for alumina. Tllick film components have becn used in hybrid microcircuits for almost 40 years. Nevertheless, so Par there has hcen no full explmation of the different physicochcmical processes. which occur during their processing. It seems chac such cxplaiiation is possible only for model thick-film systems with well-known initial composition and fabrication procedure. For cxample. knowledge about interactions among five resislor subsystems. i.e. metallic phase, glass, organic vehiclc, modifiers and substrate, makes easicr to obtain deviccs with prcdictable eIectricaI and stabiiity propertics. Most of such invcstigattions is related to cermet components [8-9,34-433. RI[ of the experimentat results permit to cmcludc that the firing process uf ii past^ resulting in proper thick-film components is accompanied by a sequmcc of chemical reactions influencing the state of the functional phase. Differential thcrmal analysis (DTA), thermogravimetry, energy dispersive X-ray ffuoresceacc, X-raydiffraction, thermomechanical mcasurementr, stomic absorption spcctroscopy (AAS), Pourior Transform Infrared Spectroscopy (FTIR).Secondary Ian Mass Spcctroscopy (SIMS), and UV-VISoptical spectroscopy are used in investigation of morphology, chemical composition and to
crystalline phases of Bred films, structures and components. For cxampic, the final propcrtics of the most popukar silver-palladium thick-film conductors have been correlated in [43] to a number of factors, including thermodynamics and kinetics of Pd oxidation (luring bumout and firing; physical and chemical reaction of the PdlAg with thc ceramic substratc, organic vehiclc, and soldcr; Ag difCusion and migration; inorganic and organic additives; powder characteristics and paste formulation. All of ihcse investigations are vcry important becausc different thickfilm components, in particular rcsistors, arc certniriiy metastable systems. This nieaiis that different interadom make the tiljcmstructure, composition and electrical properties uf the layers very variable according to the firing conditions. The scparatc attcntinn has to bc paid on microscopic investigations of surface morphology and sample cross scctions. Observations in scanning eleclron microscopy (SEM) are connected very oftcn with crtergy diapcrsive spcctcoscopy (EDS).Rut only transmission clcctron microscopy (TEM)images give the possibility for analysis nf suhtle modifications in the glass matrix in the vicinity of conductive graidglass inccrhcc 144-471.The above investigations show that conductor particles (bah KuOz and Ph2Ru2U7) are separated al equilibrium by a nanometer-thick film of glass. T h e r e h e the properties of these thick-film resislors are intimately ticd to thc thickncss, composition, and arcs of thc nanometer-thick glass film separating conductor particles. Vcry recently the complcnmrltary invcstigations of sptciillly preparcd Ru@-bascd thick-film resistors by electric force microscopy (RFM) and SEM gave an insiglii into the two-dimeiiaional elcctrical traisporl of lhcsc dcvices [48].This way thc 2D “percolative only” paths nf the electrical current near the resistor surface have hccn jmaged for thc first time and have bccn relatcd to the net of RuOl grains inhomogeneously dispersed in the glass mti-
trix.
One should remember that 011 the other hand ihe percolation and percolation-like theories are applied Tor description af the electrical propcrties for inorc than 20 ycars [Z]. However, the recent physicwhemical, cspccially microscopic, investigations makc the theoretical analyscs connected fnr example with pcrcol~tionthreshold i n carbon blacklpolycthylene coniposites 1491, conduction meclianism describing behaviour of rcsistors on diclectrics [50] as wcll as temperature dcpendcnce of resistance 1511, lowfrcqucncy noise [52,53],AC conductivily and relntcd ckc( r i d properties [54] of thick-film resistors much morc reliable. Much less papers is focused on thc interactions thai occur between LTCC compancnts and t a p s . The three cakgorios of inlcrfaccs: abrupt, broad and diffuse have boen distinguished based on SEM obsctvation of the various cofired resistodtape dielectric material cross sccljons 1551, Any interaction that occurs between the resistor and the tape dielcckic is a result of the diffusion of the glass c o m
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ponents. A ralio of components that increase the glass uansition temperature, T, (SiQz. A1103) to those components that decrease T, (PbO, A203,B1203) correlate well with the type of interface observed in the microstructure of various resistor material within the DP 851 tapc. Most of thc above physicochemical test techniques neccssitate a long preparation of the samples and are almost always destructive. Compared to other microinspection methods, the Scanning Acoustic Microscope ( S A M ) , using high frequency iiltrasonic waves as an invcsligation tool, is vcry attractivc because or thrcc particular characteristics: this technique is non-destructive, * i t allows subsurface imaging, it provides infarmation about different propercics of the sample (hardness, viscosity, adhesion, density, and topography) under the surfacc [SG]. In ordcr to satisfy the varied needs inhcrcnt in hybrid technology, it is necessary to have high frequency lenses (0.4 to 2 GHz) needed for surface or near subsurface analysis and lower ultrasonic freqi'ency Icnses (0.03 to 0.1 GHz) for dccper subsiirface analysis. This test technique is to bc cspecially suitable for investigation o€delamination and/or cxistencc of the air film inside thc LTCC circuits 157,581. Adhcsion strength of conductive films and clcctrical joints has beco~tie 811 important problem with the downsizing trend in ctcctronic devices. Generally, the adhesion strength of thick-film conductors to the substrate i s evaluated by the pccl or pull tcst methods. But they require soldcring a wire to the thick film, which results in the Formation of intermetallics from tho mctal clomcnts in the conductor and solder. T o avoid the effect of soldering a new adhesion strength test has been develaped in [59];two substrates have been bonded with lhick-film paste and pulled vertically to the substratcs until thcy scparatcd. Moreover the acoustic emission (AE) technique has been used to analyse thc Fracture mechanism 1601. fn the casc of interactions betwccn PdAg inctaltization and PbSnAg solder the metallization laycr gradually disappearing caused by elemcntal interdiffusion, with subsequent formation of inttcrmctalh may be key factors to affect thc fatigue lifetime and adhesion strength of the solder joints [61], Simultaneous measurement of shear farcc and contact electrical resistivity belwzen wire m d joining medium can describe the differences of debonding process of diffcrcnt joining mcdia [62]. An interesting question is influence of ion and lascr beam on bchaviour of thick films, in particular thick-film resistwrs. The laser trimming of ccrmct TFRs is commonly used. But there arc vcry few literature reports about bchaviuur of laser trimrncd polymcr TPRs. Meanwhile the polymer thick-film resisrors trimmed under proper conditions have the same degree of reliability as that of utitrimmed resistors [63,64].A novel laser applicalion Tor controlling ckctrical resistance of TFRs by the surface inadification without cutting a groovc has been described in 165,661. In this process the resistance is decreased, bccause thc amorphous glass in thick-film resistors is super-
saturated with Ru ions during the loser irradiation process regarded as rapid heating and rapid cooling, and the specific resistivity of the glass is decreased. Inn implantation appears to be a promising technique to improve both mechanical (wear rcsjstance, coefficient of friction) and cleclrical (variation of resistiviiy during friction) properties of resistive materials bascd on RuOz. The nitrogen and hydrogen ions me tlic most cffective for tnodifying surfacc properties 1671.
I V . NON-STANDARD ELECTRICAL CHARACTEREATION OF THICK-FILMS The AC properties of thick-film componcnts are intcresting because of their possiblc application to high Gequency and rnicrowavc hybrid circuits, Complctc ctiaricterization of AC propcrtics (impcdance spectroscopy) requires sophisticated incasuring itistmmcntation [&]. Thc term irripednnce spectroscopy indicates a . group of smallsignal measurements of lincnr eleccrictil response of testcd materials (devices) with furthcr spectra analysis and identitication of physicochemical phenomena. These phenomena are represented by the elements of electrical equivateni circuit. The method of impedance spcctroscopy has bccn applied €or charactcrization of high-tempcraturc thick-film cermets [69-71] as well as carbon (medium or high structurc carbon b1ack)lpolycstcrimide thick-film systcms [7,72,73] and phenolic-based polymer thick-film resistors [74]. AI this very moment impedance spectroscopy is thc only merhod which makes possible direct separation of volume (intrinsic) and electrodc (interface) effects. This is very useful when deterfining the influence of environmental exposures such as long-term temperature ageing or lung-term moisturization [73.74]. An interesting fact. that in most cilscs resistors with low noise indices showcd nearly ideal resistor response, while those with higher noisc had a largcr imaginary part, have been presented in [711 but its full confirmation requires further rcscarch. Somewhat different problcms arc connected with the use of [hick-filtn circuits in the gigahertz range, where it should hc taken into consideration that the high-frequency behaviour of thick-film rcsistnrs depends not only on the matcrials paratlleters of rcsistor pastes and substrates but also on its geometry [75]. Thc samc the resistors with similar DC resistances may have vcry different HF behaviours. Some peoplc can be surpriscd that noisc mcasuretneril is numbered among non-standard olec~ricalmeasurements, Hut in this casc it is not concerned with measurement ot' current noise index (CNI) according to MIL-STD-202 or1 a Quantech Noise Metcr. It is conncctcd with the measurcment OF rclative power spectral dcnsity, S in as widc frcquency range as pssible for dtffercnt bias voltage and for example at different environmental exposures (tcmperature, humidity). For a homugcneous electric field
s = sl/v'=:c/fn which means that the relative power spectral densiiy is invcrscly proportional to the sample volume, The above
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dependence forces one to use the product C = JX.2 (called the noise intensity) when comparing noisy properties of samples with various geometry. Thus C appears as a most universal quantity that should be used to characterize the material noisy properties. The measurements of the volume dependence of SV are performed rathcr rarely because they require specially designed test samples. Such meastiremeiits have been done, for example, for cermet I761 and polymer [77] thick-film resistors and in general they conFirm S - I/.Qproperty. Moreover it has been shown in [77] that for high structure carbon blncWpolyestcrimide resistors made on alumina substrate with W A g electrode8 the contact noise reaches 8% of bulk resistance noise. It has been shown in 1781 that the noise intensity of carbon black/polyeslerimide resistors is almost always lower than that of model cermet TFRs.But the noise intensity of (carbon black + gr~phite)/polyestecimideresistors usually is larger than the noise intensity of cermet ones. The power relationship C - (R Iv has been found both for polyiner [78] as well as cermet [79] components with exponent 17 from the range 0 5 2 . Such behaviour may be interpreted in term of percolation theory. Trimming the resistors to the final values increases the noise by Ihe factor of 10 [79]. but i t has been proved that the type of laser cut mostly induces the increase of current noise. Compariiig simple P-cut and L-cut it is visible that the incrensc of currcnt noisc is noticeably larger for the Pcuts while for the L-cuts there are only small changes in current nojse 1801. Modern circuits used for such noise measurements arc described in [78-801. According to theoretical considerations of macroscopically disordered systems both llf noise as wcll as third harmonics component generated in these media arc interpreted as a measure of the ciirrent distribution - see e.g. 18 1.521. Vohage susceptibility of weakly nonlinear composites is measured much rarely than their noise properties. Two methods can be used - “classical”, i t . measurement of amplitude of a third harmonics voltage aiter powering of tested resistors by very pure sinusoidd current [82-841 and “pulse” one, whcre thc amplitude of 5 1 0 ms voltage pulses {with 2+5 1 pulse off time) is changed for example according to’logarithmic stair pulse mode and the current is measured at the end of every pulse 184,851. As has been shown in [82] a resistor which indicated quite large initial TWI showed a remnrkable variation in resistance and had a defective surface in most cases. As a result i t has been evident that the initial third harmonic index has been available to estimate the degree of resistor reliability in a nondestructive test. However, it is interested to check if the mathematical equivalence of Ilf noise and third harmonic index is confirmed by equivalent experimental results. The measurements of both quantities for carbon blacWpolyesterimlde thick resistive films 178,841 confirm qualitative correlation between voltage nonlinearity and current noise but the quantitative correlation exists only inside the particular examined systems.
One should suppaee that the importancc of third harmonics measurement would be larger if it will be made not only at onc frequency (typically 10 Hid) but at some range of frequency; a power-law dependence V , dRhas been found in h u and Ag setnicotilinuous metal filtns for tl limited frequency range [81]. When the pulse duration in the pulse method describcd above is limited lo tens ps, proper waveform is creatcd and high electric field is generated during the pulse iiihide tested sample then high-voltage durability could bc invcstigated. The diagnostics of thick-film resistors afkcteti by
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scries of “short” valtage pulses has been presented e.g. iii [85-891, One should note that a pnlse voltage trimming method hafi been developed to realise a noncut trimming of cermet ,and I X C thick-film resistors without any darnagc to the resistor surfacc, The high voltage discharge method is important in investigations and optimization of thickfilm resistors for fabricntion of pulse infrared emitter 1901 or lighting surge protection [SI]. The mcasurcmcnts of resistance, capaccitatice and dissipation factor of polymer, cermet and LTCC resistors and capacitors in a wide temperalure range (for example Yrom liquid nitrogen up to 130°C) [92-471 as well as resistancc changes under high hydrostatic prcssure 1981also should be mentioned as examples of non-standard electrical mensurements of thick-film components. They are very important when conduction processes in such systems are ana-
iyscd.
V. RELTABU‘I‘Y INVESTIGATIONS Some aspects of reliability have been prcsented in prcvious chapters. BcIow some investigations connected with long-term high-temperature drift, moisture stability and power handling capability are briefly described. A standard long-term stability test conditions (for cermet nnd LTCC components) would be 150°C for 1000 hours at normal mom humidity; they have been used e.g. in [9,85,96,99,100].Almost the same thermal ageing conditions have been applied for polyiner thick-film composites [6,73,101].These cxposurcs art extremely high as l o r polymer thick-film rcsistors. The iaek of this acceleritied test by temperature overstress is to stimulate Ihe lifetime of 20 years at normal operation (at 70’C). This conventional ageing technique is also called accelerated but in m;my cases it is difficult and time consuming to study the inwinsic behaviour of modern high-stability thick-film resistor system. The limited resolution of the above method call be greatly improved by measuring the resistance drift directly at the ageing temperature, with so-caved in-situ method [lOZ,lO3]. The high-temperature stability is essenfial for this technique, since thc temperature stability is thc main limiting factor with respect to resolution. Therefore special furnace with stability of about 0.02”C for 24 hours has been specinlly designcd for in-sit14 measurements. Thanks to this furnace the stability characterization at fixed ttlmperilture takes about SO hours instead of 1000 hours. Morcover, by
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REFERENCES
means of in-situ electromotive force measurements, I&-
impedance spectroscopy, it has been possible for the first time to detect spontaneous and forced blistering in thick film multilayers during formation at high temperatures C1041. Some physical and chemical processes can cause resistive shorts between adjacent metallization stripes during circuit operation. One of these phenomena is the clectrochemical migration, i.e. transport of ions between two metallization paths under bins through an aqueous clectrolyte. Typicatly water drop (WD) and temperaturehumidity-bias (THB - 4S°C/95%R€€‘1 OVDC) tcsts have been performed on thick-film samples [lO5], bur also ultrasonic inspection permitted to alalyse this phenomenon in LTCC multilayers [JS].The problem of dendritic growth of meral appears also in some thick-film resistors [lo61 where copper dendrites propagates across the laser trims during bum-in at elevated temperature. Two mechanisms, surface migration of gas-phase migration, have been postulated to explain how the CuO on the surface of thick-film conductor material migrated froom t h e conductor into the resistor laser trim region. The thick-film resistors formed on thick-film multilayer substrates exhibit meaningful resistance ddfi. l’he E M stress analysis has been conducted to study the reason of this instability. It has becn stated that the stress creating a age current measurement and
crack in the overglaze formed on the thick-film resistor i s one ofthe basic sources of this drift. It has becn found, that drift in resistance has been drastically reduced by reducing the overglaze thermal expansion coefficient below 5 ppmK [ 1071. The above information treated mainly about resistor and dielectric reliability. However properties of conductor tracks arc important in equal degree. For example, modern automotive electronics demand thick-fdm conductors for 175DCoperation [IOX]. The 6:1 Ag:Pd seems the best cost and performance candidatc for the above generation canductor systems. But the eutectic tin-lead solder is not suitable for 175% operation; to maintain at least 15% margin for 175°C operation the solidus of the solder has to be above 515 R (242°C). This limits the choice of available solders to a few high lead solders. However because of the general toxicity problem of lead the conductive epoxy adhesives provide an altemative to high lead solder. The interconnections (made coga from polymer conductive silver paste) are exposed to perform under variety of environmental coflditions, and with an applied voltage. Thus knowledge of their corrosion and dissolution resistance is of utmost importance, It has been proved in [log] that polymer used in the pasto formulation provides the coverage of mare than 90% of Ag particles. The Ag corrosion and dissolution is reduced in t h e same degree. Moreover the anodic dissolution of Ag particlcs is greatly reduced in squcous solution, which contain benzotriazole.
[I] A. Dziedzic, ‘Physicochemicd investigations and nonstandard electrical measurements of inks and thick films - bibliography,’,Microe. ~ C ~ F O FReiiub, I. vo1.3 I (1991), p.537-548 [2] A. Dziedzic, ‘Bibliography on electrical conduclion in thick film resistors’,MlCroeleckun8Rehab., vo1.31 (1991). p.549--558 [3] T.Khosla, A. Inman, ‘Noncontact inspection twls mensurq wet, dricd and fired thick film circuits’. Advanced Puckoging, vol.8, no 5 (Mny 19991, p.36,38 141 A. aziedzic, H. Czarczynska. B.W. Licmerski. ‘In situ resistance nic&purementsBS 0 method of polycondensation investigation in carbonfilled polyesterimide fibs', 1nI. J. Elearonfcs, vo1.73 (1992), p.1071-
1072 [5] R Cmrczyiiska e/ d.‘Fabrication and electrical properties of carbonipolyesterimidethick resistive filnis’, Microelectronics J., vol. 21 (1993), p.689.696 [6]A. D2iedzic ei ai, ‘Further examinations of carbodpolyateriniidc thick-film resistors‘. L Marer. Sei.: Mum. in Eiectronm. vol.4 (i9931, p m - 2 4 0 ~
[71 _ _ A. Dzieiedzic, K.Nitsch. A. Kolek, ’Polymer hick-film resistor system basal on IiIgIi slructrrk carbon black;, I‘roc. 11’ European M&aleciuonics CO*, Venice 1997, p.622-626 IS] A. Dziedzic, L.Ciolonkn, ‘Electrical properties of cotlduclive materials used in thick-film resistors’, J. Muter. Scb, vo1.23 (1988). p.3151-
3155
[9]A , Driedzic,‘Thick film resistors with 1101 and Calr.TiI.,OJ -- examples of chemically reactive and unreactive systems,Miwoelecfromc J., vo1,19 (I 989), no.6. p.24-42 [IO] P. Barnwell, ‘ A novel thick film materials technology offering high performaicr. packaging solutiorir’, PFUC. MiurnMut 1997, Bcrl in 1997, p.84-89 Ill] T. Yamaguchi, ‘Sol-gcl processing and conduction mechnnisrii of RuU&~ss thick-film rcsistors’, J. Am. Ceram. Sm., voI.78 (199S), p.1372-1374 [12] T,Hori er U!, ‘The novel typa of miductive paste using ruiictiwnrlly gradient Ag-Cu powder’, Fruc. IEMI‘/IML‘ JN7, p.337-311 [I 31 T.Masaki el U!, ‘Photosensitive conductive paste’, Pr’roc. IEW/IMC 1997,p.355361 [14] M.H. LaBranclte et a/, ‘Next-generution,advmwd hick film multilayer systeni’. Proc, IGMT/IMC 1997, p,72-77 [IS] T.Mori el al, ‘High-rated voltage Y5S multilayer ceraniic capacitors’, Prw. IEW/MC 1997. p.378-382 116) T. Fukatuchi er 01, ‘Preparation of Pb(Mg1,$lb,)O,-PbTiO~ dielectricthick films‘, Proc. IEWYIMC 1997,p.122-12G [17] H. LUX,W. Sinetana ‘Diamond:a novcl substrate for thick film technology’. Sud and Conriwgs Technology, vo1.47 (1991), p.S53558 [18] H.-l. Krokosziiiski, ‘Abrmioii resistmice of diamoiid-like carbori coatings on thick film faistive material’, 31rrfaceand Courings Techn d ~ f lVOl.47 , (lWl), y,761-769 [ 19 S. Gouvemeur el or,‘New densification process of thick fib”. 1LKh Trow on Comp., f&br., mdMonuf: l ~ c ~ i n o vo1.16 l., (19931, p.SD5510 [20] K.R. Bube. C. Fisher, ‘The influence of fest infrared firing on tliick film materials’, 1EEE Trum. on Comp,,Hybr., and Munut ? L c h o l . , v01.6(1%3), p,436-442 1211 S,‘hkduschi @tal,‘Thedevelopinvnt of II short-time curing resistive paste for IMST HICs’, Pruc. I997 IEMT,,lMC, p.127-132 [22] A. Dziedzic, M. Miasz~l&‘Infrared and box oven cured polymcr thick-film rcsistors’,Prac. ZUb ISHM-PolandConJ, 1997,p.113-116 [23]T. Nakmo, T. Yamaguchi, ‘Studies on sintering of R u 0 2 - g I ~ TFRs s by in-situ resistance measurement’, In). J. Micuocircui/s and xkcfronlc PacRrrghgsvol. 16 (19931,p.61-70 [24] T. Nakano, T. Yamaguchi, Tffect of 4 concentration in firing atmosphcre on resistance of RuO,-glass thick-film resistors’, ,j. Am. Ceram. .h vol.78 . (INS),p.1703-1707 [25] P. Johnson, G.M.Croshie, W.T Donlon, ’Theeffects of processing conditions on the resistivity and microstruchire of ruthmatebased
502
thick film resistors’, J. Mafer. Sci.: Morerids In Ekctrodcs, v01.8 (1997), p.29-37 [24
G.M.Crosbic, F. Iolmson, W. Trela, ‘Processing factor dependence of rosistivig parameters of ruthmale-based thick film resistors with low temperature coefficicnls’, J. &d. P h p , ~01.84(IN@,p.29132919
[27] D,Klosteman, Li Li, J,E. Morris, ‘Materials characterization, conduction development and curing effects on reliability of isotropically conductive adhesives’, IEEE ‘fium. on Comp.. Puck, and Manirf: lkchnoi - Purl A., vo1.21 (1998). p.23-32 [28] S. Kotthaus et d, ‘Current-induced degradation of ~aotropicfilly conductive adhesives’, I I L W Tram, OII Camp,.,Pack, utid Manill: Technol-.Pari A., ~01.21(1998), p.259-265 [29] R.6,Prinic, ‘Characterimtioii and cure o f dieleclrio and conductiny polymer thick films’, Pol. Kflgn. unrl Science, v01.32 (1W). p.1286l28g [30] M.SeiQ R. Hitthe, M. Polczynski, ‘A ncw technique for monitoring curing of polymer thick filin resistor materials’, Proc. h r . Synip. un Micraelectronics(ISHM-USA), 1990, p.295-302 [31] C. Kretzschmar et nl, ‘The reaction between ruthenium dioxide and aluminium nitride in resistor pastes’, J. Murer. Scl, val.28 (1993),
[49] S. Nakatnura et 01, ‘Percolation thrcshold of mbon black-polyethylenc composites’, Jpn. J. Appl. P b y . , vo1.36(1997),p.5163.5168 [SO] K. Pitt, ‘Chemical canstitution and conduction medianisms in thick fihi resistors’, J. Mater. Scj.: Materials in E/eoronlc,~,vol.? (1996), p. 187-199 [5l] A.A. Snluskii, A. Di&c, B.W. Liwnerski, ‘Temperature behav. iour of percolation and percolation-like systems’,Int. J. Ekcwurr/cs, VOl.81 (1996), p.363-370 [S2] A A . Snarskii, A.E. Morozovsky, A. Kolek, A. Kusy, ‘I/f noise in percolation and percalationlike systems’, P h y Rev, B, vo1.53 (1996),
p.5596-5605
M.M.Jevtic. 2. Stsnimirovic, 1, Mrak, 'Low-frequency noise in thick-film resistors due to two-step fiinncling process in insulntor layer of elemental MM cell’, M E E T r m ~on . Componenfs ond I’uckaging Technology, vo1.22 (1989), p.120-125 I541 8.W. Licmcrski. ‘Thick-film cermets, their physical pmpeiqios ancl applications’, h r . 1 Efechnics. ~01.69 (1990), ~ ~ 7 9 . 8 6 [55] R.C. Sunerlin, G,O. Dayton, J.Y. Biggers, ’Thick-film resistoddieleciric interactions in n Low Tempernture Cc-fired Ceramic Package’, 1EEE Trow. on Cony., PackagtnE, and ManuJr Techo?. ’- Part B, ~01.18(1995), p.346-351 ~.$713-5716 [56j J. Krsuse et ol, ‘Scanning aconstio microscope: on attractive tool far [321 M.G. Norton. ‘Glass-ceramic interrctions and thick-film metallimthe thick f i t a technology cheracterisation’, Proc. b Inf. Klccironic ManufacrurIw Technology*mp.. Stresa 1990, p,313-321 tion of aluminium nitride’, 1 Muler. Scl, vo1.26 (1991), p.2322-2328 1331 M.G.Norton, ‘Thermodynamic considerations in the thick-film IS71 I. Kita et al., ‘~llVe8tlgRtiOnSon a gas sensor in LOW temperature rnetallization of &minium nitride substrates’, J. Mater. $ci, Letrers, Cofiriny Ceramics Tcchnology’, Proc. 2@ In#. Sprig Seminar on ~01.9 (1 WO), p.9 143 &clrunic TechnoloD (I$sE’97), Srklarska PorJba (Poland), 1981, [34] M. Hroyat, J. Holc, D.Kalar, ’Phase equilibria in the RuOd’b0p.39-44 TiOi and RuO#bO-NiO systems’, J. Mofer. Sci. Letters, vol. 13 [SS] G. Harsanyi ef al, ‘Analyzing MCM-C multilayer defects by using (1994), p.14061407 amustic micro imaging’, Proc Inf. Micrwkctronics Symp.,MAPSUSA 1998, p,$71-576 [35] R.Krausse ef U!, ‘Inletactions bstwecn ethylcelluiose and thick-film resistors containing ruthenium’, J. Muter. Sci. lerten, vol. IO (19i)l), [59] Y. Enokido, T. Yamaguchi, ‘Adhesion sbength of silver thick-film conductors by solder-free test‘. J. Mater. Sci.. vo1.32 (19971, p.4967p. 1392.1393 4971 I361 R.Monen er ai, ‘Evrtluation of ruthenabbased fhick film cermet [60] S, Uiokido. T. Yamaguchi, ‘Study on fraclurc of silver thick illin resistors’, J. Phys. Ll: Appl. Phys, vol,27 (1994), p.2227-2235 [37j R. Morten r f al, ‘Lead-free ruthcnium-based Ihick-film resistors: a conductors by acoiisric emission’. J. Mmr. Sci. Lefiers, vol, 14 study of model systems’,J. Mater. SCI.: Materids In ,Y~~cfronlcs, (1995), p.1646-1648 [Gl] 0.Y.Li, Y.C. Chan, ‘Interactions between silver-palladium nictalliV d . 2 ( l w l ) , p.46-53 zauion and tin-lead-silver solder’, Physlca Sruttrr ,Solidi (U). ~01.166 [38] M. Pntdenziati ef al, ‘Influence of the preparing conditions on the (19981, p.RI3-RI 4 pliysicochemicnl cliaracteristcs of glasses for thick film hybrid micraeleclronici’. .I. Mtdr0r. Res., vo1.9 (1994), p.230rl-2313 [621 X.Luo. D.D.L. Cliung, ‘A compmallve study ofsilvcr-epoxy and firv [39] S. lmmovilli et ul, ’Interactions between bismuth oxide and ceramic lead solder in their joints wilh copper, through mechanical and elecsubstrates for thick film technology’, J. Mater. Res., vol. I 3 (1W8), trical measurements durihg debonding’, J. Mater. Sci, vo1.34 (1W9). p.1865-1874 P.273-276 [40] M.Bersani fit a/, ’Interactionsbeween lead oxide and mamic sub1631 K Murakami, M. Tanaka, R. Ikedo. ‘Laser trimming of polymer strates for thick film technology’, J. Mater. R~J.,vol.12 (1997), thick film resistors’, Prw. Inf. Symp. on A4Icroelectronic.v (ISHMp.501-508 USA). 198.5, p.245.252 [41]‘r.N&mo et ai, ‘Analysis of chemical interaction belween RuOl and [MI A. Dziedzic, M. Micsznla, ‘Laser trimming of carbon/polyesterimide glass by Ostwald ripening’. h a c . h r . Symp. on interface, Willimsthick-film resistors’, Prac. 21” ISHM-Poland CmJ,Ustro9 (Polarid) 1997, p.27-32 burg 1593 [42] H. Moriwaki et ni, ‘Interactions between thick film resistors and [651 E. Gofuku. T Ogama,H. Takasago, ‘Surfammodificd RuOZ-baxed ilumina substrale’, Proc. In#. Ehcironic Mareriub and Technology thick film resistors using NdLYAG laser’, J. Appl. P h y ~ ,vo1.66 , Sytnp., Kanmwa 1993, p.4G-49 (19891, p.G 126-61 3 1 I431 S.F.Wang el ai, ‘Silver-palladium thick-film conductors’. J Awt. I661 11. G n i u h el U/., ‘EIectric conduction in surftlcc-modified thick film resistors using laser’, Prm. h t , Mlcroekctronlcs Con$, Tokyo 1990, Cerum. Soc., vo1.77 (1994), p.3051-3072 [44] K. Adachi e/ d,‘Mctoswcturd glass modificatians in as-fired and p.587-594 high-voltage-surged RuOrbased thick film resistors’, J Marev. Res., [61) A.V. Byeli, S.K,Shykh,V.P. Beresina, ‘Ion implantation to improve vol.6 (1991). p.1729-1735 mechanical and electrical properties of resistive materials based on 1451 K. Adachi, ‘TEMmicroanalysis of glass matrix md origin of electrirutltcnhun dioxide’, 1 Muter. Sci.: Materials in Eieclronics. v o l 7 cal conduction in RuO&sed tliick film resistors’, Proc. ht.Qmp. (1996), p.1119-422 011 MiCr#?ecWOMCS [ISHM-USA), 1991, p.426-430 [68] k. Nitsch, B.W. Licmerski, ‘Impedance spectroscopy in investi[46] N. Nicoluso ef al, ‘SEM and TEM/EDX analysis of interfaces in gation of electronic materials‘, Prw. UXMPoland Micraeiecfrunics inultiwmponent efectroceramics’, J. Eur. Cer. Soc., vol. 11 (19931, Symp.,WrooOaw 1995, p.35-40 p 347-352 I691 A. Kubovy, 0. Stefm, ’Remark a b u t the impednice ColvCule [47] Y-M.Chiang et nl, ‘Thin glws film between ultrafine conductor diagrams of thick-film resistors’. Czech. 4 Phys. vol,B36 (1986), p.659-662 particles In thick-film resistors’,J. Am. Cerrrm. Sac., vo1.77 (1994), p. 1143-1152 [701 Y.L.Chen, M.P. Harmer, ’A new model for thick film resistors’, J, [481 k Alessmdrini et al. ‘Correlation behem electric force microscopy Am. Cer. Soc., vo1.76{1933), p.U796 and scanning ek”l microscopy for the characterisation of gercolb [71] M. Hrovat I I al, ‘Characterisation of “equilibrated” thick film resistive conduction in electronic devices’, Philasophid Muguzine 8, tors’, Prm 36’ Int, Con$ on Microelecmnics, Devices and Materi~01.79 [ISaS), p.517-526 ak. RogdkaSlatina 1998, p.311-316 E531
503
[72] K.Nitsch e?or, ‘Impedance spectrosmpy of carbon black-fllled polyesterimidethick films’, Int. J. Ekctronlcs, ~01.76(l9!?4), p.981-986 [73JA. Dziedzic, K.Nitsch, B.W. Licmerski. h d y s i s of seeing effects in polymer thick film resistors based on DC measuments and impe+ dance spectroscopy*, Proc Iffh E w o p n n Microelectronics ConJ, Copenhagen 1995, p.238-2.16 [74] S,Jussila, K Stubb, 5. Picnimaa, ‘Impedance spectroscopy of the polymer thick film resistorhnductor interfacc’, Proc. f hElectronics Puckugin$ Murertuis AW%meSymp., Boston 1990,p.41-46 [7S] K.H. Dnie. H, Thust, ‘RFbchavior of printed resistors in the frequency range up to 6 GHz’. Proc. In!. &mp. on Mlcrwleclronks (iSHM-USA), 1996, p.66.70 1761 A. Masoero er ul, ‘Excess noise in thick film resistors: volumo depcndence’. Microdectronics Inb. No.37 w a y INS).p.S-8 [77] A. Kolek, A. Dzi&c, ‘Law-frcquencynoko of polymer thick-film resistors: analysis of volume depdence and contact cffect’, Proc 22nd In,. ConJ on’Micrwlecrrorr/cs(MIELW),NiS 1999 1781 A. Dziedzic. A. KoIek. ‘I/f noise io polymer thick-film rPsiSWrS’, J. fhy8. D: &p/. Phys., VO1.31 {1998),p.209t-2098 I791 A. Peled et U!, ’Ilf noise in bismuth nithenate based thick-film resistors’, IEEE Tram. an Comp., Pa&, and M a n d Techiiol - Part A., ~01.20 (1997), p.355-360 [80] A, Raab, C.Jung, P. Pullenkopf, ‘Current noise of trimmed tliickfilm rmistors: mensuremeiit and simulation’. MicrodecPonics IvlL vol. 15 (1998), NO.1, p . 15-22 [SI] Y. Yagil, G. Deutscher, Third-harmonic generation in semicantinuousmetalfilms’, PhpRew. B,vo1.46(1992),p.16 115-16 121 [82] S. Kasukabe, M.Tanaka, ‘Reliability evaluation of diicl; filni resistors though measurement of third hannonic index’, E‘iectrocomp. Sei,
mdTech~~d.v~I.8(1981),p.167-174 1831 P. Mach, ‘Nonlincariiy and noist of thick film resistors’, h o c . 17’‘ h i , @ringSeminar on k~fecirantcTccIIpIol.,Weissig 1994, p. 197-204 [84] A. Dziedzic. J. Kita, P. Mach, ‘Voltage nonlinearity of carbon blacldpolyesterimide thick resislive films’,Vacuum, vol.50 (I998), p. 125.130
[SS] J. Kim, A. Dziedzic, L.I. Golonka, G. Zuk, ‘Pulse durability of polymer, ccrrnet and LTCC thlck-film resistors,, Proc. 12” E’ur. Mtcrwleclrontca ConJ. HarmgaIC 1999, p.313-319 [86] T.Yamagtichi, T. Naknno, ‘ESD characteristics of RuO, bsscd thick film resistors,. Proc. h t . S p p . OR Mtcroelectronics (ISHM-UAX], 1990,p.48-52 [87] T.Tobita, 1-1. Takasago. ‘NewIrimming tectinique for a lhick film resistor by the pulse voltage method’, IEI& ?’’rum.on Comp., Hybr., andMan{$ Technol.,vol.14 (IWI), p.613-617 [88] T.Tobitn, H, Takasago, K. Kariya ‘Investigation of conduction mechanism in tldck film wistora trimmed by the pulse voltage method‘,IEEE Tmm. on Comp.. Hybr., and Manlyr Technol., voI.15 (1492), p.S83-588 [89]Y , Sririvasa Rao, M. Satyam, ‘Theeffect of high voltage pulses on PVC-gyaphite (hick flni rcsistors’, Inr. J. MuoC/rcuits and Elecf r o n i c P m W n g , vol. 20 (19971, p.51-55 [W] D.W. Knodlc, P. Graham,J.O. S m s , ‘Optimisatian of a thick film resistor for uw as a pulsed infrared emitter’, ProE. CO$ on @ h e lecrronic Devices and AppIIc(llim, San Diegn 1990, p, 10% IO9
504
[91] S. Vtiaudww, ‘Effect of design parameters on overstress chi” ierization of thick film resisiors for righting surge protection’, Proc Int. Symp. on Microelcctronl~{ISHM-USA), 1997, p.634-640 I921 J. Steinberg, B. Kistler, R. Cooper, ‘Materials and applications for thick film RC neiworks’, Pruc I M Microeleclronics ,Qmp,, ISHMUSA 19M, p.276-284 [33] H. U i d a d a!, ‘8uricd resistors and cnpacitors for multilayer h y ~ brids, Proc. Itrr. Micraelectr0plk.s Symp., ISHM-USA 1995, p.47-51. [94]A. Dziedzic, L.J. Golonka, M. Hcnke, ‘Temperahre properties of Low Temperature Cofuing Ceramics (LTCC) and Multilayer Capaci. tors’, P r m #3dInt, Scientflc Coll., Ilmenhu 1998, v01.2. p,198-202 /95] L.J.Golonka. A. Ihjedzjc, M. Henke, ‘Temperature properties of thick film rcjistors for LTCC applications’, Proc. 43M Int, Scieriffic Coll., Ilmenau 1498, va1.2, p.203-207 [%] k Dziedzic, L.J.Galanka. W. Mielcarak. ‘New configuration of LTCC passive components’, Prm. 12” Europew Microelectronics Con$, Harrogatc 1999,p.3-9 [97] K. Dclaney er ai, ‘Chmcterization and perfon” prcdictioli k r integral resistors in Low Toinperamre Cc-fired Ceramic Tcchnoiogy’, IEEE Tram. on AdvancedPackaging, voI.22 (19991,p.78-85 1981 A. Dziedic, A Magiera, R. WiUuiewski,‘Hydrostatic high ptcssure btudie4 of p o l p e r thick-film rezisrors’, Mlcroeleclrun. Reiinb., vol. 38 (19981, p.1893-1898 [99] K.S.R.C. Murthy, A. Vijay Kumw, ‘Failurcmechanisms in bisinurh rutlienate resistor systems’, 1 Muler. Scl.: Mater. in Mechmics, vol. I (1990), 11.61-71 [IOO]P.K. Khanm, S.K. Bhamagar, W.Gust, ‘ORthe themally ageing of thick film resistors’, Plty$icu SIuIw Solidl (a), vol. t 4 3 (t991), p.K33-K36 [ 1011 A. Dzicdzic. ‘Potymer thick-film resistors - chosen physicochenw caI wd electrical properties’ h o c . 21’‘ In!. C:mJ on Microelecrroriics (MIEL’97). NIS 1W7,vol. 1, p.427-430 [IO21 L.De Schcpper et ai, ‘A new approach to the study of the intrinsic ageing kinetics of thick film resistors’, Hybrid Circuits, No. 23 {Sept. 1990),p.5.13 [I031 L. De Schepper, L.M.Stab, R. Vanden Berghe, ‘ A new methud to test the long-term stability uf thick film resistors’&ticales Indwtriels, vol. 3-4 (19901 JI 77-80 [1M]J. Manca ef a!, ‘in dihd failure detection in thick film multilayer systems’, Quuli~aM‘Re/labili&h g n . h i . , vol.1 I(19951,p.307-31 I [lOS] 0.Harsmyi, ‘The effect of ionic impurities on electroctienical migration failure reliability of microcircuits’, Proc Int. Mlcrueicclronics Symp., MAPS-USA 1998. pS97-M)2 [IO61 J.B. Dixon, M.R. Northrup, D.T. Rooncy, ‘Failure analysis of a hybrid device exhibiting copper dendrite growth on thick film resistors’, Pro&.4j‘E/eclronrc Cottpmennls and Technolop C‘(J$, 1991, p. 1 c9-119 [I071T.Nagasaka, Y.Ootani. K. aka, ‘The application of FBM for thick filmmaterial design’, Proc. IEAt”E/IMC1997, p.312-316 [lo81 D.Nabatian et al, ‘Thick film conductors for I75C opemtiotl in automotive elecUonics’, Proc I n t Microelectronics Symp., IMAPSUSA 1991, p.522-528 [I%’] V. Bnssic et U!, ‘Corrosion And protection of a conductive silvcr paste’, J. Electrochem. Soc., ~01.142(1995), p.2591-2594
