Transient Liquid Phase Bonding Research Articles

Joined AZ31B Magnesium Alloys with Ag Interlayer by Ultrasonic-Induced Transient Liquid Phase Bonding in Air

Joined AZ31B Magnesium Alloys with Ag Interlayer by Ultrasonic-Induced Transient Liquid Phase Bonding in Air

Towards a self-healing aluminum metal matrix composite: Design, fabrication, and demonstration

This paper presents a novel approach to designing and synthesizing a self-healing aluminum-based metal matrix composite (MMC) at the macro-scale. The composite comprises an Al 5083 matrix embedded with low melting point particles (LMPPs) that act as healing agents. A two-step electroless micro-encapsulation process is developed to create LMMPs with a diffusion and thermal barrier designed to protect the Zn-8Al core with a Co-P shell. The MMC is fabricated using spark plasma sintering. Following controlled total fracture under tension, external compressive force is applied during heat treatment to heal the fracture effectively. The evolution of phases and interfaces is characterized using electron microscopy, and transient liquid phase bonding (TLPB) is identified as the fracture-healing mechanism, facilitated in areas with sufficiently high Zn concentration to fill the crack. The design can be expanded to incorporate other matrix and LMMP materials, mechanical crack volume reduction by integrating shape memory alloy (SMA) reinforcement during MMC synthesis, and processing of the self-healing MMC using Directed Energy Deposition additive manufacturing.

Interfacial intermetallic compounds growth kinetics and mechanical characteristics of Ga-Cu interconnects prepared via transient liquid phase bonding

Driven by continuous miniaturization, higher performance, and functional robustness in three-dimensional (3D) embodiments of electronic devices, Ga which possesses a low melting point (29.8°C) has shown its potential uses in electronics packaging and integration. The use of Ga metal as a solder material to achieve low-temperature transient liquid phase bonding (TLPB) has emerged as a viable solution for reliable interconnections of future-generation products. This study investigates the interfacial intermetallic compounds (IMCs) structure, growth kinetics, and mechanical characteristics of Ga-Cu TLPB joints in the temperature range of 150–220°C. The Cu9Ga4 phase were observed and the growth rate of Ga-Cu IMCs has been investigated. The research findings indicate that the growth mechanism of interface IMCs is primarily diffusion-controlled, with CuGa2 grains exhibiting anisotropic growth. Their shear strength has reached 23.8 MPa, with a porosity of 1.82±0.07%. Furthermore, the fracture interface is presented and correlated with the experimental observations.

Anand constitutive modeling of multilayer Silver-Tin transient liquid phase foils using tensile and creep testing

Purpose This paper aims to present two Anand’s model parameter sets for the multilayer silver–tin (AgSn) transient liquid phase (TLP) foils. Design/methodology/approach The AgSn TLP test samples are manufactured using pre-defined optimized TLP bonding process parameters. Consequently, tensile and creep tests are conducted at various loading temperatures to generate stress–strain and creep data to accurately determine the elastic properties and two sets of Anand model creep coefficients. The resultant tensile- and creep-based constitutive models are subsequently used in extensive finite element simulations to precisely survey the mechanical response of the AgSn TLP bonds in power electronics due to different thermal loads. Findings The response of both models is thoroughly addressed in terms of stress–strain relationships, inelastic strain energy densities and equivalent plastic strains. The simulation results revealed that the testing conditions and parameters can significantly influence the values of the fitted Anand coefficients and consequently affect the resultant FEA-computed mechanical response of the TLP bonds. Therefore, this paper suggests that extreme care has to be taken when planning experiments for the estimation of creep parameters of the AgSn TLP joints. Originality/value In literature, there is no constitutive modeling data on the AgSn TLP bonds.

Investigations of selected influencing process factors for transient liquid phase soldering (TLPS) as a die-attach method for automotive power modules

Increasing the operating temperatures in power electronic applications cause a decreasing lifetime of the die-attach interconnection. Transient liquid phase soldering (TLPS) is able to create a reliable and high temperature resistant connection layer via diffusion processes in the form of intermetallic phases with melting points up to > 400°C. This study concentrates on a TLPS reflow-soldering process with a tin-copper-tin (Sn-Cu-Sn) layered preform. During the soldering process the influence of the selected process parameters for the Sn-Cu-Sn on the grown intermetallic phase interconnections between the preform and the components are investigated via the average void percentage and a process capability analysis (cpK). The application of mechanical pressure decreases the average void percentage below 10%. Due to the lower average void percentage the influence of the holding time, peak temperature and heating gradient are examined under low pressure. The biggest impact shows the heating gradient. With a slow heating gradient, the thermomechanical stress decreases by increasing the solubility and the average void percentage could be reduced to less than 2.7 %. In combination of the optimized selected process factors it is possible to reach a process capability value of 1.

Cu-Cu joint with Sn-58Bi/Porous Cu/Sn-58Bi transient liquid phase bonding under formic acid atmosphere

PurposeThis paper aims to examine the effects of bonding temperature, bonding time, bonding pressure and the presence of a Pt catalyst on the bonding strength of Cu/SB/P-Cu/SB/Cu joints by transient liquid phase bonding (TLPB).Design/methodology/approachTLPB is promising to assemble die-attaching packaging for power devices. In this study, porous Cu (P-Cu) foil with a distinctive porous structure and Sn-58Bi solder (SB) serve as the bonding materials for TLPB under a formic acid atmosphere (FA). The high surface area of P-Cu enables efficient diffusion of the liquid phase of SB, stimulating the wetting, spreading and formation of intermetallic compounds (IMCs).FindingsThe higher bonding temperature decreased strength due to the coarsening of IMCs. The longer bonding time reduced the bonding strength owing to the coarsened Bi and thickened IMC. Applying optimal bonding pressure improved bonding strength, whereas excessive pressure caused damage. The presence of a Pt catalyst enhanced bonding efficiency and strength by facilitating reduction–oxidation reactions and oxide film removal.Originality/valueOverall, this study demonstrates the feasibility of low-temperature TLPB for Cu/SB/P-Cu/SB/Cu joints and provides insights into optimizing bonding strength for the interconnecting materials in the applications of power devices.

Effects of Transient Liquid Phase Bonding Time on Microstructure, Mechanical and Corrosion Properties During Bonding of Inconel 617/AISI 310 Stainless Steel

Effects of Transient Liquid Phase Bonding Time on Microstructure, Mechanical and Corrosion Properties During Bonding of Inconel 617/AISI 310 Stainless Steel

Transient liquid phase bonding assisted spark plasma sintering of La-Fe-Si magnetocaloric bulk materials

The poor mechanical properties of La-Fe-Si based alloys restrict the potential of these magnetocaloric materials. Hence, a novel transient liquid phase bonding (TLPB) processing technique was deployed during spark plasma sintering (SPS) of La-Fe-Si based bulk materials. A series of binder-free LaFe11.8Si1.2 bulk materials were prepared by SPS and hot-pressing sintering (HPS). Transient melting, which occurred during SPS, accelerated the decomposition of the 1:13 phase, resulting in low porosity and high strength. Compared to HPS samples, SPS samples have significantly larger maximum compressive strength (σbc)max of ∼637.9 MPa at a strain of 4.7%, good thermal conductivity of ∼7.6 W·m−1·K−1 at 300 K, and a large (−ΔSM)max value of ∼11.7 J·kg−1·K−1 at TC= 193 K under a magnetic field change of 0 − 5 T. Thus, binder-free La-Fe-Si based bulk magnetocaloric materials with an excellent property set have been successfully prepared by TLPB assisted SPS technology.

Retaining multi-oriented and fine grain structure with Ni doping in Cu/Sn-3.0Ag-0.5Cu/Cu transient liquid phase bonding under isothermal aging treatment

Transient liquid phase bonding has been proven to offer exceptional joining strength and dependable high temperature service in chip stacking applications. Nevertheless, conventional Cu/Sn/Cu transient liquid phase bumps had shortcomings, such as smooth phase boundaries and coarsening grains. In this study, the variation of microstructure in Cu/Sn-3.0Ag-0.5Cu/Cu, Cu/Sn-3.0Ag-0.5Cu/Ni, and Ni/Sn-3.0Ag-0.5Cu/Cu transient liquid phase bonds with the sizes less than 10 μm before and after long term aging were investigated. Due to the dissolution of Ni atoms from the substrates at the cold or hot end, the structure exhibited randomly-oriented and small-sized grains. After 1000 h aging treatment, the Ni-containing specimen still retained the abundant grain structure and appeared network-like morphology of Cu3Sn near phase boundaries. Additionally, the shear testing was applied in the aged samples, Ni-doped joints demonstrated better mechanical properties than Ni-free joining. The enhancement of shear strength was attributed to Ni addition, retaining the advantageous grain structure. This present work showed that doping Ni to micro-bumps could halt the deterioration of grain structure over extended usage of electronic devices in 3D-IC technology.

Microstructure and Shear properties of Sn–xZn Transient Liquid Phase Bonding in 3D-Chip Stacking Packaging

Microstructure and Shear properties of Sn–xZn Transient Liquid Phase Bonding in 3D-Chip Stacking Packaging

High temperature shear and thermal aging behavior of dissimilar transient liquid phase bonded Hastelloy X to Ni3Al intermetallic compound

Nickel super alloys and intermetallic compounds (IMCs) are candidate as strategic materials for turbine industry, because of its excellent high temperature properties. In this study, mechanical properties and thermal aging behavior (post thermal exposure) of the transient liquid phase (TLP) bonds between Hastelloy X to Ni3Al IMC at temperature range of 800–900 °C were investigated. The microstructure and fracture surfaces of the joints were examined by optical and scanning electron microscopes as well as XRD analysis. The optimum joint bonding strength was achieved for the sample treated at 1100 °C–180 min equaling to 355 ± 4.5 MPa. XRD patterns of semi-cleavage fracture surfaces revealed nickel solid solution matrix containing BNi3 and Ni3Si compounds generated at ASZ/ISA interface. The ultimate tensile strength reaches 36.5 ± 1 and 20.5 ± 1 MPa at temperatures of 800 °C and 900 °C, respectively. Fracture occurred in the IMC substrates for both temperatures were due to shrinkage porosity during solidification of IMC and mismatch of crystal lattice constants with the matrix. The thermal aging process at 900 °C for 50–500 h had a minor effect on the joint microstructure but generated TCP phases in the Hastelloy X.

Laminated transient liquid phase preform and bond characterization for high-temperature power electronics application

Laminated transient liquid phase preform and bond characterization for high-temperature power electronics application

Low-Temperature Transient Liquid Phase Bonding Technology via Cu Porous-Sn58Bi Solid–Liquid System under Formic Acid Atmosphere

This study proposes a low-temperature transient liquid phase bonding (TLPB) method using Sn58Bi/porous Cu/Sn58Bi to enable efficient power-device packaging at high temperatures. The bonding mechanism is attributed to the rapid reaction between porous Cu and Sn58Bi solder, leading to the formation of intermetallic compounds with high melting point at low temperatures. The present paper investigates the effects of bonding atmosphere, bonding time, and external pressure on the shear strength of metal joints. Under formic acid (FA) atmosphere, Cu6Sn5 forms at the porous Cu foil/Sn58Bi interface, and some of it transforms into Cu3Sn. External pressure significantly reduces the micropores and thickness of the joint interconnection layer, resulting in a ductile fracture failure mode. The metal joint obtained under a pressure of 10 MPa at 250 °C for 5 min exhibits outstanding bonding mechanical performance with a shear strength of 62.2 MPa.

Simultaneous intermetallics suppression and residual-stress relaxation of heat-resistant Nb-interlayer-inserted Ti-6Al-4V/Si3N4 joints via one-step transient liquid phase bonding and brazing

• One-step bonding of Ti-6Al-4V/Nb/Si 3 N 4 joints by simultaneous transient liquid phase bonding and brazing. • Suppression of intermetallics in Ti-6Al-4V/Nb side of joints by transient liquid phase bonding. • Tailoring of filler's thickness for sound interfacial bonding in Nb/Si 3 N 4 side of joints. • Enhancement of residual-stress relaxation with highly ductile Ag-rich filler. • Elevated temperature strength of joints determined by tradeoff between stress relaxation and filler's weakening. This work has successfully proposed a solution to produce robust Nb-interlayer-inserted Ti-6Al-4V/Si 3 N 4 joints optimized for a maximum operating temperature of 873 K; transient liquid phase bonding (TLPB) of Ti-6Al-4V/Nb side was carried out with Cu and Ni fillers to suppress brittle intermetallic compounds (IMCs), whereas brazing of Nb/Si 3 N 4 side was performed using a highly ductile Ti-added Ag-rich filler for effective residual-stress relaxation. A sound yet simple one-step bonding process incorporating simultaneous TLPB and brazing was achieved with a relatively short holding time of 10 min at 1213 K. TLPB of Ti-6Al-4V/Nb side with Cu and Ni foils of 2-µm-thick each as a laminated filler suppressed brittle Ti-based IMCs and developed a homogenized microstructure consisting mainly of (α + β)-Ti via isothermal solidification. Meanwhile, brazing of Nb/Si 3 N 4 side with 100-µm-thick SILVER-ABA filler (92.75Ag-5Cu-1Al-1.25Ti mass%) foil enhanced interfacial bonding with sufficient total Ti content and accommodated residual stress better than conventional eutectic Ag-Cu-based fillers, and it was verified by finite element analysis with consideration of materials’ temperature-dependent elasto-plastic properties. All joints with a bonding area of 10 mm × 10 mm were tested via symmetrical four-point bending from room temperature (RT) to 873 K fractured from Nb/Si 3 N 4 side. When re-heating the joints from RT to 673 K, fracture initiation gradually shifted from Si 3 N 4 towards interfacial-compounds/Si 3 N 4 interface and bending strengths maintained ∼220 MPa as weakening of SILVER-ABA filler was compensated by residual-stress relaxation in Si 3 N 4 . When tested at 873 K, joints fractured mainly across the Ag-rich solid solution in a ductile manner and bending strength degraded by ∼20% to 171 MPa as weakening of SILVER-ABA filler dominated.

Microstructural and mechanical characteristics of Cu-Sn intermetallic compound interconnects formed by TLPB with Cu-Sn nanocomposite

Transient liquid phase bonding (TLPB) is a promising technology for three-dimensional integration of circuits (3D IC), but it can be slow and less productive. A novel Cu-Sn nanocomposite interlayer (Cu-Sn NI) composed of Sn matrix with an embedded Cu nanowire array prepared by electrodeposition can significantly accelerate the bonding process, approximately by 20 times. Bonding time with a Cu-Sn NI can be as short as ~2 min to achieve a full Cu-Sn intermetallic compound (IMC) joints, whereas it can take ~60 min with a pure Sn interlayer of the same thickness under the same bonding conditions (250 °C). Unlike the columnar Cu 6 Sn 5 grains commonly formed with Sn interlayer, refined equiaxed Cu 6 Sn 5 grains with an average size of ~1.6 µm are found to be formed with Cu-Sn NI. Such grain refinement has significantly contributed to the improvement of shear strength of IMC joints formed with Cu-Sn NI (23.1 ± 3.3 MPa), higher than those bonded with pure Sn interlayer (17.9 ± 2.1 MPa). The underlying mechanisms of the new TLPB process and the formation of finer microstructure when bonding with Cu-Sn NIs are also illuminated and validated based on the experimental observation. • A unique Cu-Sn nanocomposite interlayer with Cu nanowire array embedded in Sn. • TLPB with this layer is >20 times faster than conventional Cu-Sn TLPB. • IMC joint bonded with this layer possesses refined equiaxed Cu 6 Sn 5 grains. • Strength of IMC joint bonded with this layer is higher than pure Sn layer. • Clarified the growth mechanisms of IMC in the joints bonded with this layer.

Transient liquid phase bonding with Ga-based alloys for electronics interconnections

Significant demands on electronics packaging are driven by miniaturization, energy efficiency, high performance, and minimal carbon footprint. Liquid Ga and Ga-based alloys as interconnect materials exhibit a great potential in these applications due to the benefits including low melting points, non-toxicity, and stable high melting point intermetallic compounds (IMCs) formed with other metals such as Cu. Taking advantages of transient liquid phase bonding (TLPB) technology, the uses of Ga-based alloys can be attractive as a more efficient and environmentally friendly method for interconnections. This study aims to address the technical challenges in the applications of Ga and Ga-based alloys for Cu bonding through the TLPB process. These include solderability of Ga-based solders on Cu, interfacial reactions during bonding, as well as the microstructure and properties of the resultant joints. In addition, the porosity and shear strength of the joints have been evaluated for better understanding of the reliability of the joints. The results show that Ga-based solders present an acceptable solderability given their wetting behavior observed. The constituent of the resultant joints consists of θ − CuGa2 and γ3 − Cu9Ga4 IMC phases as identified, which are formed as the results of interfacial reactions between liquid Ga-based alloys and Cu substrate. Indium, as an alloying element in the solders, has been found to be able to accelerate γ3 − Cu9Ga4 formation and reduce the porosity in the joints. It is also found that the pressure applied during TLPB also helps the reduction of porosity, as well as the increase of mechanical strength of the joints. These results provided not only new insight into the mechanism of the interfacial reaction between Ga-based liquid metals (GLMs) and solid Cu systems, but also a new manufacturing route for electronics integration.

Evaluation of the Forming Limit Diagram (FLD) for St-Mg-St Multilayer Sheet Manufactured by Transient Liquid Phase (TLP) Bonding

Evaluation of the Forming Limit Diagram (FLD) for St-Mg-St Multilayer Sheet Manufactured by Transient Liquid Phase (TLP) Bonding

Measurement and simulation of residual stresses in transient liquid phase bonded ferritic steels

Ferritic steel bars—25 mm in diameter—were welded by transient liquid phase bonding (TLPB) using Fe-based amorphous metallic foils as filler material. The resulting residual stress (RS) field shows a low peak magnitude—of 147 MPa—as measured by neutron diffraction. The most distinctive feature of TLPB is the heat input delivered simultaneously at the whole joint that allows much lower cooling rates compared with arc welding (AW). Therefore, the elapsed time between 800 and 500 °C (t 8/5) was particularly long reaching 390 s. As a result, a low RS peak magnitude (147 MPa) was obtained in the as-welded condition. This value is well below the RS peak magnitude obtained with AW which typically attain the yield strength of the base metal (276 MPa). The numerical simulation of RS at the welded bars was performed by a thermal and mechanical analysis. It shows that TLPB produced a large austenized region, low cooling rates and a remarkable t 8/5. Consequently, the large volume in which the heat input is delivered is the driving force to reduce RS peak magnitudes. From the mechanical analysis, it was found that the simulated RS was in good agreement with the measured RS. Therefore, the proposed numerical simulation model can be used to predict RS in TLPB weldments.Graphical abstract

Low Temperature Transient Liquid Phase Bonding of Alumina Ceramics with the Bi2O3-ZnO Interlayer.

Alumina ceramics were joined by a transient liquid phase (TLP) bonding method at relatively lower temperatures, using mixed powders of Bi2O3 and ZnO with different weight ratios as interlayers between the ceramic components. Bonding was achieved at 750 °C for several of the prepared interlayer mixtures, which makes the applied approach attractive due to the relatively lower joining temperature and potentially low fabrication costs. Measurements by SEM and EDX were used to study the microstructure and chemical analysis of the obtained joints. It also allowed us to investigate the diffusion mechanism occurring in the systems, which resulted in the hypothesis that Zn2+/ZnO diffuses through the ceramics. XRD and Raman spectra were acquired to examine the reaction products that formed during the thermal treatment. The results showed that both ZnO and Bi2O3 react with each other as well as with alumina to form spinel and other products.

Defect formation and mitigation in Cu/Cu joints formed through transient liquid phase bonding with Cu-Sn nanocomposite interlayer

Joining based on transient liquid phase bonding (TLPB) has a great prospect in microelectronic packaging. However, this process is plagued with its low throughput. In this work, we designed and utilised a preformed Cu-Sn nanocomposite interlayer (Cu-Sn NI) to speed up the TLPB process. Comparing with the uses of a Sn interlayer only, the preformed Cu-Sn NI enabled the bonding process to be accelerated by >20 times. Furthermore, instead of columnar Cu6Sn5 grains, Cu-Sn intermetallic compounds joints formed with Cu-Sn NIs were mostly filled by refined equiaxed Cu6Sn5 grains with an average size of ~1.6 μm. As a result, the shear strength of IMC joints achieved with Cu-Sn NI was found to be higher than those bonded with Sn interlayer. However, various kinds of defects, one of the main drawbacks in TLPB, were still found from this unique bonding process, which is likely to deteriorate the performances and long-term reliability of resultant TLPB joints. This study aims to observe and analyse various defects formed during TLPB with Cu-Sn NI, hence propose possible mitigation solutions to prevent their occurrence and consequently improve the reliability of the joints obtained by TLPB with Cu-Sn NIs.