Thickness Of Interfacial Intermetallic Compound Research Articles

Achieving outstanding mechanical property after long-cycle thermal shock of reflow/ultrasonic-assisted Kovar/SnSb10 interfaces

The present study analyzed the microstructure evolution corresponding to the mechanical properties of reflow/ultrasonic-assisted Kovar/SnSb10/Fe joints after long-cycle thermal shock (TS). The results indicate that the thickness of interfacial intermetallic compounds (IMCs) at Kovar/SnSb interface with ultrasonication was less than 1 μm even after 2000 cycles, and almost no defects were detected, exhibiting superior microstructure stability. The ultimate shear strength with and without ultrasonication reached 58 MPa and 45 MPa, respectively. From TEM analysis, the nanoprecipitates inside Sn or IMC region primarily consisted of Ni3Sn4 and Ni3Sn phases. The ultimate outstanding mechanical property after long-cycle TS was attributed to dispersed strengthening and dislocation strengthening. This work provides valuable insights into the stability and reliability of the Kovar/SnSb10 system.

Improved shear property of Sn-3.0Ag-0.5Cu/Ni micro solder joints under thermal shock between 77 K and 423 K by adding TiO2 nanoparticles

The rapid development of space exploration technology was intensifying the desire for lead-free solders with high performance and reliability under extreme temperature environments. In this study, the influence of TiO2 nanoparticle addition on the microstructure, growth behavior of interfacial intermetallic compounds (IMCs) and shear property of Sn-3.0Ag-0.5Cu (SAC305)/Ni micro solder joints under thermal shock from 77 K to 423 K was systematically investigated. The results indicated that the grain size of β-Sn, IMC (Ag3Sn and (Cu,Ni)6Sn5) particles inside the solder was refined by adding 0.05 and 0.1 wt% TiO2 nanoparticles. Due to the spalling of interfacial IMCs into the solder occurring in all micro joints during thermal shock, the thickness of interfacial IMCs did not show a monotony increasing trend with increasing thermal cycles. However, the micro composite solder joint added with 0.05 and 0.1 wt% TiO2 nanoparticles always exhibited thinner interfacial IMC thickness and higher shear force compared with the plain micro joints during thermal shock. The inhibiting effect of TiO2 nanoparticles on the interfacial IMC growth could be explained by the adsorption theory and grain boundary pinning theory. The improvement in shear property of micro composite solder joints was primarily induced by the refinement of IMC particles in the solder and the reduced growth rate of interfacial IMCs by adding TiO2 nanoparticles.

Microstructure and Properties of Electromigration of Sn58Bi/Cu Solder Joints with Different Joule Thermal Properties

Electromigration is one of the most important research issues affecting the reliability of solder joints. Current-induced Joule heating affects the electromigration behavior of solder joints. Solder joints with different cross-sectional areas were designed to obtain different Joule heating properties. The effects of the interfacial intermetallic compound (IMC) and mechanical properties of Sn58Bi/Cu solder joints were studied for different Joule heating properties. The results showed that as the cross-sectional area of the Sn58Bi/Cu solder joints increased, the Joule heating of the joint increased. The anode IMC thickness of the joint thickened and transformed into a planar shape. The Bi migrated to the anode region to form a Bi-rich layer and gradually increased in thickness. The cathode IMC thickness first increased, then decreased, and gradually dissolved. The Sn-rich layer formed near the solder side and gradually increased in thickness, with microcracks occurring when the cross-sectional area of the joint increased to 0.75 mm2. The joint shear fracture path moved from the soldering zone near the cathode IMC layer to the interfacial IMC layer. The fracture mechanism of the joint changed from a mixed brittle/tough fracture, dominated by deconstruction and secondary cracking, to a brittle fracture dominated by deconstruction. The joint shear strength was reduced by 60.9% compared to that in the absence of electromigration.

Effects of Bi and Cu addition on mechanical properties of Sn9Zn alloy and interfacial intermetallic growth with Ni substrate

Sn9ZnxBixCu (x = 0, 1.0, 2.0, 3.0 and 4.0 wt%) solder alloys were prepared by adding different contents of Bi and Cu elements, and the effects of Bi and Cu addition on the mechanical properties, wettability, and interfacial intermetallic compound (IMC) layer were researched. The addition of Bi and Cu can significantly improve the mechanical properties and creep resistance of the alloy. When the addition of Bi and Cu reaches 2 wt%, small Bi phases are dispersed in the matrix, and moderate Cu5Zn8 phases appear, which strengthens the solder matrix. The ultimate tensile strength (UTS) of the Sn9Zn2Bi2Cu alloy reaches 51.01 MPa, which is 149.32% higher than that of the Sn9Zn alloy, and the elongation reaches 26.56%. Nanoindentation results show that the holding displacement of the Sn9Zn4Bi4Cu alloy decreased by 28.48% compared with that of the Sn9Zn alloy at a loading rate of 0.1 mN/s. In addition, proper addition of Bi and Cu can improve the wettability of the solder alloy and inhibit the growth of interfacial intermetallic compounds (IMCs) between the solder and Ni substrate. When the reflow time reaches 40 min (min), the interfacial IMC thickness of the Sn9Zn2Bi2Cu/Ni solder joint is 1.93 µm, which is 46.09% smaller than that of the Sn9Zn alloy. Moreover, the shear strength of the Sn9Zn2Bi2Cu/Ni solder joint increases by 33.3%, reaching the maximum value (38.76 MPa). When the Bi and Cu addition reaches 2 wt%, the wetting area reaches a larger value (13.525 mm2), which is 28.35% higher than that of Sn9Zn alloy.

Reliability of laser soldering using low melting temperature eutectic Sn Bi solder and electroless Ni-electroless Pd-immersion Au-finished Cu pad

The demand for flexible wearable devices/substrates with miniaturization and improved integration in microelectronic devices has intensified the research interest in low-temperature laser soldering processes as an alternative to conventional reflow soldering processes owing to their advantages, such as local heating, non-contact heating, and short bonding time. In this study, we compared and evaluated the reliability of laser soldered and conventional reflow soldered joints using representative low melting temperature eutectic Sn Bi solder and thin electroless Ni-electroless Pd-immersion Au (ENEPIG)-finished Cu pads. Laser soldering was performed using various laser powers (130, 150, and 170 W) and times (2 and 4 s). Furthermore, an aging test was performed at 110 °C for 2000 h to evaluate the long-term reliability of the soldered joints. The mechanical properties, including the top and cross-sectional views and fracture surfaces, of the soldered joints were analyzed by conducting shear tests after aging. During laser soldering, various intermetallic compounds (IMCs) were formed at the joints depending on the applied energy. The metallization layer and Cu reacted with Sn in the solder after different aging durations, and additional IMCs were formed and grown. After aging for 2000 h, the shear strength decreased, and the interfacial IMC thickness increased. As the aging time increased, the fracture mode changed from an initial ductile fracture to brittle fracture (between the solder and IMCs and/or between IMCs and the Cu pad). The reflow soldered joints exhibited stable shear strength, resulting in ductile fracture until aging for 500 h. However, the shear strength decreased sharply after aging for 1000 and 2000 h, and Bi-segregation was observed after aging for 1000 h, resulting in inferior long-term reliability. After laser soldering at 150 and 170 W for 4 s, the strength of the samples decreased sharply after aging for 1000 and 250 h, respectively, and Bi-segregation was observed after aging for 2000 h. The shear strength of the sample laser soldered at 170 W for 2 s gradually decreased with increasing aging time and maintained a stable shear strength until aging for 2000 h. Therefore, laser soldering at 170 W for 2 s was considered as the optimal condition for long-term reliability. • Soldering properties of laser soldered Sn-58Bi/Au/Pd/Ni-finished Cu joints evaluated. • Laser soldering results were compared with conventional reflow soldered joints. • Various IMCs were formed depending on laser power and irradiation time. • Laser conditions with low applied energy displayed superior long-term reliability. • Selection of the optimal laser conditions is crucial to ensure reliable solder joints.

Growth behavior and reliability of interfacial IMC for Sn58Bi/Cu and Sn58Bi–AlN/Cu solder joints applied in IGBT modules

The IMC (interfacial intermetallic compound) produced by the metallurgical reaction between the solder and the Cu plate enables the packaging of IGBT (insulated gate bipolar transistor) modules. In this paper, the growth behavior of IMCs of Sn58Bi/Cu and Sn58Bi-0.05AlN/Cu at different times (10, 30 and 60 min) and temperatures (200, 250 and 300 °C) was investigated, which can provide a reference for the connection of IGBT. It was shown that the interfacial IMC thickness of both solders increased with time and temperature, but the growth of interfacial IMC was suppressed for Sn58Bi solder containing 0.05 wt% AlN. The effect of AlN on the inhibition of grain growth was also observed by EBSD testing. Because of the adsorption effect of AlN nanoparticles, they can adhere to the surface of IMC layer and decrease the effective the diffusion path of unreacted Cu atoms, thereby inhibiting the growth of interfacial IMC. And the effect of AlN particles on interfacial IMC was analyzed via phase field simulation. In addition, under the heating conditions with high temperature and long time, there were fewer cracks in the solder joints containing AlN particles, compared to the Sn58Bi solder. Therefore, AlN nanoparticles can enhance the reliability of Sn58Bi/Cu solder joints.

Properties of Cu/SAC0307 mixed solder balls/Cu joints with different Zn-particles content at low-temperature under ultrasonic assisted

Purpose This study aims to research properties of Cu/SAC0307 mixed solder balls/Cu joints with different Zn-particles content at low-temperature under ultrasonic assisted. Design/methodology/approach A new method that 1µm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 µm were mixed to fill the joint and successfully achieved micro-joining of Cu/Cu under ultrasonic-assisted at low temperature. Findings The results showed that with a continuous increase in the Zn-particle content, the interfacial intermetallic compounds (IMCs) of the upper and lower interfaces of joints gradually changed from scallop-shaped Cu6Sn5 to wavy-shaped Cu5Zn8. Moreover, the IMC thickness of the upper/lower interface of joints first decreased and then increased with increasing Zn-particle content. The shear strengths of joints increased with Zn-particle content, the shear strength of joints went to a maximum of 29.76 MPa when the Zn-particle content was 40%, an increase of 62.6% compared to joints without Zn particles. However, as the Zn-particle content continued to increase, the shear strengths of the joints decreased. Additionally, when the Zn content increased to 50%, because the oxidation degree of Zn particles increased, the joints were mainly broken among Zn particles. Originality/value A new method that 1µm Zn particles and Sn-0.3Ag-0.7 (SAC0307) with a particle size of 25–38 µm were mixed to fill the Cu/Cu joint at 180°C.

Phase field study on the effect of roughness on interfacial intermetallic compounds of micro-solder joints under multifield coupling

In order to investigate the influence of roughness on the evolution of interfacial intermetallic compounds (IMCs) and stress states at the micro-solder joints under the strongly coupled thermo-mechanical-electric diffusion, the two-dimensional model of the rough interface for the Cu/Sn/Cu sandwich micro-solder joints was established using phase field method. Parameter A as the evaluation parameter of the interface roughness was used to represent the contour arithmetic mean deviation Ra. The evolutions of the average thickness of the interfacial IMCs and stress distribution at the Cu/Sn/Cu micro-solder joints were investigated with the variation of A. The thickness of interfacial IMCs in anode reached its maximum when A was 0, while obtained the minimum when A was 9. In cathode, the average thickness of the interfacial IMCs at A = 0 was thicker than that at A = 1, 3, 5, but thinner than that at A = 7 and 9. In other words, the growth of the interfacial IMCs was inhibited by the interface roughness in anode. While in cathode, the interfacial roughness inhibited the growth of the interfacial IMCs when 0 ≤ A ≤ 5, but promoted the growth of the interfacial IMCs when 7 ≤ A ≤ 9.

Welding characterization evolutions for dual spot laser welded-brazed Al/steel joint with various spot configurations

In this research, satisfactory Al/steel butt joint was obtained by the dual spot laser welding-brazing technology with various spot configurations (+45° biased to steel side, in-line, -45° biased to Al side). The results showed that the interfacial IMC (Intermetallic compound) were composed of η–Fe2(Al,Si)5 and θ–Fe(Al,Si)3 for three joints. The interfacial IMC thickness reduced when the laser spot was biased from steel to Al side. In addition, IMC with larger thickness was produced at the top and middle regions than that of bottom region. The η–Fe2(Al,Si)5/steel interface would be changed from straight to finger-shaped with the reduction of η–Fe2(Al,Si)5 layer thickness. Numerical simulation showed that interfacial IMC thickness variations were resulted from the difference of peak temperatures: higher peak temperatures, thicker interfacial IMC. Analysis of fractured behaviors presented that fractured locations would be changed with the reduction interfacial IMC thickness: from η–Fe2(Al,Si)5 layer to η–Fe2(Al,Si)5 layer and θ–Fe(Al,Si)3 and finally to θ–Fe(Al,Si)3 and partial weld seam when interfacial IMC thickness reduced from 6.1 μm to 5.1 μm and finally to 3.4 μm. Tensile strength values showed that fractured location of θ–Fe(Al,Si)3 and partial weld seam in the interface joined with 2.9–3.5 μm Fe2(Al,Si)5 layer and θ–Fe(Al,Si)3 was most beneficial for interfacial strength and highest tensile strength of 142 MPa was obtained.

Microstructure and shear properties of ultrasonic-assisted Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints under thermal cycling

Through ultrasonic wave assisted Sn2.5Ag0.7Cu0.1RExNi/Cu (x = 0, 0.05, 0.1) soldering test and − 40 to 125 °C thermal shock test, the microstructure and shear properties of Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints under thermal cycling were studied by the SEM, EDS and XRD. The results show that the Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints with high quality and high reliability can be obtained by ultrasonic assistance. When the ultrasonic vibration power is 88 W, the ultrasonic-assisted Sn2.5Ag0.7Cu0.1RE0.05Ni/Cu solder joints exhibits the optimized performance. During the thermal cycling process, the shear strength of ultrasonic-assisted Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints had a linear relationship with the thickness of interfacial intermetallic compound (IMC). Under the thermal cycling, the interfacial IMC layer of ultrasonic-assisted Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints consisted of (Cu,Ni)6Sn5 and Cu3Sn. The thickness of interfacial IMC of ultrasonic-assisted Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints was linearly related to the square root of equivalent time. The growth of interfacial IMC of ultrasonic-assisted Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints had an incubation period, and the growth of IMC was slow within 300 cycles. And after 300 cycles, the IMC grew rapidly, the granular IMC began to merge, and the thickness and roughness of IMC increased obviously, which led to a sharp decrease in the shear strength of the solder joints. The 0.05 wt% Ni could inhibit the excessive growth of IMC, improve the shear strength of solder joints and improve the reliability of solder joints. The fracture mechanism of ultrasonic-assisted Sn2.5Ag0.7Cu0.1RExNi/Cu solder joints changed from the ductile–brittle mixed fracture in the solder/IMC transition zone to the brittle fracture in the interfacial IMC.

Effects of ultrasonic treatment on mechanical properties and microstructure evolution of the Cu/SAC305 solder joints

The effects of different ultrasonic treatment time on microstructure evolution and mechanical property of Cu/Sn-3.0Ag-0.5Cu (SAC305) solder joints were investigated. Experiments were set to obtain Cu/SAC305 solder joints, which were compared with solder joints without ultrasonic treatment. The application of short-term ultrasonic treatment on the solder joints would alter the morphology of interfacial intermetallic compound (IMC) layer, IMC thickness and grains size were reduced. Besides, ultrasonic treatment could significantly improve the shear strength of solder joints. In addition, the liquid solder would further flow along the direction of ultrasound, resulting in the reduction of contact angle. Due to the increase of ultrasonic time, the optimal growth direction of grains was changed after the ultrasonic treatment. However, excessive ultrasonic time would reduce the shear strength of solder joints and increase the IMC thickness, which would reduce the stability of solder joints.

Study on the microstructure and mechanical property of Cu-foam modified Sn3.0Ag0.5Cu solder joints by ultrasonic-assisted soldering

Cu-foam sheets with the thicknesses of 0.15 mm and 0.5 mm were utilized as strengthening structure to improve the performances of the Sn3.0Ag0.5Cu (SAC305)/Cu solder joints. The ultrasonic-assisted soldering was applied to manufacture the solder joints. The effects of Cu-foam and ultrasound-assisted soldering time on microstructure and mechanical property of solder joints were researched. Experimental results showed that excellent metallurgical bonding was generated between the copper substrate and the Cu-foam/SAC305 composite solder layer. The average thickness of interfacial intermetallic compound (IMC) layer decreased with the increase of ultrasonically soldering time, and a thinner interfacial IMC layer was found in the joints with ultrasonic treatment in narrow channels. With the ultrasonic soldering time prolonged, the Cu 6 Sn 5 grains became more refined. Some round-shape Cu 6 Sn 5 grains were transformed into hexagonal prismatic with the increase of the ultrasonic soldering time. The shear test was conducted for the solder joints under different soldering conditions. It was found that the shear strength of the Cu-foam/SAC305 composite solder joints were higher than that of SAC305 solder joints. The grain refinement caused by ultrasonic cavitation significantly improved the shear strength of the solder joints. Besides, the fracture behavior of solder joints without ultrasonic vibration was classified to be ductile-brittle mixed type while that with ultrasonic vibration was changed to be ductile type.

Performance of Sn-3.0Ag-0.5Cu Composite Solder with Kaolin Geopolymer Ceramic Reinforcement on Microstructure and Mechanical Properties under Isothermal Ageing.

This paper elucidates the effect of isothermal ageing at temperature of 85 °C, 125 °C and 150 °C for 100, 500 and 1000 h on Sn-3.0Ag-0.5Cu (SAC305) lead-free solder with the addition of 1 wt% kaolin geopolymer ceramic (KGC) reinforcement particles. SAC305-KGC composite solders were fabricated through powder metallurgy using a hybrid microwave sintering method and reflowed on copper substrate printed circuit board with an organic solderability preservative surface finish. The results revealed that, the addition of KGC was beneficial in improving the total thickness of interfacial intermetallic compound (IMC) layer. At higher isothermal ageing of 150 °C and 1000 h, the IMC layer in SAC305-KGC composite solder was towards a planar-type morphology. Moreover, the growth of total interfacial IMC layer and Cu3Sn layer during isothermal ageing was found to be controlled by bulk diffusion and grain-boundary process, respectively. The activation energy possessed by SAC305-KGC composite solder for total interfacial IMC layer and Cu3Sn IMC was 74 kJ/mol and 104 kJ/mol, respectively. Based on a lap shear test, the shear strength of SAC305-KGC composite solder exhibited higher shear strength than non-reinforced SAC305 solder. Meanwhile, the solder joints failure mode after shear testing was a combination of brittle and ductile modes at higher ageing temperature and time for SAC305-KGC composite solder.

Property of Sn-37Pb solder bumps with different diameter during thermal shock

PurposeThe impact strength of solder joint under high strain rate was evaluated by board level test method. However, the impact shear test of single solder bump was more convenient and economical than the board level test method. With the miniaturization of solder joints, solder joints were more prone to failure under thermal shock and more attention has been paid to the impact reliability of solder joint. But Pb-free solder joints may be paid too much attention and Sn-Pb solder joints may be ignored.Design/methodology/approachIn this study, thermal shock test between −55°C and 125°C was conducted on Sn-37Pb solder bumps in the BGA package to investigate microstructural evolution and growth mechanism of interfacial intermetallic compounds (IMCs) layer. The effects of thermal shock and ball diameter on the mechanical property and fracture behavior of Sn-37Pb solder bumps were discussed.FindingsWith the increase of ball size, the same change tendency of shear strength with thermal shock cycles. The shear strength of the solder bumps was the highest after reflow; with the increase of the number of thermal shocks, the shear strength of the solder bumps was decreased. But at the time of 2,000 cycles, the shear strength was increased to the initial strength. Minimum shear strength almost took place at 1,500 cycles in all solder bumps. The differences between maximum shear strength and minimum shear strength were 9.11 MPa and 16.83 MPa, 17.07 MPa and 15.59 MPa in φ0.3 mm and φ0.4 mm, φ0.5 mm and φ0.6 mm, respectively, differences were increased with increasing of ball size. With similar reflow profile, the thickness of IMC decreased as the diameter of the ball increased. The thickness of IMC was 2.42 µm and 2.17 µm, 1.63 µm and 1.77 µm with increasing of the ball size, respectively.Originality/valuePb-free solder was gradually used to replace traditional Sn-Pb solder and has been widely used in industry. Nevertheless, some products inevitably used a mixture of Sn-Pb and Pb-free solder to make the transition from Sn-Pb to Pb-free solder. Therefore, it was very important to understand the reliability of Sn-Pb solder joint and more further research works were also needed.

Pengaruh Agen Kimia Berbeza terhadap Penguraian Terma dan Pembentukan Fasa Bahan La0.6SR0.4CoO3- δ yang Disediakan melalui Kaedah Sol-Gel

Sifat penguraian terma dan pembentukan fasa bahan lantanum strontium kobalt oksida, La0.6Sr0.4CoO3-δ (LSC) yang disediakan melalui kaedah sol-gel berbantu agen kimia berbeza, iaitu agen serakan, agen pempolimeran dan agen permukaan aktif atau surfaktan telah dicirikan secara sistematik masing-masing melalui analisis termogravimetrik (TG) dan pembelauan sinar-X (XRD). Penguraian terma bahan organik dan bahan bukan organik yang tidak diperlukan dalam serbuk pelopor bahan LSC telah lengkap pada suhu kurang daripada 1000 °C bagi serbuk pelopor yang disediakan dengan menggunakan agen serakan dan agen pempolimeran, dan suhu melebihi 1000 °C bagi serbuk pelopor yang disediakan dengan menggunakan surfaktan. Sifat penguraian terma ini dipengaruhi oleh suhu pengeringan serbuk pelopor tersebut dan berat molekul agen kimia. Pembentukan fasa tunggal perovskit LSC telah disahkan dalam serbuk pelopor yang disediakan dengan menggunakan agen serakan, iaitu karbon teraktif dan agen pempolimeran, iaitu etilena glikol selepas serbuk pelopor tersebut dikalsin pada suhu 900 °C. Sebaliknya, fasa tunggal perovskit LSC tidak terbentuk secara lengkap dalam serbuk pelopor yang disediakan dengan menggunakan surfaktan (polietilena glikol, Triton-X-100, Brij-97 dan Tween-80) walaupun selepas serbuk pelopor tersebut telah dikalsin pada suhu yang lebih tinggi iaitu 1100 °C. Kepekatan surfaktan, nisbah molar surfaktan kepada logam kation dan nilai pH larutan bahan pelopor yang tidak sesuai telah menyumbang kepada keputusan tersebut.

Effect of Bismuth Additions on Wettability, Intermetallic Compound, and Microhardness Properties of Sn-0.7Cu on Different Surface Finish Substrates

The influence of bismuth (Bi) addition on wettability, thickness of interfacial intermetallic compound (IMC), and microhardness properties of Sn-0.7Cu + xBi solder alloy using different types of substrate were examined. The 0.5, 1.0, 1.5, and 2.0 wt. % Bi was added into Sn-0.7Cu and fabricated using the casting process. The result shows that the influence of 1.5 wt. % Bi in the Sn-0.7Cu solder soldered on copper organic solderability preservative (Cu-OSP) and immersion tin (Im-Sn) surface finish has improved the wettability and microhardness. Subsequently, the IMC thickness of Sn-0.7Cu+1.5Bi solder alloy on Im-Sn surface finish gives a better result than reflowed on Cu-OSP. Generally, with the addition of 1.5 wt. % Bi in Sn-0.7Cu solder alloy reflowed on the Im-Sn surface finish had enhanced the performance in terms of wettability, thickness of IMC and microhardness properties compared to on Cu-OSP surface finish.

Interfacial reaction and shear strength of ultrasonically-assisted Sn-Ag-Cu solder joint using composite flux

Cu modified carbon nanotubes (Cu-CNTs) doped flux were prepared in this paper, the influence of the composite flux on the evolution of microstructure and shear strength of Sn-3.0Ag-0.5Cu (SAC305) solder joints were investigated, the ultrasonic vibration (USV) was applied for the solder joint during reflowing. Experiments were designed to modify the CNTs with Cu nanoparticles through electroless modification process. Transmission electron microscopy (TEM) was utilized to obtain the graph of modified CNTs. Using X-ray photoelectron spectroscopy (XPS) spectra to prove that the CNTs were successfully modified with Cu nanoparticles. Compared with the solder joint without USV, the application of USV on the solder joint would alter the morphologies of interfacial IMC layer and grains, reduce the IMC thickness and grain size by 16.6 % and 65.6 %, respectively. Reflow process was implemented to evaluate the microstructure evolution and interfacial reaction of SAC305 solder joint with different content of Cu-CNTs doped flux with USV. It was found that the presence of Cu-CNTs could reduce the thickness and grain size of interfacial intermetallic compound (IMC) within solder joint by 3.1 % and 5.25 %, respectively. After addition of the Cu-CNTs in the flux, the thickening of IMC layer and the coarsen of interfacial IMC grain were suppressed, the optimal inhibition effect was gained when the content of Cu-CNTs was 0.1 wt.%. The shear test was conducted for the Cu/SAC305/Cu solder joint with flux containing Cu-CNTs under different soldering condition, the results indicated that as the content of the Cu-CNTs in the flux increased, the shear strength was significantly enhanced by up to 16.8 %. Furthermore, the application of USV could enhance the shear strength by up to 14.2 % as well, The fracture type of solder joints without USV treatment also changed from ductile-brittle mixed type to ductile type as the content of Cu-CNTs in the flux increased. While, the fracture type of all the solder joints with USV treatment was ductile type.

Shear Strength and Aging Characteristics of Sn-3.0Ag-0.5Cu/Cu Solder Joint Reinforced with ZrO2 Nanoparticles

This study investigates the shear strength and aging characteristics of Sn-3.0Ag-0.5Cu (SAC 305)/Cu joints by the addition of ZrO2 nanoparticles (NPs) having two different particle size: 5–15 nm (ZrO2A) and 70–90 nm (ZrO2B). Nanocomposite pastes were fabricated by mechanically mixing ZrO2 NPs and the solder paste. ZrO2 NPs decreased the β-Sn grain size and Ag3Sn intermetallic compound (IMC) in the matrix and reduced the Cu6Sn5 IMC thickness at the interface of lap shear SAC 305/Cu joints. The effect is pronounced for ZrO2A NPs added solder joint. The solder joints were isothermally aged at 175 °C for 24, 48, 144 and 256 h. NPs decreased the diffusion coefficient from 1.74 × 10–16 m/s to 3.83 × 10–17 m/s and 4.99 × 10–17 m/s for ZrO2A and ZrO2B NPs added SAC 305/Cu joints respectively. The shear strength of the solder joints decreased with the aging time due to an increase in the thickness of interfacial IMC and coarsening of Ag3Sn in the solder. However, higher shear strength exhibited by SAC 305-ZrO2A/Cu joints was attributed to the fine Ag3Sn IMC’s dispersed in the solder matrix. Fracture analysis of SAC 305-ZrO2A/Cu joints displayed mixed solder/IMC mode upon 256 h of aging.

Interfacial evolution and mechanical properties of Au–Sn solder jointed Cu heat sink during high temperature storage test

The growth of interfacial intermetallic compounds (IMC) and mechanical properties by the widely used Au-Sn solder jointed Cu pillar are studied in this paper. Three concentrations of Sn (15%, 20%, and 25%) are employed to investigate the evolution of IMC growth and mechanical properties. It is found that the initial IMC growth is linear growth and surface reaction domination at the reflow step, as both Au and Sn directly react with Cu to form scallop-like (Au,Cu)Sn. Following the initial growth, IMC gradually becomes thicker, which inhibits Au/Sn penetrating into IMC to react with Cu, thus, at this stage, AuCu instead of (Au,Cu)Sn, forms the IMC and the inter-diffusion of parabolic growth dominates. By increasing HTS time, AuCu3 grows by consuming the AuCu compound. Moreover, the AuSn eutectic precipitations gradually decreased, which resulted in reduced hardness. Ductile fractures appeared among all the samples, and the appropriate IMC thickness improved the adhesion ability of the Au-Sn solder on the Cu pillar.

Influence of energy ratio on dual–spot laser welded–brazed Al/steel butt joint

Al/steel butt joints were successfully obtained using a dual–spot laser welding–brazing process with different R (R = E Fe :E Al = 4:6, 5:5, and 6:4; E Fe and E Al represented the energy ratios of the laser near steel and Al, respectively). The molten filler metals wet and spread well along the front and back surfaces of the steel when R was 5:5 and 6:4, whereas an undercut occurred when R was 4:6. The interfacial intermetallic compound (IMC) along the brazing interface consisted of only thin–layered τ 5 –Fe 1.8 Al 7.2 Si when R was 5:5 and 4:6. The IMC had a greater thickness when R was 5:5 owing to its higher peak temperatures than when R was 4:6. A mixed IMC (θ–Fe(Al,Si) 3 +τ 5 –Fe 1.8 Al 7.2 Si) was newly formed in the top region of the brazing interface when R was 6:4. TEM observations revealed that two types of grains existed in θ–Fe(Al,Si) 3 : normal and twinned. Numerical simulations for the thermal cycles along the brazing interface indicated that the IMC thickness was determined by the interfacial peak temperature, while the IMC homogeneity was determined by the temperature gradient. The results of an experiment involving the tensile properties indicated that the highest average joint strength (193 MPa) and largest average fracture displacement (0.64 mm) when R was 5:5, owing to its satisfactory weld formation and reasonable IMC distribution.