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By M. Hamamoto, M. Furuta, S. Tanaka

The Tamano smelter and refinery has expanded its production from 228kt/y to 260kt/y since 2006. It was not a big jump, but efficient and economical improvements were executed. These were not only de-bottlenecking and modernization of the smelting plant, including the acid plant, but also additional processes were commissioned, e.g. slag cleaning furnace and steam dryer. On the other hand, a conversion to permanent cathode process in the #2 tank house made the biggest impact on production efficiency for the refinery plant. In order to overcome the drastic change of copper business, although each scale is not so big, continuous improvements are very important to survive. This paper mainly describes the recent improvements of the smelting plant.

Jan 1, 2007

By Patrick J. Doig

The Crosstown 7 Collector System, Contract C28G11, is part of the Milwaukee Metropolitan Sewerage District's Waste Pollution Abatement Program. The contract involves the construction of 1.6 km (1 mile) of 3 m (10 ft.) diameter tunnel in soft ground. The tunnel is 10 m (35 Ft.) below surface and passes through a variety of soils. The eastern leg of the tunnel along Bruce Street is mainly in till material, a stiff, relatively dry clay. The northern leg along 16th Street starts in till, and continues in estuarine deposits - moist sticky clay, with intrusions of alluvial sand and gravel. The contract specifications required that the tunnel be constructed either under compressed air or with an earth pressure balance tunnel boring machine. The S. A. Healy Co., the general contractor, chose the latter option. Additionally, a single pass, pre-cast concrete segmental liner was selected as the lining system. The mining machine was manufactured by Lovat Tunnel of Canada and the segments were made by the Sehulster Company of Milwaukee. The use of this combination of machine and lining is relatively new to the United States and this tunnel is the most extensive built to date with a gasketed, segmental single pass lining for transportation of fluids. This paper details the various aspects of the construction of the tunnel and associated shafts.

Jan 1, 1989

By A. J. Nugent

Investigations were undertaken to evaluate peroxygen compounds for effective­ness in alkaline cyanide leaching of gold. The addition of peroxygens improved the leach results. Calcium peroxide was the best performed reagent to be employed. Improved reagent consumption followed the trend of calcium peroxide> hydrogen peroxide> no peroxygen addition. In general, preaeration stages could be eliminated, and improved leach rates achieved with no detrimental impact on leach perfor­mance. Interox has not developed an Au Plus (Trade Mark pending) system to utilise this new leach reagent. Initial plant trials are verifying its potential to give additional benefits.

Jan 1, 1990

By Thomas L. Hurst, Joseph M. Hans

INTRODUCTION The former Shiprock uranium mill site is located in the community of Shiprock, New Mexico on a bench overlooking the San Juan River (Figure 1). Both Shiprock and the mill site are located on the Navajo Indian Reservation. The millsite was built on a 230 acre tract leased by Kerr-McGee Oil Industries Inc., and was operated from 1954 to 1963. The Vanadium Corporation of America and its successor, the Foote Mineral Company, operated the mill from 1963 to 1968. During its entire operation, 1.5 million tons of uranium ore was milled producing 3711 tons of U308 concentrate. The concentrate was sold to the former U.S. Atomic Energy Commission. During milling, the ore was crushed to less than 35 mesh and acid leached to remove the uranium. The [ ] uranium was removed from the leach solution by solvent extraction and the uranium-barren solution discharged into raffinate ponds for disposal by evaporation and seepage. The spent solids (tailings) were pulped with waste process fluids and water and discharged to form tailings piles. The piles (ponds or dams) were formed with earth starter dikes. The dike walls were then raised using the separated sand fraction of the tailings. The slime fraction of the tailings were discharged into the diked impoundment. Since only a small fraction (0.25 percent) of the ore was U308 by weight, most of the ore bulk ended up as wastes. The wastes contain nearly all of the uranium decay chain radionuclides present in the ore except uranium. The mill was shut down and partially dismantled before the lease expired in 1973, and the remainder of the mill and wastes reverted back to the Navajo Tribe which was the lessor. Portions of the millsite were then occupied by the Navajo Engineering and Construction Authority (NECA), a Tribal enterprise. In order to provide skilled personnel to operate earth moving equipment, a heavy equipment operator's training school was also established on the mill site and was administered and operated by NECA. The U.S. Public Health Service (PHS) and the Environmental Protection Agency (EPA) staff conducted radiation surveys at four inactive uranium millsites on the Navajo Reservation in April 1974. During the survey of the Shiprock millsite, it was noted that the training activities were degrading its radiological condition. Both the PHS and EPA staff recommended that the training activities be directed towards the decontamination of the millsite area and interim stabilization of the tailings piles. Preparation for the decontami-nation work commenced in April 1974. In order to facilitate the decontamination activities, the mill site and its contaminated environs were divided into major areas labeled A through F (Figure 2). Areas A, B, and C are defined as "perimeter" areas and contained surface contamination ranging from 5 to 30 cm deep. Area D defined the mill yard and contained contamination ranging from 0.6 to 5.5 m deep. Area E contained several raffinate ponds which were removed to line up the northwest boundary of the tailings pile and to move the contaminants away from the vicinity of the occupied on-site buildings. The contaminants in Area E ranged from 0.05 to 5.5 m in depth. Area F encompassed the ore storage yard. Contaminants in this area ranged from 0.18 to 1.2 m deep. Washes, however, had contamination exceeding 7.6 m deep.

Jan 1, 1981

By J. W. Tsai

Both diamond crystals and diamond films were grown on silicon and copper substrates using a methane/hydrogen gas mixture as a precursor with thermal CVD techniques at low pressure environment. In addition to diamond particles, other crystalline phases including graphite and aluminum silicon carbide were observed on the substrate surface. ?The grown materials were analyzed with X-ray diffraction, electron microscopy, Auger electron spectroscopy and optical microscopy. Most synthesized diamond crystals were twinned. The flow rate of reactant gases, substrate nature, substrate temperature, decomposition temperature of the precursors, total pressure of reaction chamber, methane/hydrogen ratios and other possible parameters were varied during the growth processes, and the significant effects of these factors on nucleation and growth rate were evaluated.

Jan 1, 1989

By Francois E. Heuze

Today, the favored option for disposal of high-level nuclear wastes is their burial in mined caverns. As an alternative, the concept of deep disposal by rock melting (DRM) also has received some attention. DRM entails the injection of waste, in a cavity or borehole, 2 to 3 kilometers down in the earth crust. Granitic rocks are the prime candidate medium. The high thermal loading initially will melt the rock surrounding the waste. Following resolidification, a rock/waste matrix is formed, which should provide isolation for many years. The complex thermal, mechanical, and hydraulic aspects of DRM can be studied best by means of numerical models. The models must accommo¬date the coupling of the physical processes involved, and the temper¬ature dependency of the granite properties, some of which are subject to abrupt discontinuities, during [a]- ß phase transition and melting. This paper outlines a strategy for such complex modeling.

Jan 1, 1982

By G. F. Bolling

Single crystals of each metal were deformed at 77°K and heated at constant rates, variously in the range 0.125" to 4o°Kper min from 77" to -390oK, while being monitored in an X-ray diffractometer. Changes in diffraction-peak heights and line breadths were used to ascertain the temperature ranges of recrystalliza-tion. The results were subjected to the analysis of nicholas' in order to obtain the rate-controlling activation energies,Q. In this analysis no recourse to a separate and distinct nucleation stage is required and the results of studying recrystallization proved consistent with the hypothesis of a constant number of nuclei or equivalent hypotheses. The values Pb = 5.5 ± 0.5 keal per mole Zn ~ 7.5 Sn - 5 Bi - 9. 5 correspond for lead, zinc, and tin to activation energies obtained elsewhere for grain boundary migration, and for bismuth and lead to previous studies of re-crystallization by Barrett.6 This correlation allows the conclusions that interference from recovery was minimal and that the observed recrystallization rates in these pure metals are effectively governed by grain boundary migration. Good agreement was not found between the results of this kind of study in zone-refined aluminum and previous work; and supplementary isothermral experiments involving hardness tests and metallography did not resolve the discrepancy. Nevertheless, at least a range,Q = 11.5 ± 2 keal per mole, can be assigned to the activation energy for boundary migration in aluminum. An experimental study of one aspect of the recrystallization process is presented here for four metals of different crystal structure. The metals chosen for study were all zone-refined to reduce impurity effects, but the attendant high purity presented a difficulty. For any reasonably high driving force a "re-crystallization temperature", TR, is in the range of 0.25 T,, where T, is the absolute melting point, and study was therefore restricted to lower temperatures. An X-ray technique under constant heating-rate conditions adequate above 90°K was devised for the study; in consequence, a newer type of analysis following Nicholas1 had to be used to obtain quantitative information about activation energies. The standard methods of studying recrystallization have involved the comparable analyses of Johnson and Mehl2 and Avrami3 which are reviewed by Burke and Turnbull.* The general analysis4 which is applied only to isothermal studies using any of various investigative techniques states:

Jan 1, 1968

By S. N. Monteiro, E. B. Zanelato, J. Alexandre, M. T. Marvila, A. R. G. Azevedo, G. C. Xavier

One of the parameters used in the study of mortars is the adhesion resistance, which indicate show much the mortar adhered to the substrate. The usual study is done at 28 days, to worldwide standardization. Few researchers study the adhesion of mortars to ages other than 28 days. In this scenario, the adhesion strength tests of conventional mortar with a 1:1:6 mass scale (cement, and sand) at 7, 14, 28, 56, 91, 182 and 364 days were performed in order to understand the behavior of this material. The usual characterization tests of the mortars were carried out to correlate the values obtained with the adhesion results. The obtained results demonstrate that the mortar continues to gain resistance with the passage of time. For the trait studied the gain was considerable, indicating that over time the cement continues to hydrate, reacting and contributing to the strength of the material.

Mar 1, 2018

By Regis M. N. Pelloux, N. J. Grant

Five or six alloys each in the systems Ni-C.v, Ni-Mo, and NL-W, spaced to cover the single phase areas as well as a part of the adjacent two-phase field, were prepared as uacuum-melted alloys. Tensile tests at room temperature and stress rupture tests at 1200° and 1500°F we.ve run for time periods to give fracture in 0.1 to 500 hr. Observations mere made of solid-solution and second-phase strengthening or uleakening, coupled with studies of ductility and the role of structure on the noted behavior patterns. THE development of stable creep-resistant alloys while broad and systematic is also highly empirical. A number of simple rules have been suggestedL-" but these are based on scant data. Whereas rules for low-temperature alloy strengthening can be applied with some success in more simple systems, the extension to behavior at high temperatures (greater than about 0.4 of the absolute melting temperature) is very poorly understood and has encountered important exceptions and deviations in terms of atom size or valency effects. In particular, the occurrence of both solid-solution weakening4,5 and second-phase weakening2 at high temperatures is of interest. MATERIALS AND PROCEDURE Nickel was chosen as the base material because of its important role in current high-temperature alloy applications, because of its freedom from a phase transformation, and because of wide solubilities for many elements of interest. The selected alloys were single- and two-phase structures in the Ni-Cr,6 Ni-Mo,7 and Ni-w 8 systems. The alloys were vacuum melted and cast, utilizing high-purity raw materials, in the form of 15 lb ingots. They were readily forged into 1/2-in. bar stock (except the two highest chromium alloys). The alloy compositions are shown in Table I. Typical impurity values are: Carbon: Max 0.03 pct (except for 30 and 35 pct Cr alloys which had 0.07) Nitrogen: Max 0.005 pct (except for two of the Cr alloys which had 0.05) Sulfur: Max 0.004 pct Silicon: Max 0.05 pct Each alloy was solution treated (air quenched) to produce comparable grain size. The two-phase alloys were then overaged in an effort to produce a stable structure for testing at 1200° and 1500°F, The results are summarized in Table 11. Following the heat treatments outlined in Table 11, the bars were machined to a gage section of 1.25-in. long by 0.250-in. diam. In addition to room-temperature tensile tests, stress-rupture tests were run at 1200" and 1500°F for time periods from 0.1 to about 500 hr. RESULTS Room-Temperature Mechanical Properties—The ultimate tensile strength, total elongation, and reduction of area values for all the alloys are plotted vs atomic percent of the solute element in Fig. 1. It can be seen that for the same amount of solute element the ultimate tensile strength increases in the order chromium, molybdenum, tungsten. Elongation increases (reduction of area decreases) with increasing amounts of solute for all the solid solution alloys, the values ranging from 50 to 70 pct. The ultimate tensile strength values for the two-

Jan 1, 1961

The adsorption of gold onto activated carbon in iodide solutions has been studied. The adsorption rates were determined as a function of temperature, salt concentration and pH as well as activated carbon concentration. A kinetic model was also developed for the adsorption. The adsorption rate was believed to be controlled by a mixed mechanism of film diffusion and pore diffusion, but the film diffusion had a major contribution to the overall rate. Experimental findings were in good agreement with the model developed. The apparent activation energy was found to be 14.9 kJ/mol.

Jan 1, 1993

By C P. Kramers

The need to provide a sufficient quality and quantity of backfill continues to increase in South Africa, particularly as related to the increasing depth of mining. More and more applications require well designed fill systems either as classified or cemented backfill, and in some applications even tailings/aggregate based backfills. The paper discusses developments in backfill technology in South Africa with special emphasis on reliable system designs and operations, particularly as related to the preparation and hydraulic transportation aspects. Approaches for the alleviation of previous problems associated with premature pipe failures in vertical shaft columns for the distribution of tailings based backfills are discussed. Resulting from CSIRÆs developmental work, reliable full-flow systems, which can operate at low system pressures, have become a common practice, provided that backfill flowrates and internal pipe sizes are well matched. This aspect is reviewed. With regard to the tailings/aggregate based backfills the paper reviews some of the results of comprehensive in situ monitoring and the development of such systems. It is shown that a thorough understanding of the effects of aggregate top size, fines content and slurry relative density is required in order to ensure the restartability of temporarily shut-down pipelines. Some innovative technologies for the comminution of development waste underground to yield aggregate products potentially suitable or hydraulic transportation and backfilling, are briefly discussed.

Jan 1, 1998

Upgrading of a Flow Sheet Selection PC Algorithm for Refractory Concentrates Treatment

Sep 13, 2010

By E Cunha, D Roldao, TáTamantini, J F. C L Costa, T Webber, C Monteiro

The main problem of geostatistical simulations is to reproduce the real characteristics of the mineral deposit when there are few conditioning data. In this case, the geological interpretation, based on structures, geophysics and geological maps, plays the major role in terms of resource evaluation.The paper investigates the use of principal component analysis (PCA) to help classify multiple geostatistical categorical simulations considering the similarity among them and the interpreted model, herein referred as training image (TI).An iron deposit with four lithological facies, in a specific horizontal plane, was used as case study for two-dimensional (2D) simulations. Sequential indicator simulations (SIS) was used to obtain ten equally probable 2D images, which were generated and compared against the interpreted model (TI).In this study, 11 random variables are comprised by the vector of ten SIS realisations plus the training image (TI). The similarity between the TI and each SIS realisation is measured using the angle between the TI and SIS vectors projected in the new coordinate systems (PCA factors). It is possible to order the SIS realisations from the highest to the lowest PCA factor taking into account the TI similarity.The visual analysis of the images shows coherence in the PCA results as a method to measure similarity. This methodology can be used as a post-processing tool to rank simulation results and to select the ones which better represent the prior known geology or to compare the quality of different methods of simulation.

Sep 26, 2011

By D Craw

Uplift of the antiformal ranges in Central Otago, New Zealand , has resulted in the progressive evolution of eluvial placer deposits in tectonic sediments on the range flanks and along their margins. The placers are derived from the reworking of fine-grained gold from the auriferous Manuherikia Group fluvial sediments which covered the basement prior to uplift of the ranges. Gold in the tectonic sediments at Matakanui shows a progressive increase in grainsize in successively younger sediments and nuggets in the youngest gravel sequence are up to two orders of magnitude larger than gold grains in the parent alluvial source. Most of the gold in the tectonic sediments is highly irregular in shape, commonly with delicate surface textures which could not have survived fluvial transport and are indicative of authigenic precipitation. Some coarse grains have been rounded by recycling, and further addition of authigenic gold has occurred. Placer gold values result from both physical and chemical enrichment during sedimentary recycling. Continued range uplift and back-thrusting of sediments on to the ranges results in recycling of earlier formed placer sediments. They also result in further enrichment of gold values through the incorporation of additional supplies of the parent alluvial source sediment The host sediments are widespread along the ranges and are not confined to sites of historic mining activity.

Jan 1, 1992

By Edmilson Renato de Castro

O presente trabalho apresenta um forno para a produção de ferro gusa por redução carbotérmica estimulada por micro-ondas de minério de ferro, na forma de pelotas autoredutoras. O forno de redução com potência regulável de até 15 kW de micro-ondas de 2.45 GHz foi especialmente projetado e construído para este processo. A estrutura do forno é em aço inoxidável e utiliza três geradores de micro-ondas focados para o centro de um aplicador cilíndrico. Com esta configuração conseguiu-se produzir um campo eletromagnético de alta densidade energética. As cargas de pelotas auto-redutoras, com massas em torno de 90 g e 30 g foram reduzidas em um cadinho de carbeto de silício. A potência de micro-ondas irradiada foi de 6 kW. A montagem do forno dispõe de uma balança elétrica adaptada para suportar o cadinho de redução. O presente forno dispõe de controle e medida da potência fornecida e refletida, permitindo medir a energia de micro-ondas efetivamente aplicada à carga. Esta característica permite realizar balanços de massa e de energia além de determinar a evolução da taxa de reação através da medida contínua da massa das pelotas sob redução, ao longo do tempo de processamento. Obtiveram-se curvas cinéticas de redução carbotérmica de minério de ferro incentivada por micro-ondas e de seu consumo de energia durante o processo.

Aug 16, 2017

By Minge Zhao, Yuandong Pei, Zhixing Zhao, Zejun Ma, Lili Ban

"Confocal scanning laser microscope (CSLM) has been applied to carry out the in-situ observation of melting and solidifying characteristics during iron ore sintering process, accompanied with TG-DSC test. It can be found that apparent Liquid phase forming temperature(LFT) and ending solidifying temperature(EST) is about 1190? and 1160?, respectively. Forming liquid phase during sintering process goes through four courses, these are shrinking, expanding, shrinking and expanding coexisting and expanding totally. For Yandi fine, the corresponding temperature of these four courses is about 1120-1160?, 1190-1196?, 1218-1220? and 1233-1270?, respectively. Although CAJ fine has more difficulty in forming initial liquid phase, but when liquid phase expands, it may have better fluidity and easier for liquid phase formation. Adding enough CaO, CAJ fine takes on high fluidity like Yandi fine, because liquid phase during sintering process is formed mainly by reaction between CaO and Fe2O3.IntroductionConfocal scanning laser microscope (CSLM for short) has been applied to carry out the in-situ observation of metallurgical phenomena, especially in steelmaking process. Recently, many researches on ironmaking process were conducted with CLSM. While for high temperature properties during sintering process, there are limited reports on in situ observation1-2). In this paper, melting and solidifying characteristics of iron ore were observed with CLSM under simulated sintering temperature, and high temperature properties of iron ore during sintering process was clarified based on the in situ observation results and TG-DSC research."

Jan 1, 2012

By John F. Elliott

Six major trends that have had and are continuing to have major effects on the use and supplies of pig iron and scrap in the United States are (a) gradual replacement of the basic open hearth furnace (OH) by the basic oxygen furnace(BOF); (b) use of the electric furnaces for the production of plain-carbon steels, a trend which is closely related to the first; (c) United States changing from being a net exporter to a net importer of steel; (d) replacement of ingot casting by strand casting; (e) increased exportation of scrap; and (f) the lack of growth of the capacity of the U. S. steel industry to produce pig iron in the last 5 to 8 years. This report gives an analysis of the relationships between these trends and the use of processes for the production of raw steel in solidified form.

Jan 1, 1975

By Hillary W. St. Clair

This report describes a mathematical procedure for analyzing size distribution data by the method of moments. The method was applied to Andreasen's data on a variety of grinding mill products. It was found that the observed size distributions could be represented by gamma and beta distribution functions over a wide range of sizes. A computer program, written in BASIC, is described for calculating moments, distribution parameters, and the weight fraction in any size range.

Jan 1, 1969

The Annual Business Meeting of the members of The Rocky Mountain Coal Mining Institute held during he 84th Regular Meeting of the Institute was called to order by the president, H. Dean Jacot at 11:30 a.m Tuesday, June 28. 1988 in Peak Room 5 of Beaver Run Resort at Breckenridge, Colorado. Twenty three were present and a quorum was established. The president stated the purpose of the annual meeting is to inform members of the status of the affairs and activities of the corporation during the year. It was moved by Loren Linville, seconded and carried to approve the minutes of the previous meeting as published in the 1987 Proceedings. The chair called for reports of the various com¬mittees and these reports will he placed on file in the RMCMI office. Bylaws and Resolutions. Chairman Loren V. Linville reported there were no bylaws revisions. He further reported that the Board had adopted two resolutions: (I) Noting the passing of members since the last convention-Richard T. Brownrigg. Don A Dewey, John T. Maulshy. Hugh D. Nyquist and Mike Zakotnik. (2) Recognizing the superior skills of J. Brett Harvey. RMCMI Vice President of Utah. For recruiting 26 new members from the State of Utah and named him as #1 Recruiter in the Institute?s 1988 membership drive. Linville further commended the Executive Secretary officers, chairmen and committees loran excellent job in planning the 84th Regular Meeting and convention. Membership. In the absence of chairman Ed Sullivan. the secretary reported there are currently 718 active or dues paying members, 51 Life Members and 250 delinquent in dues payment. In the 1988 membership drive. 132 new members have been recruited and 74 of them attended this convention making up 27V, of the total attendance. Patrons of the Institute. This report was given by the secretary for chairman Ira McKeever. A total of 124 plaques has been prepared during the low year life of the program. It has been culled to 119 possible donors as some firms have gone out of business or consolidated. Of this number 46 renewed their annual $100 donation and three new Patrons have joined prior to the convention for a total of 49. During the convention. four new Patrons donated $100 each. tour former Patrons pledged $100 each and seven would be-new Patrons pledged $100 each for a total of 15. This would bring the grand total to 64 if all pledges are received prior to the close of this fiscal year as opposed to 59 renewals in 1987. Program. Co-Chairman Pete Nielsen announced the convention program theme "Broadening OUR Horizons" was well received despite the loss of three speakers during the final days prior to convention. Because the remarks of the Monday luncheon keynote speaker ran over the first time-to-be-tried Monday afternoon Poster Session was delayed almost an hour in beginning. This well thought out feature will he run again next year but in a different time frame. Nielsen thanked his co-chairmen, Bill Balaz and the Poster Session chairman Marcie Greenberg. Publicity. Chairman Tom Egan reported three newsletters including the convention newspaper were sent members during the year. He and Bob Jacob of Bob Jacob Public Relations were at registration daily to secure business card ads and to solicit advertising for the Proceedings. Scholarship. Chairman Keith McGinnis reported that six of the seven scholarship recipients were present at the convention. The University of Arizona at Tucson was added this year and it was the only university visited this year by the chairman. Each scholarship recipient was introduced to the membership at the Monday morning Welcome Session, presented a plaque and responded. The input Iron each winner was most favorable to the program. Each was appreciative of the many contacts made and the educational seminars and programs. McGinnis noted that the mining engineering department at the University of Wyoming may be dropped during the coming year. Joe Dunlap suggested that every member rally support of this department. Scholarship Award Winners: (top) Christine Gorrell-WY, Brian Memmott-UT and Andrew Kuchera-ND. (bottom) Anthony Bowler-AZ, LaVerne West-NM and Steve Newman-MT. Convention Committees Arrangements. Doris Finnie presented the following report: "In addition to the usual arrangements for this or any convention, there were others made for Special Events which included a Sunday historical tour and luncheon for 40, a Monday morning fashion show attended by 70 women. an afternoon scarf tying program for 47 with RMCMI red

Jan 1, 1988

By M. Khorouzan, L. Thomas

Designers of semiconductor devices have been strivi,ng to resolve problems associated with Au-A1 alloys in bonded in.tercomzeclions. One approach now being- used is that of waintaining a physical seyav-atioz between the two metals in bond areas. This is accolrzplished by alunzincnz-plating a bonding area on the tips oJ the kovar leads and using alcminurn wires to join the senzicondictor device to the leads. The portion of the kovar lead which is on the externul side of the sealed package is gold-plated to provide an oxide-free surface for soldering or welding. A discoloration condition originally thought to be sinilar to purple plague, occuving in the yluled uluninur bonding area after package sealing, has been investigated to determine its efiects ipm bond integrity. Electron-micro-probe analysis determined that no1 only gold, but lead, zinc, and silicon were also present in the discolored area. A series of samples conlaining' conkrolled umonts of these inzpitrities weve prepared and subjected to a sil.zuluted sealing process. The investigations swcued that, of the contawiinants, only zinc toas detrinenlul to Lhe bond integily. The discoloration condition itself was found not to be detrimental to the bond integrity. DESIGNERS of semiconductor devices have been striving to resolve problems associated with Au-A1 alloys in bonded interconnections. One approach now being used is that of maintaining a physical separation between the two metals in bond areas. This is accomplished by aluminum plating a bonding area on the tips of the kovar leads and using aluminum wires to join the semiconductor device to the kovar leads. The portion of the kovar lead which is on the external side of the sealed package is gold-plated to provide an oxide-free surface for soldering or welding. Contamination as evidenced by discoloration of the aluminum-plated area was observed in a number of integrated circuits undergoing examination for defect characteristics which cause electrical failures.' This paper contains the results of an investigation to determine the nature of this discoloration, its cause, and its effect upon the integrity of the interconnection bond. I) THE NATURE AND EXTENT OF ALUMINUM-BOND CONTAMINATION The initial hypothesis in the investigation was that the discoloration was caused by reaction of the aluminum film with some unknown contaminants during the sealing of the hermetically sealed integrated-circuit flat package. The package is a rectangular ceramic container sealed with glass which surrounds the kovar leads as well as joining the top to the bottom. The seal is made hermetic by heating and cooling the package to devitrify the glass. In the case of the packages under investigation, the hermetic sealing had been accomplished with dry air as internal atmosphere. The apparent effect of contaminations as observed by microscopic examination was the formation of surface oxides having variations in color encompassing the whole spectrum of visible light. The contamination appeared to be related to one of the more notorious examples of these colorations, the so called purple plague.' In addition to purple plague, Fig. 1 shows the tarnish in the luster of the aluminized surface in the bond area which had been observed in many of the integrated circuits. To identify the contaminant in the bond area electron-probe microanalysis techniques were used.3 Fig. 2 shows the result of this analysis. The contaminants identified were gold, aluminum, zinc, lead, silicon, and cobalt. Fig. 2(a) is a back-scatter display of the area under study. The back-scattered electrons provide a general indication of the distribution of elements in the specimen surface. Elements with higher atomic number scatter more electrons back from the surface and are seen as light areas in the picture. The sample current, Fig. 2(b), is the amount of current conducted by the specimen as a result of electron-beam striking it and is an indication of element distribution. The Sample current is the reverse of back-scatter and complements it. Other pictures in Fig. 2 are produced by characteristic X-rays generated by the elements, allowing the isolation of the element of interest. The isolated element appears white and all other elements are dark. In this manner a comparative study provides a correlation between different surface areas and the elements which are in these areas. The area covered by the gold film, Fig. 2(c), shows that the boundary between the gold film and the kovar is not sharp as expected and that some sort of diffusion has taken place. Fig. 2(c) shows that some gold particles have been carried to the bond area and are in the proximity of the bonded wire in spite of the presence of a physical barrier in the form of the un-

Jan 1, 1967