Title :
Electromigration study of high lead solders in flip-chip packages using the Wheatstone bridge method
Author :
Min Ding ; Matsuhashi, H. ; Guotao Wang ; Ho, Paul S.
Author_Institution :
Lab. for Interconnect & Packaging, Texas Univ., Austin, TX, USA
Abstract :
A new approach based on the Wheatstone bridge method was employed to investigate electromigration behavior of high lead solder balls in flip chip CPGA packages. EM tests at four temperatures were performed with a current density of 1.1×104 A/cm2. Electromigration failure was observed only in solder balls with electron current flow from UBM to the substrate. SEM/EDS analysis revealed mass migration of Pb, Sn and Cu along the electron flow direction resulting in the dissolution of Cu3Sn compound. The depletion of Cu3Sn induced dewetting and crack formation at UBM/solder interface. Subsequent growth of interfacial crack under EM caused the final open failure of the solder ball. EM damage evolution was found to follow 3 stages: (i) Cu3Sn formation and dissolution, (ii) crack growth, (iii) open failure. The EM activation energy of 97Pb/3Sn solder ball was determined to be 0.91±0.19eV. Test data also indicated that stress can superimpose onto EM to degrade solder reliability.
Keywords :
X-ray chemical analysis; bridge circuits; ceramic packaging; current density; electromigration; failure analysis; flip-chip devices; lead alloys; reflow soldering; scanning electron microscopy; solders; CPGA packages; PbSn; SEM-EDS analysis; Wheatstone bridge method; ceramic substrate; crack formation; dewetting; electrical bridge circuit; electromigration behavior; flip-chip packages; high lead solders; interfacial crack; mass migration; open failure; small resistance changes; Bridge circuits; Electromigration; Electrons; Flip chip; Lead; Packaging; Performance evaluation; Temperature; Testing; Tin;
Conference_Titel :
Electronic Components and Technology Conference, 2004. Proceedings. 54th
Print_ISBN :
0-7803-8365-6
DOI :
10.1109/ECTC.2004.1319456
