Morphology changes in solder joints––experimental evidence and physical understanding

Müller, Wolfgang

doi:10.1016/j.microrel.2004.04.020

Cited by 25 publications

(8 citation statements)

References 25 publications

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“…Besides size and constraining effects, lead-free solder materials have shown very complex elasto-visco-plastic behaviours 11,12 with strong dependencies on time, 20,23,29 strain history, 15,17,19,24,28 temperature, 16,18,19,22, and processing parameters. 8,21 Due to these various influences, the macroscopic stress-strain constitutive law of lead-free solder materials should be determined in the most realistic conditions in order to maximize the consistency of the identified mechanical properties.…”

Section: In Situ Characterization Methodsmentioning

confidence: 99%

Experimental and numerical studies on size and constraining effects in lead‐free solder joints

Botsis

Sivasubramaniam

Janczak‐Rusch

2006

Fatigue Fract Eng Mat Struct

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A B S T R A C TThe durability and reliability of lead-free solder joints depends on a large number of factors, like geometry, processing parameters, microstructure and thermomechanical loads. In this work, the nature and influence of the plastic constraints in the solder due to joining partners have been studied by parametric finite element simulation of solder joints with different dimensions. The apparent hardening due to plastic constraints has been shown to strongly depend on the solder gap to thickness ratio with an inversely proportional evolution. Due to interaction of several parameters, the macroscopic stress-strain constitutive law of lead-free solder materials should be determined in the most realistic conditions. In order to identify the elasto-plastic constitutive law of Sn-Ag-Cu solders, a sub-micron resolution Digital Image Correlation technique has been developed to measure the evolution of strain in solder joints during a tensile test. Experimental results of the stress-strain response of Sn-Ag-Cu solder joints have been determined for several solder gaps. The measured loaddisplacement curves have been used in an inverse numerical identification procedure to determine the constitutive elasto-plastic behaviour of the solder material. The effects of geometrical constraints in a real solder joint with heterogeneous stress and strain fields are then studied by comparing the apparent (constrained) and constitutive (non-constrained) stress-strain relationships.Once the size dependant constraining effects have been removed from the stress-strain relationship, the scale effects can be studied separately by comparing the constitutive elasto-plastic parameters of joints with a variable thickness. Experimental stress-strain curves (constrained and unconstrained) for Sn-4.0Ag-0.5Cu solder in joints of 0.25-2.4 mm gap are presented and the constraining and the size effects are discussed.

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Section: In Situ Characterization Methodsmentioning

confidence: 99%

Experimental and numerical studies on size and constraining effects in lead‐free solder joints

Botsis

Sivasubramaniam

Janczak‐Rusch

2006

Fatigue Fract Eng Mat Struct

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“…The increasingly environmental concern over the toxicity of lead (Pb) combined with strict environmental regulations around the world have been targeted to eliminate the usage of Pb-bearing solders in electronic assemblies and to adopt lead-free solder alloys [1][2][3][4][5]. The European Union Waste Electrical and Electronic Equipment (WEEE) Directive, published in 2002 and Restriction of Hazardous Substances (RoHS) Directive of European Community, published in 2003 restricted the usage of certain toxic materials including Lead (Pb) in production of electronic devices used in European Union effective on 1 July 2006 [6].…”

Section: Introductionmentioning

confidence: 99%

Effect of Lanthanum Doping on the Microstructure Evolution and Intermetallic Compound (IMC) Growth during Thermal Aging of SAC305 Solder Alloy

Yasmin¹,

Sadiq²,

Khan³

2013

J Material Sci Eng

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Citation: Yasmin T, Sadiq M, Khan MI (2014) Effect of Lanthanum Doping on the Microstructure Evolution and Intermetallic Compound (IMC) Growth during Thermal Aging of SAC305 Solder Alloy. J Material Sci Eng 3: 141. SAC305Among the various lead-free solders SAC-305 alloy has emerged as the most widely accepted to replace Sn-Pb solders. It is widely used as lead-free solder for surface mount technology (SMT) card assembly and for ball-grid-array (BGA) interconnection in the microelectronic packaging industry as solder balls and pastes. More than 70% market for reflowing lead-free solders are in the SAC series. Due to having good mechanical properties, acceptable wetting properties, and suitable melting points, the International Printed Circuit Association has suggested that SAC-305 and SAC-396 will be the most widely used alloys in the future [10][11][12][13][14][15][16].Although SAC-305 alloy is widely used in electronics industry, it has several problems to be solved. One of the core issues pertaining to Abstract Sn96.5Ag3Cu0.5 (SAC305) is widely used as lead-free solder for surface mount technology (SMT) card assembly and for ball-grid-array (BGA) interconnection in the microelectronic packaging industry as solder balls and pastes. In this study the effects of Lanthanum (La) doping on SAC305 under thermal aging was investigated as function of intermetallic compounds (IMCs) growth and grain size evolution. The morphology of the microstructure was analyzed under Scanning Electron Microscope (SEM) and optical microscope, the elemental distribution was confirmed by Energy Dispersive Spectroscopy (EDS) and phase identification of the crystalline structure formed during thermal aging was confirmed by x-ray diffraction (XRD). It was found that the microstructure of SAC305 solder alloy changes significantly with addition of La. Quantitative analysis of grain size and intermetallic particle size was performed both for undoped and La-doped SAC305 alloys.The XRD and EDS tests found that the doping elements La exist in SAC305 solder alloy in two forms: as La element or as La5Sn3 IMC.The La-Sn IMC has complex branch structure [89], which is usually look like clusters of snowflakes [57] in SEM images. With the help of EDX analysis very high amount of La concentration of observed in these snowflakes. Moreover It was also observed that quantity La5Sn3 IMC depend upon the concentration La doping i.e. with high 0.5wt% of lanthanum bigger snowflakes has be observed as shown in Figure 8 while small isolated snow can be seen with less La doping which is consistent with the results of Min et al [25].La doping greatly reduces the Ag 3 Sn and Cu 6 Sn 5 particle size particle during thermal aging. Surface area averaged particle size of Cu 6 Sn 5 particles was obtained as per ASM handbook [95]. The particle sizes for the full data set are plotted in Figure 9 as function of La doping level. It can be seen that La doping effectively suppresses the growth of Ag 3 Sn and Cu 6 Sn 5 intermetallic particle.

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“…Such models consist of a Cahn-Hilliard system, accounting for spinodal decomposition and Ostwald ripening, coupled with an elasticity equation that represents thermomechanical interaction. In the Cahn-Hilliard system, both theoretical considerations [30,31] and practical reasoning [9,10,55] suggest a chemical energy density of logarithmic type.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of coarsening in binary solder alloys

Gräser

Kornhuber

Sack

2014

Computational Materials Science

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Morphology changes in solder joints––experimental evidence and physical understanding

Cited by 25 publications

References 25 publications

Experimental and numerical studies on size and constraining effects in lead‐free solder joints

Experimental and numerical studies on size and constraining effects in lead‐free solder joints

Effect of Lanthanum Doping on the Microstructure Evolution and Intermetallic Compound (IMC) Growth during Thermal Aging of SAC305 Solder Alloy

Numerical simulation of coarsening in binary solder alloys

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