Influence of substrate metallization on diffusion and reaction at the under-bump metallization/solder interface in flip-chip packages

2002 ◽  
Vol 17 (11) ◽  
pp. 2757-2760 ◽  
Author(s):  
F. Zhang ◽  
M. Li ◽  
C. C. Chum ◽  
K. N. Tu
Keyword(s):  
Flip Chip ◽  
Interfacial Reactions ◽  
Under Bump Metallization ◽  
Ni Substrate ◽  
Enhanced Dissolution ◽  
Substrate Side ◽  
Influence Of Substrate ◽  
Solder Interface ◽  
Eutectic Snpb ◽  
Thermal Stability Of

In flip-chip packages, the effect of Ni metallization on the substrate side on interfacial reactions between solders and an Al/Ni(V)/Cu under-bump metallization (UBM) on the chip side was investigated during the reflow process. The Ni substrate metallization greatly accelerated interfacial reactions on the chip side and quickly degraded the thermal stability of the UBM due to a fast consumption of the Ni(V) layer. This phenomenon can be explained in terms of rapid Ni or Sn diffusion in the ternary (Cu,Ni)6Sn5 phase, which was formed in the solder adjacent to the Ni(V) layer and the enhanced dissolution of (Cu,Ni)6Sn5 into the molten solder. Without the Ni metallization on the substrate side, the Al/Ni(V)/Cu UBM remained very stable with both eutectic SnPb and Pb-free solders.

Electromigration Performance of Pb-Free μPILR™ Flip-Chip Packages

2010 ◽  
Vol 2010 (1) ◽  
pp. 000234-000241
Author(s):  
Rajesh Katkar ◽  
Laura Mirkarimi
Keyword(s):  
Thin Film ◽  
Flip Chip ◽  
Solder Joints ◽  
Void Formation ◽  
Current Direction ◽  
Under Bump Metallization ◽  
Substrate Side ◽  
Solder Interface

The μPILR interconnect is a copper pillar manufactured as a part of a substrate pad. In this paper, we discuss the electromigration (EM) performance of Pb-free μPILR interconnects in a multi-pair daisy chain within 150μm pitch flip-chip packages. Electromigration performance of μPILR interconnects has shown a significant improvement and noticeably delayed electromigration induced failures. Voids initially begin to appear at Cu6Sn5 and solder interface on the die side, with eventual open failure due to excessive void formation along with a severe depletion of Cu Under Bump Metallization (UBM). No failure was observed on the substrate side of the interconnect regardless of the current direction. The enhanced performance of the μPILR interconnect along with other reliability benefits makes it an excellent alternative to conventional solder joints including thin film stack UBMs, thicker copper UBM as well as copper pillar on die.

scholarly journals Cross interactions on interfacial compound formation of solder bumps and metallization layers during reflow

2004 ◽  
Vol 19 (12) ◽  
pp. 3654-3664 ◽  
Author(s):  
T.L. Shao ◽  
T.S. Chen ◽  
Y.M. Huang ◽  
Chih Chen
Keyword(s):  
Flip Chip ◽  
Driving Forces ◽  
The Other ◽  
Compound Formation ◽  
Bump Height ◽  
Performance Requirements ◽  
Substrate Side ◽  
Solder Bumps ◽  
Snpb Solder ◽  
Eutectic Snpb

While the dimension of solder bumps keeps shrinking to meet higher performance requirements, the formation of interfacial compounds may be affected more profoundly by the other side of metallization layer due to a smaller bump height. In this study, cross interactions on the formation of intermetallic compounds (IMCs) were investigated in eutectic SnPb, SnAg3.5, SnAg3.8Cu0.7, and SnSb5 solders jointed to Cu/Cr–Cu/Ti on the chip side and Au/Ni metallization on the substrate side. It is found that the Cu atoms on the chip side diffused to the substrate side to form (Cux,Ni1−x)6Sn5 or (Niy,Cu1−y)3Sn4 for the four solders during the reflow for joining flip chip packages. For the SnPb solder, Au atoms were observed on the chip side after the reflow, yet few Ni atoms were detected on the chip side. In addition, for SnAg3.5 and SnSn5 solders, the Ni atoms on the substrate side migrated to the chip side during the reflow to change binary Cu6Sn5 into ternary (Cux,Ni1−x)6Sn5 IMCs, in which the Ni weighed approximately 21%. Furthermore, it is intriguing that no Ni atoms were detected on the chip side of the SnAg3.8Cu0.7 joint. The possible driving forces responsible for the diffusion of Au, Ni, and Cu atoms are discussed in this paper.

Interface reactions and phase equilibrium between Ni/Cu under-bump metallization and eutectic SnPb flip-chip solder bumps

2003 ◽  
Vol 18 (4) ◽  
pp. 935-940 ◽  
Author(s):  
Chien-Sheng Huang ◽  
Jenq-Gong Duh
Keyword(s):  
Multilayer Structure ◽  
Electron Probe ◽  
Flip Chip ◽  
Electronics Packaging ◽  
Elemental Distribution ◽  
Under Bump Metallization ◽  
Interface Reactions ◽  
Solder Bumps ◽  
Different Thickness ◽  
Eutectic Snpb

Ni-based under-bump metallization (UBM) for flip-chip application is widely used in today's electronics packaging. In this study, electroplated Ni UBM with different thickness was used to evaluate the interfacial reaction during multiple reflow between Ni/Cu UBM and eutectic Sn–Pb solders in the 63Sn–37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure. During the first cycle of reflow, Cu atoms diffused through electroplated Ni and formed the intermetallic compound (IMC) (Ni1−x, Cux)3Sn4. After more than three times of reflow, Cu atoms further diffused through the boundaries of (Ni1−x, Cux)3Sn4 IMC and reacted with Ni and Sn to form another IMC of (Cu1-y, Niy)6Sn5. After detailed quantitative analysis by electron probe microanalysis, the values of y were evaluated to remain around 0.4; however, the values of x varied from 0.02 to 0.35. The elemental distribution of IMC in the interface of the joint assembly could be correlated to the Ni–Cu–Sn ternary equilibrium. In addition, the mechanism of (Cu1−y, Niy)6Sn5 formation was also probed.

Measurement of electromigration activation energy in eutectic SnPb and SnAg flip-chip solder joints with Cu and Ni under-bump metallization

2010 ◽  
Vol 25 (9) ◽  
pp. 1847-1853 ◽  
Author(s):  
Hsiao-Yun Chen ◽  
Chih Chen
Keyword(s):  
Activation Energy ◽  
Flip Chip ◽  
Void Formation ◽  
Under Bump Metallization ◽  
Solder Bumps ◽  
Snpb Solder ◽  
Snag Solder ◽  
Temperature Coefficient Of Resistivity ◽  
Eutectic Snpb ◽  
Real Temperature

Electromigration activation energy is measured by a built-in sensor that detects the real temperature during current stressing. Activation energy can be accurately determined by calibrating the temperature using the temperature coefficient of resistivity of an Al trace. The activation energies for eutectic SnAg and SnPb solder bumps are measured on Cu under-bump metallization (UBM) as 1.06 and 0.87 eV, respectively. The activation energy mainly depends on the formation of Cu–Sn intermetallic compounds. On the other hand, the activation energy for eutectic SnAg solder bumps with Cu–Ni UBM is measured as 0.84 eV, which is mainly related to void formation in the solder.

Under Bump Metallization Development For High Sn Solders

1997 ◽  
Vol 505 ◽  
Author(s):  
T. M. Korhonen ◽  
S. J. Hong ◽  
P. Su ◽  
C. Zhou ◽  
M. A. Korhonen ◽  
...  
Keyword(s):  
Flip Chip ◽  
Silicon Wafers ◽  
Under Bump Metallization ◽  
Shear Tests ◽  
Adhesion Layer ◽  
Solder Balls ◽  
Sputter Deposited ◽  
Pure Cu ◽  
Solder Interface ◽  
Intermetallic Layers

ABSTRACTSeveral under bump metallisation (UBM) schemes using Ni or CuNi alloys as the solderable layer were investigated. Cr or Ti was used as the adhesion layer. The UBM pads of different compositions were sputter deposited on silicon wafers and patterned using standard photolithographic processes. Eutectic Sn-Pb solder balls were reflowed on top of the pads. The resulting interfacial microstructures were examined by SEMIEDX analysis of cross-sectioned samples. The integrity of the UBMIsolder interface was characterized by micromechanical shear testing of flip chip test samples. Growth of intermetallic layers was found to be significantly slower in Ni and CuNi schemes compared to pure Cu. The joints on Ni and CuNi had also a better adhesion at the UBM/solder interface, and in the shear tests the fracture occurred through the solder

Effects of substrate metallizations on solder/underbump metallization interfacial reactions in flip-chip packages during thermal aging

2003 ◽  
Vol 18 (6) ◽  
pp. 1333-1341 ◽  
Author(s):  
F. Zhang ◽  
M. Li ◽  
C. C. Chum ◽  
C-H. Tung
Keyword(s):  
Porous Structure ◽  
Thermal Aging ◽  
Flip Chip ◽  
Interfacial Reactions ◽  
Snagcu Solder ◽  
Solution Type ◽  
Snpb Solder ◽  
Underbump Metallization ◽  
Eutectic Snpb

Effects of Ni and Au from Ni/Au substrate metallizations on the interfacial reactions of solder joints in flip-chip packages during long-term thermal aging were systematically investigated. It was found that both Au and Ni influenced the solid-state interfacial reactions, underbump metallization (UBM), and intermetallic compound (IMC) evolution. Because large amounts of Ni could incorporate into IMC to form a multicomponent (Cu, Ni)6Sn5 phase during assembly reflow, while Au could only affect the reaction during thermal aging through the reconfiguration of AuSn4 phase, Ni had stronger effects on solid-solution type Ni–V UBM consumption than Au. It was found that the UBM consumption process was faster in the eutectic SnPb solder system than that in the SnAgCu solder system during aging. A porous structure was formed in the UBM layer after Ni in UBM was consumed. Electrical resistance of flip-chip packages increased significantly after the porous structure reached certain extents. The results showed that the diffusion process of Ni from UBM and Sn from solder in the presence of (Cu, Ni)6Sn5 or (Ni, Cu)3Sn4 phase at solder joint interfaces could be much faster than that in the case of binary Cu6Sn5 or Ni3Sn4 IMC.

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