Solderable films

FIG. 19 Stereo photographs showing the cases of (a) wetting, (b) nonwetting, and (c) dewetting of a 40Pb-60Sn solder film on an Fe Ni alloy. (Courtesy of Sandia National Laboratories.)... 

The Fe, Co, and Ni deposits are extremely fine grained at high current density and pH. Electroless nickel, cobalt, and nickel—cobalt alloy plating from fluoroborate-containing baths yields a deposit of superior corrosion resistance, low stress, and excellent hardenabiUty (114). Lead is plated alone or ia combination with tin, iadium, and antimony (115). Sound iasulators are made as lead—plastic laminates by electrolyticaHy coating Pb from a fluoroborate bath to 0.5 mm on a copper-coated nylon or polypropylene film (116) (see Insulation, acoustic). Steel plates can be simultaneously electrocoated with lead and poly(tetrafluoroethylene) (117). Solder is plated ia solutioas containing Pb(Bp4)2 and Sn(Bp4)2 thus the lustrous solder-plated object is coated with a Pb—Sn alloy (118). 

PVF resins have also been used in a variety of other appHcations, including conductive films (152), electrophotographic binders (153), as a component for inks (154), and in membranes (155,156), photoimaging (157), solder masks (158), and reprographic toners (159). 

Films have been used for insulating electric motors, in capacitors requiring a heat resistance not met by conventional polyester and polycarbonate dielectrics and as a soldering-resistant base for flexible printed circuits. 

In its resistance to liquid metals, titanium shows variable behaviour, the rate of attack often depending upon temperature and increasing with rise in temperature. By thickening the surface film of oxide, resistance to attack is enhanced, and, for example, repeated repair of the surface film renders titanium resistant, on a limited-time basis, to molten zinc in galvanising baths. A surface-oxide thickening technique also enables titanium to be employed in contact with molten aluminium. Titanium equipment is also used in applications involving lead-tin solders, and it is resistant to mercury, at least up to 150 C. 

These qualities have also lead to its use on printed circuit boards and on electrical connectors, although the persistent oxide film obstructs easy solderability and produces too high a contact resistance for satisfactory switching at low voltages. 

The fired-on silver films on glass can be soft-soldered. They should be tinned with a solder containing some silver ordinary soft solder can bring about complete dissolution of the silver film. Matthey Ceramic Solder No. i is a suitable solder for the films. A resin-type flux should be used. Tinning can be carried out by dipping into the molten solder. 

Noncontact printing is used in the microelectronics industry to print low-viscosity electronic-grade materials solder fluxes, dielectric films, anti-static... 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

The major drawback of poly(p-xylylene) is that it reverts to a monomer when thin films are heated above ca. 400°C and it cracks when the films are annealed at 300-350°C in nitrogen. During module assembly the chip-joining (soldering)... 

Solar-grade silicon, production of, 22 507-508 Solar heat control, use of gold in, 12 703 Solarization effect, 19 203 Solar photocatalysis, 23 23-24 Solar photocatalytic detoxification, 19 76 Solar photocatalytic processes, 19 100-101 Solar photocatalytic reactor, using deposited titania, 19 99 Solar photoreactors, 19 95-99 Solar salt harvesting, 22 802, 806-808 Solar spectrum, 23 2 Solar still, 26 89-92 Solar thermal converters, 23 10-13 Solar transmittance, for thin films, 23 19 Solatene, 24 558 Solder, 3 53... 

In some instances, to improve solderability, tin is deposited on nickel surfaces. In a short time, however, interdiffusion of the two metals results in the growth of an inter-metallic NiSn3 compound that is much less amenable to soldering. For tin over elec-trolessly deposited nickel surfaces, the interdiffusion results in pores in both films. Pores are to be avoided, of course, if conductivity and/or contact resistance is an issue. 

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