Metal containers solder

Tin [7440-31 -5] is one of the world s most ancient metals. When and where it was discovered is uncertain, but evidence points to tin being used in 3200—3500 BC. Ancient bron2e weapons and tools found in Ur contained 10—15 wt % tin. In 79 ad, Pliny described an alloy of tin and lead now commonly called solder (see Solders and brazing alloys). The Romans used tinned copper vessels, but tinned iron vessels did not appear until the fourteenth century in Bohemia. Tinned sheet for metal containers and tole (painted) ware made its appearance in England and Saxony about the middle of the seventeenth century. Although tinplate was not manufactured in the United States until the early nineteenth century, production increased rapidly and soon outstripped that in all other countries (1). 

There is an accelerating trend away from the use of lead-containing solders in contact with potable water. The effects of galvanic corrosion of one of the substitute alloys (Sn3%Ag) in contact with a number of other metals including copper have therefore been studied . The corrosion of tin/Iead alloys in different electrolytes including nitrates, nitric and acetic acids, and citric acid over the pH range 2-6 were reported. The specific alloy Pb/15%Sn was studied in contact with aqueous solutions in the pH range... 

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. 

Many of uses of tin are also those of lead, because the metals form useful alloys. When lead is alloyed with a few percent of tin, it becomes harder and more durable. Although other compositions are produced, common solder consists of about an equal mixture of tin and lead. An alloy known as type metal contains about 82% Pb, 15% Sb, and 3% Sn, and pewter contains approximately 90% tin that is alloyed with copper and antimony. Babbitt, an alloy used in making bearings, contains 90% Sn, 7% Sb, and 3% Cu. Tin is also used to coat other metal objects to retard corrosion, and a tin-niobium alloy is used in superconducting magnets. 

Catalytic forms of copper, mercury and silver acetylides, supported on alumina, carbon or silica and used for polymerisation of alkanes, are relatively stable [3], In contact with acetylene, silver and mercury salts will also give explosive acetylides, the mercury derivatives being complex [4], Many of the metal acetylides react violently with oxidants. Impact sensitivities of the dry copper derivatives of acetylene, buten-3-yne and l,3-hexadien-5-yne were determined as 2.4, 2.4 and 4.0 kg m, respectively. The copper derivative of a polyacetylene mixture generated by low-temperature polymerisation of acetylene detonated under 1.2 kg m impact. Sensitivities were much lower for the moist compounds [5], Explosive copper and silver derivatives give non-explosive complexes with trimethyl-, tributyl- or triphenyl-phosphine [6], Formation of silver acetylide on silver-containing solders needs higher acetylene and ammonia concentrations than for formation of copper acetylide. Acetylides are always formed on brass and copper or on silver-containing solders in an atmosphere of acetylene derived from calcium carbide (and which contains traces of phosphine). Silver acetylide is a more efficient explosion initiator than copper acetylide [7],... 

It is not possible to precisely define sampling conditions and storage media for all situations. Certain general recommendations can, however, be made. Solder seams in metal containers often used for sampling are to be avoided. Exposure of samples to metal surfaces may be reduced by coating... 

THn plates are thin sheets of Fe, coated with Sn. Tin foil consists of thin laminae of Sn, frequently alloyed with Pb. Copper and iron vessels are tinnml, after brightening, by contact with molten Sn. Pewter, bronze, bell metal, gun meUd, britannia metal, speculum metal, type metal, solder, and fusible metal contain So. 

The majority of food cans are now made without lead or tin solder, thus metal cans are no longer manufactured by tin-coated three-piece and side-soldered techniques. Modem cans are made either from two pieces (body and one end piece) or from three pieces with a welded side seam. This necessitated the utilization of improved can interior coating. Polymeric materials are used as barriers for coating metal containers to provide protection for various food substrates from attack by aggressive components of ambient environments. The fundamental function of the... 

Table 3.1-159 Noble metal containing soft solders [1.217]...

Solder Paste. The dispensing of solder paste is the most widely used means of providing flux and solder metal to the joint for the reflow process. The primary components of the solder paste are the solder metal and the flux. The solder metal is typically 80-90 wt. percent of the paste. Aside from the In- and Zn-containing solders, there is very little sensitivity of the paste properties to the solder metal composition for Sn-based alloys. Important properties of the paste with respect to dispensing are the solder powder particle size and weight percent or metal loading of the paste. 

The best current 100% solids epoxy adhesives contain about 70% aluminum oxide by weight and give thermal conductivities in the range of 0.8-1 in the English units shown in Table 2. For convenience, a conversion chart is included in Table 2 to permit conversion to any other set of units. The k values for the best alumina-filled epoxies are 10-12 times greater than for unfilled epoxy resins, but are still much lower than for pure metals or solders. Nevertheless, heat flow is adequate for bonding most components. For example, an adhesive with a thermal conductivity of 0.91 and a bond thickness of 3 mils would be able to transfer about 20 W/cm of surface area, with a AT only about 10 C above the heat sink temperatures ... 

Being inexpensive and providing an excellent shear strength, alumina is broadly used to formulate thermally conductive adhesives. The best solventless epoxy adhesives contain about 70% of aluminum oxide and give thermal conductivities in the range of 1.4—1.7 W m These values are 8—10 times more than for the unfilled epoxy resins but are still much lower than for pure metals or solders. Never-... 

When solid wastes are disposed in landfills, rainfall and chemical reactions within the wastes release metals contained in the wastes solder, components, and circuit boards. As these metals are leached from the waste, the metals may enter the local groundwater. In many communities, groundwater is the source for drinking water. The metal-contaminated leachate liquid may also deposit into surface soils and rocks where humans, animals, and plants come into contact with the toxic metals. Plants may absorb toxic metals and thus enter the food web as animals eat the plants. 

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