Precious Metal Alloys Research Articles

Wafer Level Solder Bumping and Flip Chip Assembly with Solder Balls Down to 30μm

The most important technology driver in the electronics industry is miniaturization mainly driven by size reduction on wafer level and cost. One of the interconnection technologies for fine pitch applications with the potential for highest integration and cost savings is Flip Chip technology. The commonly used method of generating fine pitch solder bumps is by electroplating the solder. This process is difficult to control or even impossible if it comes to ternary or quaternary alloys. The work described in this study addresses the limitations of existing bumping technologies by enabling low-cost, fine pitch bumping and the use of a very large variety of solder alloys. This flexibility in the selection of the solder materials and UBM stacks is a large advantage if it is essential to improve temperature cycling resistance, drop test resistance, or to increase electromigration lifetime. The technology allows rapid changeover between different low melting solder alloys. Tighter bump pitches and a better bump quality (no flux entrapment) are achievable than with screen printing of solder paste. Because no solder material is wasted, the material costs for precious metal alloys like Au80Sn20 are much lower than with other bumping processes. Solder bumps with a diameter between to date 30 μm and 500 μm as well as small and large batches can be manufactured with one cost efficient process. To explore this potential, cost-efficient solder bumping and automated assembly technologies for the processing of Flip Chips have been developed and qualified. Flip Chips used in this study are 10 mm by 10 mm in size, have a pitch of 100 μm and a solder ball diameter of 30 μm, 40 μm or 50μm, respectively. Wafer level solder application has been done using wafer level solder sphere transfer process or solder sphere jetting technology, respectively. The latter tool has been used for many years in the wafer level packaging industry for both Flip Chip and chip scale packaging applications. It is commonly known in the industry as a solder ball bumping equipment. For the described work the process was scaled down for processing solder spheres with a diameter of 30 μm what was never done before that way worldwide. The research has shown that the underfill process is one of the most crucial factors when it comes to Flip Chip miniaturization for high reliability applications. Therefore, high performance underfill material was qualified initially [1]. Final long term reliability testing has been done according to MIL-STD883G, method 1010.8, condition B up to thirteen thousand cycles with excellent performance of the highly miniaturized solder joints. SEM/EDX and other analysis techniques will be presented. Additionally, an analysis of the failure mechanism will be given and recommendations for key applications and further miniaturization will be outlined.

Growth of Phthalocyanine Doped and Undoped Nanotubes Using Mild Synthesis Conditions for Development of Novel Oxygen Reduction Catalysts

Precious metal alloys have been the predominant electrocatalyst used for oxygen reduction in fuel cells since the 1960s. Although performance of these catalysts is high, they do have drawbacks. The two main problems with precious metal alloys are catalyst passivation and cost. This is why new novel catalysts are being developed and employed for oxygen reduction. This paper details the low temperature solvothermal synthesis and characterization of carbon nanotubes that have been doped with both iron and cobalt centered phthalocyanine. The synthesis is a novel low-temperature, supercritical solvent synthesis that reduces halocarbons to form a metal chloride byproduct and carbon nanotubes. Perchlorinated phthalocyanine was added to the nanotube synthesis to incorporate the phthalocyanine structure into the graphene sheets of the nanotubes to produce doped nanotubes that have the catalytic oxygen reduction capabilities of the metallo-phthalocyanine and the advantageous material qualities of carbon nanotubes. The cobalt phthalocyanine doped carbon nanotubes showed a half wave oxygen reduction potential of -0.050 ± 0.005 V vs Hg\HgO, in comparison to platinum's half wave oxygen reduction potential of -0.197 ± 0.002 V vs Hg\HgO.

The implant-supported milled bar overdenture: A literature review

This bibliographical review aims to determine the present situation of the implant-supported milled bar overdenture as a therapeutic option in implantology, as well as to set and compare the techniques and materials currently used for making them. By searching the main electronic bibliographical data in indexed Medline articles, we obtained a total number of 20 articles that fulfilled the requirements of this bibliographical review. The implant-supported milled bar overdenture offers excellent long-term successful results, although complication rates are higher in emergency cases of patients initially planned for a fixed prosthesis. Krenmair and collaborators found cumulative survival rates of implants on milled bars after 5 years, of 99% in mandible cases, and of 97.8% in maxilla cases. No detailed protocols specifying the necessary number of implants or their characteristics have been found, though they are never made with less than 4 implants in mandible or 4-6 in the maxilla. Milled bars are screwed, generally cast in a precious metal alloy, with a metal or acrylic suprastructure and include attachments that regulate the tightness. The suprastructure adjusts precisely and rigidly to the milled bar, and presents similar biomechanical movements to those of fixed prostheses. The overdenture is removable and its prophylaxis is simple. The implant supported milled bar overdenture is a very interesting option in the treatment of patients with moderate to severe reabsorbed maxilla problems. It offers both the advantages of removable prostheses as well as the stability and retention of a fixed prosthesis.

Study of corrosion of combinations of titanium/Ti-6Al-4V implants and dental alloys

Metal ions released in 1% lactic acid solution from combinations of titanium fixtures with superstructures made of dental precious metal alloys (dental alloys) and titanium and differences based on the fixing method were investigated. In combinations of titanium with dental alloys, the level of Ti release was influenced by micro-structure of titanium: it was lower when the grain size was smaller. In titanium-titanium combinations, differences in the micro-structure of metal also markedly influenced the dissolution: the level of release increased when the micro-structure of titanium was different. The Ti and V release levels were higher in combination with titanium alloy and titanium than with titanium alloy and dental alloys. Regarding the superstructure-fixture fixing method, the level of Ti release was significantly lower in cement than in direct fixation.

Bonding durability against water of a fluorine-containing resin for precious metal alloys

In order to clarify the effect of fluorination of an adhesive resin on the durability of the resin bond to precious metal alloys, 2,2,2-trifluoroethyl methacrylate (TFEMA)-poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA)/TBBO adhesive resin was prepared. The tensile bond strength of this resin to precious metal alloys treated with 9,10-epithiodecyl methacrylate (EP8MA) generally increased in the order Ag alloy<Pd alloy<Au alloy after thermal cycling; bond strength was decreased by thermal cycling. The water sorption of TFEMA-PTFEMA/TBBO resin was much higher than that of MMA-PMMA/TBBO resin because of phase separation. For Au alloy, the bonding durability of TFEMA-PTFEMA/TBBO resin against penetration of water was comparable to that of MMA-PMMA/TBBO resin; however, for Pd and Ag alloys the performance of the fluorinated resin was markedly inferior to that of MMA-PMMA/TBBO resin. These reduced tensile bond strengths were considered to be caused by insufficient copolymerization with EP8MA molecules adsorbed on the precious metal alloys.

Multi-Technique Approach to Understanding Phase Transformations in a Precious Metal Alloy

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Surface Treatment with N,N'-Dimethacryloylcystine for Enhanced Bonding of Resin to Dental Alloys

The aim of this study was to develop an effective primer to improve the adhesive property between all kinds of dental metal alloy and resin cement. To this end, we synthesized N,N'-dimethacryloylcystine (NDMCC) which had both disulfide functional group (to improve adhesion between precious metal alloy and resin) and carboxyl group (to improve adhesion between non-precious metal alloy and resin). With the presence of SuperBond C&B, the adhesion between precious, semi-precious, and non-precious dental metal alloys and resin cement was improved when compared to the untreated controls. However, the adhesive property between all types of dental metal alloy and resin cement was not improved with Panavia 21EX. In particular, reduced bond strength in the case of non-precious metal alloy was speculated to arise from the acid-base neutralization reaction between the carboxyl group of NDMCC and the amine present in the polymerization initiator system of Panavia 21EX.

Water Durability of Resin Bond to Pure Gold Treated with Various Adhesion Promoting Thiirane Monomers

Adhesion promoting monomers for precious metals, 2,3-epithiopropyl methacrylate (EP1MA), 4,5-epithiopentyl methacrylate (EP3MA), 9,10-epithiodecyl methacrylate (EP8MA), 10,11-epithioundecyl methacrylate (EP9MA), 9,10-epithiodecyl 4-vinylbenzoate (EP8VB), 2,3-epithiocyclohexyl methacrylate (EPCHMA), and 3,4-epithiobutyl 2,2-bis(methacryloyloxymethyl)-propionate (EP2BMA), were used as surface treatment agents for pure gold to improve the durability of resin bonds against water. Treated specimens were butt-jointed together with MMA-PMMA resins, and tensile bond strength was measured after 2,000 thermal cycles in water. Bond strength to precious metal alloys was also determined under the same condition to clarify the influence of metal composition. The adhesion performance of thiirane monomers to pure gold highly depended on their chemical structure. EP3MA, EP8MA, EP9MA, EP8VB, and EP2BMA showed excellent performance, while EP1MA exhibited a moderate one and EPCHMA a poor one. The comparison of pure gold with precious metal alloys revealed the usefulness of pure gold as a standard, common adherend for bond strength evaluations.

Soil geochemistry and detection of early Roman precious metal and copper alloy working at the Roman town of Calleva Atrebatum (Silchester, Hampshire, UK)

A geochemical soil survey was carried out over 500 m 2 of a first and second century AD house complex in insula IX of the Roman town of Calleva Atrebatum (Silchester, Hampshire, UK) where there was little prima facie evidence for non-ferrous metalworking. Preliminary analyses were made by XRF of lead, zinc and copper. These were followed by analysis for Au, Ag and Sn by ICP-MS of the samples with the highest concentrations of Pb, Zn and Cu. Certain of the Pb, Zn and Cu concentrations suggest the working of copper alloy including brass, and could be associated with archaeological evidence of hearths and burnt areas of second century AD date. Other samples have concentrations of the above metals and of gold and silver which do not appear to be associated with any physical remains of hearths and burnt areas. These concentrations date to the mid-first century AD.

Water Durability of Resin Bond to Precious Metal Alloys Using Adhesive Resins Containing Adhesion Promoting Monomers

Adhesive resins for precious metals were prepared by adding an adhesion promoting monomer to MMA-PMMA/TBBO resin. Precious metal alloys bonded by the adhesive resin were thermocycled 0, 1,000, 2,000, or 4,000 times in water between 4 and 60 degrees C, and tensile bond strengths were measured. Debonded metal surfaces after the tensile test were analyzed based on an area of cohesive failure. Three-way ANOVA revealed that all the three parameters--adherend, adhesive monomer, and number of thermal cycles--exhibited a significant influence on bond strength. Bond strength significantly decreased with increasing number of thermal cycles except for resin with 9,10-epithiodecyl 4-vinylbenzoate (EP8VB) to Au alloy. Mean bond strength of adhesive resin with 9,10-epithiodecyl methacrylate (EP8MA), EP8VB, or 3,4-epithiobutyl 2,2-bis(methacryloyloxymethyl)propionate (EP2BMA) exceeded 22 MPa after 4,000 thermal cycles. Analysis of debonded surfaces revealed the applicability of EP8MA, EP8VB, and EP2BMA as an adhesive monomer component of adhesive resin formulations.

Ceramic Bonding Strength of Au-1.6wt% Ti Alloy

The aim of this investigation was to evaluate the metal-ceramic bonding of Au-1.6 wt% Ti alloy. Therefore, the coefficient of thermal expansion, modulus of elasticity, ceramic bonding strength, and hardness of Au-1.6 wt% Ti alloy were measured. The metal-ceramic interface was observed by EPMA to investigate its bonding mechanism. The Au-1.6 wt% Ti alloy showed a coefficient of thermal expansion close to that of conventional precious metal alloys for metal-ceramics. Bonding strength was 25 MPa or higher for all specimens--whether ceramic-fired directly after casting, or following oxidation treatment or age hardening. Specimens subjected to oxidation treatment showed slightly lower post-firing hardness than those age-hardened. EPMA observation showed an accumulation of Ti and O contents on the alloy side at the metal-ceramic interface.

Adhesive Properties and Kinetic Polymerization Behavior of Resins Containing Adhesion Promoting Monomers for Precious Metals

Adhesion promoting monomers -5-(4-vinylbenzyl)-2-thiobarbituric acid (5VS), 9,10-epithiodecyl methacrylate (EP8MA), 9,10-epithiodecyl 4-vinylbenzoate (EP8VB), and 3,4-epithiobutyl 2,2-bis(methacryloyloxymethyl)propionate (EP2BMA)--were added to the MMA liquid of a MMA-PMMA/TBBO resin. Three dental precious metal alloys were butt-jointed together with the MMA-PMMA/TBBO adhesive resin, and tensile bond strength was measured after 2,000 thermocycles in water. Polymerization kinetics of MMA by 2,2'-azobis (isobutyronitrile) at 70 degrees C in the presence of 5VS, EP8MA, EP8VB, or EP2BMA were examined quantitatively using a DSC to clarify the relationship between the adhesive properties of MMA-PMMA/TBBO adhesive resin and the kinetic polymerization behavior thereof. Obtained kinetic parameters indicated that 5VS was not suitable as an adhesive monomer for adhesive resin formulations and that EP2BMA possessed the latent potential as an adhesive monomer. Further, tensile test results revealed the applicability of EP8MA, EP8VB, and EP2BMA as an adhesive monomer component of adhesive resin formulations.

Corrosion behavior of dental alloys in various types of electrolyzed water.

The corrosion behavior of dental alloys was examined in electrolyzed strong acid water, weak acid water and neutral water using a 7-day immersion test. The precious metal alloys, gold alloy. Au-Ag-Pd alloy and silver alloy showed the greatest surface color change and dissolution of constituents in the strong acid water and the smallest in the neutral water. The release of Au from gold alloy was especially marked in the strong acid water. Co-Cr alloy showed greater corrosion and tarnish resistance in the strong acid water rather than in the weak acid water and the neutral water. X-ray microanalysis revealed that the corrosion products on the precious metal alloys were silver chloride crystals and the thin brown products on Co-Cr alloy were cobalt and chromium oxides. Ti was sound in all three types of electrolyzed water. The neutral water appeared the least corrosive to metals among the three types showing equivalent bactericidal activity.

Chemical structures of adhesion promoting monomers for precious metals and their bond strengths to dental metals.

Adhesion promoting monomers for dental metals, 5-(4-vinylbenzyl)-2-thiobarbituric acid (5VS), 6- (4-vinylbenzyl-n-propyl) amino-1,3,5-triazine-2,4-dithione (VBATDT) and 9,10-epithiodecyl methacrylate (EP8MA), were synthesized and surface treatment agents were prepared by dissolving each monomer in ethanol or acetone. Four non-precious and three precious metal adherends treated with each agent were butt-jointed together with MMA-PMMA resins. After 2,000 thermal cyclings in water, tensile bond strengths were measured and the percentage of area of cohesive failure after the tensile test was determined. The bond strengths to precious metal alloys generally increased in the order of 5VS<VBATDT<EP8MA. Bonding durability against water based on overall failure mode analysis was improved in the following order: for precious metal alloys; 5VS<VBATDT< or =EP 8MA, and for non-precious metal alloys; EP8MA, VBATDT<<5VS.

Water Durability of Resin Bond to Precious Metal Alloys Treated with Various Thiirane Monomers

Water Durability of Resin Bond to Precious Metal Alloys Treated with Various Thiirane Monomers

Jewellery-Related Properties Of Platinum

The performance of precious metal alloys can be usefully compared by the application of engineering design theory and heat flow properties on the small scale that is required for jewellery production. Some of the physical and mechanical properties of Platinum jewellery alloys differ sufficiently from typical gold and silver alloys to require modifications in the processing techniques, but these properties may allow for stronger slender designs. The thermal diffusivity of Platinum jewellery alloys is significantly lower than that of other precious metal jewellery alloys. This explains why laser welding is so efficient when used in making platinum jewellery and why it also allows most of the cold work hardening to be retained in components.

Tensile Bond Strength of Resin to Precious Metal Alloys Treated with Thiirane Bifunctional Monomer

Tensile Bond Strength of Resin to Precious Metal Alloys Treated with Thiirane Bifunctional Monomer

Corrosion resistance in different environments and structural features of dental casting alloys for resin bonding

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Structural characterisation and corrosion resistance of Ga-precious metal alloys formed by liquid–solid reaction at room temperature

An attempt to eliminate Hg from dental amalgams was made by substituting it with low melting Ga-based alloys, liquid at room temperature. However more information is needed on the influence of alloy composition and their questioned corrosion resistance. In this paper the reaction of some liquid Ga alloys and some solid precious metal alloys with different nobility was studied. Structural features, hardness and corrosion resistance of the obtained composite materials were investigated as a function of composition of the starting alloys, liquid/solid ratio and different mixing methods. Every combination of the solid precious metal powders and the liquid Ga-alloys gives rise to similar composite materials. The structure always consists of unreacted solid alloy particles embedded in a complex matrix composed of many reaction phases. The formation of some phases depends on the composition of the solid alloy, others originate all the time; however their topography and morphology may be different as well as their compositional range. The high porosity generally present in the composite materials markedly affects hardness values; nevertheless some prepared materials reach hardness comparable with the one of commercial amalgams. The nobility of the solid alloy and porosity percentage play a determinant role on the corrosion behaviour. In all cases the low corrosion resistance of the experimented materials may be attributed to a galvanic coupling between the reaction intermediate phases and the unreacted liquid alloy remained inside the pores.

Mechanism of adhesion between 4-META resin and alloys based on Bolger's acid-base interaction.

The water durability at adhesion interfaces between 4-META resin and Au-In or Au-Si alloys was investigated by the peeling test and by surface analysis using X-ray photoelectron spectroscopy (XPS) as well as theoretical consideration based on Bolger's acid-base theory. XPS spectra demonstrated that several-nm thick layers of In2O3 and SiO2 were formed on the Au-In and Au-Si alloys. The water durability of the Au-In alloys increased with increases in In content. The Au-Si alloy and quartz glass specimens showed a total absence of water durability. Bolger's theory suggested that the interaction of 4-MET with In2O3 was considered to be ionic and stable in the presence of water while that of 4-MET with SiO2 was due to hydrogen bonds, which can easily be dissociated in the presence of water. These findings suggest that Bolger's theory is useful for evaluating chemical interactions between an adhesive monomer and oxides on a precious metal alloy.