Title :
Fluxless solder bumping in flip chip package by plasma reflow
Author :
Hong, Soon-Min ; Kang, Choon-Sik ; Jung, Jae-Pil
Author_Institution :
Sch. of Mater. Sci. & Eng., Seoul Nat. Univ., South Korea
Abstract :
A new fluxless reflow process using Ar+10%H2 plasma was investigated for application to solder bump flip chip packaging. The 100 μm-diameter Sn-3.5wt%Ag solder balls were bonded to 250 μm pitch Cu/Ni under bump metallurgy (UBM) pattern by laser solder ball bumping method. Then, the Sn-Ag solder balls were reflowed in Ar+H2 plasma. Without flux, the wetting between solder and UBM occurred in Ar+H2 plasma. During plasma reflow, the solder bump reshaped and the crater on the top of bump disappeared. The bump shear strength increased as the Ni3Sn4 intermetallic compounds formed on initial reflow stage but began to degrease as coarse (Cu,Ni) 6Sn5 grew at solder/UBM interface. As the plasma reflow time increased, the fracture within solder bulk decreased and the fracture along solder/UBM interface increased. The off-centered bumps self-aligned to UBM pattern during plasma reflow. The solder ball defect occurred in high power and a long time plasma reflow
Keywords :
encapsulation; flip-chip devices; fracture; laser beam applications; packaging; reflow soldering; shear strength; wetting; 100 micron; 250 micron; Ar-H2; Sn-Ag; bump shear strength; flip chip package; fluxless solder bumping; fracture; laser solder ball bumping; off-centered bumps; plasma reflow; under bump metallurgy; wetting; Bonding; Cleaning; Flip chip; Materials science and technology; Plasma applications; Plasma materials processing; Portable computers; Semiconductor device packaging; Soldering; Solvents;
Conference_Titel :
Electronic Materials and Packaging, 2001. EMAP 2001. Advances in
Conference_Location :
Jeju Island
Print_ISBN :
0-7803-7157-7
DOI :
10.1109/EMAP.2001.983973
