Lead-indium alloys

Howard, R.T. Optimization of indium-lead alloys for controlled collapse chip connection application. IBM J. Res. Develop. 1982, 26, 372-378. 

Lead-tin Lead-tin-indium Lead-tin-silver alloys Lead-tin solder Lead titanate... 

Nickel on nickel Gold on gold Platinum on platinum Copper on copper Indium on indium Lead on lead Aluminium on aluminium Silver on silver Iron on iron Tin on tin Steel on tin alloy Steel on steel Steel on Pb alloy Steel on Al. bronze Steel on cast iron Steel on brass Steel on bronze Steel on Pb. brass... 

Of the elements commonly found in lead alloys, zinc and bismuth aggravate corrosion in most circumstances, while additions of copper, tellurium, antimony, nickel, silver, tin, arsenic and calcium may reduce corrosion resistance only slightly, or even improve it depending on the service conditions. Alloying elements that are of increasing importance are calcium especially in maintenance-free battery alloys and selenium, or sulphur combined with copper as nucleants in low antimony battery alloys. Other elements of interest are indium in anodesaluminium in batteries and selenium in chemical lead as a grain refiner ". 

Low level wastes (LLW), 23 592. See also Low-level radioactive waste (LLW) from reactors, 77 598 Low-melting lead alloys, 14 779 Low-melting-point indium alloys, 14 196 Low-melting thiodiols, DBTDL-catalyzed step-growth solution and melt polymerization reaction of, 23 744 Low-methoxyl pectins (LM pectins), 4 728 13 69... 

The discussion in the previous section makes it clear that there are significant differences between lead-free, tin-based solder systems and other solders successfully used in the past. The anomalous crystal structure and allotropic transformations in tin-based alloys can affect the material properties that control the ultimate performance and reliability of these solders in microelectronic assemblies. Table 5 provides a comparison of several solder systems including high-lead and eutectic tin-lead alloys, white and gray tin, a lead-indium solder, gold-tin eutectic, and a fictitious ideal alloy. 

The abundance of indium in the earth s cmst is probably about 0.1 ppm, similat to that of silver. It is found in trace amounts in many minerals, particulady in the sulfide ores of zinc and to a lesser extent in association with sulfides of copper, tin, and lead. Indium follows zinc through flotation concentration, and commercial recovery of the metal is achieved by treating residues, flue dusts, slags, and metallic intermediates in zinc smelting and associated lead (qv) and copper (qv) smelting (see Metallurgy, EXTRACTIVE Zinc and zinc alloys). 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

Platiaum and its alloys are also used as biomedical electrodes, eg, platiaum—indium wires for permanent and temporary pacemaker leads and defibrillator leads. Electrophysiology catheters, which contain platinum electrodes and marker bands, have been used to map the electrical pathways of the heart so that appropriate treatment, such as a pacemaker, can be prescribed. 

Solders. In spite of the wide use and development of solders for millennia, as of the mid-1990s most principal solders are lead- or tin-based alloys to which a small amount of silver, zinc, antimony, bismuth, and indium or a combination thereof are added. The principal criterion for choosing a certain solder is its melting characteristics, ie, soHdus and Hquidus temperatures and the temperature spread or pasty range between them. Other criteria are mechanical properties such as strength and creep resistance, physical properties such as electrical and thermal conductivity, and corrosion resistance. 

Steels and austenitic stainless steels are susceptible to molten zinc, copper, lead and other metals. Molten mercury, zinc and lead attack aluminum and copper alloys. Mercury, zinc, silver and others attack nickel alloys. Other low-melting-point metals that can attack common constructional materials include tin, cadmium, lithium, indium, sodium and gallium. 

Soldered joints present their own characteristic corrosion problems usually in the form of dissimilar metal attack often aided by inadequate flux removal after soldering. Such joints have always been a source of concern to the electrical industry. Lead-containing solders must be used with caution for some types of electrical connection since PbfOHjj.PbCOj may be found as a corrosion product and can interrupt current flow. Indium has been found to be a useful addition to Sn-Pb solders to improve their corrosion resistanceHowever, in view of the toxicity of lead and its alloys, the use of lead solders, particularly in contact with potable waters and foodstuff s, is likely to decline. 

The Al-Zn-Sn alloys require careful heat treatment in their production. Inevitably this leads to more expense and inconvenience. The advent of the alloys containing mercury or indium rendered these alloys very much less attractive. Presently Al-Zn-Hg alloys are under some pressure because... 

Aluminium anodes comprise essentially three generic types Al-Zn-In, Al-Zn-Hg and Al-Zn-Sn. Since Al-Zn-Sn alloys have largely been superseded, they will not be discussed further. Indium and mercury are added to aluminium to act as activators, i.e. to overcome the natural passivation of aluminium. Despite this, aluminium anodes are not suitable for low chloride environments which would lead to passivation. These anodes are therefore not used for land-based applications (although examples of use in environments such as swamps do exist). Similarly their use in low chloride aqueous environments such as estuaries must be viewed with caution. 

The low-melting-point (157 °C), silver metal is mainly used in alloys to decrease the melting point. Combined with tin, lead, and bismuth to produce soldering metal for wide temperature ranges. The element is highly valuable in the electronics age as its unique properties are ideal for solar cells, optoelectronics, and microwave equipment. The arsenide is used in lasers and is also suitable for transistors. ITO (indium tin oxide) is a transparent semiconductor with wide application in displays, touchscreens, etc. In the household, indium as an additive prevents the tarnishing of silverware. Some electronic wristwatches contain indium batteries. 

Another main use is as an alloy with other metals when it will lower the melting point of the metals with which it is alloyed. Alloys of indium and silver and indium and lead have the ability to carry electricity better than pure silver and lead. 

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