Electroplating Solder

E. K. Yung and I. Tbrlik, Electroplated Solder Joints for Flip-Chip Applications, IEEE Comp., Hybrids., Manuf. TechnoL, 14, No. 3, 549-559 (1991). 

Mistry, A. Lee, S. Enman, C. Carroll, B. Mitchell, D. Mathew, V. Characterization of low alpha emissivity system on electroplated solder bumps. Proc. 50th Electronic Comp, and Technol. Conf. Las Vegas, NV, May 2000 1587-1593. 

Roughness has important implications in wetting applications. While the eutectic solder, SnPb, normally forms a contact angle of 15-20° with copper, it completely wets the surface of rough electroplated copper and forms a fractal spreading front [69]. 

Fluoroboric acid is used as a stripping solution for the removal of solder and plated metals from less active substrates. A number of fluoroborate plating baths (27) require pH adjustment with fluoroboric acid (see Electroplating). 

In the early 1970s, the first companies to apply low cost, mass production techniques to photovoltaics, a technology that had previously been considered an exotic aerospace technology, emerged. These techniques included the use of electroplated and screen printed metal paste electrical conductors, reflow soldered ribbon interconnects, and by 1977, low cost, automobile windshield-style, laminated module constmction. Such processes benefitted from a substantial existing industrial infrastmcture, and have become virtually ubiquitous in the present PV industry. 

Molten tin wets and adheres readily to clean iron, steel, copper, and copper-base alloys, and the coating is bright. It provides protection against oxidation of the coated metal and aids in subsequent fabrication because it is ductile and solderable. Tin coatings can be appHed to most metals by electro deposition (see Electroplating). 

Because of the ease with which they can be soldered, electroplated tin—lead coatings of near eutectic composition (62 wt % tin) are extensively used in the electronics industry for coating printed circuit boards and electrical coimectors, lead wires, capacitor and condenser cases, and chassis. 

Tin. Apphcation of tin on strip steel for can stock has decreased. Nevertheless, tin plating is still done in large volume, and tin plate for can stock was estimated at 11,750 t in 1990 (11). Additionally, 603 t of tin anodes were used for electroplating in electronic apphcations in the United States in 1990. The use of tin in solder manufacture is reported to exceed that used in can stock (12). The cost of tin in early 1993 was 7.50/kg (see Tin and tin alloys). 

Uses. The metal is used in electroplating, in solder for aluminum, as a constituent of easily fusible alloys, as a deoxidizer in nickel plating, in process engraving, in cadmium-nickel batteries, and in reactor control rods. Cadmium compounds are employed as TV phosphors, as pigments in glazes and enamels, in dyeing and printing, and in semiconductors and rectifiers. 

Metal powder can also be coated onto the workpiece. The 3M Company has developed a cold welding technique in which the workpiece, the metal powder, water, glass shot and additives are tumbled together in a barrel. Coatings are limited to ductile metals such as Cd, An, Sn, Pb, In, Ag, Cu, brass, and tin/lead solder the method is generally suitable only for small parts, and it doesn t produce a fine surfaced, cosmetic coating. Costs are comparable to those for electroplating with afterbake (Kirk-Othmer 1981). 

Bus bars -brazing filler metals for [SOLDERS AND BRAZING FTT.T.HR METALS] (Vol 22) -use m electroplating [ELECTROPLATING] (Vol 9)... 

---