Thickness Of Interfacial Intermetallic Compound Layer Research Articles

Microstructural and shear strength properties of GNSs-reinforced Sn-1.0Ag-0.5Cu (SAC105) composite solder interconnects on plain Cu and ENIAg surface finish

In this study, the combined effect of GNSs (graphene nanosheets) and ENIAg (Electroless Nickel Immersion Silver) surface finish on the formation of intermetallic compounds (IMCs) and shear strength of the Sn-1.0Ag-0.5Cu (SAC105) solder system was studied. Both plain and composite solder systems (SAC105-xGNS; x = 0, 0.01, 0.05 and 0.1 wt%) were successfully prepared using the powder metallurgy technique and thereafter soldered on the plain Cu and ENIAg surface finish substrates. From the microstructural analysis, the Cu6Sn5 IMC was observed at the solder/substrate interface of the SAC105-xGNS/Cu solder joints. Moreover, the Ni3Sn4 and (Cu,Ni)6Sn5 IMC phases were observed at the solder/substrate interface of the SAC105-xGNS/ENIAg counterparts. The GNSs and ENIAg surface finish provided huge barrier for Sn and Cu atoms diffusion required for IMC formation. The interfacial IMC layer thickness decreased with increasing addition of GNSs for both sample grades. The SAC105-xGNS/ENIAg demonstrated lower IMC thicknesses that ranged between 2.98 and 2.53 μm relative to the 5.23–3.35 μm exhibited by the SAC105-xGNS/Cu. In general, the strengthening potential of the GNSs was well marked in both sample grades, with the SAC105-0.01GNS/Cu and SAC105-0.01GNS/ENIAg demonstrating the highest shear strengths of 11.2 MPa and 12.1 MPa, respectively.

Effect of heat input on interfacial microstructure, tensile and bending properties of dissimilar Al/steel lap joints by laser Welding-brazing

Laser welding-brazing technique was used for lap joining of Q235 steel to AA5052 aluminum alloy using a flux-cored Zn-22Al filler wire. The influence of heat input on microstructure, joint strength and bending property of laser Al/steel joints was investigated. The results showed that the types of interfacial intermetallic compounds (IMCs) were kept unchanged with the different laser powers, i.e., Fe2Al5-xZnx phase and FeZn10; while the thickness and morphology of IMC layer changed significantly. This was mainly ascribed to the large increase of the interfacial temperature with the rising laser power, which led to an intensified diffusion reaction. The fracture load first increased and then reached a plateau with the increasing laser power. However, the laser power had very limited influence on the joint bending property because of the formation of dispersed tough FeZn10. Numerical simulation indicated that the interfacial temperature along the interfacial region varied, decreasing from the weld root to weld toe. The peak temperature increased by 700 ℃ and liquid–solid reaction time increased 3.41 s with the increased laser power, which was responsible for the change of IMCs layer.

Effect of bonding time on the microstructure and shear property of Cu/SAC-15Ag/Cu 3D package solder joint fabricated by TLP

In this paper, Cu/SAC-15Ag/Cu 3D package solder joints were prepared by transient liquid phase (TLP) bonding technology. The effects of bonding time on the microstructure and shear property of solder joints were investigated. The results indicated that the microstructure of solder joints is coarsened with increasing bonding time. The intermetallic compounds (IMCs) in the interfacial reaction zone consist of Cu3Sn and Cu6Sn5 phase, and the IMCs in the in situ reaction zone include Ag3Sn phase, Sn-rich phase, and Ag particles. The thickness of interfacial IMCs layer initially decreases due to the volume contraction caused by the transformation from Cu6Sn5 to Cu3Sn, and then increases as a result of the coarsen of Cu3Sn. The minimum porosity of the solder joints reaches 0.24% under bonding time of 30 min. The shear strength of solder joints increases first and then declines with the extension of bonding time, and the maximum shear strength of 45.3 MPa is obtained by bonding for 30 min. The shear fracture mechanism of solder joints changes from ductile fracture to ductile–brittle mixed fracture, and then changes to brittle fracture. Cracks nucleate at the voids and propagate quickly with prolonging bonding time, and the cracks could be restrained by the voids.

Microstructures and mechanical property of 5052 aluminum alloy/Q235 steel butt joint achieved by laser beam joining with Sn-Zn filler wire

Butt joining of 5052 aluminum alloy and Q235 low carbon steel was achieved using laser beam welding with Sn-30Zn filler wire. The weld formation, microstructures, and mechanical property were investigated with varied laser power. The results show that joining of 5052 Al/Q235 steel dissimilar metals in a butt configuration by laser beam welding with Sn-30Zn filler wire is feasible. The solid solution interface formed at the aluminum side and the reaction layer formed at the steel side. With increasing laser power, the joining mode transformed from brazing to welding-brazing due to the melt of aluminum alloy. The thickness of the interfacial intermetallic compounds (IMCs) layer was also increased with laser power. However, when the laser power was 1200 W, the thickness of the interfacial IMCs layer sharply decreased due to the detachment of the IMCs layer. The fracture of the joint occurred at the steel interface and partially through the weld seam on the top surface. The fracture surface was characterized by both brittle and ductile fracture. When the joints were obtained at the laser power of 800 W and 1200 W, the tensile strength reached 79 MPa and 78 MPa, respectively. Furthermore, the formation mechanism of microstructures and its influence on mechanical property was discussed.

Effects of Ni Nanoparticles on the Growth Rate of Intermetallic Compounds (IMCs) Between Sn-3.0Ag-0.5Cu (SAC305) Solder and Cu-2.0Be Substrate

The effect of Ni nanoparticles on the microstructure evolution of a Sn-3.0Ag-0.5Cu (SAC305)-xNi (x = 0, 0.1)/Cu-2.0Be solder joint during reflow and aging was investigated. The results showed that the doped Ni nanoparticles changed the intermetallic compound (IMC) morphology from a scallop-like structure into a planar-like structure. The interfacial IMC layer thickness of the SAC305/Cu-2.0Be solder joint was greater than that of the SAC305-0.1Ni/Cu-2.0Be solder joint after reflow and aging. During reflow, the average IMC growth rate of the SAC305/Cu-2.0Be solder joint was 1.62 × 10−2 μm/s, while the average IMC growth rate of the SAC305-0.1Ni/Cu-2.0Be solder joint was 1.56 × 10−2 μm/s. During aging, the growth rates of the interfacial IMC layer of the SAC305/Cu-2.0Be solder joint and SAC305-0.1Ni/Cu-2.0Be solder joint were 1.86 × 10−5 μm/s and 1.46 × 10−5 μm/s, respectively. The results show that a trace amount of Ni nanoparticles can impede the growth rate of the interfacial IMC layer.

Kinetics of Ultrasonic and Current Coupling-Enhanced Dissolution of Copper in Liquid Tin

With the development trend of high speed, light weight, continual miniaturization, and multifunctionality of microelectronic products, the size of solder joints continues to shrink. Therefore, higher requirements are being placed on soldering techniques. This study used the immersion method to investigate the dissolution kinetics of copper in liquid tin at temperatures in the range of 240–300°C with ultrasonic and current coupling. The amount of dissolution and the thickness of the interfacial intermetallic compound (IMC) layer were measured and the dissolution activation energy was calculated. Results showed that the composite fields of ultrasonic and current coupling accelerated copper dissolution in liquid tin and decreased the dissolution activation energy. The dissolution rate was 5–7 times higher compared to that without ultrasound and current, and was 2–3 times higher compared to that using only current. At a certain temperature, with the increase in immersion time, the thickness of the interface IMC layer demonstrated parabolic growth. The sound pressure caused by the ultrasound and the temperature gradient caused by current in the liquid tin were simulated by finite element modeling. The results show that the sound pressure distribution in liquid tin was uneven, and the temperature gradient inside the liquid tin increased with current.

Microstructural evolution and micromechanical properties of SAC305/CNT/CU solder joint under blast wave condition

Purpose The purpose of this paper is to investigate the effect of carbon nanotube (CNT) addition on microstructure, interfacial intermetallic compound (IMC) layer and micromechanical properties of Sn-3.0Ag-0.5Cu (SAC305)/CNT/Cu solder joint under blast wave condition. This work is an extension from the previous study of microstructural evolution and hardness properties of Sn-Ag-Cu (SAC) solder under blast wave condition. Design/methodology/approach SAC/CNT solder pastes were manufactured by mixing of SAC solder powder, fluxes and CNT with 0.02 and 0.04 by weight percentage (Wt.%) separately. This solder paste then printed on the printed circuit board (PCB) with the copper surface finish. Printed samples underwent reflow soldering to form the solder joint. Soldered samples then exposed to the open field air blast test with different weight charges of explosives. Microstructure, interfacial IMC layer and micromechanical behavior of SAC/CNT solder joints after blast test were observed and analyzed via optical microscope, field emission scanning microscope and nanoindentation. Findings Exposure to the blast wave induced the microstructure instability of SAC305/Cu and SAC/CNT/Cu solder joint. Interfacial IMC layer thickness and hardness properties increases with increase in explosive weight. The existence of CNT in the SAC305 solder system is increasing the resistance of solder joint to the blast wave. Originality/value Response of micromechanical properties of SAC305/CNT/Cu solder joint has been identified and provided a fundamental understanding of reliability solder joint, especially in extreme conditions such as for military applications.

Effect of doping Ni nanoparticles on microstructure evolution and shear behavior of Sn–3.0Ag–0.5Cu(SAC305)/Cu–2.0Be solder joints during reflowing

The Cu–2.0Be alloy is widely used as the substrate in aircraft electronic device, which has a potential trend to replace the pure Cu substrate. However, few studies have investigated the influence of the doped Ni nanoparticles on interfacial reaction between Cu–2.0Be substrate and the SAC305 solder during reflowing. In this study, the effect of Ni nanoparticles on wettability, microstructure evolution and mechanical behavior of SAC305/Cu–2.0Be solder joint was investigated. The results showed that a certain amount of Ni nanoparticles could increase the spreading area and mechanical property of the SAC305/Cu–2.0Be solder joint. The interfacial intermetallic compound (IMC) layer thickness could be reduced significantly by adding Ni nanoparticles. Moreover, the interfacial IMC layer thickness of SAC305/Cu–2.0Be solder joint was obviously thicker than that of SAC305-0.1Ni/Cu–2.0Be solder joint after different soldering times, which meant that a certain amount of Ni nanoparticles could hinder the IMC growth during soldering process. The growth kinetic of interfacial IMC layer after adding 0.1 wt% Ni nanoparticles showed that the growth coefficient of interfacial IMC layer changed from 1.21 µm/s0.28 to 1.82 µm/s0.32. In addition, the value of the shear strength of SAC305-0.1Ni/Cu–2.0Be solder joint was larger than that of SAC305/Cu–2.0Be solder joint with a typical mixture ductile and brittle fracture mode, which contributed to increasing the shear strength. Therefore, SAC305-0.1Ni solder alloy is a promising potential solder alloy in aircraft electronic device.

Effects of laser power on the interfacial intermetallic compounds and mechanical properties of dual-spot laser welded–brazed Ti/Al butt joint

A sound Ti/Al butt joint was successfully obtained by dual-spot laser welding–brazing with a Al-12Si wire as the filler. The influence of laser power on the weld appearance, microstructure of the interfacial intermetallic compounds (IMC), and tensile strength of joints was investigated. With an increase in laser power, the thickness of IMC layer also increased and the morphology of IMC layer changed from a cellular-shape to a serrated-shape, and finally to a club-shape. The microstructure of the interface IMC comprised a brazed zone in which Ti(Al, Si)3 was dominant and the microstructure at the Ti/Ti(Al, Si)3 interface was composed of nano-sized granular Ti5Si3, and Ti7Al5Si12. The highest tensile strength of the joints could reach up 75% of that of the Al base metal. The inhomogeneous IMC layer at the brazing interface caused a decrease in the tensile strength of joints and induced a deflection of fracture path during the tensile process.

Effect of laser-arc offset and laser-deviation angle on the control of a Ti-Al interlayer

Butt joining of an AA6061 aluminum alloy and a Ti-6Al-4V titanium alloy with a 3 mm thickness was carried out using laser-metal inert-gas hybrid welding-brazing without a bevel or an air gap. The uniformity of the interfacial intermetallic compound (IMC) layer was improved by changing the laser-arc offset and the laser-deviation angle. The weld appearance, IMC layer microstructure and tensile strength of the welded-brazed joints were investigated. A uniform serrated 1 μm thick TiAl3 layer was formed along the butt plane by using a laser-deviation angle. The tensile strength of the joint was closely related to the IMC layer morphology and thickness. Joints with excellent wetting and spreading on both sides achieved a maximum tensile strength of 230 MPa when the laser-arc offset was 1.2 mm and the laser-deviation angle was 5°. Three different fracture phenomena existed during the tensile test that correspond to different fracture positions at the interface layer, weld seam and heat-affected zone of the aluminum base metal.

Unique interfacial reaction and so-induced change in mechanical performance of Sn–3.0Ag–0.5Cu/Cu solder joints formed during undercooled and eutectic liquid soldering processes

A novel technique is proposed to prepare Sn–3.0Ag–0.5Cu/Cu joints at three different processing temperatures, which are called undercooled liquid (UL, 213.0 °C), eutectic liquid (EL, 217.0 °C) and normal liquid (NL, 231.0 °C) soldering temperatures correspondingly, and each of them is lower than, equal to and higher than Sn–3.0Ag–0.5Cu solder’s melting point (217.0 °C), respectively. The interfacial reaction, intermetallic compound growth and mechanical performance of Sn–3.0Ag–0.5Cu/Cu joints formed during UL, EL and NL soldering processes were investigated systematically. Results show that for Sn–3.0Ag–0.5Cu solder as the undercooled liquid melt or eutectic liquid melt or normal liquid melt in the formation of joints, the thickness of interfacial intermetallic compound (IMC) layer in the joints increases with prolonging dwelling time. For three different liquid soldering processes, the change tendency of the interfacial IMC layer thickness is distinct. For joints formed at UL and EL temperatures, the excessive growth of primary Cu6Sn5 and interfacial IMC (mainly Cu6Sn5) can be suppressed during isothermally dwelling in the liquid state for more than 5 min. Ball shear test results show that solder joints formed at UL and EL temperatures have lower value of the maximum shear force (MSF) than those formed during the NL soldering process. For UL and EL types of joints, the fracture occurs either by shear slide fracture totally along the shear tool tip movement plane (i.e., in-plane shear slide fracture) or by shear slide fracture initially along the shear tool tip movement plane and afterwards shear deformation fracture in the solder matrix under the plane (i.e., out-of-plane shear slide and deformation mixed-mode fracture), while the fracture takes place in NL joints only by in-plane shear slide fracture mode.

Effect of Revolutionary Pitch on Interface Microstructure and Mechanical Behavior of Friction Stir Lap Welds of AA6082-T6 to Galvanized DP800

Friction stir lap welding of 1.5-mm thick 6082-T6 aluminum alloy to 2-mm thick galvanized DP800 steel (Zn-coated) was carried out. Optimal welding conditions were obtained aiming to defect-free joints with good mechanical properties. The interfacial intermetallic compounds (IMCs) at the stir zone and hook zone were characterized under different revolutionary pitches. With a revolutionary pitch of 1.0 mm/rev, maximum joint strength reached 71% of that of the aluminum alloy. In the meantime, the average thickness of IMC layer is less than 1 μm; Al3.2Fe in the Al-rich side and Al5Fe2 in the Fe-rich side at the interfaces of stir zone while Al6Fe and nanocrystalline close to Al3.2Fe at the interface of the hook zone. At a relatively lower revolutionary pitch (0.5 mm/rev), Zn was found with the aggregation of Si and Mn at the hook-zone interface, leading to the generation of Al-Fe-Si phase thus decreasing the thickness of the IMC layer. In the stir zone, the revolutionary pitch has a significant influence on the interfacial microstructures. The interfacial IMC layer at 1.0 mm/rev is simple and flat, but the one at 0.5 mm/rev becomes thicker and more complex. Stir zone aluminum under different revolutionary pitches is similar in microhardness and tensile behavior. The mechanical response of joints was modeled based on linear mixture law with an iso-strain assumption and neglection of the IMC layer. The modeling results are in good agreement with the experimental ones indicating the resultant interfaces act as good as the good boundaries between dissimilar Al/steel joints.

Microstructure, interfacial IMC layer and mechanical properties of Cu/Sn-9Zn-xZrC/Cu solder joints

The effect of trace ZrC on the wettability, microstructure and mechanical properties of Sn-9Zn composite solder alloy joints was investigated. The results indicated that the wettability of the Sn-9Zn based composite solder alloy was improved and the microstructure was refined by adding appropriate amount nanoparticle ZrC. The microstructure of Sn-9Zn based composite solder alloys consists of primary Sn and Sn-Zn eutectic, and the excellent wettability and refined microstructure can be obtained by adding about 0.06 wt% ZrC. The interfacial intermetallic compounds (IMC) layer in the Sn-9Zn based composite solder alloy joints consists of Cu5Zn8 and Cu6Sn5. IMC layer thickness of Sn-9Zn based composited solder alloys joints is increased with increasing ZrC content. The tensile strength and the shear strength of Sn-9Zn based composite solder alloys joints relate to the ZrC content, and the maximum mechanical properties of solder joints are obtained by adding about 0.06 wt% ZrC, and the fracture mechanism of the Cu/Sn-9Zn-(0-0.09) ZrC/Cu solder joints is ductile fracture.

Interfacial microstructure evolution and shear strength of Sn0.7Cu–xNi/Cu solder joints

The microstructure and growth behaviors of interfacial intermetallic compounds (IMCs) between the Sn–0.7Cu–xNi (x = 0, 0.1, 0.25, 0.5, and 1.0 mass%) solder alloys and copper pad were explored to reveal the influence of the Ni addition into the Sn–0.7Cu based solder on the formation of interfacial IMCs and shear strength of the solder joints in the present study. The impacts of adding different Ni on the growth behavior and total thickness of Cu6Sn5/(Cu, Ni)6Sn5 and Cu3Sn IMCs layers were compared and discussed after reflowing at 533 K for 600 s and aging at 423 K for various aging durations. The thickness of interfacial IMC layers increased drastically with addition of small amount of Ni into the Sn0.7Cu solder alloy, however, the particle sizes of the IMC grains obviously decreased with the addition of Ni into the solder, compared to the Sn0.7Cu/Cu system. The results indicated that, Cu6Sn5 turned into (Cu, Ni)6Sn5 due to the addition of Ni element and would enhance the growth rate of interfacial IMC resulted from more Ni added. It is quite obvious that 1 wt% Ni addition to the Sn–0.7Cu solder alloy extremely enhance growth and formation of the IMC in Sn–0.7Cu–xNi/Cu joints. In addition, the single-lap shear tests were also carried out to evaluate the mechanical properties of the as-reflowed Sn0.7Cu–xNi/Cu solder joints. The results of shear tests indicated that the shear stress of Sn–0.7Cu–xNi/Cu solder joints gradually increased with the increase of Ni concentration, and the maximum shear strength was reached with 1 wt% Ni addition. Besides, doping Ni element into the Sn–0.7Cu solder changed the shear fractures morphology of Sn–0.7Cu/Cu joints, which were revealed to be ductile essentially with the moderate strain rate (3.33 × 10−3 s−1) and mainly occurred in the solder matrix rather than through the IMCs layer.

Effect of Mn Nanoparticles on Interfacial Intermetallic Compound Growth in Low-Ag Sn-0.3Ag-0.7Cu-xMn Solder Joints

Interfacial intermetallic compound (IMC) growth between Cu substrates and low-Ag Sn-0.3Ag-0.7Cu-xMn (x = 0 wt.%, 0.02 wt.%, 0.05 wt.%, 0.1 wt.%, and 0.15 wt.%) (SAC0307-xMn) solders was investigated under different isothermal aging temperatures of 100°C, 150°C, and 190°C. Scanning electron microscopy (SEM) was employed to observe the microstructural evolution of the solder joints and measure the IMC layer thickness. The IMC phases were identified by energy-dispersive x-ray spectroscopy and x-ray diffraction. The results showed that a Cu6Sn5 IMC layer formed in the as-soldered solder joints, while a duplex structure consisting of a Cu6Sn5 IMC layer near the solder matrix and a Cu3Sn IMC layer was observed after isothermal aging. A considerable drop in the IMC layer thickness was observed when 0.1 wt.% Mn nanoparticles were added. Beyond this amount, the thickness of the IMC layer only slightly increases. Adding Mn nanoparticles can increase the activation energy and thus reduce the interdiffusion rates of the Sn and Cu atoms, which suppresses excessive IMC growth. The solder joint containing 0.1 wt.% Mn nanoparticles has the highest activation energy. SEM images revealed that the number of small particles precipitated in the channels between the Cu6Sn5 IMC layers increases with an increasing proportion of Mn nanoparticles. Based on the microstructural evolution of the solder joints, this study revealed that grain boundary pinning is one of the most important mechanisms for IMC growth inhibition when Mn nanoparticles are added.

Effects of Metallic Nanoparticles on Interfacial Intermetallic Compounds in Tin-Based Solders for Microelectronic Packaging

Tin (Sn)-based solders have established themselves as the main alternative to the traditional lead (Pb)-based solders in many applications. However, the reliability of the Sn-based solders continues to be a concern. In order to make Sn-based solders microstructurally more stable and hence more reliable, researchers are showing great interest in investigating the effects of the incorporation of different nanoparticles into them. This paper gives an overview of the influence of metallic nanoparticles on the characteristics of interfacial intermetallic compounds (IMCs) in Sn-based solder joints on copper substrates during reflow and thermal aging. Nanocomposite solders were prepared by mechanically blending nanoparticles of nickel (Ni), cobalt (Co), zinc (Zn), molybdenum (Mo), manganese (Mn) and titanium (Ti) with Sn-3.8Ag-0.7Cu and Sn-3.5Ag solder pastes. The composite solders were then reflowed and their wetting characteristics and interfacial microstructural evolution were investigated. Through the paste mixing route, Ni, Co, Zn and Mo nanoparticles alter the morphology and thickness of the IMCs in beneficial ways for the performance of solder joints. The thickness of Cu3Sn IMC is decreased with the addition of Ni, Co and Zn nanoparticles. The thickness of total IMC layer is decreased with the addition of Zn and Mo nanoparticles in the solder. The metallic nanoparticles can be divided into two groups. Ni, Co, and Zn nanoparticles undergo reactive dissolution during solder reflow, causing in situ alloying and therefore offering an alternative route of alloy additions to solders. Mo nanoparticles remain intact during reflow and impart their influence as discrete particles. Mechanisms of interactions between different types of metallic nanoparticles and solder are discussed.

Polarized evolution of interfacial intermetallic compounds (IMCs) in interconnects under electromigration (EM)

In situ observation of electromigration (EM) has been carried out on cross-sectioned copper/tin–copper/copper (Cu/Sn0.7Cu/Cu) line-type interconnects. The surface vertical variation after EM is measured by step profiler, which indicates serious mass migration during EM. The EM rate is calculated using two distinct methods, in situ mark movement and the growth of anode intermetallic compounds (IMCs). Defects and IMCs grains in the bulk solder are used as marks to measure the atomic flux. It is calculated that the atomic flux under a current density of 4.77 × 103 A cm−2 and a temperature of 60 °C is 5.241 × 1012 cm−2 s−1. Calculation based on the growth of the anode IMCs layer thickness determines the atomic flux as 4.114 × 1012 cm−2 s−1. The top morphology of IMCs layers is studied by etching away the bulk solder. It is found that the initial scalloped IMCs in the as-reflowed interconnect evolves towards different directions as a serrated IMCs layer with deep grooves forms at the cathode side, while a thick planar IMCs layer forms at the anode side. This phenomenon is defined as polarized evolution. The mechanisms for the polarized evolution rely on the fast diffusion of Cu atoms along the IMCs grain boundaries. The planar IMCs at the anode is due to the stacking of Cu atoms, which fills the grooves by reacting with Sn to form Cu6Sn5 IMCs. This polarized evolution threatens the reliability of interconnects since a thick planar IMCs layer tends to be brittle, while a thin serrated IMCs may suffer from accumulated voids.

Microstructure and mechanical properties of Co/Sn-10Bi couple and Co/Sn-10Bi/Co joint

The growth behavior of interfacial intermetallic compounds (IMCs) layer of Co/Sn-10Bi and Co/Sn-10Bi/Co couple has been studied by scanning electron microscope. The critical temperature and shear strength of Co/Sn-10Bi/Co joints were tested by universal testing machine. The results showed that the thickness of CoSn3 IMCs layer increased as the increase of aging time and temperature. The growth rate of CoSn3 IMCs layer of Co/Sn-10Bi/Co couple was suppressed and was lower than that of Co/Sn-10Bi couple as the decline in Sn concentration of residual Sn-Bi layer. The critical temperature of Co/Sn-10Bi/Co joint that could hold a load of 1N changed as the chemical composition of residual Sn-Bi layer changed. The shear strength of Co/Sn-10Bi/Co joints bonded at 240°C for 20min, 30min, 40min, and 50min was between 58MPa and 82MPa. The shear strength of Co/Sn-10Bi/Co joint bonded at 240°C for 60min was only about 17MPa. The damage in shear strength of Co/Sn-10Bi/Co joint bonded for 60min was led by the crack in residual Bi layer.

The Intermetallic Compound Formation for the Wire Bond Between an Al Pad and Ag-xPd Alloy Wire

Silver-palladium alloy wire has been shown as an economical and reliable substitute for gold wire in various applications in the electronic packaging industry. The success of wire bonding relies on the formation of an interfacial intermetallic compound (IMC). This study is aimed to investigate the formation behavior of IMCs between an Al pad and Ag-Pd alloy wire with various Pd concentrations of 1.0–6.0% for the as-bonded commercial Ag/Al joint. The interfacial IMCs were investigated with scanning electron microscopy and energy-dispersive x-ray spectroscopy. The IMCs formed are separate (Ag, Pd)2Al and (Ag, Pd)3Al2 for a Ag6Pd wire bond, while (Ag, Pd)2Al and (Ag, Pd)3Al2 are mixed for the other Ag(1–4.5)Pd alloy wire bonds. The thickness of the total IMC layer varies from 0.65 μm for Ag1Pd to 0.91 μm for Ag6Pd, yet a minimum of 0.44 μm exists for Ag3.5Pd. The compound formation behavior was found to correspond with the Ag–Al phase diagram. After pressure cooker tests, a less stable IMC (Ag, Pd)3Al formed at the AgxPd/Al interface.

Effect of P and Ge doping on microstructure of Sn-0.3Ag-0.7Cu/Ni-P solder joints

Purpose The purpose of this paper is to comparatively investigate the microstructure and interfacial intermetallic compound (IMC) layer of Cu/SACPG/Ni and Cu/SAC0307/Ni solder joints after thermal aging. Design/methodology/approach The specimens were thermally aged at 150°C for 0, 24, 168 and 500 h. The microstructure and morphology of the interface IMC layer were observed by means of scanning electron microscope. The IMCs and the solder bump surface were analyzed by EDS. Moreover, the thickness of IMC layer was measured by using the image analysis software. Findings The morphology of IMC of Cu/SAC0307/Ni solder joint was consistent with that of the Cu/SACPG/Ni joint, which indicates that the addition of P and Ge had little effect on the IMC formation. The needle-like (Cu,Ni)6Sn5 was formed at the interface of solder/Ni solder joints. Meanwhile, the tiny particles inferred as Ag3Sn phase attached to the surface of (Cu,Ni)6Sn5. The growth rate of IMC layer of the Cu/SACPG/Ni joint was smaller than that of Cu/SAC0307/Ni joint with aging time increasing, which means the addition of trace P and Ge can slightly suppress the diffusion rate of the interfacial IMC. Originality/value There are no previous studies on the formation mechanism of the IMC layer of SAC0307 solder alloys with P and Ge addition.