Approaches to flip chip technology using electroless nickel-gold bumps

A chemical bumping technology developed and implemented at IZM is presented. The maskless process is based on electroless nickel deposition. Nickel bumps offer a surface which is very suitable for flip chip soldering. They are also appropriate for adhesive interconnections, e.g. with isotropic, anisotropic and non conductive adhesive. The deposition of solder and adhesives can be achieved by different methods on wafer and chip as well on substrates. Therefore, this paper demonstrates the broad spectrum and the high flexibility of these techniques with regard to low cost processes. The interconnections are performed on cost effective ceramic substrates, rigid printed circuit boards (FR-4) and flexible circuit materials. As an example of these approaches, the development of a flip chip interconnection method using dies with Ni/Au bumps and solder printing on ceramic substrates is presented. First reliability results of these joints after thermal cycling are also shown.

[1]  Herbert Reichl,et al.  Electroless deposition of bumps for TAB technology , 1990, 40th Conference Proceedings on Electronic Components and Technology.

[2]  J. Lau,et al.  Experimental and Analytical Studies of Encapsulated Flip Chip Solder Bumps on Surface Laminar Circuit Boards , 1993 .

[3]  Andreas Ostmann,et al.  Flip chip soldering and adhesive bonding on organic substrates , 1995, Proceedings of 1995 Japan International Electronic Manufacturing Technology Symposium.

[4]  Herbert Reichl,et al.  Reliability investigations of fluxless flip-chip interconnections on green tape ceramic substrates , 1995, 1995 Proceedings. 45th Electronic Components and Technology Conference.

[5]  D. Suryanarayana,et al.  Enhancement of flip-chip fatigue life by encapsulation , 1991 .

[6]  Koji Yamakawa,et al.  Maskless bumping by electroless plating for high pin count, thin, and low cost microcircuits , 1990 .

[7]  H. Reichl,et al.  Fluxless Flip‐chip Bonding on Flexible Substrates: A Comparison between Adhesive Bonding and Soldering* , 1996 .

[8]  Andreas Ostmann,et al.  The pretreatment of aluminum bondpads for electroless nickel bumping , 1993, Proceedings 1993 IEEE Multi-Chip Module Conference MCMC-93.

[9]  T. M. Tam,et al.  Reaction mechanism for the electrodeposition of copper using cyclic voltammetry , 1988 .

[10]  S. Lalu,et al.  Electroless Ni/Au bumps for flipchip-on-flex and TAB applications , 1994, Proceedings of 16th IEEE/CPMT International Electronic Manufacturing Technology Symposium.