IMC Formation Research Articles

STUDY OF Co/Sn MULTILAYER SYSTEM WITH VARIOUS TIN LAYER THICKNESS AND REFLOW TEMPERATURES

Co–Sn–Co multi-layer films with various Sn-layer thicknesses have been deposited by using the electrodeposition technique. The deposition was performed at room temperature on gold coated silicon substrates. The thickness of Sn layer was kept [Formula: see text]4.5, 2.5, 1.5 and 1[Formula: see text][Formula: see text]m, while the thickness of each Co layer was fixed to [Formula: see text]0.75[Formula: see text][Formula: see text]m. The Sn layer was sandwiched between two Co layers. The total thickness of the films was [Formula: see text]6, 4, 3, 2.5[Formula: see text][Formula: see text]m, respectively. The intended ratio of Sn was about 25 at.% while Co was about 75 at.%. The separation inside the Sn-layer has been observed at higher Sn-layer thicknesses with increasing reflow temperature. It may be due to the combined effect of thermal stress arising during cooling from elevated reflow temperatures and solidification shrinkage in the thick Sn layer due to the formation of IMC CoSn2. However, 1[Formula: see text][Formula: see text]m has been found to be a critical thickness, which remains intact when sandwiched between two cobalt layers. The structure of these multi-layer films was studied as a function of temperature. It has been observed from X-ray diffraction (XRD) that the as-deposited films exhibit strong peaks belonging to elemental Co and Sn. At temperatures of 270–290∘C, CoSn2 begins to appear and grow at the interfaces and in the middle of Sn layer with the decrease in elemental Sn. However, sufficient amount of Co is still present in pure form as is evident by the XRD and field emission scanning electron microscopy images at all temperatures. This study confirms that only one reaction product, viz. CoSn2, formed in as-deposited during reflow at temperatures 270–290∘C for a fixed time of 10[Formula: see text]min, although several other stable IMCs, e.g. Co3Sn2, CoSn, CoSn2, CoSn3 exist in the Co–Sn system at 250∘C according to phase diagram. It is not uncommon that all the thermodynamically stable IMCs do not form in the system due to kinetic reasons. Accordingly, the formation of IMCs through interfacial reaction has been discussed in this paper.

Effect of Cooling Rate on Intermetallic Compounds Formation in Sn-Ag-Cu-In Solder

The effect of the cooling rate in bonding on IMCs formation and their morphology in the solder joint with Sn-3.0Ag-0.7Cu-5.0In (mass%) lead-free solder was investigated. As the substrate, the Cu plate and the Cu plate with electroplated Ni were prepared. Bonding was conducted in the vacuum atmosphere, and bonding temperature and time were 300°C and 10 minutes, respectively. The cooling rates in the bonding were changed from 0.02°C/s to 0.2°C/s. In both Cu/Cu and Cu/Ni joints, scallop-shaped IMCs form at the joint interfaces regardless of the cooling rate. In the Cu/Cu joint, Cu6(Sn,In)5 and Cu3(Sn,In) layers form at the joint interface. In the Cu/Ni joint, (Cu,Ni)6(Sn,In)5 and (Cu,Ni)3(Sn,In) layers form at the joint interface with Cu and the (Cu,Ni)6(Sn,In)5 layer forms at the joint interface with Ni. Die shear force of the Cu/Ni joints are a little larger than those of the Cu/Cu joints. Fracture occurs in the boundary between the scallop-shaped layer or the granular IMC layer and the layered IMC in both joints. The cooling rate from the peak temperature to solidification is an important factor to decide the shape of formed IMC. When the cooling rate is high and supercooling becomes large, formation of pillar-shaped IMCs occurs easily.

Dissimilar joining of TC4 alloy to ST16 steel by GTAW

The feasibility of direct fusion welding of TC4 alloy to ST16 steel by GTAW using CuSi3 filler wire was investigated. Defect-free fusion welded joints were obtained. Various intermetallic compounds, such as Ti2Cu, TiCu, AlCu2Ti, TiCu2 and Ti5Si3 phases, orderly formed in Ti/weld transition zone. Ti and Si diffused into ST16 steel, and an interface formed between copper weld and ST16 steel substrate. The resultant joints fractured at the ST16 steel substrate, and the tensile strength reached 282 MPa. The formation of various TixCuy IMCs and the solution strengthening induced by diffusion of Ti and Si led to the increase of microhardness in Ti/weld transition zone and copper/steel interface, respectively.

Influence of Rotation Speed on Microstructure and Mechanical Properties of Friction Stir Lap Welded Joints of AA 6061 and Ti6Al4V Alloys

Three-mm-thick AA 6061 plate and 2-mm-thick Ti6Al4V plate were friction stir lap welded using a W-Re pin tool. Defect-free joints were obtained at various rotation speeds ranging from 800 to 1400 rpm with a constant welding speed of 100 mm/min. The influence of rotation speed on the microstructure and mechanical properties of the Al/Ti friction stir lap welding (FSLW) joints was investigated. At low rotation speed within 1000 rpm, the obtained joint has no obvious mechanical Al/Ti intermixing at the interface. However, a significant mechanical mixture of Al and Ti alloys accompanied by hooks could be found in the joint welded at a rotation speed over 1000 rpm. Only diffusion layer was observed in the joint obtained at low rotation speed. Further, IMCs could be found in the Al/Ti mixture and hook when the rotation speed increased to 1400 rpm. The highest microhardness was measured at the interface due to the formation of IMCs. The tensile shear load of the welded joints reached the maximum at 1000 rpm and the specimens failed along the interface during the test.

Controlling the intermetallics growth in the SiO2-BN/Invar brazed joint by vertical few-layer graphene

For active brazing, excessive formation of brittle intermetallics in the brazed seam is always a big issue, which has an adverse effect on the joint property. Herein, an innovative vertical few-layer graphene (VFG) buffer layer was directly grown on the Invar surface prior to brazing. SiO2-BN ceramic and the Invar alloy with and without the VFG were first brazed using a Ag-Cu-Ti braze alloy. Interfacial microstructure and fracture morphologies of the brazed joints were then put into comparison. Results show that there is a 20% increase in shear strength after the VFG modification. To further discuss the effect of the interfacial microstructure variation on the joint property, Invar alloy was self-brazed. The fracture path and the tensile-shear strength of the Invar/Invar joints were discussed. Finally, the interaction between the VFG and Ti was characterized and the controlling mechanism of the intermetallic compounds formation by the VFG was proposed. This novel surface modification approach reported in this paper was promising particularly for the active brazing associated with the brittle IMCs formation issue.

Laser joining of Mo and Ta sheets with Ti6Al4V or Ni filler

Joining of Mo to Ta is important in manufacturing of high temperature microwave device. However, it is difficult to weld these two refractory metals directly because of their limited weldability. This study presents a laser joining method of Mo and Ta using Ti6Al4V or Ni as filler metal to prevent the mixture of two base metals in molten pool. The bulk of the Mo and Ta remained solid and joined by the liquid filler metal since the melting point of filler metal is considerably lower than that of base metals, resulting in two interfaces formed in each joint. The tensile strength of the Mo/Ni/Ta joint fractured from Ni/Ta interface is 19% lower than that of Mo/Ti6Al4V/Ta joint broken at base metal of Ta due to the formation of IMCs. These results offer a reference to filler metals selection for the joining of Mo to Ta, and highlight a possible method when dissimilar joining of two hard-to-weld metals especially refractory metals.

Development of Pb-Free Nanocomposite Solder Alloys

As an alternative to conventional Pb-containing solder material, Sn–Ag–Cu (SAC) based alloys are at the forefront despite limitations associated with relatively poor strength and coarsening of grains/intermetallic compounds (IMCs) during aging/reflow. Accordingly, this study examines the improvement of properties of SAC alloys by incorporating nanoparticles in it. Two different types of nanoparticles were added in monolithic SAC alloy: (1) Al2O3 or (2) Fe and their effect on microstructure and thermal properties were investigated. Addition of Fe nanoparticles leads to the formation of FeSn2 IMCs alongside Ag3Sn and Cu6Sn5 from monolithic SAC alloy. Addition of Al2O3 nano-particles do not contribute to phase formation, however, remains dispersed along primary β-Sn grain boundaries and act as a grain refiner. As the addition of either Fe or Al2O3 nano-particles do not make any significant effect on thermal behavior, these reinforced nanocomposites are foreseen to provide better mechanical characteristics with respect to conventional monolithic SAC solder alloys.

Electrochemical Behavior of Sn-9Zn-xTi Lead-Free Solders in Neutral 0.5M NaCl Solution

Electrochemical techniques were employed to study the electrochemical corrosion behavior of Sn-9Zn-xTi (x = 0, 0.05, 0.1, 0.2 wt.%) lead-free solders in neutral 0.5M NaCl solution, aiming to figure out the effect of Ti content on the corrosion properties of Sn-9Zn, providing information for the composition design of Sn-Zn-based lead-free solders from the perspective of corrosion. EIS results reveal that Ti addition was involved in the corrosion product layer and changed electrochemical interface behavior from charge transfer control process to diffusion control process. The trace amount of Ti addition (0.05 wt.%) can refine the microstructure and improve the corrosion resistance of Sn-9Zn solder, evidenced by much lower corrosion current density (icorr) and much higher total resistance (Rt). Excess Ti addition (over 0.1 wt.%) led to the formation of Ti-containing IMCs, which were confirmed as Sn3Ti2 and Sn5Ti6, deteriorating the corrosion resistance of Sn-9Zn-xTi solders. The main corrosion products were confirmed as Sn3O(OH)2Cl2 mixed with small amount of chlorine/oxide Sn compounds.

Refill friction stir spot welding of dissimilar aluminum alloy and AlSi coated steel

AA5754 Al alloy and coated steel were successfully joined by refill friction stir spot welding through the eutectic Al-Si coating. The overlap shear strength increased with plunge depth and reached a high strength plateau which was attributed to maximum bonding size and strong Al/AlSi coating joint interface. The AlSi coating in the as-received coated steel consisted of AlSi eutectic phase and two main intermetallic phases (Al7Fe2Si and Al5Fe2(Si)) with an average width of 8.5μm and around thickness of 1μm, respectively. The former played a key role in dissimilar welding, the latter effectively restrained the formation of additional IMCs and the growth of exiting IMCs during welding. Microstructural evolution showed the high strength of joints is also associated with fine silicon particles, elimination of defects and control of intermetallics at the joint interface. Fracture of full bonding welds initiated from the partial metallurgical bonds (PMBs) or kissing bonds, then propagated through the AlSi coating and AlSi/Al7Fe2Si interface, final fracture occurred at Al7Fe2Si/Al5Fe2(Si)/steel substrate interfaces.

Geometrical outline evolution and size-inhibiting interaction of interfacial solder bubbles and IMCs during multiple reflows

By utilizing synchrotron radiation X-ray imaging technique for in situ observation, the geometrical outline evolution and size-inhibiting interaction of solder bubbles and IMCs during multiple reflows were investigated in this work. It was found that the interfacial bubbles can inhibit the growth of IMC grains caused by the hindering effect of bubbles on contact and reaction between solder and substrate; meanwhile, following the growth of IMC grains, the bubble size in return got smaller and its aspect ratio became larger with reflow cycle, which is the result of inhibiting effect of solid IMC grains on solder voids; Because of boundary segregation and thermomigration, Cu atoms tend to gather on the bubble boundary and form a Cu-rich phase, consequently resulting in the formation of IMCs at the gas/solder interface area.

Effect of Ge addition on wettability, copper dissolution, microstructural and mechanical behavior of SnCu–Ge solder alloy

This paper explores the effects of Germanium (Ge) addition on the wetting behavior, copper dissolution, IMC formation, microstructure and mechanical behavior of SnCu alloy. Static copper dissolution was conducted as a function of contact time and in the temperature range of 260–300 °C. The results show that the Ge doped alloy has the lowest copper dissolution rate compared to SnCu, SAC305, and very much comparable with SnPb solder thus making it suitable alloy for the wave soldering process. Two solderability standards measurement (JIS vs. IPC) have been executed on different surface finishes such as OSP, ENIG, ImAg commonly used in industrial soldering process. The results showed that addition of Ge significantly improves the wetting/spread performance for all the surface finishes (ENIG, OSP and ImAg). Contact angles range from 17°–30°, the lowest contact angles being observed on ENIG surface. Microstructural analysis showed Ge addition refine the grain structure of SnCu–0.01Ge alloy. A thin IMC layer was observed, and IMC growth was not significant after multiple reflows as compared to Sn–Cu alloy. Similarly, Ge addition increases the hardness value due to uniform microstructure of SnCu–Ge alloy. The tensile testing results also showed an increase in tensile strength and tolerable ductility.

Characterization the microstructure of pulsed Nd:YAG welding method in low frequencies; correlation with tensile and fracture behavior in laser-welded nitinol joints

The precise controllability of heat input in pulsed Nd:YAG welding method provided by two additional parameters, frequency and pulse duration, has made this method very promising for welding of alloys sensitive to heat input. The poor weldability of Ti-rich nitinol as a result of the formation of Ti2Ni IMC has deprived us of the unique properties of this alloy. In this study, to intensify solidification rate during welding of Ti-rich nitinol, pulsed Nd:YAG laser beam in low frequency was employed in addition to the employment of a copper substrate. Specific microstructure produced in this condition was characterized and the effects of this microstructure on tensile and fracture behavior of samples welded by two different procedures, full penetration and double-sided method with halved penetration depth for each side were investigated. The investigations revealed although the combination of low frequencies, the use of a high thermal conductor substrate and double-sided method eliminated intergranular fracture and increased tensile strength, the particular microstructure, built in the pulsed welding method in low frequencies, results to the formation of the longitudinal cracks during the first stages of tensile test at weld centerline. This degrades tensile strength of welded samples compared to base metal. The results showed samples welded in double-sided method performed much better than samples welded in full penetration mode.

The Influence of Intermetallic Compounds, (IMC), on High Speed Shear Testing with a Specific Interest in Electroless Palladium / Autocatalytic Gold

Increasing IO counts have led to ever increasing solder performance expectations. A predominant measure of solder joint integrity is gained through HSS testing. This article will statistically evaluate the solderability of final finishes after substrate and IMC ageing. Lead free solder balls will be used in this exercise to simulate lead free production. The finishes selected are: Immersion tin, Organic Surface Protection (OSP), Electroless Nickel/ Immersion Gold (ENIG), Electroless Nickel /Electroless Palladium and Immersion Gold (ENEPIG) and Electroless Palladium / semi Autocatalytic Gold (EPAG). Where necessary, the adaptions of the final finishes will be included for testing. An example of this is ENEPIG with thin nickel. This is a measure to enable high frequency and or improve flexibility. For the purpose of the paper, the evaluation will endeavor to relate HSS performance and physical and chemical characteristics of the related deposit layer. To ensure that a comparative analysis is possible, an “as received” (ASR) population will be used as a base line. This fully data driven evaluation will aim to increase the understanding of key indicators that can ensure good quality soldering performance. In the field, there are assertions that the IMC is a good indicator of the solder joint integrity. However this is usually as far as this particular statement is taken. A key question that is still outstanding is what particular attribute of the IMC is important for solder joint reliability. The shape and size of the IMC is often cited as crucial to quality assurance. Such indicators may be valid but this study will couple this kind of observation with elemental quantification (EDX), high resolution microscopy and finally mechanical failure techniques. A comprehensive test plan will be executed to more fully understand the role of IMC formation in terms of solder joint reliability, (SJR).

Effect of Added Elements on Microstructures and Joint Strength of Lead-Free Sn-Based Solder Joint Dispersed IMC Pillar

To create a high reliability solder joint using IMCs dispersed in the joint, the joints with four types of lead-free solder were investigated. The joint with Sn-3.0Ag-0.7Cu-5.0In (mass%) has high die shear force compared to other joints investigated, and the joint with the Ni-electroplated Cu bonded at 300 oC for 30 min showed the maximum die shear force due to formation of a large number of fine IMCs. In the joint with Sn-0.7Cu-0.05Ni (mass%), uniform dispersion of a large number of IMCs was achieved, although the die shear force of the joint is lower than that of the joint with Sn-3.0Ag-0.7Cu-5.0In. In the joint with Sn-5.0Sb (mass%), a solder area was remained in the center of the joint although a large number of columnar IMCs form at the joint interface. The die shear force of the joint with Sn-5.0Sb increased with increasing the bonding time due to formation and growth of IMCs. In the joint with Sn-3.0Ag-0.5Cu (mass%), IMCs formed at the joint interface and did not disperse in the entire joint.

Controlling of IMCs layers formation sequence, bond strength and electrical resistance in Al[sbnd]Cu bimetal compound casting process

This research aimed to produce Al/Cu bimetal through the compound casting process. The control of the thickness and type of IMCs layers at Al/Cu interface were investigated by controlling of Al melts pouring temperature and Cu preheating temperatures. By these methods it was tried to reach an increase in Al/Cu bond strength and electrical conductance of the produced bimetal. The microstructure and mechanism of IMCs formation at the Al/Cu interface were evaluated by Optical Microscope (OM) and Electron Probe Micro-Analysis (EPMA). From the experiments, it was observed that the interface comprised three major layers including, Layer I: α-Al/Al2Cu (α+θ) eutectic structure, Layer II: the intermediate intermetallic compound of Al2Cu (θ), and finally the solid state diffusion Layer III which included several IMCs such as AlCu, Al3Cu4, Al2Cu3, and Al4Cu9. From experiential evidences it was concluded that the control of the preheat temperature of solid copper was far more influential on the formation, thickness, and type of intermetallic phases than the controlling the melt pouring temperature of aluminum. According to the experimental results, Al2Cu3 and Al3Cu4 phases with a higher hardness and lower toughness in comparison with Al2Cu, AlCu, and Al4Cu9 phases, had a more destructive effect on the bond strength.

Investigation of Al–Cr alloy targets sintered by various powder metallurgy methods and their particle generation behaviors in sputtering process

Al–Cr–N films for tribological application are commonly prepared by sputtering on Al–Cr alloy targets in an Ar + N2 mixed atmosphere. Generally, a film is manufactured by co-sputtering on an Al and Cr target, which tends to produce an arbitrary composition. It is difficult to produce an alloy target with a high Al ratio by melting technology due to the formation of brittle intermetallic compound phases (IMCs). In this study, alloy targets were manufactured by various powder metallurgy methods, included hot pressing (HP), hot isostatic pressing (HIP), and low temperature novel forming (LTNF). The results showed that at higher temperature, HP targets were dense and developed a large amount of IMCs, giving the target poor mechanical properties. Cracking tended to occur on the target surface, and many particles were generated during the sputtering process. At a lower temperature, IMC formation was inhibited in these targets, but the density was poor. The HIP method produced similar results to those of HP. LTNF was developed to achieve a dense target free of IMCs. Furthermore, the sputtering performances of the alloy targets were verified. For the LTNF target, almost no arcing count was recorded, fewer particles were generated and better film uniformity was obtained. The target and sputtering characteristics of conventionally-made (HP and HIP) methods were less desirable.

Povacoat affecting solid-state polymorphic changes of indomethacin after co-evaporation from different types of solvents via conventional and microwave drying techniques

The effect of Povacoat on the solid state characteristics and polymorphic transformation of γ-form of indomethacin (γ-IMC) after solvent co-evaporation via two drying methods was investigated by thermoanalytical and FTIR spectroscopic studies. The types of solvents (water, ethanol, and water:ethanol (1:9 ~ 2:8, v/v)), weight ratios of Povacoat:IMC (4:1 ~ 4:10, w/w), and drying methods (air-drying and microwave-drying) were selected as variables in this study. A physical mixture of Povacoat and γ-IMC was also carried out by neat grinding process. The results indicate that there was no interaction between Povacoat and γ-IMC or no polymorphic change of γ-IMC after the neat co-grinding process. Since Povacoat was only soluble in water or <30% ethanol aqueous solution but γ-IMC was only soluble in organic solvents, different solvents and drying methods might significantly influence the solid-state characteristics of IMC formed in the presence of Povacoat. It was found that the amorphous IMC was formed in the Povacoat/IMC evaporates after dissolving both Povacoat and γ-IMC in water:ethanol (mixed ratio=1:9 and 2:8, v/v) and co-evaporation via microwave-drying, whereas the α-IMC was formed in the Povacoat/IMC evaporates via the air-drying method. In addition, the predominate α-IMC formation was only found in all the Povacoat/IMC evaporates with different weight ratios prepared by previously dissolving in water:ethanol (1:9, v/v) and co-evaporation via air-drying, but the amorphous IMC formation after co-evaporation via microwave-drying was obtained except the 4:10 (w/w) weight ratio. The thermal effect of microwave irradiation and the presence of Povacoat might be responsible for the amorphous IMC formation in the Povacoat/IMC evaporates.

Analysis of 16 QFN Device I/O Pads for Solderability Failures

In-process failures were experienced during printed circuit board (PCB) SMT assembly of a 16 Quad Flat No Leads (QFN) device. The failures appeared to be solderability related with QFN unit I/O pads not soldering robustly and sometimes leading to QFN detachment following board mounting. When assembly did take place on affected QFN units, the resulting solder joint was observed to be weak. This paper reports on very systematic analyses of the QFN device I/O pads using optical inspections, AES surface, AES depth profiling, SEM/EDX, SIMS, FIB and TEM cross-sectional measurements to determine the root cause of the failure and the failure mechanism. The detached QFN units, suspect and good unsoldered units, passing and failing units obtained from customers were examined. The industry standard surface mount solderability testing was performed on good and suspect parts, and all were observed to pass as evidenced by &amp;gt;95% coverage of the I/O pads. Optical inspections and a wide variety of physical analysis of the pads on fresh parts showed no anomalies with only the expected Au over Pd over Ni found. AES analysis was performed including depth profiling to look for any issues in the NiPdAu over base Cu plating layers that could be contributing the solderability failures. The AES depth profiling indicated AuPd film on the Ni under layer for the I/O pads as expected. No unexpected elements or oxide layers were observed at any layer. Then, one failing and one passing units were compared by doing FIB cross-section, FIB planar section and TEM cross-section analysis. The cross-sectional analysis showed rough Ni surface for the failing units, while the Ni surface was relatively smooth for the passing unit. Further, finer Cu grains and Ni grains were observed on the passing units. Additionally, the lead frame fabrication process mapping showed rough Cu, Ni “texturing” and use of low electro chemical polishing (ECP) current on the bad units compared to that of the good units. All affected bad units were confirmed coming from a second source Cu supplier with the rough Cu. The weak and irregular NiSn IMC formation on the bad units caused IMC separation and possible spalling during board solder reflow primarily due to the rough base Cu and irregular grain sizes and resulting lower ECP lead frame plating current. A possible final factor was marginally low Pd thickness. In conclusion, the 16 QFN device solderability failure root cause summary and the lessons learned from a wide variety of analysis techniques will be discussed.

Cu–Al intermetallic compound investigation using ex-situ post annealing and in-situ annealing

In Cu wire technology, it is observed that the Cu–Al IMC formation increases from a very thin layer of a few nm to a few μm after subjected to annealing process. The identified IMC phases are mainly CuAl2, CuAl and Cu9Al4, whereas the other three phases which are less reported are Cu4Al3, Cu3Al2 and Cu3Al. The reliability risk of Cu–Al IMC is commonly known, with the degradation of voids or crack propagation from ball periphery to internal ball bond direction after long duration of annealing. However, the cause of the degradation is not well established. This paper will focus on the study of the degradation of Cu–Al IMC layers with and without the presence of a mold compound by using ex-situ post annealing and in-situ annealing method on the same assembled sample. The ex-situ post annealing sample is studied using focus ion beam (FIB) after the molded sample had underwent a standard High Temperature Storage (HTS) at 150°C for 1000h. The in-situ annealing sample is studied using a transmission electron microscope (TEM) on a lamella with Cu–Al interface but without the presence of a mold compound. The result shows that the IMC formed are identified as CuAl2, CuAl and Cu9Al4via Energy Dispersive Spectrometer (EDX). These IMC are seen to grow increasingly with the duration of annealing process for both methods. The native Al oxide lines are seen for both methods and were embedded in between the IMC. The degradation starts at the ball periphery with cracks and voids at IMC are seen for the ex-situ postannealing sample but it is not observed under in-situ annealing sample. It is found that the degradation of the IMC is not caused by propagation of microcrack; instead it is assumed to be the influence of additive within the mold compound itself.

Effect of reflow soldering profile on intermetallic compound formation

Reflow soldering in a nitrogen atmosphere is a common process in surface mount technology assembly since it can increase solder joint reliability. The present study investigated the effect of different reflow soldering atmospheres, either air or nitrogen, on intermetallic compound IMC formation and growth. Several techniques of materials characterisation including optical, image analysis, scanning electron microscopy and energy dispersive X-ray analysis were used to characterise the intermetallics. Besides, the effects of cooling rate and isothermal ageing were also studied. In summary, reflowing under nitrogen atmosphere had better effect on IMC formation and growth compared to reflowing under air. Besides, the cooling rate of solder during reflow also appears to have an effect on the final structure of the solder joint, and controlling the growth behaviour of the IMC during subsequent isothermal ageing. However, further research can be carried out to determine the solder joint's strength produced by both reflow soldering profiles.