Active Solder Research Articles

Characterization of an Active Soldering Zn-Mg Alloy and the Study of Ultrasonic Soldering of SiC Ceramics with Copper Substrate

The aim of this study was to characterize a Zn-Mg type soldering alloy and direct soldering of SiC ceramics with a copper substrate. The Zn1.5Mg solder exerts a wider melting interval. The temperature of the eutectic reaction was 365 °C, and the liquidus temperature was 405 °C. The microstructure of the soldering alloy is comprised of a zinc matrix. Segregation of binary eutectics in the form of (Zn) + Mg2Zn11 lamellas occurred on the boundaries of Zn grains. Additionally, the presence of a MgZn2 magnesium phase was observed in the solder matrix. The SiC/solder bond was formed due to magnesium distribution from solder to the boundary with SiC ceramics, where magnesium reacts with silicon, which is infiltered in SiC ceramics. By a mutual interaction, a new Mg2Si phase is formed. An interaction between the molten zinc solder and Cu substrate occurred on the boundary of the Cu/substrate joint at the formation of a transition zone composed of two new phases, namely the γCu (Cu5Zn8) non-wettable phase type, approximately 30 µm wide, and a wettable (CuZn4) phase type ε, approximately 12 µm wide. The average shear strength of a combined SiC/Cu joint fabricated using Zn1.5Mg solder was 44 MPa.

Joining of SiO2 glass and substrate using In49Sn active solder in air

Joining of SiO2 glass and substrate using In49Sn active solder in air

Ultrasonic soldering of Al<sub>2</sub>O<sub>3</sub> ceramics and Ni-SiC composite by use of Bi-based active solder

<abstract> <p>The aim of this research was to study the interaction and solderability of Al<sub>2</sub>O<sub>3</sub> ceramics and Ni-SiC composite by use of an active solder type Bi11Ag1.5Ti1Mg. The chemical composition of the solder is 86.5 wt% Bi, 11 wt% Ag, 1.5 wt% Ti, 1 wt% Mg. Soldering was performed by ultrasonic activation. This solder has a wide melting interval with the initial melting temperature of 263 ℃, what corresponds to the eutectic reaction. The liquidus temperature of this solder was determined at 437 ℃. The bond between the ceramic and the solder is formed by the interaction of the active metals Bi, Ag and Mg with the surface of the substrate Al<sub>2</sub>O<sub>3</sub>. The thickness of the Mg reaction layer at the interface was approximately 0.8 μm. The bond at the interface between Ni-SiC and solder was formed due to the interaction of the active metals Bi, Ag, Mg and Ti. Feasibility of Bi11Ag1.5Ti1Mg solder was assessed on the basis of analyses of joint boundaries and joint shear strength measurements. The average shear strength of Al<sub>2</sub>O<sub>3</sub>/Bi11Ag1.5Ti1Mg/Ni-SiC joint was 54 MPa.</p> </abstract>

Study of Wettability and Solderability of SiC Ceramics with Ni by Use of Sn-Sb-Ti Solder by Heating with Electron Beam in Vacuum.

The aim of this research was to study the wettability and solderability of SiC ceramics by the use of an active solder of the type Sn5Sb3Ti in a vacuum by electron beam heating. This solder exerts a narrow melting interval, and only one thermal effect, a peritectic reaction, was observed. The liquidus temperature of the solder is approximately 243 °C. The solder consists of a tin matrix where the Ti6(Sb,Sn)5 and TiSbSn phases are precipitated. The solder wettability on a SiC substrate decreases with decreasing soldering temperature. The best wetting angle of 33° was obtained in a vacuum at the temperature of 950 °C. The bond between the SiC ceramics and the solder was formed due to the interaction of Ti and Ni with silicon contained in the SiC ceramics. The formation of new TiSi2 and Ti3Ni5Si6 phases, which form the reaction layer and thus ensure the bond formation, was observed. The bond with Ni is formed due to the solubility of Ni in the tin solder. Two phases, namely the Ni3Sn2 and Ni3Sn phases, were identified in the transition zone of the Ni/Sn5Sb3Ti joint. The highest shear strength, around 40 MPa, was attained at the soldering temperature of 850 °C.

Bonding mechanism in ultrasonic-assisted soldering of ZrO2 and 304 stainless steel using a micro-alloyed active solder alloy

Ceramic-metal soldering joints are widely needed in various industries and a key factor in soldering is the interfacial bonding between the ceramic and solder alloys. Active elements, such as Ti and rare earth, are often added to solder alloys to realize interfacial bonding. The content of the active elements is usually 2 ∼ 4 wt%, which can significantly increase the melting temperature of the solder alloys. In this research, a micro-alloyed reactive solder comprising Sn-3.0Ag-0.5Cu alloy with 0.2 wt% Ti was used to solder ZrO2 ceramics and 304 stainless steel. The effective interfacial reaction was achieved with the aid of the ultrasound. The reaction product was Zr0.5Ti0.35Sn0.15O2 and Ti11.3Sn3O10 at the Sn-Ag-Cu-Ti/ZrO2 interface, and the maximum shear strength of the soldered specimens was 30.75 ± 9.92 Mpa. The melting temperature of the soldering alloy was not significantly increased compared to regular Sn-Ag-Cu solder alloy.

Characterization of Sn-Sb-Ti Solder Alloy and the Study of Its Use for the Ultrasonic Soldering Process of SiC Ceramics with a Cu-SiC Metal-Ceramic Composite.

The aim of this research was to characterize soldering alloys of the type Sn–Sb–Ti and to study the ultrasonic soldering of SiC ceramics with a metal–ceramic composite of the type Cu–SiC. The Sn5Sb3Ti solder exerts a thermal transformation of a peritectic character with an approximate melting point of 234 °C and a narrow melting interval. The solder microstructure consists of a tin matrix, where the acicular constituents of the Ti6(Sb,Sn)5 phase and the sharp-edged constituents of the TiSbSn phase are precipitated. The tensile strength of the soldering alloy depends on the Ti content and reaches values from 34 to 51 MPa. The average strength of the solder increases with increasing Ti content. The bond with SiC ceramics is formed owing to the interaction of titanium, activated by ultrasound, with SiC ceramics, forming the (Ti,Si)6(Sb,Sn)5 reaction product. The bond with the metal–ceramic composite Cu–SiC is formed owing to the solubility of Cu in a tin solder forming two phases: the wettable η-Cu6Sn5 phase, formed in contact with the solder, and the non-wettable ε-Cu3Sn phase, formed in contact with the copper composite. The average shear strength of the combined joint of SiC/Cu–SiC fabricated using the Sn5Sb3Ti solder was 42.5 MPa. The Sn–Sb–Ti solder is a direct competitor of the S-Bond active solder. The production of solders is cheaper, and the presence of antimony increases their strength. In addition, the application temperature range is wider.

Sapphire optical viewport for high pressure and temperature applications.

We describe the design of a soldered sapphire optical viewport, which is useful for spectroscopic applications of samples at high temperatures and high pressures. The sapphire window is bonded via active soldering to a metal flange with a structure of two c-shaped rings made of different metallic materials in between, so as to mitigate thermally induced stress. A spectroscopic cell equipped with two of the optical viewports has been successfully operated with alkali metals in a noble gas environment at temperatures in the range of 20-450 °C at noble gas pressures from 10-6 mbar to 330 bars. In the upper pressure range, we observe a leakage rate smaller than our readout accuracy of 30 mbar per day.

The thermodynamical analysis algorithm at sapphire-metal soldering design in plasma electronics devices

This project is devoted to the design of algorithm of the possibility analysis of phys-ical-chemical reaction course at sapphire-metal soldering, based on the known equations of thermodynamics. There are stated the results of the thermodynamical analysis of the general methods of sapphire compounds obtaining with usage of molybdenum and wolfram metallization, and active soldering with titanium

Fluxless Direct Soldering of Transparent Conductive Oxides (TCOs) to Copper

Due to the combined advantages of low cost, good soldering properties, and appropriate melting temperature range, novel Sn8Zn3Bi1Mg active solder was developed for direct soldering of transparent conductive oxide (TCO) ceramic targets with oxygen‐free copper at 200°C in air. The TCO specimens have aluminum‐doped zinc oxide (AZO) and zinc oxide (ZnO) ceramics. The direct soldering process was performed without the need for flux or pre‐metallization of the two transparent conductive oxides. The microstructure, phase constitution, melting characteristics, and soldering properties of the Sn8Zn3Bi1Mg active solder were investigated. The liquidus temperature of the Sn8Zn3Bi1Mg active solder was 198.6°C, which was very close to the binary Sn‐Zn eutectic temperature of 198.5°C. The effect of temperature on the bonding strength of the solder joints was evaluated. The shear strengths of AZO/Cu and ZnO/Cu joints soldered with Sn8Zn3Bi1Mg active solder were 10.3 and 7.5 MPa at room temperature, respectively. Increasing the temperature from room temperature to 180°C reduced the bonding shear strengths of AZO/Cu and ZnO/Cu joints to 3.3 and 3.7 MPa, respectively.

Joining of SiO2 glass and 316L stainless steel using Bi\u2013Ag-based active solders

Active brazing is a commonly used method for joining dissimilar materials with at least one non-metallic component. In the present study, joining of SiO2 glass to 316L stainless steel was performed utilizing Bi–Ag-based solders. Ti up to a concentration of 4 and Mg up to 1 wt.% were added as active elements. Microstructures of the solder alloys in the as-cast state and of cross sections of the joined compounds were analysed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. In the as-cast state of the solder, Ti is found in Bi–Ti intermetallic phases; Mg is partially dissolved in the fcc-(Ag) phase and additionally contained in a ternary Ag-Bi-Mg phase. After soldering, a tight joint was generated using several alloy compositions. Ti leads to the formation of reaction products at the steel/solder and glass/solder interfaces, and Mg is exclusively accumulated at the glass/solder interface.

Composition design of Sn-based active solder for soldering SiC ceramic using density functional theory calculation

Soldering SiC using Sn-based solder can lower residual interface stress due to low soldering temperature. Active elements can play key roles in interfacial bonding between Sn-based solder and SiC ceramics. In this study, density functional theory (DFT) calculation was performed to evaluate whether Ti, Al, Zr and Ag atoms can act as active elements to solder SiC. Work of adhesion (Wad), charge density difference and density of states were used to study the interfaces without and with active elements. β-Sn(001)/β-SiC(111) interface was built first and the C-terminated hollow site interface was found to have the largest Wad of 3.13 J/m2. It is found that with doping of Ti and Zr atoms, Wad values of interfaces increase to 5.70 and 5.35 J/m2, and thermodynamics stability of interfaces are also improved. In contrasting, Al and Ag atoms have the opposite effects. The electronic structure analysis shows that Ti and Zr can form strong ionic bonds with C atoms. Therefore, Sn–Ti and Sn–Zr alloys can be used as active solders to join SiC ceramic at low temperature.

Wetting behaviours and interfacial characteristics of Co-binder sintered polycrystalline diamond by Sn[sbnd]Ti active solder

The reactive wetting and interfacial characteristics of the Sn2Ti active solder were experimentally investigated on sintered polycrystalline diamond (PCD) substrates containing 8–18 wt.% Co binders. The initial spreading temperature of Sn2Ti on PCD was determined by the continuously elevating temperatures wetting experiment. The Sn2Ti started to spread on PCD at 500–630 °C. The higher the cobalt content, the lower the initial spreading temperature. Meanwhile, the spreading kinetics analysis through isothermal wetting experiment indicated the spreading process of Sn2Ti on PCD can be well described by the classic chemical reaction-controlled model at 650–900 °C. Both rod-like TiC carbide and faceted CoSnTi intermetallics (IMCs) were observed at the wetting triple line, with the formation morphologies strongly depending on wetting temperatures. The results obtained in this work are believed to be of importance for the optimization of brazing technique for sintered PCD, and hence the development of PCD diamond machining tools with minimized thermal damages.

Reactive Infiltration and Microstructural Characteristics of Sn-V Active Solder Alloys on Porous Graphite.

In this work, the reactive wetting and infiltration behaviors of a newly designed Sn-V binary alloy were comprehensively explored on porous graphite for the first time. It was discovered that 0.5 wt.% addition of V can obviously improve the wettability of liquid Sn on porous graphite and the nominal V contents in Sn-V binary alloys has minor effects on the apparent contact angles wetted at 950 °C. Moreover, the V-containing Sn-V alloys were initiated to spread on porous graphite at ~650 °C and reached a quasi-equilibrium state at ~900 °C. Spreading kinetics of Sn-3V alloy on porous graphite well fitted in the classic product reaction controlled (PRC) model. However, our microstructural characterization demonstrated that, besides vanadium carbide formation, the adsorption of V element at the wetting three-phase contact line spontaneously contributed to the reactive spreading and infiltrating of Sn-V alloys on porous graphite. Meanwhile, the formation of continuous vanadium carbides could completely block the infiltration of Sn-V active solder alloy in porous graphite. Affected by the growth kinetics of vanadium carbides, the infiltration depth of Sn-V alloys in porous graphite decreased at increased isothermal wetting temperatures. This work is believed to provide implicative notions on the fabrication of graphite related materials and devices using novel V-containing bonding alloys.

Reactive wetting of Sn-V solder alloys on polycrystalline CVD diamond

In this paper, the reactive wetting of polycrystalline chemical vapour deposition (CVD) diamond by a novel Sn-V solder alloy was critically examined using the sessile drop method. It has been found the Sn-V solder alloys start to spread on the CVD diamond at around 600 °C. Moreover, 0.5 wt% addition of V is adequate to induce an outstanding spreading of Sn-V active solder alloys on CVD diamond; while the original V content in Sn-V alloys has a negligible influence on final contact angles after wetting at 950 °C. The spreading kinetics of Sn-3V alloy on CVD diamond can be described using the classical chemical reaction-limited model at 700–850 °C. However, ultrafast adsorption of V element to the fresh diamond surface was evidenced by the formation of precursor film on the periphery of solidified Sn-V droplets. Hence, both interface reaction and adsorption of active element are accountable for the reactive spreading of Sn-V alloy on CVD diamond, especially during the early stage of spreading at relatively low temperatures. Results obtained in this study are therefore significant for not only the development of diamond bonding technique, but also the understanding of reactive wetting of metals on diamond and other carbonous materials.

Characterization of ultrasonic soldering of Ti and Ni with Ni/Al reactive multilayer deposition

The joining of Ti and Ni at low temperatures was analysed in this work. For joining pure Ti and Ni coins of 1.5 mm in thickness were used. Reactive multilayer thin films/foils with nanometric period (bilayer thickness), in particular Ni/Al multilayers, have been used to promote joining in two thickness of 28 and 55 nm. The ultrasonic soldering with SnAgTi active solder has been used for “hard-to-solder” material. The structural evaluation of soldered joint was studied by optical microscopy and EDX analysis. The structural analysis was focused to the creation of intermetallic layers in the joint interface. The mechanical properties of solder joints were tested by shear strength.

Dissimilar Joining of Pure Aluminum to SiCp/Al-MMCs Using an AlMgGaLi Active Interlayer Foil

To broaden the application of advanced metal matrix composites in the electronic packaging industry, a lead-free AlMgGaLi interlayer was developed for active soldering of aluminum to aluminum metal matrix composites. The effect of joining pressure on the microstructure evolution, interfacial wettability and mechanical properties of the dissimilar joints was investigated. The experimental results indicated that as the joining pressure increased, the mean thickness of the bond seam was 46.02 μm, and solidification of a solid solution occurred (detected by SEM/XRD analysis). The composition of the Al-based solid solution (in atom%) was 86.52% Al, 9.32% Mg, 2.56% O, 1.5% Ga and 0.1% Si. The pressure improved the interfacial wettability by enhancing the atom diffusion between the interlayer and parent materials. The joint shear strength initially increased and then decreased, and a sound joint with a maximum shear strength of ~ 45 MPa was produced at 450 °C and 0.75 MPa. The fracture crack initially occurred at the interfaces of the Al/filler metal and then propagated mainly along the Al2O3 layer on the Al side. A novel model describing the pressure-induced microstructure changes within the joint and the formation of an Al2O3 diffusion barrier layer at the Al/filler metal interface is proposed.

Application of AlMgGaLi foil for joining copper to SiCp/Al-MMCs for high-temperature and high-power electronics

A novel lead-free foil (AlMgGaLi) with a melting point of 398.3 ~ 414.8 °C was developed for active soldering of copper to aluminum matrix composite. The effect of joining pressure on the microstructure, interface wetting and shear strength of the dissimilar joints was analyzed. When the joining pressure increased to 1 MPa, an Al-based solid solution with an atomic composition of 89.62% Al, 6.5% Mg, 3.1% O, 0.46% Cu, 0.23% Ga and 0.09% Si was formed within the bond seam and the thickness of the transition layer with copper dissolution was approximately 4.9 μm. The joining pressure improved the interfacial wettability of the dissimilar joint by enhancing mutual diffusion with a shortened interface layer, tailored the runout and the formation of bond seam, and controlled an appropriate thickness of the copper dissolution transition layer. Sound joint with a maximum shear strength of 94 MPa (~ 80% of parent composites) is achievable at 450 °C using the joining pressure of 1 MPa. The failure mechanism of the joints with the AlMgGaLi foil under shear stress has been revealed from the analysis on the interface layers of the joints with SEM/EDX/XRD. Our studies provide an important guideline for using an AlMgGaLi and other similar fillers for a successfully joining of copper to Al-MMCs for high-temperature and high-power electronic devices.

Low-temperature wetting of sapphire using Sn–Ti active solder alloys

Monocrystalline alumina, known as sapphire, is one of the most commonly used ceramics in electronic devices. Understanding its wettability is thus of great importance for its engineering applications. In this work, the low-temperature wetting mechanisms of Sn–Ti active solder alloy on C-plane sapphire was comprehensively studied using the sessile drop method. The addition of 0.1 wt % Ti was found to effectively improve the wettability of Sn–Ti alloys, and the lowest contact angle on the sapphire substrate was achieved at 950 °C when Ti content was increased to 3 wt%. Thermal dynamics analysis and experimental results indicated that the isothermal spreading of Sn–3Ti alloy is controlled by the Ti adsorption in the vicinity of wetting triple line. Moreover, sapphire was successfully brazed using Sn–3Ti alloy at 500, 550, and 600 °C, and the maximum shear strength was measured as 30.3 MPa. Our understanding of the wettability of sapphire provides the fundamental theory for developing new bonding technique for this important crystal.

Research on soldering AlN ceramics with Cu substrate using Sn-Ag-Ti solder

PurposeThis study aims to solder AlN ceramics with a Cu substrate using an active type Sn-Ag-Ti solder. Soldering was performed with power ultrasound. The Sn3.5Ag2Ti alloy was first studied.Design/methodology/approachIt was found to contain a Sn matrix, where both Ag phase – ɛ-Ag3Sn – and Ti phases ɛ-Ti6Sn5 and Ti2Sn3 – were identified. Ti contained in these phases is distributed to the interface with ceramic material. A reaction layer was thus formed. This layer varies in thickness from 0.5 to 3.5 µm and ensures the wettability of an active solder on the surfaces of ceramic materials.FindingsX-ray diffraction analysis proved the presence of new NTi and AlTi2 phases on the fractured surface. Sn plays the main role in bond formation when soldering the Cu substrate with Sn-Ag-Ti solder. The Cu3Sn and Cu6Sn5 phases, which grow in direction from the phase interface to solder matrix, were found in all cases within the solder/Cu substrate interface. The combination of AlN ceramics/Cu joint maintained a shear strength of 29.5 MPa, whereas the Cu/Cu joint showed a somewhat higher shear strength of 39.5 MPa.Originality/valueThe present study was oriented towards soldering of AlN ceramics with a Cu substrate by the aid of ultrasound, and the fluxless soldering method was applied. Soldering alloy type Sn-Ag-Ti was analysed, and the interactions between the solder and ceramic and/or Cu substrate were studied. The shear strength of fabricated soldered joints was measured.

Ultrafast air bonding between SiC ceramic and SnAgTi alloy under the action of ultrasounds

With the aim of overcoming the limitations of traditional soldering ceramic methods for power device packaging, a simple but ultrafast bonding technology is reported. The effect and mechanism of ultrasonic action on the interfacial bonding and microstructure is investigated and thoroughly discussed. An ultrafast interfacial bond between SiC ceramics and SnAgTi active solder has been successfully achieved through a reaction at the interface at a low temperature of 250 °C in the extremely short time. High-resolution transmission electron microscopy (HRTEM) revealed that a silica layer on the surface of SiC reacted with Ti from the SnAgTi active solder to form a nanometer-thickness amorphous titania layer at the interface under the ultrasonic action, which creates an exceptional interfacial structure and facilitates bonding between the two dissimilar crystals. A discontinuous titania layer at the interface was identified within 0.1 s. With further increasing ultrasonic action time to 1 s, a continuous titania layer with a thickness of 7.6 ± 0.5 nm formed at the interface. A new interfacial reaction mechanism was revealed and it was found that ultrasound accelerated the reaction of liquid active solder/ceramic. Our finding demonstrated that ultrasound could be an effective approach for joining ceramics which is difficult to wet by a liquid metal at low temperature. The combined impact of ultrasonic cavitation and streaming dominated the mechanism and kinetics of the rapid interfacial reaction.