Shear Strength Of Solder Joints Research Articles

Fabrication of Ni–P coating film on diamond/Al composite and its soldering reliability

Although the diamond/Al composite is a good heat sink material due to its high thermal conductivity and low cost, its surface cannot be wetted directly for microelectronic packaging. Using modified electroless plating procedures and recipes, a glossy, continuous, and uniform Ni–P film was successfully fabricated on the diamond/Al composite surface for the first time with a bonding strength of 15.1 MPa. This Ni–P coating layer is solderable for both lead-free SAC305 and Sn63Pb37 alloys on Cu dummy chips. A continuous intermetallic compound (IMC) layer was formed at the interface without any crack or void defects, and the shear strength of both solder joints was in the range of 39.9–41.2 MPa. During thermal storage tests, the growth of IMC was slow at 125 and 150 °C, but it elevated sharply at 175 °C. According to growth kinetics analyses, a Ni element can hinder IMC growth. The diffusion activation energy (Q) of (Cu,Ni)6Sn5 was calculated as 62.6 kJ/mol in SAC305 and 97.7 kJ/mol in Sn63Pb37 solder joints. Both microstructures and mechanical properties of the solder joint using the Ni–P coated diamond/Al composite can satisfy the requirement of microelectronic industrial applications.

Solder joint quality evaluation based on heating factor

PurposeThe purpose of this paper is to increase the reliability of manufactured electronics and to reveal reliability significant factors. The experiments were focused especially on the influence of the reflow oven parameters presented by a heating factor.Design/methodology/approachThe shear strength of the surface mount device (SMD) resistors and their joint resistance were analyzed. The resistors were assembled with two Sn/Ag/Cu-based and one Bi-based solder pastes, and the analysis was done for several values of the heating factor and before and after isothermal aging. The measurement of thickness of intermetallic compounds was conducted on the micro-sections of the solder joints.FindingsThe shear strength of solder joints based on the Sn/Ag/Cu-based solder alloy started to decline after the heating factor reached the value of 500 s · K, whereas the shear strength of the solder alloy based on the Bi alloy (in the measured range) always increased with an increase in the heating factor. Also, the Bi-based solder joints showed shear strength increase after isothermal aging in contrast to Sn/Ag/Cu-based solder joints, which showed shear strength decrease.Originality/valueThe interpretation of the results of such a comprehensive measurement leads to a better understanding of the mutual relation between reliability and other technological parameters such as solder alloy type, surface finish and parameters of the soldering process.

Morphologies and evolution of intermetallic compounds formed between Sn1.0Ag0.7Cu composite solder and Cu substrate

This study investigated the morphologies of the intermetallic compounds (IMC) formed during soldering reaction between Sn1.0Ag0.7Cu–1.0SnO2 composite solder and Cu substrate at various temperatures. The prism-type Cu6Sn5 forms when the soldering temperature is 260 or 280 °C, while those grains transform from prism type to scallop type at the temperatures of 300 and 320 °C. It can be found that the morphologies of Cu6Sn5 grains affect adsorption of Ag3Sn nanoparticles during soldering reaction. The scallop-type grains with a higher growth rate need to adsorb large amounts of Ag3Sn particles. In terms of mechanical behavior, the shear strength of solder joint is improved from 40 to 46 MPa at soldering temperature of 300 °C. In addition, the thickness of IMC increases with the extension of aging time. During aging, the morphology of Cu6Sn5 grains remains scallop type, but the number of Ag3Sn nanoparticles is reduced largely. The scallop-type Cu6Sn5 can increase in size and flatten in morphology with the aging time increasing. When the soldering temperature changes from 260 to 360 °C, the morphologies of Cu6Sn5 grains transformed from prism-type to scallop-type. The shear strength of solder joint is improved from 40 to 46 Mpa at 300 °C soldering temperature

Shear strength of LED solder joints using SAC-nano Cu solder pastes**Project supported by the National Natural Science Foundation of China (No. 51604090) and the Zhejiang Province Key Laboratory of Soldering & Brazing Materials and Technology (No. 1402).

The addition of Cu nanoparticles into the solder pastes by mechanical mixing method creates a positive effect on the microstructure refinement of the LED solder joints. The grain size of β-Sn and Cu6Sn5 decrease obviously due to the increasing concentration of the nanoparticles in the solder pastes. However, the addition of nanoparticles facilitates the formation of voids in the solder joints, especially when the concentration of nanoparticles is higher than 0.5 wt% in the solder pastes. Both the microstructure refinement and void percentage affect the shear strength of the solder joints. Since the increase of the void percentage is limited when the concentration of nanoparticles increases from 0 to 0.5 wt%, the microstructure refinement shows a dominant effect on the shear performance and thus improves the shear strength of the solder joints from 49.8 to 55 MPa. Further addition of nanoparticles in the solder pastes leads to a sharp increase of the void percentage. Consequently, the shear strength of the solder joints decreases from 55 to 48.8 MPa when the concentration of doped particles increases from 0.5 to 1 wt% in the solder pastes.

Multi-objective optimization on laser solder jet bonding process in head gimbal assembly using the response surface methodology

This paper aims to investigate the effect of laser solder jet bonding parameters to the solder joints in Head Gimbal Assembly. Laser solder jet bonding utilizes the fiber laser to melt solder ball in capillary. The molten solder is transferred to two bonding pads by nitrogen gas. The response surface methodology have been used to investigate the effects of laser energy, wait time, nitrogen gas pressure, and focal position on the shear strength of solder joints and the change of pitch static attitude (PSA). The response surface methodology is employed to establish the reliable mathematical relationships between the laser soldering parameters and desired responses. Then, multi-objective optimization is conducted to determine the optimal process parameters that can enhance the joint shear strength and minimize the change of PSA. The validation test confirms that the predicted value has good agreement with the actual value.

Interfacial Reaction and Mechanical Properties of Sn-Bi Solder joints

Sn-Bi solder with different Bi content can realize a low-to-medium-to-high soldering process. To obtain the effect of Bi content in Sn-Bi solder on the microstructure of solder, interfacial behaviors in solder joints with Cu and the joints strength, five Sn-Bi solders including Sn-5Bi and Sn-15Bi solid solution, Sn-30Bi and Sn-45Bi hypoeutectic and Sn-58Bi eutectic were selected in this work. The microstructure, interfacial reaction under soldering and subsequent aging and the shear properties of Sn-Bi solder joints were studied. Bi content in Sn-Bi solder had an obvious effect on the microstructure and the distribution of Bi phases. Solid solution Sn-Bi solder was composed of the β-Sn phases embedded with fine Bi particles, while hypoeutectic Sn-Bi solder was composed of the primary β-Sn phases and Sn-Bi eutectic structure from networked Sn and Bi phases, and eutectic Sn-Bi solder was mainly composed of a eutectic structure from short striped Sn and Bi phases. During soldering with Cu, the increase on Bi content in Sn-Bi solder slightly increased the interfacial Cu6Sn5 intermetallic compound (IMC)thickness, gradually flattened the IMC morphology, and promoted the accumulation of more Bi atoms to interfacial Cu6Sn5 IMC. During the subsequent aging, the growth rate of the IMC layer at the interface of Sn-Bi solder/Cu rapidly increased from solid solution Sn-Bi solder to hypoeutectic Sn-Bi solder, and then slightly decreased for Sn-58Bi solder joints. The accumulation of Bi atoms at the interface promoted the rapid growth of interfacial Cu6Sn5 IMC layer in hypoeutectic or eutectic Sn-Bi solder through blocking the formation of Cu6Sn5 in solder matrix and the transition from Cu6Sn5 to Cu3Sn. Ball shear tests on Sn-Bi as-soldered joints showed that the increase of Bi content in Sn-Bi deteriorated the shear strength of solder joints. The addition of Bi into Sn solder was also inclined to produce brittle morphology with interfacial fracture, which suggests that the addition of Bi increased the shear resistance strength of Sn-Bi solder.

Effect of Cu electroplating parameters on microvoid formation and high-speed shear strength in Sn-3.0Ag-0.5Cu/Cu joints

The effect of Cu electroplating parameters, i.e., the bath composition and current density, on the impact strength of Sn-3.0Ag-0.5Cu (SAC)/Cu joints was investigated using a high-speed ball shear test. An SAC solder ball was attached to an electroplated Cu layer by a reflow at a peak temperature of 260 °C. Thermal aging at 180 °C formed a Cu3Sn intermetallic compound (IMC) between the Cu6Sn5 IMC and the electroplated Cu, and microvoids were formed within the Cu3Sn IMC layer. The total microvoid area increased with increased Cu electroplating current density. When Cl− ions alone were added to the electroplating bath, the total microvoid area decreased with thermal aging. In contrast, when both polyethylene glycol (PEG) and Cl− ions were added to the bath, the total microvoid area increased. However, the overall IMC thickness was similar for all samples, irrespective of the electroplating parameters. The shear strength of the SAC solder joint reflowed on the electroplated Cu decreased with increased aging time. For the same aging time, the shear strength decreased with increased current density. In addition, the shear strength decreased when the electroplating bath contained both PEG and Cl− ions. As the aging time increased, the fracture site shifted from the solder/Cu6Sn5 interface to the Cu3Sn/Cu interface. An increase in the total microvoid area in the Cu3Sn IMC as well as an increase in the IMC thickness decreased the shear strength of the SAC solder on the electroplated Cu.

Optimization of solder paste quantity considering the properties of solder joints

PurposeThe purpose of this paper is to find an optimum between the quantity of solder paste and the desired properties of the soldered joint. A reduction of solder paste quantity is recognized as an opportunity to save money. On the other hand, the quantity of solder paste significantly influences the final properties of the soldered joint. The purpose is also to design recommendations for manufacturers of electronic assemblies.Design/methodology/approachThe processing of the paper was initiated by a literature review. The expert analysis was the next step. The result of analysis was a fishbone diagram. Subsequently, the experiment was designed. Seven types and three volume of solder pastes and two aperture shapes of the stencil were used. The measured parameters were mechanical strength, electrical resistance, voids area and intermetallic compound (IMC) thicknesses. The results of the experiment were evaluated and recommendations for practice were defined.FindingsThe carried out research has confirmed the influence of solder paste quantity on the shear strength, electrical resistance, voids area and IMC thickness of solder joint. The article presents the results achieved for solders Sn42Bi58, Sn42Bi57.6Ag0.4, SnAg3.0Cu0.5, SnCu0.7Ag1.0NiGe, SnAg3.5Bi0.5In8.0 and Sn62.5Pb36.5Ag1.0. Reduction of solder paste quantity down to 74 per cent (i.e. one quarter of quantity) decreases mechanical shear strength less than 10 per cent. Recommendations relating to the optimal reduction of solder paste quantity have been designed for each solder paste.Originality/valueContribution of the paper is impact assessment of solder paste quantity on the properties of the soldered joint. It was carried out a large number of experiments and measurements which verify this effect. Such a comprehensive overview of the results is not yet available in the literature. Recommendations for manufacturers of electronic assemblies are also the benefit of article.

Influence of Ce addition on Sn-3.0Ag-0.5Cu solder joints: Thermal behavior, microstructure and mechanical properties

The present study investigates the influence of Ce addition on the thermal behavior, microstructure, and mechanical properties of Sn-3.0Ag-0.5Cu (SAC305) solder alloy. The intermetallic compound (IMC) layer evolution and shear strength of SAC305-xCe solder joints were also studied under different aging processes. Four different alloys with Ce concentrations ranging from 0 wt% to 0.5 wt% were prepared by vacuum induction melting, followed by pouring into a steel mold and cooling to room temperature. The microstructure was characterized using optical microscopy, scanning electron microscopy, X-ray diffraction analysis and electron probe microanalysis, tensile and shear tests were conducted to evaluate the mechanical properties of the solder alloys and solder joints. The results show that the addition of Ce can refine the microstructure and improve the tensile strength of SAC305 alloys. The joints fabricated with Ce-bearing alloys possessed thinner IMC layers and slower IMC growth rate, and exhibited higher shear strength. Moreover, the addition of Ce can facilitate the aggregation of nano-Ag3Sn particles on the surface of Cu6Sn5 particles at the interface between the solder alloy and the Cu substrate. These Ag3Sn particles can act as small connection skeletons and contribute to strengthening the solder joints. The best mechanical performance during both reflowing and isothermal aging was achieved for SAC305 joints with a Ce concentration of 0.15 wt%.

Interfacial reaction, ball shear strength and fracture surface analysis of lead-free solder joints prepared using cobalt nanoparticle doped flux

In this research study, we investigated the interfacial reaction and fracture modes in BGA solder joints prepared using Co nanoparticles doped flux. Solder joints were formed in a reflow oven at 240 °C for 45s and subsequently aged at 150 °C up to 1008 h. One set of aged solder joints was used in both microstructural characterization to examine the morphology and growth of interfacial IMC layer and nano-mechanical characterization to determine the hardness and Young's modulus of different phases. Another set was experimented in ball shear test to determine the average shear strength and crack paths in different failure modes. Results showed that the growth of Cu6Sn5 enhanced and that of Cu3Sn suppressed due to the profound stability of Cu6Sn5 in the presence of Co atoms. In the case of undoped condition, the direction of crack changed from a ductile failure mode to a brittle failure mode with respect to aging time. No catastrophic brittle failure mode was observed for Co doped solder joints. The mechanisms for the better fracture behavior in Co-doped solder joints are suggested and correlated to Cu6Sn5/Cu3Sn interfacial reaction.

Morphology and Shear Strength of Lead-Free Solder Joints with Sn3.0Ag0.5Cu Solder Paste Reinforced with Ceramic Nanoparticles

To date, additions of different oxide nanoparticles is one of the most widespread procedures to improve the mechanical properties of metals and metal alloys. This research deals with the effect of minor ceramic nanoparticle additions (SiO2, TiO2 and ZrO2) on the microstructure and mechanical properties of Cu/solder/Cu joints. The reinforced Sn3.0Ag0.5Cu (SAC305) solder alloy with 0.5 wt.% and 1.0 wt.% of ceramic nanoparticles was prepared through mechanically stirring. The microstructure of as-solidified Cu/solder/Cu joints was studied using scanning electron microscopy. The additions of ceramic nanoparticles suppressed the growth of the intermetallic compound layer Cu6Sn5 at the interface solder/Cu and improved the microstructure of the joints. Furthermore, measurements of mechanical properties showed improved shear strength of Cu/composite solder/Cu joints compared to joints with unreinforced solder. This fact related to all investigated ceramic nanoinclusions and should be attributed to the adsorption of nanoparticles on the grain surface during solidification. However, this effect is less pronounced on increasing the nanoinclusion content from 0.5 wt.% to 1.0 wt.% due to agglomeration of nanoparticles. Moreover, a comparison analysis showed that the most beneficial influence was obtained by minor additions of SiO2 nanoparticles into the SAC305 solder alloy.

Intermetallic growth and shear strength of SAC305/EN-Boron

Purpose This paper aims to study the effect of aging and cooling rate on the reliability of the solder joint using electroless nickel boron (EN-Boron) as a surface finish in the electronic packaging area. Design/methodology/approach EN-Boron was plated on a Cu substrate through electroless plating method. This process was followed by reflow soldering of Sn–3.0Ag–0.5Cu solder alloy on metallized Cu substrate to form a joining. Then, the specimens were cooled using different cooling mediums such as air (slow cooling) with 15.7 °C/min and water (fast cooling) with 110.5 °C/min. After that, the specimens were subjected to isothermal aging at 150°C for 0, 250 and 1,000 h. Finally, they went through a lap shear test following ASTM D1002. Optical microscope and scanning electron microscopy were used for intermetallic compound (IMC) characterization. The type of IMC formed was confirmed by field emission scanning electron microscope-energy-dispersive X-ray spectroscopy (FESEM-EDX). Findings The results showed that the IMC type changed from the combination of Ni3Sn4 and (Ni, Cu)3Sn4 after reflow soldering into fully (Ni, Cu)3Sn4 when aged for 1,000 h. The formation of (Ni, Cu)3Sn4 and Cu3Sn underneath the IMC layer played a role in reducing the shear strength of joining. Overall, water cooling was reported to provide higher shear strength of solder joint compared to air cooling medium. Originality/value The shear strength when using EN-Boron as the surface finish is comparable to the surface finish conventionally used.

The shear strength of transient liquid phase bonded Sn–Bi solder joint with added Cu particles

In a previous study, the transient liquid phase bonding of the Sn–Bi solder joints with added Cu particles was successfully performed, causing the melting point of the solder joints to increase from 139 to 201°C. However, the solder joints processed in that study contained large voids resulting in a considerable degradation in shear strength. Thus, this study aims to reduce the extent of void formation and consequently improve the shear strength of the particulate-reinforced solder joints. Two distinct phenomena causing the formation of voids at early and final stages of the TLP bonding process are discussed and thermo-compression reflow method is studied as an alternative reflow method. The proposed method was proven to be capable of reducing the formation of voids in the solder joints, resulting in an improvement in the shear strength of the as-reflowed and as thermally aged particulate-reinforced Sn–Bi solder.

Microstructure, mechanical and electrical performances of zirconia nanoparticles-doped tin-silver-copper solder alloys

The present study investigates the influence of ZrO2 nanoparticles addition on microstructure, material properties i.e., elastic moduli, creep behavior, hardness, shear strength and electrical resistivity of Sn–3.0Ag–0.5Cu (wt%)-based interconnected alloys. From microstructure observation it was revealed that in the plain Sn–Ag–Cu bulk solder a needle-shaped Ag3Sn and irregular shaped Cu6Sn5 IMC particles were formed in the elongated-like β-Sn grains. However, in the composite solder alloy, very fine needle-shaped Ag3Sn and irregular shaped Cu6Sn5 IMC particles were formed in equiaxed β-Sn grain matrix. Further, material properties like elastic moduli, hardness, creep behavior and electrical resistivity of Sn–Ag–Cu solder were improved significantly after adding the ZrO2 nanoparticle. Sn–Ag–Cu-based composite solder joints were prepared on Au/Ni-metallized Cu pad ball grid array (BGA) substrate and investigated their performance after exposing a thermal shock chamber at –40 to 90 °C. From this test, it was confirmed that the degradation behavior of plain solder joints was much faster as compared to the composite solder joints and also detected some micro-cracks at the interface and solder matrix. Further, the shear strength of plain solder joints was decreased significantly as compared to the composite solder joints.

Improving shear strength of Sn-3.0Ag-0.5Cu/Cu joints and suppressing intermetallic compounds layer growth by adding graphene nanosheets

This study investigated the effects of adding 0.1wt% of graphene nanosheets (GNSs) into Sn-3.0Ag-0.5Cu solder matrix on the growth of intermetallic compounds (IMC) layer with Cu substrates during isothermal aging at temperatures of 100, 125, 150 and 175°C for up to 7 days. The results indicated that the GNSs could provide huge diffusion barrier for the diffusion of Sn and Cu atoms in solder matrix, and the activation energy for IMC layer growth was calculated as 46.20 and 59.72kJ/mol for Sn-3.0Ag-0.5Cu solder and Sn-3.0Ag-0.5Cu-0.1GNSs composite solder, respectively. Compared with Sn-3.0Ag-0.5Cu solder joints, the IMC layer morphology transformation from scallop-type to layer-type and the IMC layer growth for composite solder joints were suppressed. After aging 7 days at 175°C, the shear strength of composite solder joints, whose IMC layer was comparatively thin, was 30% higher than that of Sn-3.0Ag-0.5Cu solder joints.

Intermetallic compounds growth suppression in ZSCB solder with RE addition on Cu substrate

Growth kinetics of triple structure (ε, γ and β) layers at ZSCB-RE/Cu interface and the effect on the shear strength of solder joints were studied at various temperatures. In particular, the role of RE addition in suppressing layers growth on Cu substrate has been determined. The results showed that the growth of ε and γ layers can be described by kinetic theory for diffusional growth with relatively higher activation energy with RE addition at ZSCB-RE/Cu interface, which effectively inhibited the growth of intermetallic compounds and lead to the improvement of the reliability of solder joints. Furthermore, the ripening suppression mechanism of ε grains at ZSCB-0.05RE/Cu interface was also discussed.

열시효 처리된 무연 솔더 볼 연결부의 충격 전단강도 평가

The present study investigates the impact shear strength of thermal aged Sn-3Ag-0.5Cu lead-free solder joints at impact speeds ranging from 0.5 m/s to 2.5 m/s. The specimens were thermal aged for 24, 100, 250 and 1000 hours at . The experimental results demonstrate that the shear strength of the solder joint decreases with an increase in the load speed and aging time. The shear strength of the solder joint aged averagely decreased by 43% with an increase in the strain rate. For the as-reflowed specimens, the mode II stress intensity factor () of interfacial IMC between Sn-3.0Ag-0.5Cu and a copper substrate also was found to decrease from to in the speed range tested here. The degradations in the shear strength and fracture toughness of the aged solder joints are mainly caused by the growth of IMC layers at the solder/substrate interface.

Aging resistance and mechanical properties of Sn3.0Ag0.5Cu solder bump joints with different bump shapes

The effects of bump shape on the aging resistance and mechanical properties of Sn3.0Ag0.5Cu (SAC) solder bump joints were investigated by high-temperature aging test and shear test. Three different SAC solder bump joints with barrel type, cylinder type, and hourglass type, respectively, were provided by controlling solder process. The results indicate that as the bump volume decreases from barrel bump to hourglass bump in the reflow, the thickness growth rate of intermetallic compounds (IMCs) between different solder joints and Cu substrates in the isothermal aging of 150 °C decreases. And the change of shear strength of hourglass interconnection solder joint with the increase in temperature is the minimum in the three interconnection solder joints. Thus, as the solder dosage decreases properly, hourglass interconnection solder joint is obtained, which is avail to enhance the solder joint reliability at the high-temperature aging and the ability to adapt to the change of environment temperature suddenly.

Effects of Ag content on the reliability of LED package component with Sn–Bi–Ag solder

The effects of Ag content on the mechanical and electrical properties of the Sn–58Bi solder joints in light emitting diode (LED) package were studied. The Sn–58Bi, Sn–57.6Bi–0.4Ag and Sn–57Bi–1Ag solder were used as solder joints. The LED package was bonded on the printed circuit board (PCB) with the organic solderability preservative (OSP) surface finish, and then it was aged at 85 °C for 100, 300, 500 and 1000 h, respectively. In order to evaluate the mechanical and electrical properties, the shear test was conducted and the change of current versus voltage was measured. The shear strength and electrical conductivity of solder joints decreased with an increasing aging time. With an addition of 1.0 wt% Ag, the shear strength was improved and higher than those of other solder joints. The microstructure and composition of the solder joints were investigated with a scanning electron microscope, an energy dispersive spectrometer and an electron probe micro analyzer. The Cu6Sn5 intermetallic compounds (IMCs) formed between solder and OSP surface finished Cu pad of PCB. The thickness of the IMCs increased with an increasing aging time. By an addition of 0.4 wt% Ag, fine Ag3Sn particles were dispersed inside the solder matrix and large-sized primary Ag3Sn IMCs were formed with 1.0 wt% Ag addition.

Influence of intermetallic growth on the mechanical properties of Zn–Sn–Cu–Bi/Cu solder joints

The formation of intermetallic reaction layers and their influence on shear strength and fractography was investigated between the Zn–Sn–Cu–Bi (ZSCB) and Cu substrate during the liquid state reaction at 450 °C after 10–90 s. Results showed that reliable solder joints could be obtained at 450 °C after 15–30 s of wetting, accompanied by the creation of scallop ε-CuZn5, flat γ-Cu5Zn8 and β-CuZn intermetallic layers in ZSCB/Cu interface. However, with excess increase of soldering time, a transient intermetallic ε-CuZn4 phase was nuclear and grew at ε-CuZn5/γ-Cu5Zn8 interface, which apparently deteriorated the shear strength of solder joints from 76.5 MPa to 51.6 MPa. The sensitivity of the fracture proportion was gradually transformed from monotonic ε-CuZn5 to the mixture of ε-CuZn4 and ε-CuZn5 intermetallic cleavage. Furthermore, the growth mechanism of ε-CuZn4 intermetallic phase at the ZSCB/Cu interface was discussed.