Solid-liquid reactions: The effect of Cu content on Sn-Ag-Cu interconnects

Lu, Henry Y.; Balkan, H.; Simon, Katya

doi:10.1007/s11837-005-0133-y

Cited by 17 publications

(4 citation statements)

References 21 publications

(14 reference statements)

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“…3(a) cuts through these Cu 6 Sn 5 rods at different angles, revealing different cross-sections of these rods. Lu et al 10 recently published an excellent article relating the cross-sectional morphology of such Cu 6 Sn 5 rods to their real threedimensional microstructure.…”

Section: A Electromigration In Molten Sn35agmentioning

confidence: 99%

Pronounced electromigration of Cu in molten Sn-based solders

et al. 2008

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The high local temperature in flip-chip solder joints of microprocessors has raised concerns that the solder, a low melting temperature alloy, might locally liquefy and consequently cause failure of the microprocessors. This article reports a highly interesting electromigration behavior when the solder is in the molten state. A 6.3 × 10 3 A/cm 2 electron current was applied to molten Sn3.5Ag solder at 255°C through two Cu electrodes. The high current density caused rapid dissolution of the Cu cathode. The dissolved Cu atoms were driven by electrons to the anode side and precipitated out as a thick, and sometimes continuous, layer of Cu 6 Sn 5 . The applied current caused the dissolution rate of the Cu cathode to increase by one order of magnitude. A major difference between the electromigration in the solid and molten state was identified to be the presence of different countering fluxes in response to electromigration. For electromigration in the molten state, the back-stress flux, which was operative for electromigration in the solid state, was missing, and instead a countering flux due to the chemical potential gradient was present. An equation for the chemical potential gradient, d/dx, required to balance the electromigration flux was derived to be d/dx ‫ס‬ N°z*eJ, where N°is Avogadro's number, z* is the effective charge of Cu, e is the charge of an electron, is the resistivity of the solder, and J is the electron current density.

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Section: A Electromigration In Molten Sn35agmentioning

confidence: 99%

Pronounced electromigration of Cu in molten Sn-based solders

et al. 2008

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“…With the increasing environmental and health concerns induced by lead, the development of lead-free solders was promoted (Kamal et al , 2008; Lu et al , 2005). Among the potential candidates, SnBi solder alloys were widely used in the low temperature packaging because of its low cost, low melting point, low thermal expansion coefficient and high creep resistance (Tsai et al , 2011; Hu et al , 2014).…”

Section: Introductionmentioning

confidence: 99%

Effects of nano-copper particles on the properties of Sn58Bi composite solder pastes

Zhang

Liu

Sun

et al. 2017

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Purpose This paper aimed to investigate the effects of nano-copper particles on the melting behaviors, wettability and defect formation mechanism of the Sn58Bi composite solder pastes. Design/methodology/approach In this paper, the mechanical stirring method was used to get the nano-composite solder pastes. Findings Experimental results indicated that the addition of 3 wt.% (weight percentage) 50 nm copper particles showed limited effects on the melting behaviors of the Sn58Bi composite solder paste. The spreading rate of the Sn58Bi composite solder paste showed a decreasing trend with the increase of the weight percentage of 50 nm copper particles from 0 to 3 wt.%. With the addition of copper particles of diameters 50 nm, 500 nm or 6.5 μm into the Sn58Bi solder paste, the porosities of the three types of solder pastes showed a similar trend. The porosity increased with the increase of the weight percentage of copper particles. Based on the experimental results, a model of the void formation mechanism was proposed. During reflow, the copper particles reacted with Sn in the matrix and formed intermetallic compounds, which gathered around the voids produced by the volatilization of flux. The exclusion of the voids was suppressed and eventually led to the formation of defects. Originality/value This study provides an optimized material for the second and third level packaging. A model of the void formation mechanism was proposed.

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“…Often, the IMC layer is brittle in nature, and moreover, its microstructure differences from the solder and the substrate makes the situated in the both sites of the IMC layer more sensitive to stress. These will make the crack initiation and propagation much more easily at the IMC layer and make it prone to mechanical failure under relatively low load (Tu et al, 1997, Miric and Grusd, 1998, Amagai et al, 2002, Lu et al, 2005.…”

Section: Intermetallic Reactions Between Metallizations and Solder Jomentioning

confidence: 99%

“…The National Electronic Manufacturing Initiative (NEMI) organization recommends 95.5Sn-3.9Ag-0.6Cu (±0.2%) as the lead-free alloy candidate to replace 63Sn-37Pb (Cannis and Syed, 2001, Bradley et al, 2002, Chung et al, 2002, NEMI, 2003. Following this announcement, a lot of research work on this family of lead-free alloy has been carried out (Tonapi et al, 2002, Amagai et al, 2004, Nurmi et al, 2004, Lu et al, 2005, Wable et al, 2005.…”

Section: Introductionmentioning

confidence: 99%

Study of microstructures and mechanical properties of lead-free solder joints

Ngoh¹

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Reliability of solder joints is a most critical issue in electronic packaging. There is the urgent need to understand reliability of lead-free solder joints because lead-free solders are replacing the conventional tin-lead solders due to environmental concerns and legislation to ban use of lead in electronic products. In soldering process, formation of thin intermetallic compounds (IMC) due to reaction between the solder and substrate is essential to achieve a good metallurgical bond. However, excessive IMC growth in service could cause premature failure of the joint. Therefore, the primary objective of the project was to understand IMC growth in lead-free solder joints. Bulk solders were studied but special attention was paid to the solder-substrate interface. The project aimed to study 95.5Sn-3.8Ag-0.7Cu solder because it is a type of lead-free solder especially recommended by the National Electronic Manufacturing Initiative, but 99.3Sn-0.7Cu solder was also studied because the binary alloy contains single type of IMC and thus makes it easier to monitor the IMC growth quantitatively. Various factors influencing IMC growth were studied, including temperature, time, stress and surface finishes of the substrate. Great effort was made to study effect of the factors on IMC growth separately in a controlled manner. For example, study of the bulk SnAg -Cu solder either by varying temperature to 60, 125 and 190 °C at a fixed time of 1 hr or by change of heating time at a fixed temperature of 190 °C clearly reveals the effect of temperature and time on the IMC growth. Worth special note is that a new technique was adopted to monitor IMC growth in-situ. The technique made it possible to show quantitatively that initial growth of IMC in the Sn-Cu solder is linear with time. This is in contrast with the observation that the growth of IMC at the soldersubstrate interface is proportional to square root of time, highlighting the fact that the mechanism for IMC growth in bulk solders is different from that in the presence of a substrate. Extensive researches were carried out to study IMC growth in the SnAg -Cu solder joints with either Cu or FR4 as substrate during various thermal loading conditions, including isothermal aging (125, 150 and 175 °C), thermal cycling (-40 to 125 °C) and thermal shock tests (-55 to 125 °C) up to 2000 cycles. Ripening of interface IMC was vii

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Solid-liquid reactions: The effect of Cu content on Sn-Ag-Cu interconnects

Cited by 17 publications

References 21 publications

Pronounced electromigration of Cu in molten Sn-based solders

Pronounced electromigration of Cu in molten Sn-based solders

Effects of nano-copper particles on the properties of Sn58Bi composite solder pastes

Study of microstructures and mechanical properties of lead-free solder joints

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