Conductive adhesive for plated Sn or Sn/Pb electrode

New isotropic conductive adhesive (ICA) for plated Sn or Sn/Pb electrode was developed. The new ICA and our existing ICA were evaluated for SMT as lead containing solder replacement, using on-chip resistors with plated Sn/Pb (90/10) and fired Ag/Pd terminations, from contact resistance and adhesion strength points of view. The new ICA gave more stable contact resistance and adhesion strength through reliability testing, even in the case of using 0/spl Omega/ chip resistor with plated Sn/Pb termination. Formation of boundaries or Sn grains on the surface and diffusion of Ni into Sn/Pb layer in the cross section, after chip resistors with plated Sn/Pb termination exposed to several reliability conditions, were observed by SEM and EDX. Though degree of these changes of plated Sn/Pb termination depends on each exposure condition, it can be estimated that the new ICA gets less influence by the changes of plated Sn/Pb termination and that it has some effect which prevents changing by plated Sn/Pb termination before it occurs.