Simulation and measurement of the flip chip solder bumps with a Cu-plated plastic core

• First validated simulation of solder balls with plastic core.
• Determination of the influence of different geometrical parameters.
• Electromigration in the solder material with a copper surrounded plastic core.

With the aim to miniaturize and to reduce the cost, the increasing demand, regarding to advanced 3D-packages as well as high performance applications, accelerates the development of 3D-silicon integrated circuits. The trend to smaller and lighter electronics has highlighted many efforts towards size reduction and increased performance in electronic products. The radio frequency (RF) performances are limited by parasitic effects due to the resistor–inductor–capacitor (RLC) network, between the wire bond connections from the dies to the lead frame. The use of flip-chip bonding technology for very fine pitch packaging allows high integration and limits parasitic inductances. Electromigration (EM) and thermomigration (TM) may have serious reliability issues for fine-pitch Pb-free solder bumps in the flip-chip technology used in consumer electronic products. A possibility to extend the reliability is the use of plastic ball in the solder bumps. Bumps containing a plastic solder balls have an excellent reliability. Using a plastic ball with a low Young modulus, the solder hardness is moderated and the stress on a ball is relaxed. Due to this, the stress does not concentrate on the solder joint which prolongs the lifetime. In this investigation, the thermal–electrical–mechanical coupling of electromigration on bumps containing a plastic solder is studied.