Growth Of Compound Layer Research Articles

Effect of Zinc Element on Mechanical and Welding Properties of Cu–1.8Ni–0.45Si Alloy

Cu–Ni–Si alloy is widely used as the main material of lead frame. The process of alloying is an important method to improve the comprehensive performance of the alloy. Herein, Cu–1.8Ni–0.45Si (−0.5Zn) alloys are prepared. The variation trend and mechanism of Zn on the mechanical properties and welding properties are analyzed with scanning electron microscopy and electron backscattering diffraction. The results show that the addition of 0.5 wt% Zn can improve the brazing properties of the alloy while ensuring the tensile strength and conductivity of the material. Further quantitative analysis reveals that Zn addition enhances the contribution of precipitation strengthening to the alloy's mechanical properties, which is due to the reduction of the size of the particles of the precipitated phase by the addition of Zn. In addition, the addition of Zn can form a Zn‐enriched layer at the welding interface of the alloy, which has an obstructive effect on the diffusion and growth of the intermetallic compound (IMC) layer, effectively reducing the thickness of the IMC layer, inhibiting the formation of the Cu3Sn phase, and improving the mechanical properties of the alloy brazed joints.

Interfacial IMC growth behavior of Sn-3Ag-3Sb-xIn solder on Cu substrate

PurposeThe reliability of solder joints is closely related to the growth of an intermetallic compound (IMC) layer between the lead-free solder and substrate interface. This paper aims to investigate the growth behavior of the interfacial IMC layer during isothermal aging at 125°C for Sn-3Ag-3Sb-xIn/Cu (x = 0, 1, 2, 3, 4, 5 Wt.%) solder joints with different In contents and commercial Sn-3Ag-0.5Cu/Cu solder joints.Design/methodology/approachIn this paper, Sn-3Ag-3Sb-xIn/Cu (x = 0, 1, 2, 3, 4, 5 Wt.%) and commercial Sn-3Ag-0.5Cu/Cu solder were prepared for bonding Cu substrate. Then these samples were subjected to isothermal aging for 0, 2, 8, 14, 25 and 45 days. Scanning electron microscopy and transmission electron microscopy were used to analyze the soldering interface reaction and the difference in IMC growth behavior during the isothermal aging process.FindingsWhen the concentration of In in the Sn-3Ag-3Sb-xIn/Cu solder joints exceeded 2 Wt.%, a substantial amount of InSb particles were produced. These particles acted as a diffusion barrier, impeding the growth of the IMC layer at the interface. The growth of the Cu3Sn layer during the aging process was strongly correlated with the presence of In. The growth rate of the Cu3Sn layer was significantly reduced when the In concentration exceeded 3 Wt.%.Originality/valueThe addition of In promotes the formation of InSb particles in Sn-3Ag-3Sb-xIn/Cu solder joints. These particles limit the growth of the total IMC layer, while a higher In content also slows the growth of the Cu3Sn layer. This study is significant for designing alloy compositions for new high-reliability solders.

Linear growth behaviour of intermetallic compound layer in electronic interconnections

We observed a linear behaviour of intermetallic compound (IMC) layer growth in electronic metallurgical interconnections, although the time required was twice that of commercial reliability standards for electronic packaging. This finding contradicts the classical parabolic growth law, which is widely reported to represent growth behaviour. We suggest that the parabolic growth law may be inadequate to thoroughly explain the IMC layer's growth by considering (a) one-directional growth and (b) reactions between elements for formation and growth. Further analysis has been carried out to analyse the logical judgment of the parabolic growth law and support our finding over linear IMC layer growth behavior.

Effect of Sn Plating Thickness on Wettability, Solderability, and Electrical Connections of Electronic Lead Connectors for Surface Mount Technology Applications

The wettability of solder is important to achieve good solderability between the electronic component and printed circuit board (PCB). Tin (Sn) plating is widely used to promote the wettability of the solder on the substrates. However, an adequate amount of Sn plating thickness must be taken into consideration to acquire good wettability and solderability. Thus, this study investigates the Sn plating thickness of the electronic lead connector and their effect on the wettability and electrical connection. Two types of Sn plating thicknesses, ~3 μm, and 5 μm were applied on the electronic lead connector surface. It was found that the thin Sn plating thickness of ~3 μm has shown failure in electrical connections and lack of solder joint wettability and solderability properties. A thicker Sn plating thickness of 5 μm, has shown better wettability and solderability properties. In addition, the electrical connections also passed which implies that the thicker Sn plating thickness provides good solder joint establishment leading to good electrical connections. It is also observed that the better wettability of solder has been achieved for thicker Sn plating thickness. The finding from the field emission scanning electron microscope (FESEM) shows that the intermetallic compound (IMC) layer growth in the lead connector surface is regarded as abnormal for thin Sn plating thickness (~3 μm), in which the IMC layer was consumed and penetrating up to the surface of Sn-coating. This has led to poor solderability of the thin Sn plating with the solder to establish solder joint. The findings from this study have shed some light upon a better understanding of the importance of considering the adequate amount of Sn coating thickness to avoid IMC consumption at the Sn plating, better wettability properties, solderability, and solder joint quality for surface mount technology (SMT) especially for electronic lead connector applications.

Formation of columnar grains during diffusional growth of Nb3Sn layer and its suppression

The manufacturing process of multifilamentary Nb3Sn superconducting wire includes annealing for diffusional growth of the Nb3Sn intermetallic compound layer. During the process, the formation of columnar Nb3Sn grains should be suppressed to maximize the flux pinning effect. However, the detailed mechanism underlying the formation of columnar Nb3Sn grains has not been clarified yet, and is an obstacle to finding optimal process conditions. In the present work, we investigated the fundamental reason for the columnar grain formation, using a novel Monte Carlo Potts model which can simultaneously predict grain growth and interfacial reactions. We found that a decrease in thermodynamic driving force due to insufficient Sn at the interface causes the formation of columnar Nb3Sn grains. Accordingly, columnar grain formation is expected to be suppressed when abundant Sn atoms are supplied rapidly to the reaction front. Based on the fundamental understanding of columnar grain formation, possible ways to suppress columnar grain formation are suggested. We especially focused on the difference in the columnar grain fraction depending on the wire strand type (bronze processed wire vs. internal-tin processed wire). Based on simulations and experimental analyses, we suggest a brief guideline for the design of wire strand geometry to avoid columnar grain formation.

Achieving balanced enhancement of mechanical performance and heat resistance in Cf/SiC-superalloy joints by regulating active element Ti in brazing filler

The application of Cf/SiC-superalloy joints in aerospace typically demands high strength and good heat resistance. However, the simultaneous improvement of the two properties is a pressing problem that needs to be addressed. This paper proposes the addition of diamond (C) powder to the Cu-Ni-Ti brazing filler to regulate the interface reaction between the filler and Cf/SiC composite and the initial liquefaction temperature of the interlayer, thereby achieving a balanced enhancement in both the mechanical performance and high-temperature resistance of the Cf/SiC-GH3044 joints. The results indicate that during the joining process, a brittle compound layer composed of TiC, Ti5Si3, and Ni16Ti6Si7 is formed at the Cf/SiC/interlayer interface. The thickness of the compound layer increases with elevated joining temperatures or prolonged holding times, which is detrimental to the strength of the joint. The added C particles react with the active element Ti to synthesize in situ some TiC reinforcing particles with the low thermal expansion coefficient in the interlayer. This not only suppresses the excessive growth of the brittle compound layer but also alleviates the residual thermal stress in the joint. Additionally, since Ti is a lowering-melting element in the Cu-Ni-Ti filler, the consumption of Ti by the C/Ti reaction raises the initial liquefaction temperature of the interlayer, thus improving the heat resistance of the joint. When the joining temperature and holding time were kept constant, the shear strength of the joint reached a maximum value as the C particle content increased. If the joining temperature was elevated or the holding time was extended, the C content associated with the peak strength also increased. By optimizing the C particle content, both the shear strength and heat resistance of the joint were improved. The maximum shear strength of the joint at room temperature and 900 °C were measured to be 245 MPa and 138 MPa, respectively. Moreover, the joint exhibited a maximum temperature capability of 1064 °C.

Potential of Nitrided and PVD-MoS2:Ti-Coated Duplex System for Dry-Running Friction Contacts

Self-lubricating coatings can be used to increase the service life of machine parts which are subjected to high mechanical loads. The present work is concerned with the combination of nitriding and a subsequent Ti-doped MoS2 coating. The focus of the investigations is on the impact of the compound layer on the wear behavior of the coating since the changes in the surface topography due to compound layer growth and pore formation inside the compound layers are expected to have an impact of the adhesion strength and the wear behavior. For this purpose, compound layers with varying thickness and porosity were formed in the surface area of the material EN31CrMoV9 by gas nitriding. A MoS2:Ti PVD monolayer was applied directly on the compound layers. The wear behavior was evaluated using the pin-on-disc test. The MoS2:Ti solid lubricant coatings show good adhesion on the compound layers without any interlayer. Compared with the nitrided reference state, the coating significantly improved the wear behavior of the surface treated material.

Contribution of Mechanical Activation on the Growth of Intermetallic Compound Layers at the Cu/Al Interface During Vacuum Hot Pressing

Contribution of Mechanical Activation on the Growth of Intermetallic Compound Layers at the Cu/Al Interface During Vacuum Hot Pressing

Effect of SiO2 nanoparticle addition on growth of interfacial Ag3Sn intermetallic compound layers between lead-free solder and silver conductor

This study investigated the effects of silver powder modification on intermetallic compound (IMC) formation and silver leaching during soldering at high temperatures. Silica nanoparticles (NPs) were deposited onto a silver powder surface to inhibit silver leaching, which can lead to soldering joint failure during high-temperature soldering. The NPs were deposited through hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) based on the Stöber method. Fourier transform infrared spectroscopy and scanning electron microscopy were used to observe the microstructures of silver powders after the deposition of silica NPs with various TEOS concentrations and various deposition times. As the deposition time increased, the amount of silica NPs on the surface of the silver powder increased. The transmission electron microscopy results show that silica NPs were located at the IMC grain boundaries, which can hinder the dissolution of IMCs by lead-free solder melt along grain boundaries during soldering, retarding silver leaching. The growth kinetics and mechanism of IMCs during soldering were investigated. The results show that the growth of IMCs is mainly dominated by bulk diffusion. The activation energy for IMC growth increased and the growth rate decreased with increasing silica NP addition and deposition time.

Impact of different aging conditions on the IMC layer growth and shear strength of Ni-modified MWCNTs reinforced Sn-Ag-Cu composite solder

PurposeThe purpose of this paper is to develop a new composite solder to improve the reliability of composite solder joints. Nano-particles modified multi-walled carbon nanotubes (Ni-MWCNTs) can indeed improve the microstructure of composite solder joints and improve the reliability of solder joints. Although many people have conducted in-depth research on the composite solder of Ni-MWCNTs. However, no one has studied the performance of Ni-MWCNTs composite solder under different aging conditions. In this article, Ni-MWCNTs was added to Sn-Ag-Cu (SAC) solder, and the physical properties of composite solder, the microstructure and mechanical properties were evaluated.Design/methodology/approachIn this study, the effect of different aging conditions on the intermetallic compound (IMC) layer growth and shear strength of Ni-modified MWCNTs reinforced SAC composite solder was studied. Compared with SAC307 solder alloy, the influence of Ni-MWCNTs with different contents (0, 0.1 and 0.2 Wt.%) on composite solder was examined. To study the aging characteristics of composite solder joints, the solder joints were aged at 80°C, 120°C and 150°C.FindingsThe experimental results show that the content of Ni-MWCNTs affects the morphology and growth of the IMC layer at the interface. The microhardness of the solder increases and the wetting angle decreases. After aging at moderate (120°C) and high temperature (150°C), the morphology of the Cu6Sn5 IMC layer changed from scallop to lamellar and the grain size became coarser. The following two different phase compositions were observed in the solder joints with Ni-MWCNTs reinforcement: Cu3Sn and (Cu, Ni)6Sn5. The fracture surface of the solder joints all appeared ductile dents, and the size of the pits increased significantly with the increase of the aging temperature. Through growth kinetic analysis, Ni-modified MWCNTs in composite solder joints can effectively inhibit the diffusion of atoms in solder joints. In short, when the addition amount of Ni-MWCNTs is 0.1 Wt.%, the solder joints exhibit the best wettability and the highest shear strength.Originality/valueIn this study, the effects of aging conditions on the growth and shear strength of the IMC layer of Ni modified MWCNTs reinforced SAC307 composite solder were studied. The effects of Ni MWCNTs with different contents (0, 0.1 and 0.2 Wt.%) on the composite solder were examined.

A systematic study on the effect of coating type and surface preparation on the wettability of Si-Bronze brazing filler material on GI and GA-coated DP600

Zn-coated advanced high strength steels are popular in the automotive industry due to their excellent combination of mechanical strength and ductility as well as superior corrosion resistance provided by the Zn-coating – with hot-dip galvanized and galvannealed coatings being the most popular. Gas metal arc brazing technology is a non-fusion joining method, proposed as an alternative to the gas metal arc welding process due to several advantages: The arc-brazing process delivers significantly lower heat input to the substrate, which minimizes the Zn-coating burn-off leading to higher corrosion protection for the joined parts, and reduces the HAZ softening phenomenon which affects the mechanical integrity of the substrate, while at the same time reduces welding defects such as porosity and blowholes. The strength of an arc-brazed joint depends on the spreading of the molten filler material over the joint to create a bond between the parts as the molten braze solidifies. Existing literature on the subject suggests that heat input is the main driving factor controlling the wettability of the molten braze material with the type of shielding gas used also having an effect. However, the influence of different types of Zn-coatings and their respective surface condition (i.e., clean, or unclean) on the wettability of Cu-based molten braze materials during arc-brazing has not been investigated. The present work investigates the effect of surface morphology of galvanized and galvannealed DP600 steel in the as-received and plasma cleaned conditions on the wettability of molten Si-Bronze (CuSi3Mn1) brazing filler material in the bead-on-plate configuration. The findings of this work clearly demonstrate that the type of coating and its surface condition has a significant effect on the spreading of the molten filler material and on the growth of the intermetallic compound layer at the joint interface and therefore, should be taken into consideration as a factor that can impact the efficacy of an arc-brazed joint. • Evaluating surface morphology of different Zn-coatings to calculate their surface free energy. • Establishing a clear link between the surface roughness of Zn-coated steels on the wettability of molten Si-Bronze filler material. • The study shows that the wettability of the molten filler material is also affected by the presence of organic contaminants on the coating surface. • This work shows the relevance of surface morphology in controlling the wetting length of weld brazed joints. • The thickness of the intermetallic compound layer at the braze interface can be controlled by using oxygen plasma cleaning.

Nitriding of White‐Solidified Fe–C–Si Alloys: Diffusion Path Concept Applied to Inhomogeneous Microstructures

The microstructure formation during nitriding of white‐solidified Fe–C–Si alloys, relevant to advanced surface treatments for cast irons, is studied. The as‐cast microstructures mainly contain Si‐free, C‐rich eutectic cementite and Si‐enriched, C‐lean ferrite/pearlite. The spatial extent of these microstructure regions is significantly larger than the diffusion distance of Si during nitriding. The phases and microstructure forming during nitriding vary with the local Si content in the substrate. Nitriding conditions only allowing to form γ′–Fe4N from pure α‐Fe generate a compound layer composed of γ′–Fe4(C, N), ε–Fe3(C, N)1+x , and Si‐rich nitride, X. ε is the main constituent, whereas γ′ only forms from Si‐free eutectic cementite. Different nitriding experiments elucidate the interrelated thermodynamic and kinetic effects of C and Si on the phase evolution and the compound layer growth. A schematic model of the microstructure evolution is developed. Information on the topology of the largely unknown Fe–C–Si–N phase diagram is derived from the experimental observations. For this, the diffusion path concept is adapted to describe the microstructure formation during nitriding of compositionally inhomogeneous alloys, in which substitutional alloying elements are heterogeneously distributed and largely immobile. α + ε and α + ε + X phase fields are identified as particular features of the Fe–C–Si–N phase diagram at 540 °C.

Effects of Carbon Content Change on Growth of Compound Layer in Surface of Nitrided Steel

When steel is nitrided, a compound layer mainly composed of iron nitrides, ε-Fe2~3N and the γ’-Fe4N phase, is formed on the steel surface. It is an extremely important industrial issue to clarify factors governing the formation of the compound layer during nitriding and to establish unified views on the mechanism of compound layer formation. Therefore, in order to clarify the effect of change in carbon concentration on the growth of the ε phase and the γ’ phase in the compound layer on nitrided steel, we evaluated the change over time in the concentration of the alloy elements in the surface layer, and the phases of the compound layer on nitrided steels containing various amount of carbon in the matrix. The results were that the change over time in the carbon concentration in the compound layer was mainly responsible for the change over time in the phases of the compound layer. Furthermore, it was discovered that the change over time in the carbon concentration distribution occurred because both increasing of carbon from the matrix to the compound layer, and decreasing of carbon from the surface of compound layer to the atmosphere. That caused the gradient change of chemical potential of carbon in the through-thickness direction of compound layer, and the phases of the compound layer were changed with the treatment time.

Effects of doping Ti3SiC2 with Al on interfacial microstructural evolution, growth kinetics and mechanical properties of Ti3SiC2/TiAl joints

Investigations of the interfacial microstructural evolution, the growth kinetics, and the mechanical properties in the Al-doped joint can derive guidelines for the knowledge-based parameter optimization of dissimilar Ti3SiC2/TiAl joining process. The interfacial microstructural evolution, the growth kinetics of the Ti3SiC2/TiAl joints was greatly altered by doping Ti3SiC2 with Al. The interface in the Ti3(Si0.94Al0.06)C2/TiAl and Ti3(Si0.91Al0.09)C2/TiAl joints changed from γ + α2/TiAl3 + Ti5Si3 + Ti5Si4/Ti3SiC2 to γ + α2/TiAl2/TiAl3 + Ti5Si3 + Ti5Si4/Ti3SiC2, to γ + α2/γ/TiAl2/TiAl3 + Ti5Si3 + Ti5Si4/Ti3SiC2, and to γ + α2/γ/TiAl2/TiAl3 + Ti5Si3 + Ti5Si4/Ti5Si3/Ti3SiC2 as the bonding temperature and duration increased. The growth of the interfacial compound layer in the Ti3(Si0.94Al0.06)C2/TiAl and Ti3(Si0.91Al0.09)C2/TiAl joints followed the cubic law and was controlled by grainboundary diffusion. The Al was the mainly diffusion elements in the Al-doped joints, and its diffusion in the Ti3(Si,Al)C2 substrate and in the interfacial layer was both along the grainboundaries. The bonding activation energies for the Al-doped joints were about 180 kJ/mol, which were much lower than the value (225 kJ/mol) for the undoped Ti3SiC2/TiAl joint. The highest shear strength of the Al-doped joints was about 65 MPa and was about 23% higher than the value of the undoped joint.

Intermetallic Compound Layer Growth at the Interface between Sn-Ag and ENImAg Surface Finish

Intermetallic Compound Layer Growth at the Interface between Sn-Ag and ENImAg Surface Finish

Experimental and Theoretical Studies of Cu-Sn Intermetallic Phase Growth During High-Temperature Storage of Eutectic SnAg Interconnects

In this paper, the growth of intermetallic compound (IMC) layers is considered. After soldering, an IMC layer appears and establishes a mechanical contact between eutectic tin-silver solder bumps and Cu interconnects in microelectronic components. Intermetallics are relatively brittle in comparison with copper and tin. In addition, IMC formation is typically based on multi-component diffusion, which may include vacancy migration leading to Kirkendall voiding. Consequently, the rate of IMC growth has a strong implication on solder joint reliability. Experiments show that the intermetallic layers grow considerably when the structure is exposed to heat. Mechanical stresses may also affect intermetallic growth behavior. These stresses arise not only from external loadings but also from thermal mismatch of the materials constituting the joint, and from the mismatch produced by the change in shape and volume due to the chemical reactions of IMC formation. This explains why in this paper special attention is being paid to the influence of stresses on the kinetics of the IMC growth. We develop an approach that couples mechanics with the chemical reactions leading to the formation of IMC, based on the thermodynamically sound concept of the chemical affinity tensor, which was recently used in general statements and solutions of mechanochemistry problems. We start with a report of experimental findings regarding the IMC growth at the interface between copper pads and tin based solder alloys in different microchips during a high temperature storage test. Then we analyze the growth kinetics by means of a continuum model. By combining experiment, theory, and a comparison of experimental data and theoretical predictions we finally find the values of the diffusion coefficient and an estimate for the chemical reaction constant. A comparison with literature data is also performed.

On the kinetics of nitride and diffusion layer growth in niobium plasma nitriding

This work reports results of a study on niobium plasma nitriding kinetics, conducted at relatively low temperatures, regarding the N-Nb system (1523 K) eutectoid temperature, and short times (on the 1253–1453 K and 1–4 h ranges). Results confirm that the niobium plasma nitriding is diffusion-controlled. The obtained nitride (compound) layer is multiphase, mainly constituted of ε-NbN, γ-Nb4N3 and β-Nb2N nitrides. The estimated compound and diffusion layer growth activation energy was 97.11 and 120.11 kJ mol−1, respectively. Considering the hardness distribution all over the nitrided layer, the transition between the compound and diffusion layers is very sharp. As example, it can vary from 18.5 GPa (⁓1850 HV) at the surface compound layer to decreasing values from ⁓480 to 100 HV, along the diffusion layer, depending on the studied condition. All results obtained from the Sa and Sz roughness characterization indicated increasing measured values for longer treatment times and higher temperatures, for atom clusters islands-like surface morphology. Finally, apparently crack-free compound layers were yielded, highlighting the importance of the use of relatively low treatment temperatures, below the N-Nb system (1523 K) eutectoid temperature, and relatively short treatment times for the plasma nitriding treatment studied here.

Morphological Effect on the Intermetallic Compound Layer Growth Kinetics of Metallurgical Joining

Evaluating the growth kinetics is one of the most important characteristic in assessing the quality and reliability of metallurgical joining, especially in electronics packaging such as soldering and wire bonding technology. The growth kinetics is normally assessed using Arrhenius equation that involves diffusion activities due to thermally activated process. The well-known factors of thermal and time together with generally accepted growth exponent have been widely used for this assessment. The intermetallic compound layer which is the by-product of metallurgical reaction during soldering process has been exposed to high temperature to accelerate its growth. The cross-section of the joining was observed using optical microscope to quantify the layer of intermetallic compound. Morphological effect and shape factor of the layer have been analysed in complement with the effect of temperature and time on the growth behaviour. Directional growth and irregularities shape of the intermetallic layer show some inconsistency on the selection of growth exponent. The effect of initial size of intermetallic layer must also be considered in this assessment. This study suggests that the morphological effect must be analysed prior to the selection the growth exponent in assessing growth behaviour and kinetics of intermetallic layer in metallurgical joining.

Effect of (Ni, Au)3Sn4 growth on the thermal resistance of Au-20 wt% Sn solder/ENIG joint in flip-chip LED packages

In this study, the effect of growth of intermetallic compound (IMC) layer between Au-20 wt% Sn solder and electroless Ni/immersion Au (ENIG) on the thermal resistance of a flip-chip (FC) light emitting diode (LED) package was investigated. Two IMC layers were formed at the interface of FC LED package, including Au5Sn and (Ni, Au)3Sn4 that were identified using a transmission electron microscopy. A thermal aging test was carried out at 200 °C for 1000 h to observe IMCs growth. After 1000 h, the (Ni, Au)3Sn4 thickness increased to about 1.5 μm and the thermal resistance of the FC LED package increased by 3.5 times compared to the initial thermal resistance of 2 K W−1. As the (Ni, Au)3Sn4 grew, a calculation of thermal resistance also increased comparing to the initial aging test, thus, the growth of (Ni, Au)3Sn4 layer can be effective factor on the increase of thermal resistances of FC LED package.

Effects of Carbon Concentration Change on Growth of Compound Layer in Surface of Nitrided Steel

Effects of Carbon Concentration Change on Growth of Compound Layer in Surface of Nitrided Steel