Special Applications


 

 Principle of arc discharge treatment process based on formation of cathodic spots

Principle of arc discharge treatment  process based on formation of cathodic spots

PROCESS DESCRIPTION

SMU’s Research Center for Advanced Manufacturing (RCAM) has been studying the effect of complex physical phenomenon of cathodic arcs in cleaning oxides layer from aluminum alloys surface before welding. It has been observed that the cathode spot generation on the surface of non-thermionic substrate such as aluminum, titanium, etc. can texture the surface. The experimental studies  have shown that arc discharge can significantly increase the wettability of treated surfaces as well as the strength of the adhesive joint.

 
INDUSTRIAL APPLICATIONS

 

  • Welding of aluminum alloys
  • Adhesive bonding and painting

ADVANTAGES OF ARC SURFACE TREATMENT

  • Environmentally friendly
  • Rapid and single-step process
  • Capability to treat 3D and/or complex geometry objects
  • No damage to  bulk material
  • Easily automated
  • Economic al

RCAM’s CAP ABILITIES

 

  (a) untreated coupon surface (b) treated coupon surface

  • Performing adhesive bonding
  • Surface characterization including optical profilometer, high accuracy vision system
  • Microstructural analysis (access to SEM, EDS, etc.) and mechanical testing of materials ( tensile testing, microhardness, etc.)
  • Real-time process monitoring  
  • Numerical simulation

RECENT PUBLICATIONS:

  • Sarrafi, R. and Kovacevic, R., “Cathodic Cleaning of Oxides from Aluminum Surface by Variable-Polarity Arc,” Welding journal, 89 (2010):1-s-10-s
  • Rouzbeh Sarrafi, Mehdi Asgharifar, and Radovan Kovacevic “Surface Texturing of Metals by Cathode Spots of Atmospheric Arc” ASME Conf. Proc. 2 (2011): 323-329
  •  Asgharifar, M., Kong, F., Carlson, B., Kovacevic, R., “Studying Effects of Arc Discharge Surface Texturing on Stress Distribution in Adhesively Bonded Joints by Using Finite Element Modeling” ASME Conf. Proc. 2 (2011): 1-7

Development of Lead-free Composite Solders Reinforced by Nanoparticles


INTRODUCTION OF NEW COMPOSITE SOLDERS
 

 

  SMU’s Research Center for Advanced Manufacturing (RCAM) has developed improved composite lead-free solders derived from Sn-Ag and Sn-Ag-Cu systems and enhanced/ reinforced with nanoparticles of various materials as well as a technique to mitigate the tin whiskers growth. Investigation has shown that copper nanoparticles will reinforce the solder itself, but they fail to strengthen the interface between the solder and substrate.  Nickel nanoparticles in solders will significantly improve the solder structure and strengthen both the solder and the solder/substrate interface. It is known that the multiple layering of Ni and Sn could prolong the appearance of tin whiskers. 

ADVANTAGES

 
• High strength and longer fatigue life
• Improved thermal reliability
• Mitigate the growth of tin whiskers
OUR CAPABILITIES
• Development of lead-free solders
• Modeling and testing solder systems
•Controlling the growth of tin whiskers
INDUSTRIAL APPLICATIONS
• Electronics packaging
• Surface mount technology
• Any critical electronic assembly
RECENT PUBLICATIONS
•D.C. Lin, R. Kovacevic, et. al. (2007), An Investigation of the Influence of Nanoparticle Reinforcements on Microstructural Development in Lead Free Tin-Silver Solder. International Journal of Nanomanufacturing, Vol. 1, No. 3, 357-369.
•D.C. Lin, R. Kovacevic, et. al. (2006), Microstructural Development of a Rapidly Cooled Eutectic Sn-3.5% Ag Solder Reinforced with Copper Powder, Powder Technology. Vol.166, pp38-46.
•Dimitrovska, A. and Kovacevic, R., ”Mitigation of Tin Whiskers Growth by Applying Multiple Ni/Sn Plating Prior to the Final Sn Finish”, the Journal of Electronic Materials, Vol.38, No. 12, 2009, pp. 2516 – 2524.
•Dimitrovska, A. and Kovacevic, R., ”The Effect of Micro-alloying of Tin Plating on Mitigation of Tin
Whiskers Growth”, IEEE, the Journal of Electronic Materials, Vol. 38, No. 12, 2008, pp. 2726-2734.