Tensile Strength Of Solder Joints Research Articles

Improved microstructure and strength of Sn-Ag-Cu/Cu solder joint with Mo nanoparticles addition

A new type of lead-free composite solder has been prepared by adding Mo nanoparticles in Sn3.0Ag0.5Cu solder. Tensile strength tests were conducted on Sn3.0Ag0.5Cu/Cu joint and composite solder/Cu joints. The results indicated that the addition of Mo nanoparticles markedly improved the tensile strength of solder joint. when Mo concentration was between 0 and 1%, with the increase of Mo concentration, the tensile strength increased significantly. EBSD (Electron Back Scatter Diffraction) analysis of microstructure was conducted. It was concluded that Mo could significantly increase grain boundary length and dislocation density, reduce the size of the β-Sn phase.

Effect of multi-walled carbon nanotubes on the microstructure and properties of Sn-58Bi solder alloys

The influence of multi-walled carbon nanotube (MWCNT) content on the melting properties, wettability, microstructure, and intermetallic compounds (IMCs) of Sn-58Bi-xMWCNT (x = 0, 0.01, 0.02, 0.03, 0.05, and 0.10 wt.%) and the effects of MWCNT on the tensile strength of Cu/Sn-58Bi-xMWCNT/Cu solder joint were analyzed. The results show that MWCNT addition at a small trace amount into Sn-58Bi solder could increase the spreading area of Sn-58Bi solder, refine the solder matrix microstructure, inhibit the growth of interfacial IMCs, and significantly improve the tensile strength of Sn-58Bi solder joints. However, the melting point and melting range remained the same or slightly changed. The wettability of Sn-58Bi alloys increased first and then decreased with the addition of MWCNT. The spreading area and the tensile strength of solder joint were the maximum when the MWCNT content was 0.01 wt.%, and they were 42.23 mm2 and 50.07 MPa, respectively. The reason may be related to the improved microstructure of solder alloys and the morphology of IMCs due to MWCNT addition at trace level.

Fracture pattern evolution of SnAgCu–SnPb mixed solder joints at cryogenic temperature

The effect of cryogenic temperatures on the mechanical properties and fracture mechanism of SnAgCu–SnPb mixed solder joints was investigated. The results showed that the tensile strength of mixed solder joints first increased with the increase of Pb content and reached its maximum at 22.46 wt.% Pb; subsequently, it decreased as Pb content increased. However, cryogenic temperatures improved the tensile strength of the solder joints. Both Pb content and cryogenic temperature caused the fracture mode of the mixed solder joints to change; however, temperature remained the main influencing factor. As the temperature fell from 298 to 123 K, the failure pattern in the solder joints transformed from ductile fracture to quasi-ductile fracture to quasi-brittle fracture and finally, to brittle fracture.

Microstructure growth and tensile strength of Cu/Sn3.0Ag0.5Cu/Cu solder joints

The reliabilities of solder joints, which are closely related to the microstructure and mechanical properties of solder joints, are important for electronic packaging. In this work, the growth behaviors of microstructure in Sn3.0Ag0.5Cu/Cu solder joints, including intermetallic compounds and Sn dendrites, were investigated when different cooling methods—quenched in water, cooling in air, and cooling in a furnace after reflow—were used. Local enrichment of element was observed with the quadrant backscattering diffraction and energy dispersive spectrometer in the sample quenched in water. The growth mechanism of microstructure in Sn3.0Ag0.5Cu/Cu solder joint was discussed. The results of tensile tests indicated that the enrichment of element induced a hardening effect. Moreover, plate-like Ag3Sn compounds and oversize Sn dendrites were apt to reduce the tensile strength of solder joint.

Size effect on microstructure and tensile properties of Sn3.0Ag0.5Cu solder joints

In the current study, the size effect on microstructure and tensile property of Sn3.0Ag0.5Cu (SAC305) solder joint is investigated. Experiments were performed to solder joints with thickness from 50 μm to 2 mm. The intermetallic compound (IMC) growth rate of solder joints is found to be dependent on the size of solder joints. After soldering procedure, the IMC of smaller size solder joints is thinner than that of larger size solder joints. It is also found that the average grain size of IMC increases with decreasing of the joint size. To better understand the difference of IMC growth during solid-state and liquid-state thermal aging, experiments were performed at 210 and 300 °C, respectively. IMC thickness of solder joints after 210 and 300 °C of thermal aging was measured. It is found that the size effect on IMC growth rate at solid-state and liquid-state is different. The IMC growth rate of smaller size solder joints is higher than larger size solder joints under solid-state thermal aging. Under liquid-state reaction, the IMC growth rate of smaller size solder joints is slower. ‘H’ type and hexagonal prism of Cu6Sn5 were observed in 2 and 1 mm thickness size solder joint, respectively. Fewer Cu6Sn5 prism was found in 50 μm thickness solder joints. Tensile strengths of solder joints with different sizes were measured. The solder joints showed ductile to brittle fracture transition with the decreasing of joints thickness. The H-field fracture criterion is employed to predict the tensile strength of Sn3.0Ag0.5Cu solder joints with different thickness.

Mechanical Behavior of Sn-3.0Ag-0.5Cu/Cu Solder Joints After Isothermal Aging

The tensile impact behavior of lead-free Sn-3Ag-0.5Cu/Cu solder joints aged at 413 K and 453 K for times ranging from 24 h to 1000 h has been investigated in this study. The activation energy for growth of the intermetallic compound (IMC) layer was estimated and compared with literature values. Additionally, the tensile strength of solder joints with IMC thickness of 17.6 μm was found to be more sensitive to the strain rate as compared with solder joints with thinner IMC layers. Equations representing the relationships among the effective stress, strain rate, aging time, and aging temperature as well as IMC thickness were established using matrix laboratory (MATLAB) software. These equations show that the tensile strength decreases with increase in the IMC thickness to about 8 μm, after which it becomes nearly constant when the IMC thickness is between approximately 8 μm and 14 μm, before decreasing significantly when the IMC thickness exceeds 14 μm. The main reason for these characteristics was excessive increase in the IMC thickness of solder joints, causing a change in the stress concentration of the tensile load from the protruding region to the inside of the IMC layer at the same tested strain rate.

Effect of Y2O3 nanoparticles addition on the microstructure and tensile strength of Cu/Sn3.0Ag0.5Cu solder joint

A sort of composite solder was produced by adding Y2O3 nanoparticles in Sn3.0Ag0.5Cu solder. The microstructure and tensile strength of solder joint were investigated. It was found that the size of intermetallic compounds and tensile strength of solder joint were notably influenced by the nanoparticles. The growth behaviors of intermetallic compounds Ag3Sn and Cu6Sn5 were suppressed due to the addition of Y2O3 nanoparticles. The tensile test results revealed that the strength of composite solder joint was higher than that of solder joint without nanoparticles addition. It is indicated that Y2O3 nanoparticles should play important roles in strengthening of joint by hampering dislocation movement.

Size and constraint effects on mechanical and fracture behavior of micro-scale Ni/Sn3.0Ag0.5Cu/Ni solder joints

Abstract Solder joints are generally regarded as the weakest part in packaging systems and electronic assemblies in modern electronic products and devices. In this study, both experimental and finite element methods were used to characterize the mechanical behavior of micro-scale Ni/Sn3.0Ag0.5Cu/Ni sandwich-structured joints with different thickness-to-diameter ratios (R varying from 1/3 to 1/12) under quasi-static tension loading using a dynamic mechanical analyzer (DMA). Experimental results show that crack initiation and propagation in the solder matrix occur in a typical ductile manner. Compared with Cu/Sn3.0Ag0.5Cu/Cu sandwich-structured solder joints, Ni/Sn3.0Ag0.5Cu/Ni solder joints have much higher tensile strengths due to the dispersion strengthening effect through the fine Ag3Sn particles. With decreasing R, both stiffness and tensile strength of solder joints increase obviously with decreasing coefficient of stress state and damage equivalent stress. Moreover, results of quantitative fractographic analysis by SEM and EDS display three fracture modes with decreasing R. Joints with R≥1/4 all fail by ductile fracture, those with R=1/6 fail by either ductile fracture or mixed ductile and brittle fractures, and for joints with R=1/12, brittle fracture is dominant. Furthermore, results obtained have also shown that the crack growth driving forces, KI and KII, as well as the strain energy release rate, GI, in the Ni3Sn4 layer and at the Ni3Sn4/Ni interface, increase significantly with decreasing R. Hence, under tensile loading the fracture mode of solder joints changes from ductile to brittle as R is decreased.

Development of ternary Mg based alloy for soldering of AZ31B magnesium alloy

Two kinds of ternary Mg based alloys were designed to join the AZ31B magnesium alloy plates by high frequency induction soldering with argon shielding gas. The microstructures and properties of the filler metals and joints were investigated by SEM, X-ray diffraction, differential scanning calorimetry, spreading test and tensile test. The results have shown that the microstructures of Mg–31·5Al–10Sn filler metal mainly consist of Mg17Al12, Mg2Sn and a trace amount of α-Mg phases, while the microstructures of Mg–29·5Zn–1Sn filler metal include α-Mg phase and Mg7Zn3 with a trace of α-Mg and Mg2Sn phases. Both of the filler metals have narrow melting zones; however, the spreading area of the Mg–31·5Al–10Sn filler metal is much larger than that of the Mg–29·5Zn–1Sn filler metal on the AZ31B base metal. The average tensile strength of solder joints with Mg–31·5Al–10Sn filler metal is a little higher than that of the latter solder joints with Mg–29·5Zn–1Sn filler metal.

Tensile properties of Cu/Sn–58Bi/Cu soldered joints subjected to isothermal aging

The effects of isothermal aging on the tensile properties of Cu/Sn–58Bi/Cu soldered joints were investigated. Experimental results show that the scallop-shaped Cu6Sn5 and planar Cu3Sn formed at the interface between solder and Cu substrate during reflowing and aging. The thickness of the intermetallic compounds (IMCs) increased almost linearly with the square root of aging time, and aging at 120 °C yielded a much faster growth of the IMCs layer than that of samples aged at 100 °C. The IMCs growth rate constants were 6.02 × 10−18 and 1.85 × 10−18 m2 s−1 for solder joints aged at 120 and 100 °C, respectively. The tensile strength of the Sn–58Bi/Cu soldered joints decreased slightly with the increasing aging time and temperature. The failure was dominated by the mixed fracturing in both the solder and the Cu6Sn5 grains irrespective of their thermal aging conditions. However, the fracture pattern tended to transform from ductile to brittle with increasing aging time and temperature. The Bi segregation and voids were observed around the Cu/Cu3Sn interface as the long term aging at high aging temperature was carried out, which resulted in reduction of tensile strength of solder joints.

Effects of the intermetallic compound microstructure on the tensile behavior of Sn3.0Ag0.5Cu/Cu solder joint under various strain rates

The effects of the intermetallic compound (IMC) microstructure and the strain rate on the tensile strength and failure mode of Pb-free solder joints are investigated. The samples of Sn3.0Ag0.5Cu/Cu solder joints are aged isothermally at 150°C for 0, 72, 288 and 500h, and the thickness of the IMC layer and the roughness of the solder/IMC interface are measured and used to characterize the microstructure evolution of the IMC layer. The tensile tests of the aged solder joints are conducted under the strain rates of 2×10−4, 2×10−2 and 2s−1. The results indicate that both the thickness and roughness of the IMC layer have influence on the strength and failure mode of the solder joint. With the increase of the aging time, the thickness of the IMC layer increases and the roughness of the solder/IMC interface decreases, as a result, the tensile strength of the solder joint decreases and the dominant failure mode migrates from the ductile fracture in the bulk solder to the brittle fracture in the IMC layer. There is a positive correlation between the tensile strength of the solder joint and the stain rate applied during the test. With the increase of the strain rate, the failure mode migrates from the ductile fracture in the bulk solder to the brittle fracture in the IMC layer.

Effect of strain rate on interfacial fracture behaviors of Sn-58Bi/Cu solder joints

The interfacial reactions and mechanical properties of Sn-58Bi/Cu solder joints reflowed at different temperatures ranging from 180 to 220 °C for constant time of 10 min were investigated with various strain rates. Only a continuous Cu6Sn5 intermetallic compound (IMC) layer was formed at the interface between the Sn-58Bi solder and the Cu substrate during reflow. The equivalent thickness of the Cu6Sn5 layer increased with increasing reflow temperature, and the relationship between Cu6Sn5 layer equivalent thickness (X) and reflow temperature (T) is obtained by using method of linear regression and presented as \( X = 0.01 \times T + 0.187 \). For the tensile property, the tensile strength of solder joint gradually decreased as the reflow temperature it increased, whereas it increased with increasing strain rate. Moreover, the fracture behavior of Sn-58Bi/Cu solder joint indicated the ductile fracture with low strain rate (5 × 10−4 and 1 × 10−3 s−1), while toward brittle fracture with high strain rate (2 × 10−3 and 1 × 10−2 s−1). The strain rate sensitivities of the solder joints fractured with various modes were also investigated, and it is found that the tensile strength of the solder is more sensitive to the strain rate than that of the IMC layer.

In-situ measurement of solder joint strength in board-mounted chip-scale packages using a quantitative laser spallation technique

A previously developed laser spallation (LS) technique for measuring the interface strengths of planar films is modified to determine the interfacial tensile strengths of solder joints, in situ, in board-mounted chip-scale packages (CSPs). The new technique is demonstrated on packages with bare Cu pads and Pb-free solders. The solder/pad interface strength is determined by first using a laser-generated stress wave to separate the geometrically heterogeneous interface, in situ, and then quantifying the failure stress by a combination of interferometry and wave mechanics simulation. The solder to pad interfacial strengths were found to be 705 ± 102, 510 ± 71, and 369 ± 55 MPa for packages stressed by baking at 150 °C for 0, 48, and 100 h, respectively. The interface strengths were found to be roughly proportional to the critical laser energies for separation of solder joints. Thus, it may suffice to use the critical laser energy as a parameter for the purposes of material selection and solder joint quality inspection during manufacturing. The quantitative capability of the LS test for testing board-level packages now provides an opportunity to enhance the board-level drop test that is widely conducted in the industry today.

Damage accumulation and fracture in aged lead-free Sn-3.5Ag solder joints

Owing to concerns regarding the environment and health, lead-containing solders have now been eliminated and substituted by their lead-free counterparts. Hence, the present article is devoted to the clarification of their mechanical strength and reliability. Lead-free Sn-3.5Ag solder joints of various thicknesses were exposed to different thermal treatments in order to study the effect of material changes due to ageing. Thereafter, tensile tests were performed showing a pronounced decrease of strength after excessive heat treatment. The theoretical analysis is facilitated by simulations according to the finite element method. Thereby, the influence of material changes in the solder could be separated from the effect of thermal recovery in the copper base material. Crack initiation in the solder is described by an approach of damage mechanics derived from a thermodynamic framework. Excessive heat treatment leads to Kirkendall voids reducing the ultimate tensile strength of solder joints. Therefrom, one can estimate the reduction of tensile strength as a function of time and temperature.

Evaluation of the joint strength between Sn–3.0Ag–0.5Cu solders and Cu substrate at high strain rates

A lack of study on the dynamic tensile strengths of Sn-based solder joints at high strain rates was the motivation for the present study. A modified miniature Chapy impact testing machine instrumented with an impact sensor was built to quantitatively evaluate the dynamic impact strength of a solder joint under tensile impact loading. This study evaluated the tensile strength of lead-free solder ball joints at strain rates from 1.8×103s−1 and 8.5×103s−1. The maximum tensile strength of the solder ball joint decreases as the load speed increases in the testing range. This tensile strength represented that of the interface because of the interfacial fracture site. The tensile strengths of solder joints between Sn–3.0Ag–0.5Cu and copper substrate were between 196.2MPa and 72.1MPa in the high strain range. The brittle interfacial fracture was likely to occur primarily in the waist of the protuberant Cu6Sn5 intermetallic layer. The fracture toughness values of interfacial IMC (intermetallic compound) between Sn–3.0Ag–0.5Cu and copper substrate were between 1.8MPam0.5 and 1.0MPam0.5 in the speed range tested.

Effect of gap distance on tensile strength of preceramic base metal solder joints.

Background and aims In order to fabricate prostheses with high accuracy and durability, soldering techniques have been introduced to clinical dentistry. However, these prostheses always fail at their solder joints. The purpose of this study was to evaluate the effect of gap distance on the tensile strength of base metal solder joints. Materials and methods Based on ADA/ISO 9693 specifications for tensile test, 40 specimens were fabricated from a Ni-Cr alloy and cut at the midpoint of 3-mm diameter bar and placed at desired positions by a specially designed device. The specimens were divided into four groups of 10 samples according to the desired solder gap distance: Group1: 0.1mm; Group2: 0.25mm; Group3: 0.5mm; and Group4: 0.75mm. After soldering, specimens were tested for tensile strength by a universal testing machine at a cross-head speed of 0.5mm/min with a preload of 10N. Results The mean tensile strength values of the groups were 162, 307.8, 206.1 and 336.7 MPa, respectively. The group with 0.75-mm gap had the highest and the group with 0.1-mm gap had the lowest tensile strength. Bonferroni test showed that Group1 and Group4 had statistically different values (P=0.023), but the differences between other groups were not sig-nificant at a significance level of 0.05. Conclusion There was no direct relationship between increasing soldering gap distance and tensile strength of the solder joints.

Effect of stand‐off height on the microstructure and mechanical behaviour of solder joints

PurposeThe purpose of this paper is to investigate the effect of stand‐off height (SOH) on the microstructure and mechanical behaviour of the solder joints in high density interconnection.Design/methodology/approachCu/Sn/Cu solder joints with 100, 50, 20 and 10 μm SOH are prepared using a reflow process. The microstructures and compositions of solder joints are observed and analyzed by scanning electron microscopy. Tensile testing is carried out to investigate the mechanical properties of the solder joints.FindingsThe SOH has a significant effect on the microstructure and mechanical behaviour of Cu/Sn/Cu solder joints. The thickness of the intermetallic compound (IMC) decreases with the reducing SOH; however, their corresponding IMC proportion increases. Meanwhile, the Cu concentration in the solder bulk experiences a marked increase, and the dissolved Cu exists in the forms of a solid solution and Cu‐rich particles at the grain boundary. Because of the higher strain rate and more dissolved Cu in the solder bulk with the reducing SOH, the ultimate tensile strength of solder joints is enhanced. When the SOH reduces to 10 μm, there is only one grain in height in the bulk, and a fracture in the IMC layer occurs. According to the mass balance of substance, a model is established to semi‐quantitatively calculate the consumed Cu thickness, and it is found that the consumed Cu thickness decreases with the reducing SOH.Originality/valueThe paper offers insights into the microstructural and mechanical property changes of the solder joints with the reducing SOH.

Fracture mechanism and strength-influencing factors of Cu/Sn–4Ag solder joints aged for different times

Tensile properties and fracture mechanisms of Cu/Sn–4Ag solder joints aged at 180 °C for different times were investigated at the strain rates of 1.25 × 10 −4 s −1 and 1.25 × 10 −1 s −1. At the low strain rate, it was found that the tensile strength of the solder joints decreased with increasing aging time in principle, though the tendency was not monotonously at the early stage of aging; and all the solder joints had similar tensile curves but different fracture morphologies and fracture processes. At the high strain rate, tensile strength of the solder joints was much higher and decreased monotonously with increasing aging time, with identical fracture process and fractographies. Evolution of the Cu/Sn–4Ag interfacial morphology during aging process and the effect of aging on tensile property of the Sn–4Ag alloy were also involved for further analysis. Based on the experimental results and observations, the fracture processes were revealed and some factors controlling the tensile strength of solder joints were discussed qualitatively.

Rate dependent strengths of some solder joints

The shear strengths of three lead-free solder joints have been measured over the range of loading rates 10−3 to ∼105 mm min−1. Binary (SnAg), ternary (SnAgCu) and quaternary (Castin: SnAgCuSb) alloys have been compared to a conventional binary SnPb solder alloy. Results show that at loading rates from 10−3 to 102 mm min−1, all four materials exhibit a linear relationship between the shear strength and the loading rate when the data are plotted on a log–log plot. At the highest loading rate of 105 mm min−1, the strengths of the binary alloys were in agreement with extrapolations made from the lower loading rate data. In contrast, the strengths of the higher order alloys were found to be significantly lower than those predicted by extrapolation. This is explained by a change in failure mechanism on the part of the higher order alloys. Similar behaviour was found in measurements of the tensile strengths of solder joints using a novel high-rate loading tensile test. Optical and electron microscopy were used to examine the microstructures of interest in conjunction with energy dispersive x-ray analysis for elemental identification. The effect of artificial aging and reflow of the solder joints is also reported.

Comparison of tensile strength of solder joints by infrared and conventional torch technique

Fabrication of a fixed partial denture may require a soldering step. This study compared soldering by a conventional torch procedure with an infrared soldering technique. Comparisons were made for tensile strength, porosity, and time efficiency between the two methods. No significant difference was found in ultimate tensile strength between the two types of solder joints and the nonsoldered control samples. Random samples photographed with a scanning electron microscope revealed no difference in joint porosity between the two techniques. Torch soldering took consistently less time that infrared soldering.