Ultrasonic Soldering

Contacts were made by the ultrasonic soldering of indium directly onto the sintered discs of Ba2YCu307, and their ohmic behavior was established by measuring their current-voltage characteristics. The sample and a thermocouple were mounted in a small cavity inside a massive copper body which was first cooled to 77 K and then allowed to warm very slowly. 

Indium and some of its alloys can wet to glass, quartz, and other normally unsolderable inorganic substrates with the aid of an ultrasonic soldering tool. Ultrasonic soldering will be discussed in the chapter on soldering techniques. 

FIGURE 47.42 The ultrasonic soldering iron is composed of four main components an ultrasonic transducer a horn tor concentrating and directing ultrasonic energy a resistance heater and the soldering tip, which emits both thermal and ultrasonic energy. 

Ultrasonic soldering has also been applied as a batch or continuous mass reflow process. In these instances, the molten solder is ultrasonically agitated while the assembly to be soldered is immersed in it. Similar arrangements have been made for ultrasonically vibrating the part while dipping it in a molten bath or wave of solder. These mass processes are more common for non-electronic assembly. 

Vianco, P.T.,Rejent,J. A., and Hosking,F.M., Applications-Oriented Studies in Ultrasonic Soldering, Proceedings of the American Welding Society Convention and Annual Meeting, Cleveland, 1993. 

Antonevich, J. N., Fundamentals of Ultrasonic Soldering, American Welding Society, 4th International Soldering Conference, Welding Journal Research Supplement, Vol. 55, July 1976, pp. 200-s to 207-s. Shoh,A., Industrial Applications of Ultrasound, / Transactions on Sonics and Ultrasonics,Yo. SU-22, March 1975, pp. 60-71. 

Ultrasonic soldering uses an ultrasonic probe to provide localized heating through high frequency oscillations. Eliminates the need for a flux, but requires pre-tinning of surfaces. 

Ultrasonic Atomization 30-50 USWA >100 Medium size distribution Solder materials, Welding electrodes, Ag-, Cu-base alloys, Dispersion-hardened allovs USWA 107 0.02-0.8 Low Spherical high quality particles, Low cost, Small unit, High EE Low volume productivity... 

Because flux is such a concern, one contractor is exploring ultrasonic bonding (10) using prepunched aluminum interconnects that are attached to electroplated copper cell metallization with a seam welder. Others are examining fluxless bonding concepts, such as vapor-phase solder reflow. 

Ultrasonic, spray-under immersion, or centrifugal for solder paste and low... 

Dual tank system for stencil (29 inch maximum) and pallet cleaning RA, RMA, no-clean synthetic and water soluble (OA) flux residues, solder paste (ambient), and wet SMT adhesives (38-43 °C, ultrasonics)... 

Aqueous based cleaners of MFC Technology Removal of adhesives and solder paste Wide process window Non-flammable Rapid drying Residue-free drying Long bath life Agitation of the cleaner (spray, ultrasonic, spray under immersion, overflow) necessary... 

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