Composite Solder Research Articles

Synergic effect of Te, Ni and MWCNT on creep behavior and microstructural evolution of Sn-1.0Ag-0.7Cu low-Ag solder

Avoiding the weak interface bonding of multi-walled carbon nanotubes MWCNT with Sn-Ag-Cu solder matrix is vital to produce high performance large scale Sn-Ag-Cu solder alloys. In this work, Sn-1.0Ag-0.7Cu (SAC107) composite solders were developed by incorporating MWCNT in SAC107 alloy with Ni and Te. The results indicate that the MWCNTs and Cu can be instantaneously adsorbed at the surface-active of Te atoms to in situ compose the core multi-shell (Te/C/Cu/C) polygonal particles, linking MWCNT with SAC solder matrix. The polygonal particles are well dispersed through the Cu6Sn5, Ag3Sn, β-Sn, SnTe and (Cu,Ni)6Sn5 IMC precipitates. These structural variations produce a combination of increased creep resistance 15 times and enlarged creep life time (14 times) than that of plain SAC107 alloy. Although Ni and Te additions decreased the creep resistance of SAC, the SAC-Ni-Te-MWCNT composite alloy exhibits significant change in dislocation creep resistance with creep stress exponent of ~ 6.6 at 25 °C: the creep threshold stress is decreased by 58.8% (5 MPa) in SAC-Ni-Te alloy, while increased by 17.6% (1.5 MPa) in SAC-Ni-Te-MWCNT composite alloy owing to the presence of polygonal particles.

Influence of Fly Ash Geopolymer Ceramic Powder Addition on Sn-3.0Ag-0.5Cu Solder Joints

This paper reports the effect of 1.0 wt.% fly ash (FA) geopolymer ceramic powder addition in Sn-3.0Ag-0.5Cu (SAC305, in wt.%) solder joint. Powder metallurgy route was used to fabricate the new composite solder. Solder balls were formed from the new composite solder and reflowed on Cu substrate. The effect of FA as ceramic reinforcement on the bulk microstructure and the interfacial intermetallic compound layer formation of solder joints were investigated under optical microscope. Microstructure observation showed that the β-Sn dendrite size was refined in SAC305-1.0FA/Cu bulk solder joint sample than that in the non-reinforced sample. The addition of FA geopolymer ceramic powder into the solder matrix also produced a thinner intermetallic compound layer.

Microstructural Evolution of Cu/Sn-58Bi/Sn-3.0Ag-0.5Cu Composite Solder Joint during Isothermal Aging

A composite solder joints made of Cu/Sn-58Bi/Sn-3.0Ag-0.5Cu (in weight percent) was successfully fabricated. The composite solder was made from combining a Sn-3.0Ag-0.5Cu solder ball and Sn-58Bi solder paste. The composite solder was reflowed on Cu-OSP (copper-organic solderability preservatives) substrate to form a composite solder joint. The microstructure evolution of the composite solder joints under different reflow temperature and thermal aging conditions were investigated using an optical microscope. This study shows that a composite solder joint of SAC305/Sn-58Bi can be assembled at lower temperature (160 °C) and gradually mixed through isothermal aging.

Synthesis of Kaolin Geopolymer as Ceramic Reinforcement in Lead-Free Solder

This paper elucidates the fabrication of kaolin geopolymer as the ceramic material. The kaolin geopolymer ceramic (KGC) was used as a new potential reinforcement in the lead-free solder. The fabrication of KGC was started through combination of alkaline solution of NaOH and Na2SiO3 reaction with kaolin material. The mixture of kaolin geopolymer were prepared and the homogenised mixture were curing for 24 hours. The kaolin geopolymer is sintered at 1200°C and then crushed to produces a fine kaolin geopolymer. The KGC were then mixed with lead-free solder through powder metallurgy technique. The elemental distribution in the KGC was investigated by using Synchrotron Micro-XRF. Meanwhile, the phase analysis involved in KGC and composite solder with addition of KGC were investigated as well.

Microstructure Transformation and Mechanical Properties of Al Alloy Joints Soldered with Ni-Cu Foam/ Sn-3.0ag-0.5cu (Sac305) Composite Solder

Microstructure Transformation and Mechanical Properties of Al Alloy Joints Soldered with Ni-Cu Foam/ Sn-3.0ag-0.5cu (Sac305) Composite Solder

Effects of Ag Shell on Electrical, Thermal and Mechanical Properties of Cu@Ag Composite Solder Preforms by Electromagnetic Compaction for Power Electronics

Effects of Ag Shell on Electrical, Thermal and Mechanical Properties of Cu@Ag Composite Solder Preforms by Electromagnetic Compaction for Power Electronics

Development of lead free solder for electronic components based on thermal analysis

In the post COVID-19 virus era, online teaching and work from home have develop a common trends so the demand of electronic component rapidly increases. The development of lead-free solder has grown rapidly because various environmental legislations have enforced laws to restrict the use of Lead (Pb), Mercury (Hg) and Cadmium (Cd), etc because this is hazardous materials. In electronic and electrical industries. Many lead-free solder composition such as Sn - Bi, Sn - Cu, Sn - Zn, Sn - Ag, Zn - Bi, Sn – Ag - Cu, Sn – Zn - Bi, Sn – Cu - Bi, Sn – Cu - Ni etc. have been developed as a replacement of Sn - Pb solder. Researcher are facing challenges due to rise in melting temperature in lead-free solder (LFS) and the formation of intermetallic compound. This review paper aimed to summarise the thermal properties of lead free solders (LFS) and analyse the effect of addition of various elements and reinforcement in Sn based lead free solder (LFS).

Effective (Pd,Ni)Sn4 diffusion barrier to suppress brittle fracture at Sn-58Bi-xAg solder joint with Ni(P)/Pd(P)/Au metallization pad

In this study, we investigated the interfacial reactions and mechanical properties of Sn58Bi solders alloyed with Ag nanoparticles (NPs) after bonding with electroless nickel-immersion gold (ENIG) or electroless nickel-electroless palladium-immersion gold (ENEPIG) surface finish. On the ENIG surface finish, Ni3Sn4, Ni-Sn-P, and Ni3P layers were sequentially formed on the Ni(P) layer. On the ENEPIG surface finish, (Pd,Ni)Sn4 intermetallic compound was formed on thin Ni3Sn4/Ni3P on the Ni(P) layer, and it survived nine reflow cycles, unlike Sn-Ag-Cu solder joints in previous studies. This effectively stopped the formation of the Ni-Sn-P layer, which acted as an effective diffusion barrier to suppress the consumption of Ni in the Ni(P) layer. A mixed-mode fracture—partially through the bulk solder (ductile mode) and partially through Kirkendall voids in the Ni-Sn-P layer (brittle mode)—was observed with the Sn-58Bi-xAg/ENIG joint, whereas only ductile fracture was observed with the Sn-58Bi-xAg/ENEPIG joint. Alloying with 0.5 wt% Ag NPs strengthened the composite solder by refining the eutectic microstructure of the Sn58Bi solder and by inducing precipitation hardening with fine Ag3Sn particles. However, the addition of more Ag NPs led to mechanical degradation by re-coarsening of the eutectic microstructure and by providing an easy fracture path along the coarsened Ag3Sn/solder interface. The highest shear strength was obtained with Sn-58Bi-0.5Ag/ENEPIG, which was suggested to be the most reliable system for low-temperature soldering at 200 °C.

Ultrasonic-assisted soldering of Mg alloy joints using Cu-foam/Sn composite solder foils

Mg alloys have been increasingly utilized in our daily life due to the low density and high specific strength and stiffness. However, the poor formability of these alloys restricted their adoption to some extent. The joining technique can effectively manufacture complex components, but some challenges are unique for Mg alloys. In this paper, reliable Mg alloy joints were realized by ultrasonically soldering at 250 °C for only 5 s. By using Cu-foam/Sn composite solder foils, the average shear strength of Mg alloy joints rose to 53.06 MPa, a 44.4% increase compared without using composite solder. The strengthening mechanism was attributed to the unique structure of 3D continuous Cu skeletons and the formation of high-hardness MgSnCu grains wrapped on skeletons after ultrasonically soldering, which could suppress crack propagation and block the excessive growth of Mg2Sn grains. The theoretical calculation confirmed that the formation energy of MgSnCu phase was lower than that of Mg2Sn or Cu6Sn5 phase despite evidence that it not existed in the Mg−Sn−Cu equilibrium phase diagram. Our study could contribute to the development of ultrasonic soldering technology with composite solder and open an opportunity for further expanding the usage of Mg alloys.

Intermetallic growth activation energy improvement in graphene doped Sn-3.5Ag solder

Sn-3.5Ag lead-free solder an appropriate candidate for soldering due to its reasonable cost. In this study, 0.07 wt% graphene nanosheets were added into the Sn-3.5Ag solder to improve the intermetallic layer growth and the solder was prepared using powder metallurgy route. The composite solder was soldered on copper substrate at 250 °C for one minute and aged until 500 h at 100, 125, 150 and 180 °C. Cu6Sn5 intermetallic layer was the first layer formed at the interface and Cu3Sn formed at higher aging conditions. The composite solder shows lower total intermetallic thickness, hence lower intermetallic growth rate. The growth rate was used to calculate the activation energies for total intermetallic layers growth and reported as 65.9 and 77.0 kJ/mol for Sn-3.5Ag and Sn-3.5Ag-0.07GNSs solder joints, respectively.

Effect of substrate surface roughness on interfacial reaction at Sn-3.0Ag/(001)Cu interface

The high reliability of solder joints is the guarantee for the miniaturization, ultra-high density, multi-functional and high performance of integrated chips. The growth of interfacial intermetallic compounds determined by solder composition, substrates, reflow temperature et al., is the key factor to achieving good bonding. In this paper, the effects of substrate surface roughness on interfacial reaction at Sn-3.0Ag/(001)Cu interface were investigated. Confocal Laser Scanning Microscope (CLSM), Scanning electron microscope (SEM), Electron backscatter diffraction (EBSD) and Shanghai Synchrotron Radiation Facility (SSRF) were used to characterize the interface reaction. Results suggest that higher Ra favors to form thicker IMC layer and more voids, as well as degrades the preferred orientation of IMC. The results have a significant meaning in improving the reliability of solder joints in the real work environment.

Mechanism on the nucleation of orientation-preferred Cu6Sn5 at different temperatures and solder compositions

In this paper, the mechanism on the nucleation of orientation-preferred Cu6Sn5 at different temperatures and solder compositions was investigated. Results suggest that affected by temperature and solder composition, the distribution of clusters in solder plays an important role in the formation of preferred orientation. Higher temperature, Ag element and an appropriate amount of Cu element are favorable for the nucleation of orientation-preferred Cu6Sn5. However, the increase of Cu-Sn clusters size with the increase of Cu addition will lead to the nucleation of Cu6Sn5 in liquid solder, which does not need to follow the rule of the minimal lattice mismatch between Cu6Sn5 and Cu substrate. Meanwhile, the addition of Cu and Ag is conducive to the increase of grain size. Besides, the difference in solder volume between the central and edge region results in the difference in grain orientation. Furthermore, a model is established to illustrate that how the reflow temperature, Cu and Ag content affect the nucleation of orientation-preferred Cu6Sn5 through affecting the cluster evolution. The results have significant meaning in understanding and controlling the formation of Cu6Sn5 preferred orientation and improving the reliability of solder joints.

Microstructural and compositional evolution of SAC305/TiN composite solder under thermal stressing

PurposeThe purpose of this paper is to investigate the effect of titanium nitride (TiN) on microstructure and composition of 96.5Sn3Ag0.5Cu (SAC305) lead-free solder joints under a large temperature gradient.Design/methodology/approachIn this paper, SAC305 lead-free composite solder containing 0.05 Wt.% TiN was prepared by powder metallurgy method. A temperature gradient generator was designed and the corresponding samples were also prepared. The microstructural evolution, internal structure and elemental content of SAC305 and SAC305/TiN solder joints before and after thermal loading were comparatively studied.FindingsThe experimental results show that the addition of the TiN reinforcing phase can effectively inhibit the diffusion and migration of copper atoms and, therefore, affect the distribution of newly formed Cu-Sn IMC in solder joints under the condition of thermal migration (TM). Compared with the SAC305 solder joint, the interconnection interface and internal structure of the composite solder joint after 600 h of TM are also relatively complete.Originality/valueThe TiN reinforcing phase is proven effective to mitigate the TM behavior in solder joints under thermal stressing. Specifically, based on the observation and analysis results of microstructure and internal structure of composite solder joint, the TiN particle can change the temperature gradient distribution of the solder joint, so as to suppress the diffusion and migration of Sn and Cu atoms. In addition, the results of Micro-CT and compositional analysis also indicate that the addition of TiN reinforcement is very helpful to maintain the structural integrity and the compositional stability of the solder joint. Different from other ceramic reinforcements, TiN has good thermo- and electro-conductivity and the thermal-electrical performance of composite solder will not be significantly affected by this reinforcement, which is also the main advantage of selecting TiN as the reinforcing phase to prepare composite solder. This study can not only provide preliminary experimental support for the preparation of high reliability lead-free composite solder but also provide a theoretical basis for the subsequent study (such as electro-thermo distribution in solder joints), which has important application significance.

Soldering methods for obtaining permanent joints of ceramic composites with metals (review article)

The article analyzes the use of soldering methods to obtain high-temperature permanent joints of silicon carbide ceramic matrix composites (CMC) with metals. The main problems in joining CMC with metals are considered, associated with poor wettability of CMC with metal melts, a significant difference in the LTEC of CMC and metals, and the formation of substances with high hardness and brittleness in the connecting layer. An analysis of the practical experience of using traditional and diffusion brazing methods for joining C f /SiC type CMC with metal alloys based on Ni, Nb, Ti, Mb and stainless steel is carried out. The most typical compositions of solders and technological modes of soldering processes are considered. It is shown that these technologies make it possible to create reliable and strong joints of parts made of CMC and various metals.

Microstructure and shear property of Ni-coated carbon nanotubes reinforced InSn-50Ag composite solder joints prepared by transient liquid phase bonding

InSn-50Ag composite solder joints doping Ni-coated carbon nanotubes (Ni-CNTs) were fabricated by transient liquid phase (TLP) bonding, and then the effect of Ni-CNTs contents (x = 0, 0.01, 0.03, 0.05, 0.07, 0.1 wt%) on the microstructure and shear property of the composite solder joints was examined. The results showed that the microstructure of Cu/InSn-50Ag-x(Ni-CNTs)/Cu composite solder joints consisted of the interfacial region bamboo-type Cu3(In, Sn), solder center region Ag3In, Ni3Sn4, Ag particles and Ni-CNTs. The appropriate amounts of Ni-CNTs (about 0.07 wt%) are conducive to form a compact composite solder joint and restrain the growth of interfacial Cu3(In, Sn) IMC layer, and the morphologies of IMC layer are determined by Ni-CNTs suppressing atom diffusion and IMC grain orientation. The shear strength of composite solder joints relates to Ni-CNTs content, and the maximum shear strength reaches 42 MPa of Cu/InSn-50Ag-0.07(Ni-CNTs)/Cu. It is regulated by uniform distribution of Ni-CNTs, refined Ag3In grains and interface IMC layer with near-continuous voids. The fracture of the composite solder joints doped Ni-CNTs occurred near to the boundary between the interfacial IMC layer and solder center region, the fracture mechanism is ductile fracture.

Effects of rare earth Ce addition on the microstructure and shear property of Cu/In-50Ag/Cu composite solder joint

The microstructure and shear property of Cu/In-50Ag-xCe/Cu (x = 0, 0.3, 0.6, 1.2, 2 wt%) composite solder joints fabricated by transient liquid phase (TLP) bonding were investigated. The results showed that the appropriate amount of Ce particles refined the microstructure in the Cu/In-50Ag/Cu solder joint, and inhibited Cu2In phase formation at the Cu/solder interface. The refined Ag2In phases contribute to suppressing the formation of microstructural defects. The Ce particles can improve the microstructure uniformity of composite solder joint, the porosity of Cu/In-50Ag-0.6Ce/Cu solder joint is only 1.05%, and the excessive (1.2–2 wt%) Ce particles are harmful to the composite solder joints. Doping 0.3–0.6 wt% Ce particles can improve the shear strength of composite solder joints by reducing microstructural defects, refining Ag2In phases and improving the phase boundaries strength. The maximum shear strength value of the Cu/In-50Ag-0.6Ce/Cu composite solder joint reaches 17.58 MPa. The fracture mechanism is mainly brittle fracture, which occurs near the in-situ reaction zone. The Cu/In-50Ag-0.6Ce/Cu composite solder joint fabricated by TLP bonding with finer microstructure and higher mechanical properties is acceptable.

Impact of different aging conditions on the IMC layer growth and shear strength of Ni-modified MWCNTs reinforced Sn-Ag-Cu composite solder

PurposeThe purpose of this paper is to develop a new composite solder to improve the reliability of composite solder joints. Nano-particles modified multi-walled carbon nanotubes (Ni-MWCNTs) can indeed improve the microstructure of composite solder joints and improve the reliability of solder joints. Although many people have conducted in-depth research on the composite solder of Ni-MWCNTs. However, no one has studied the performance of Ni-MWCNTs composite solder under different aging conditions. In this article, Ni-MWCNTs was added to Sn-Ag-Cu (SAC) solder, and the physical properties of composite solder, the microstructure and mechanical properties were evaluated.Design/methodology/approachIn this study, the effect of different aging conditions on the intermetallic compound (IMC) layer growth and shear strength of Ni-modified MWCNTs reinforced SAC composite solder was studied. Compared with SAC307 solder alloy, the influence of Ni-MWCNTs with different contents (0, 0.1 and 0.2 Wt.%) on composite solder was examined. To study the aging characteristics of composite solder joints, the solder joints were aged at 80°C, 120°C and 150°C.FindingsThe experimental results show that the content of Ni-MWCNTs affects the morphology and growth of the IMC layer at the interface. The microhardness of the solder increases and the wetting angle decreases. After aging at moderate (120°C) and high temperature (150°C), the morphology of the Cu6Sn5 IMC layer changed from scallop to lamellar and the grain size became coarser. The following two different phase compositions were observed in the solder joints with Ni-MWCNTs reinforcement: Cu3Sn and (Cu, Ni)6Sn5. The fracture surface of the solder joints all appeared ductile dents, and the size of the pits increased significantly with the increase of the aging temperature. Through growth kinetic analysis, Ni-modified MWCNTs in composite solder joints can effectively inhibit the diffusion of atoms in solder joints. In short, when the addition amount of Ni-MWCNTs is 0.1 Wt.%, the solder joints exhibit the best wettability and the highest shear strength.Originality/valueIn this study, the effects of aging conditions on the growth and shear strength of the IMC layer of Ni modified MWCNTs reinforced SAC307 composite solder were studied. The effects of Ni MWCNTs with different contents (0, 0.1 and 0.2 Wt.%) on the composite solder were examined.

Study on the correlation between spreadability and wetting driving force of Ni-GNSs reinforced SnAgCuRE composite solder

To save test time and cost, spreading area method and wetting balance method were used to study the wetting characteristics of Ni-GNSs/SnAgCuRE composite solder under different parameters and explore the correlation between spreadability and wetting driving force of the composite solder. The results showed that the composite solder had good spreadability on the Cu substrate under 270–280 °C and water-clean flux, and they had good wetting adaptability to Cu wire under the tin bath temperature of 270–280 °C, dipping time of 6 s and dipping speed of 20 mm/s. The results satisfied the requirements of production in micro-connection field. The dynamic spreading processes of Ni-GNSs/SnAgCuRE composite solder consisted of three stages: initial slow shrinkage, rapid expansion and gradual equilibrium. Added appropriate amount of Ni-GNSs into the solder alloy, they adsorbed on the surface of Ag3Sn particles to form a precursor film at the three-phase interface, which was conducive to spread. The correlation equation between spreadability and wetting driving force of composite solder was established. According to the spreading area of the composite solder on the Cu substrate, the wetting driving force and wetting balance of the immersion wetting processes could be analyzed and vice versa.

Ultrasound-Assisted Surface Modifications on Ceramic Reinforcement for Lead-Free Composite Solders : Short Review

The purpose of this paper is to review and examine the effect of ultrasound-assisted surface modifications of ceramic reinforcements on the properties of lead-free solders. The discussion will highlight the fundamental understanding, main parameters, configurations, and recent surface-modified ceramic reinforced composite lead-free solder developments. The review also identified and summarized the advantages, current trends, and significant findings in this field. The ultrasound-assisted surface modification was found to provide a crucial improvement on the wettability properties of molten solders as the matrix phase on the ceramic reinforcement. Further, the excellent distribution of ceramic reinforcement in solder matrix was also seen after the surface modification process. This has led to significant improvements in mechanical properties such as hardness and strength. The pinning of dislocation movement was seen as the reason for improving the mechanical properties. This positive impact in enhancing the ceramic reinforcement-solder interfacial reaction allows more explicit future research directions and opportunities for composite solder applications.

Factors Controlling the Defect Formation in Cu-Sn Micro Joints in 2.5D and 3D Interconnects

The Cu-Sn reaction upon soldering has been thoroughly studied and the sporadic formation of Kirkendall voids within the intermetallic bonds between ball grid array (BGA) or surface mount technology (SMT) solder joints and Cu pads has been demonstrated as well-known concern. However, in the realm of ever developing device miniaturization, there is very limited information on the impact of space confinement on the dynamics of the Cu/solder joint interface. It is known that no voiding has been found in solder joints with high-purity Cu but this phenomenon presents itself, albeit to a different extent, when the joint is realized with electroplated Cu. Also, it is believed, that the voiding propensity in the Cu3Sn intermetallic compounds (IMC) is more likely to be higher in micro joints than in BGA/CSP scale (macro) joints for a given quality of electroplated Cu. Along with that it has been shown that the IMCs on Cu surfaces seem to grow much faster when the solder becomes very thin, and this is accompanied with a greatly enhanced risk of Kirkendall void nucleation.The emphasis of this work is on understanding the voiding behavior within the intermetallic bonds of Cu-Sn micro joints (5 – 30 µm) with the eventual goal of learning how it can be controlled or prevented. Our systematic studies have corroborated the association of voiding with the incorporation of small concentrations of impurities resulting from organic additives degradation during the Cu electroplating as already illustrated for macro joints. Our results also show lack of any voiding not only in macro- but also in micro joints when the interconnection is realized with high purity Cu, likely because no organic impurities are present in sufficient amount to prompt defect nucleation and growth. Our research further demonstrates that the IMC growth rate varies with factors and parameters such as solder volume to pad area ratio, solder composition, pad finish, initial assembly process parameters, subsequent heat treatments, and specifics of the further thermomechanical history, thus impacting differently the overall voiding level. Following this lead, the analysis of micro joints subjected to different synthetic and processing treatments clearly demonstrates the propensity for voiding to be substantially higher, for a given quality of electroplated Cu, in very small solder joints (5 – 30 µm), such as those found in 3D assemblies, unlike in macro joint counterparts. The risk and severity of voiding in these thinner joints is confirmed to depend on the type and amount of incorporated organic impurities in the electroplated Cu. Therefore, in the present report we show how the bath additive chemistry and various Cu electroplating parameters play a systematic role in the type and quantity of impurity incorporation, and thus the propensity for voiding. Approaches to control the electroplating Cu quality in a way that leads eventually to void-free micro joints are also discussed.