Shear Strength Of Solder Joints Research Articles

Electroless Silver Coating on Copper Microcones for Low-Temperature Solid-State Bonding

A low-temperature solid-state bonding technology using silver-coated Cu microcones and Sn-3.0Ag-0.5Cu (wt.%) solder for three-dimensional (3D) packaging is presented. Electroless silver coating on the surfaces of copper microcones effectively reduces oxide layer growth and significantly enhances the solder joint shear strength from an average of 33.5 MPa to 43.4 MPa. Low-temperature thermocompression bonding at 463 K in ambient air was achieved using silver-coated Cu microcones, with no voids found along the bonded interface. Microscopic observation revealed that the microcones were completely inserted into the soft solder. Probable mechanisms for this bonding process are proposed and discussed.

Formation and evolution of intermetallic compounds between the In-3Ag solder and Cu substrate during soldering

The formation and growth of intermetallic compounds (IMCs) have an important effect on the reliability of the solder. In this paper, formation and evolution of IMCs between the In-3Ag solder and Cu substrate were systematically explored for different soldering time ranged from 1 to 30 min. The interface soldered for 1 or 2 min was only composed of (Ag,Cu)In2 IMCs. When the soldering time extended to 4 min, a new (Cu,Ag)11In9 IMCs layer appeared under the (Ag,Cu)In2 IMCs layer. When the soldering time exceeded 5 min, the (Ag,Cu)In2 layer was completely decomposed and replaced by the (Cu,Ag)11In9 layer. Meanwhile, the growth of (Ag,Cu)In2 and (Cu,Ag)11In9 intermetallic layers during jointing were all diffusion-controlled and the growth rates of them are 0.398 and 0.507 µm2/s, respectively. Furthermore, shear strength results showed that the shear strength of solder joints decreased with soldering time extending, and those decrease from 5.64 MPa after soldered for 1 min to 3.07 MPa when the soldering time extended to 30 min. The fracture mode also changed from typical ductile fracture mode to mixed ductile–brittle fracture mode with soldering time extending.

Effect of nano Al2O3 particles doping on electromigration and mechanical properties of Sn–58Bi solder joints

In the present study, the effect of Al2O3 nanoparticles on performances of Sn–58Bi solder were investigated in aspects of electro-migratio, shear strength and microhardness. The experimental results show that the Al2O3 nanoparticles significantly improved microstructure and mechanical performances of solder joints. With the addition of 0.5wt% Al2O3, the intermetallic compounds (IMC) reduced from 2.5μm to 1.27μm after 288 aging hours at 85°C. Furthermore, after electromigration test under a current density of 5×103 A/cm2 at 85°C, Bi-rich layers formed at the anode side of both Al2O3 doped and plain solder. Moreover, the addition of Al2O3 nanoparticles reduced the mean thickness of Bi-rich layer. In addition, the growth rate of the IMC layer of Al2O3 doped solder decreased by 8% compared with the plain solder. Besides, the Al2O3 doped solder exhibited better performance than plain solder in microhardness after different aging times. While, the addition of Al2O3 significantly impeded the degradation of the shear strength of solder joint after aging for 48 and 288h. Furthermore, it was worth noting that the fracture surface of doped solder showed a typical rough and ductile structure. However, plain solder exhibited a relatively smooth and fragile surface.

Ball shear strength and fracture modes of lead-free solder joints prepared using nickel nanoparticle doped flux

Miniaturization and the need for the replacement of lead (Pb) based solders in microelectronic devices raise concerns over their reliability in the recent years. Particularly, the rapid growth of interfacial intermetallic compound (IMC) layers in Pb free solders can lead to brittle fracture. A novel nanoparticle doped fluxing method was used to prepare ball grid array solder joints between Sn-3.0Ag-0.5Cu solder balls and Cu pads. In this method, nickel nanoparticles were mixed with a water soluble flux prior to its use. The shear strength and fracture modes of the resulting solder joints were investigated as a function of aging time. Results showed that IMC layer growth was suppressed in solder joints prepared with 0.1 wt.% Ni doped flux. The average shear strength was marginally higher for solder joints prepared using 0.1 wt. % Ni doped flux compared with the joints prepared with undoped flux. Samples prepared using Ni doped flux showed a better resistant against brittle fracture for up to 30 days of aging. Open image in new window

Effect of Bi Addition on Microstructures, Properties and Interfacial Intermetallic Compound Growth of Low-Ag Sn-Cu Lead-Free Solder

The research on a new low-Ag lead-free solder has become a hot spot in the field of electronic packaging. In this work, the effects of Bi addition on microstructure, melting temperature, wettability of low-Ag solder, shear strength of solder joint and the growth of interfacial intermetallic compound (IMC) before and after thermal cycling were investigated. A moderate amount of Bi element resulted in the microstructural refinement and melting temperature reduction of Sn-0.2Ag-0.7Cu solder. Wetting test results showed that a small amount of Bi produced the significant effect on improving the wettability. In addition, it is shown that the thickness of interfacial IMC during thermal cycling decreased first and then increased; the shear strength of solder joint increased with the increase of Bi.

Effects of Sn element on microstructure and properties of Zn–Cu–Bi–Sn high-temperature solder

The microstructures and properties of the Zn–Cu–Bi–Sn (ZCBS) high-temperature solders with various Sn contents were studied using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that the increase of Sn content can both decrease the melting temperature and melting range of ZCBS solders and it can also effectively improve the wettability on Cu substrate. The shear strength of solder joints reaches a maximum value with the Sn addition of 5% (mass fraction), which is attributed to the formation of refined β-Sn and primary ɛ-CuZn5 phases in η-Zn matrix. However, when the content of Sn exceeds 5%, the shear strength decreases due to the formation of coarse β-Sn phase, which is net-shaped presented at the grain boundary.

A Study on the Effect of Ageing and Intermetallic Compound Growth on the Shear Strength of Surface Mount Technology Solder Joints

The effect of ageing and intermetallic compound formation on the surface mount solder joints and its shear strength behavior under extreme mechanical and thermal conditions have been discussed in this paper. The specimens used are solder paste (Sn3.8Ag0.7Cu), bench marker II printed circuit boards (PCB), resistors 1206 and the fabrication of solder joints makes use of conventional surface mount technology (SMT). Reflow process was carried out at a peak temperature of 250 °C and the test samples were exposed to isothermal ageing at a constant temperature of 150 °C for a period of 600 h. Shear test was conducted on the PCB’s. The shear strength of the solder joints rapidly increased during isothermal ageing to a certain time period and then started decreasing. Field emission scanning electron microscopy (FESEM) micrograph of the solder joint and energy dispersive X-ray (EDX) was performed on the solder sample to verify the formation of intermetallic compounds.

IMC growth and shear strength of Sn–Ag–Cu/Co–P ball grid array solder joints under thermal cycling

Co–P films with P contents of 4.0 and 8.0 at.% were electroplated on printed circuit boards and used as surface finish of ball grid array (BGA) packages. Sn–3.0 wt% Ag–0.5 wt% Cu (SAC305) solder balls were reflowed on the Co–P finish to form SAC/Co–P solder joints. The morphology and growth of intermetallic compounds (IMCs) in SAC/Co–P joints under thermal cycling were systematically analyzed, and the effects of IMCs on shear strength and fractured surface of the joints were studied. SAC/Cu BGA solder joints were also prepared as a comparison. It was found that CoSn3 and (Cu, Co)6Sn5 grew at the interface of SAC/Co–4 at.% P solder joints during thermal cycling. The shear strength of SAC/Co–4 at.% P joints exceeded that of SAC/Cu joints after 100 thermal cycles, because the granule size of (Cu, Co)6Sn5 was smaller than that of Cu6Sn5 and no Kirkendall void existed at the interface of SAC/Co–4 at.% P joints. For SAC/Co–8 at.% P joints, a layer of smooth and void-free Co–Sn–P formed at the interface, and the shear strength of SAC/Co–8 at.% P joints increased by 8.4 % in comparison with that of SAC/Cu joints after 300 cycles. In addition, the fractured surface of three kinds of joints after thermal cycling was examined. The experimental data demonstrated that Co–P surface finish enhanced the shear strength of solder joints after thermal cycling and improved the reliability of BGA packages.

Microstructure and shear strength of Sn37Pb/Cu solder joints subjected to isothermal aging

The effects of isothermal aging on the microstructure and shear strength of Sn37Pb/Cu solder joints were investigated. Single-lap shear solder joints of eutectic Sn37Pb solder were aged for 1–10days at 120°C and 170°C, respectively, and then loaded to failure in shear with a constant loading speed of 5×10−3mm/s. The growth of the interfacial Cu–Sn intermetallic compounds (IMC) layer (Cu6Sn5+Cu3Sn) of Sn37Pb/Cu solder joints subjected to isothermal aging exhibited a linear function of the square root of aging time, indicating that the formation of Cu–Sn IMC was mainly controlled by the diffusion mechanism. And the diffusion coefficient (D) values of IMC layer were 1.07×10−17 and 3.72×10−17m2/s for aged solder joints at 120°C and 170°C, respectively. Shear tests results revealed that as-reflowed solder joint had better shear strength than the aged solder joints and the shear strength of all aged solder joints decreased with increasing aging time. The presence of elongated dimple-like structures on the fracture surfaces of these as-reflowed or aged for short time solder joints were indicative of a ductile failure mode. As aging time further increased, the solder joints fractured in the mixed solder/IMC mode at the solder/IMC interface.

Effect of Reflow Profile Parameters on Surface Mount Chip Resistor Solder Joint Shear Strength

The focus of this study is on the effect of reflow parameters on the joint shear strength. Eight reflow profiles were developed using four factors at two levels of Taguchi design of experiment for 1206, 0805 and 0603 chip resistors. Normal probability and main effect plots were used to provide a complete profile of the effect of reflow parameters on the chip resistor solder joint shear strength. The Normal Probability plots show effect of some reflow parameters on shear strength. Some data points did not fall on the best fit line.These outliers indicate parameter effects. The 1206 chip resistor shear strength value of 74.85N lies outside the best fit line indicating that some of the parameters are critical and significantly affect the response value. The results of the Main Effect plots help identify the unknown critical parameters in the probability plots. It indicates that the shear strength of 1206 chip resistor depends on the peak temperature, time above liquidus and preheat slope but not on cooling rate. In the case of the 0805 chip resistor, there were no exceptional departures from the line fitted to the data. It can be assumed that the factors and the levels considered here have no significant effect on the response. The normal probability plot of the 0603 chip resistor shows that the 46.68N shear strength lies outside the fitted line. This means that the factors and settings (run 3) can be further modified to improve the response. The factors which affected the 0603 resistor from the main effect plot are preheat slop and cooling rate.The results of the 1206 chip resistor show the highest shear force of 74.8 N using a peak temperature setting of 230°C (low level). The 0805 and 0603 chip resistors recorded the highest shear forces of 68.32N and 46.48 respectively using a temperature of 245°C (high level). The higher temperature may have contributed to the lower shear force due to the growth of brittle intermetallic compound in the case of the 0805 and 0603 chip resistors.

Interfacial intermetallic compound growth and shear strength of low-silver SnAgCuBiNi/Cu lead-free solder joints

The growth rule of the interfacial intermetallic compound (IMC) and the degradation of shear strength of Sn-0.8Ag-0.5Cu-2.0Bi-0.05Ni (SACBN)/Cu solder joints were investigated in comparison with Sn-3.0Ag-0.5Cu (SAC305)/Cu solder joints aging at 373, 403, and 438 K. The results show that (Cu1−x,Nix)6Sn5 phase forms between the SACBN solder and Cu substrate during soldering. The interfacial IMC thickens constantly with the aging time increasing, and the higher the aging temperature, the faster the IMC layer grows. Compared with the SAC305/Cu couple, the SACBN/Cu couple exhibits a lower layer growth coefficient. The activation energies of IMC growth for SACBN/Cu and SAC305/Cu couples are 111.70 and 82.35 kJ/mol, respectively. In general, the shear strength of aged solder joints declines continuously. However, SACBN/Cu solder joints exhibit a better shear strength than SAC305/Cu solder joints.

Effects of In/Ce to Sn-3.5Ag Lead-Free Solder on Microstructures and Properties

The Sn-3.5Ag based lead-free electronic solder doped with element In /Ce were prepared respectively using a smelting method with protection by molten salt (SMPMS). The effects of In addition and Ce addition on microstructure, melting point and wettability of Sn-3.5Ag solder were investigated comparatively. And the effects of addition on the intermetallic compound (IMC) layer formed at solder/Cu substrate interface and the shear strength of solder joint were also studied. The results showed that appropriate In or Ce addition can refine Ag3Sn grains and improve the shear strength of solder joint. Element In can significantly reduce the melting point, narrow the melting range of the solder alloy and improve wettability on Cu substrate. When the content of In was 3%, the spreading area was the largest and the wettability was the best. The addition of Ce can efficiently reduce the thickness of the IMC layer grown at the solder/Cu substrate interface and improve the shear strength of solder joint. When the content of Ce was 0.5%, the solder joint had the minimum average IMC thickness and the maximum shear strength.

Solder Joint Encapsulant Adhesive – LGA High Reliability And Low Cost Assembly Solution

More and more Land Grid Array (LGA) components are being used in electronic devices such as smartphones, tablets and computers. In order to enhance LGA mechanical strength and reliability, capillary flow underfill is used to improve reliability. However, due to the small gap, it is difficult for capillary underfill to flow into the LGA at SMT level. Due to cost considerations, there are usually no pre-heating underfill or cleaning flux residue processes at the SMT assembly line. YINCAE solder joint encapsulant SMT 256 has been successfully used with solder paste for LGA assembly. Solder joint encapsulant is used in in-line LGA soldering process with enhanced reliability. It eliminates the underfilling process and provides excellent reworkability. The shear strength of solder joint is stronger than that of underfilled components. The thermal cycling performance using solder joint encapsulant is much better than that using underfill. Bottom IC of POP has been studied for further understanding of LGA assembly process parameters. All details such as assembly process, drop test and thermal cycling test will be discussed in the full paper.

Comparative analysis of surface finishes of printed circuit boards

This article describes surface finishes which are the most common and well-established at present time at the assembly operations of electronic products. The process of further improvement of these finishes is continuing, and actively develops unlike their less common counterparts - different finishes based on palladium and galvanically deposited NiSn and SnAg finishes. Outside of the scope of this article remain important issues, such as a detailed examination of a number of lead-free coatings and methods for solderability testing, measuring the surface resistance of the coating and the shear strength of solder joints in compliance with international standards. These issues will be covered in future articles on these subjects.

Effects of minor alloying additive on the shear strength of Sn-58Bi solder joint

The use of Pb has been limited in the electronic industry because of the toxicity of lead. As the result, the research and development activities in developing lead-free solders have been accelerated and some lead-free solders were introduced as alternative. Sn-Bi-based alloys are an alternative to replace Pb-based solders in the low temperature ranges. However, Sn-Bi-based solders show brittle behavior in both the bulk and the interface. Generally, the addition of impurity elements to the solders can improve the ductility of the solder joint in both the bulk and the interface by refining the solder microstructure and suppressing the intermetallics at the interface, respectively. In this study, the effect of third elements, i.e., Ni and In (1 and 0.5wt.%) on the microstructure of the Sn-58Bi solder and thickness of the interface between Sn-58Bi solder and Cu substrate were investigated. Solid state IMC compound layer growth was also examined following the thermal aging of the solder joint. Results after aging show that minor added elements were effective in suppressing the intermetallics at the interface during solid state growth. The results also show that the added In was highly effective in limiting the Bi phase coarsening. Mechanical properties of solder joints, before and after heat treatment, were also investigated by shear and micro-vickers tests.

Effect of Ni-Coated Carbon Nanotubes on Interfacial Reaction and Shear Strength of Sn-Ag-Cu Solder Joints

In this study, varying weight percentages of Ni-coated carbon nanotubes (Ni-CNTs) were incorporated into Sn-Ag-Cu (SAC) solder matrix, to form composite solder. Up to 0.05% of Ni-CNTs were successfully incorporated. The interfacial microstructure and shear strength of solders on Ni/Au-finished Cu substrates were investigated after aging at 150°C for up to 42 days. Results revealed that, after soldering and aging for various lengths of time, the interfacial intermetallic compound (IMC) thickness of the unreinforced solder joint was observed to grow more significantly than that of the composite solder joints. Furthermore, the composite solder joints also showed lower diffusion coefficients (2.5 × 10−15 cm2/s to 3.2 × 10−15 cm2/s) compared with that of the SAC solder joints (4.9 × 10−15 cm2/s). Shear test results revealed that as-soldered and aged composite solder joints had better ultimate shear strength than their monolithic counterparts and the shear strength of all aged solder joints decreased with increasing aging time.

OSP 표면처리의 열적 열화에 따른 Cu/SnAgCu 접합부의 접합강도

Bonding strength of Sn-3.0Ag-0.5Cu solder joint due to degradation characteristic of OSP surface finish was investigated, compared with SnPb finish. The thickness variation and degradation mechanism of organic solderability preservative(OSP) coating were also analyzed with the number of reflow process. To analyze the degradation degree of solder joint strength, FR-4 PCB coated with OSP and SnPb were experienced preheat treatment as a function of reflow number from 1st to 6th pass, respectively. After 2012 chip resistors were soldered with Sn-3.0Ag-0.5Cu on the pre-heated PCB, the shear strength of solder joints was measured. The thickness of OSP increased with increase of the number of reflow pass by thermal degradation during the reflow process. It was also observed that the preservation effect of OSP decreased due to OSP degradation which led Cu pad oxidation. The mean shear strength of solder joints formed on the Cu pads finished with OSP and SnPb were 58.1 N and 62.2 N, respectively, through the pre-heating of 6 times. Although OSP was degraded with reflow process, the feasibility of its application was proven.

Effects of bump size on deformation and fracture behavior of Sn3.0Ag0.5Cu/Cu solder joints during shear testing

Abstract To elaborate deformation and fracture behavior of Sn3.0Ag0.5Cu/Cu solder joint, dynamic shear testing was designed and performed on as-reflowed and aged solder joints which contained limited numbers of grains. Polarized light microscopy (PLM) and electron backscatter diffraction (EBSD) were used to reveal the grain morphology and the grain distribution. Scanning electron Microscopy (SEM) was applied to observe the influences of microstructures and intermetallic compounds (IMCs) on the solder joints fracture behavior. The experimental results suggested that the morphology and distribution of IMCs (Cu 6 Sn 5 and Ag 3 Sn) were the main reasons for the size effect in Sn3.0Ag0.5Cu solder joints. The shear strength of as-reflowed and aged solder joints decreased with the increased joint sizes. The nano-scale particle-like Ag 3 Sn dispersed in the small solder joints had a strengthen effect on their mechanical property. While the dendritic and feather-like Ag 3 Sn brought the big solder joints the brittleness. Furthermore, obvious plastic deformation in company with dynamic recovery and recrystallization was observed in small solder joints during dynamic shear testing. The fracture occurred in the bulk solder. While the brittle fracture occurred in big solder joints and the fracture positions were at the areas close to the soldering interface. The cracks propagated by the way of transgranular fracture. After aging, dynamic recovery and recrystallization occurred in all solder joints. While the plasticity of big solder joint was enhanced and the transgranular fracture as well as the intergranular fracture occurred during dynamic shear testing.

Effect of TiO2 nanoparticles on the microstructure and bonding strengths of Sn0.7Cu composite solder BGA packages with immersion Sn surface finish

This study investigated the effects of TiO2 nanoparticles on the interfacial microstructures and bonding strength of Sn0.7Cu (SC) composite solder joints in ball grid array packages with immersion Sn surface finishes. The addition of TiO2 nanoparticles to SC solders resulted in significant changes in the interfacial microstructure. The nanoparticle addition suppressed the growth of the Cu6Sn5 IMC layer, significantly improving shear strength and reliability of solder joints after multiple reflows. The fracture surfaces of the SC solder exhibited a semi-brittle fracture mode with a relatively smooth surface, while those of the SC composite solder showed typical ductile failures with very refined dimpled surfaces.

Effect of addition of TiO 2 nanoparticles on the microstructure, microhardness and interfacial reactions of Sn3.5AgXCu solder

In this work, TiO 2 nanoparticles were successfully incorporated into Sn3.5Ag and Sn3.5Ag0.7Cu solder, to synthesize novel lead-free composite solders. Effects of the TiO 2 nanoparticle addition on the microstructure, melting property, microhardness, and the interfacial reactions between Sn3.5AgXCu and Cu have been investigated. Experimental results revealed that the addition of 0.5 wt.% TiO 2 nanoparticles in Sn3.5AgXCu composite solders resulted in a finely dispersed submicro Ag 3Sn phase. This apparently provides classical dispersion strengthening and thereby enhances the shear strength of composite solder joints. After soldering, the interfacial overall intermetallic compounds (IMC) layer of the Sn3.5AgXCu lead-free solder joint was observed to have grown more significantly than that of the Sn3.5AgXCu composite solder joints, indicating that the Sn3.5AgXCu composite solder joints had a lower diffusion coefficient. This signified that the presence of TiO 2 nanoparticles was effective in retarding the growth of the overall IMC layer.