Title :
Eutectic Pb/Sn solder bump and under bump metallurgy interfacial reactions and adhesion
Author :
Jang, Se-Young ; Paik, Kyung-Wook
Author_Institution :
Dept. of Mater. Sci. & Eng., Korea Adv. Inst. of Sci. & Technol., Seoul, South Korea
Abstract :
In flip chip interconnection on organic substrates using eutectic Pb/Sn solder bumps, a highly reliable under bump metallurgy (UBM) is required to maintain adhesion and solder wettability. Various UBM systems such as 1 μm Al/0.2 μm Ti/5 μm Cu, 1 μm Al/O.2 μm Ti/1 μm Cu, 1 μm Al/0.2 μm Ni/1 μm Cu and 1 μm Al/0.2 μm Pd/1 μm Cu, laid under eutectic Pb/Sn solder, have been investigated with regard to their interfacial reactions and adhesion properties. The effects of the number of solder reflow cycles and the aging time on the growth of intermetallic compounds (IMCs) and on the solder ball shear strength were investigated. Good ball shear strength was obtained with 1 μm Al/0.2 μm Ti/5 μm Cu and 1 μm Al/0.2 μm Ni/1 μm Cu even after 4 solder reflows or 7 day aging at 150°C. In contrast, 1 μm Al/0.2 μm Ti/1 μm Cu and 1 μm Al/0.2 μm Pd/1 μm Cu showed poor ball shear strength. The decrease of the shear strength was mainly due to the direct contact between solder and nonwettable metals such as Ti and Al, resulting in a delamination. In this case, thin 1 μm Cu and 0.2 μm Pd diffusion barrier layers were completely consumed by Cu-Sn and Pd-Sn reaction
Keywords :
adhesion; ageing; aluminium; copper; delamination; diffusion barriers; flip-chip devices; integrated circuit interconnections; integrated circuit packaging; integrated circuit reliability; interface structure; lead alloys; microassembling; nickel; palladium; reflow soldering; shear strength; surface chemistry; tin alloys; titanium; wetting; 0.2 micron; 1 micron; 150 C; 5 micron; 7 day; Al-Ni-Cu UBM; Al-Ni-Cu-SnPb; Al-Pd-Cu UBM; Al-Pd-Cu-SnPb; Al-Ti-Cu UBM; Al-Ti-Cu-SnPb; Cu-Sn reaction; Pd-Sn reaction; UBM systems; adhesion; aging time; delamination; diffusion barrier layers; direct solder-nonwettable metal contact; eutectic Pb/Sn solder bumps; flip chip interconnection; interfacial reactions; intermetallic compounds; organic substrates; reliability; solder ball shear strength; solder reflow cycles; solder wettability; under bump metallurgy; Adhesives; Aging; Artificial intelligence; Electronics packaging; Integrated circuit interconnections; Intermetallic; Materials reliability; Materials science and technology; Scanning probe microscopy; Tin;
Conference_Titel :
Electronics Packaging Technology Conference, 1998. Proceedings of 2nd
Print_ISBN :
0-7803-5141-X
DOI :
10.1109/EPTC.1998.755981
