Dewetting of molten Sn on Au/Cu/Cr thin-film metallization

Ti/Ni(V)/Cu underbump metallization (UBM) is widely used in flip-chip technology today. The advantages of Ti/Ni(V)/Cu UBM are a low reaction rate with solder and the lack of a magnetic effect during sputtering. Sn atoms diffuse into the Ni(V) layer to form a Sn-rich phase, the so-called Sn-patch, during reflow and aging. In this study, the relationship between interfacial reaction and mechanical properties of the solder joints with Ti/Ni(V)/Cu UBM was evaluated. Sn-3.0Ag-0.5Cu solder was reflowed on sputtered Ti/Ni(V)/Cu UBM, and then the reflowed samples were aged at 125°C and 200°C, respectively. (Cu,Ni) 6 Sn 5 was formed and grew gradually at the interface of the solder joints during aging at 125°C. The Sn-patch replaced the Ni(V) layer, and (Ni,Cu) 3 Sn 4 was thus formed between (Cu,Ni) 6 Sn 5 and the Sn-patch at 200°C. The Sn-patch, composed of Ni and V 2 Sn 3 after reflow, was transformed to V 2 Sn 3 and amorphous Sn during aging. Shear and pull tests were applied to evaluate the solder joints under various heat treatments. The shear force of the solder joints remained at 421 mN, yet the pull force decreased after aging at 125°C. Both the shear and pull forces of the solder joints decreased during aging at 200°C. The effects of aging temperature on the mechanical properties of solder joint were investigated and discussed.

Section: Introductionmentioning

confidence: 99%

Shear and Pull Testing of Sn-3.0Ag-0.5Cu Solder with Ti/Ni(V)/Cu Underbump Metallization During Aging

Wang

Duh

2009

“…[2][3][4][5][6] On the basis of the existing literature, the spalling mechanism can be summarized, and is illustrated step by step, in Fig. 4.…”

Section: Resultsmentioning

confidence: 99%

“…Instead, we observe balled-up Ag 3 Sn and Cu 6 Sn 5 compound grains, the so-called spalling phenomenon. 2,3 The Ag 3 Sn compound grains are plate-shaped, and the Cu 6 Sn 5 compound grains show the typical scallop shape. This spalling of the interfacial compound layer caused the molten SnPb to come into direct contact with the alloy 42 LF substrate.…”

Section: Methodsmentioning

confidence: 99%

Dewetting Retardation on Ag/Cu Coated Light Emitting Diode Lead Frames During the Solder Immersion Process

Huang

Shieu

Hsiao

et al. 2009

Self Cite

The process of SnPb immersion in Ag/Cu coated light emitting diode lead frames (LED LFs) (alloy 42) was investigated. SnPb solder was found to cause dewetting of the LF substrate after 6 s of immersion. We believed that the dewetting of the SnPb solder could be attributed to spalling of the interfacial compound grains. The addition of a small amount of Ni to the molten SnPb solder (0.1 wt.%) retarded that spalling and helped to prevent dewetting. The mechanisms for spalling retardation by the addition of Ni additives are as follows: (1) the Ni additives slow down the reaction rate between the molten SnPb solder and the Ag/Cu plating layer; (2) the Ni additives participate in interfacial reactions to form (Cu,Ni)(6)Sn(5) ternary compounds, which are more stable than binary compounds and have a slower ripening process

“…However, the following studies revealed that the solder has a tendency to dewet from the Cr surface when the Cu layer is totally consumed by Cu-Sn IMC growth. 24,25 For that reason, the phased Cr-Cu layer by evaporation was introduced between Cu and Cr layers and was expected to serve as an adhesion enhancement layer. 26 This UBM has been reported to have good interface stability with high Pb-content solders, Pb/5Sn and Pb/3.5Sn, but recent studies reported that the phased Cr-Cu layer with Pb/63Sn solder also showed the Cu-Sn IMC spalling after long-time reflow, and it may cause dewetting of the solder.…”

Section: Cr/crcu/cu Ubmmentioning

confidence: 99%

Under bump metallurgy study for Pb-free bumping

Jang

Wolf

Paik

2002

The demand for Pb-free and high-density interconnection technology is rapidly growing. The electroplating-bumping method is a good approach to meet fine-pitch requirements, especially for high-volume production, because the volume change of patterned-solder bumps during reflow is not so large compared with the stencil-printing method. This paper proposes a Sn/3.5Ag Pb-free electroplating-bumping process for high-density Pb-free interconnects. It was found that a plated Sn/Ag bump becomes Sn/Ag/Cu by reflowing when Cu containing under bump metallurgy (UBM) is used. Another important issue for future flip-chip interconnects is to optimize the UBM system for high-density and Pb-free solder bumps. In this work, four UBM systems, sputtered TiW 0.2 mum/Cu 0.3 mum/electroplated Cu 5 mum, sputtered Cr 0.15 mum/Cr-Cu 0.3 mum/Cu 0.8 mum, sputtered NiV 0.2 mum/Cu 0.8 mum, and sputtered TiW 0.2 mum/NiV 0.8 mum, were investigated for interfacial reaction with electroplated Pb/63Sn and Sn/3.5Ag solder bumps. Both Cu-Sn and Ni-Sn intermetallic compound (IMC) growth were observed to spall-off from the UBM/solder interface when the solder-wettable layer is consumed during a liquid-state "reflow" process. This IMC-spalling mechanism differed depending on the barrier layer material