Intermetallic Compound Growth Research Articles

Intermetallic compound growth behavior and mechanical performance in Sn58Bi/Cu solder joint bearing Mg particles incorporation during thermal aging

The microstructure and intermetallic compound (IMC) growth in Sn58Bi/Cu and Sn58Bi-0.4 Mg/Cu solder joints were examined in this study under varied thermal aging time (6, 12, 18, 24, and 30 h) at 120 °C. The Shear test was conducted to assess the solder joint mechanical performance. The results indicated that the precipitation of the Bi phase in Sn58Bi/Cu and Sn58Bi-0.4 Mg/Cu solder joints was not significantly inhibited by adding Mg as aging time increased. The IMC layer thickness of both solder joints increased as the aging time increased, but the Cu3Sn IMC thickness in Sn58Bi-0.4 Mg/Cu solder joint was consistently thinner than that in Sn58Bi/Cu joint. The temporal evolution of the Cu3Sn IMC layer was investigated, and it was found that the inclusion of Mg particles reduced the diffusion coefficient of Cu3Sn IMC. Furthermore, the shear test revealed that throughout the initial phases of thermal aging, fractures occurred within the solder matrix for both joints. As thermal aging time increased, fractures extended into the IMC layer, accompanied by transgranular and intergranular fractures. Simultaneously, adding Mg particles delayed brittle fracture in the solder joints, enhancing their mechanical properties.

Optimization of Wire-bonding Process Parameters for Gold Wire and Aluminium Substrate using Response Surface Method

Wire bonding is a connecting technique that uses a combination of temperature, force, ultrasonic power, and time to attach two metallic materials, a wire, and a bond pad. In electronics, gold-aluminium (Au-Al) contact wire bonds are widespread due to corrosion resistance and great conductivity of both metals. However, due to the large contact-potential difference, the intermetallic compound growth at the metal’s interaction boundary has considerably worsened the advantageous properties of Au-Al intermetallic system. This intermetallic exhibit low toughness, and possibly low corrosion resistance, which would result in poor bonding quality. In this work, the materials used are 4x8 aluminium substrates and a 100-meter-long gold wire spool. This study aims to investigate the most optimised set of parameters to be used in Au-Al wire bond system, due to how problematic this system could have towards bonding quality. The experimental array was created using a response surface methodology (RSM)-based design of experiments. The effect of parameters and their significance to bonding quality in the Au-Al bond system were studied using analysis of variance (ANOVA). A correlation model was created for the wire bond strength data. The findings suggest that, within the range of parameters examined, the proposed correlation model can be utilized to predict performance measures. The optimum value of Au-Al wire bond system parameters was established at the time of bond at the first bonding site selected for 300 milliseconds (ms), wire looping height selected for 1200 micrometre (μm), wire bond Y-axis length selected for 996 micrometre (μm), and ultrasonic force at second bonding site selected for 300 milli Newton (mN). The outcomes of this research add to our understanding of the Au-Al wire bonding contact, in addition, to enhancing the wire bond's quality.

Solid/solid state interfacial reactions in the lead-free solders/Cu- 2.3%wt. Fe alloy (C194) couples

BackgroundLead-free solders (LFSs) involve incorporating trace elements into Sn, resulting in alloys like Sn-3.0 wt.% Ag-0.5 wt.% Cu (SAC) and Sn-0.7 wt.% Cu (SC). These solder have similar properities to Sn-Pb solders. C194, renowned for its exceptional corrosion resistance, high strength, and good weldability, serves as a preferred lead-frame material in electronic packaging. In this study, we investigated the solid/solid state interfacial reactions between the LFS and Cu-2.3 wt.% Fe alloy (C194). MethodsThree LFS including Sn, SAC, and SC were first reflowed with C194 to form the LFS/C194 couple. Then the LSF/C194 couples were aged at 125–175 ℃ for 100–2000 h. Significant findingsThe results revealed that only the (Cu, Fe)6Sn5 phase was formed in the Sn/C194 couple aged at 125 ℃. At higher temperatures and longer aging times, the (Cu, Fe)3Sn phase was formed in all three couples. The Fe addition into Cu could inhibit the (Cu, Fe)3Sn phase growth. Kirkendall voids in this study occur more frequently with the increase in aging temperatures and times, but the intensity varies in each system. Meanwhile, the thickness of total intermetallic compound (IMC) was increased with the increase in aging times and temperatures in these three couples. The IMC growth mechanism is diffusion controlled in all LFSs/C194 couples.

Enhancement of SAC105 solder for vacuum soldering with Cu substrates through incorporation of activated Ti nanoparticles

This study incorporated activated Ti nanoparticles (Ti NPs) into Sn1·0Ag0·5Cu (SAC105) solder for vacuum soldering with Cu substrates. The wettability, microstructure, interfacial, and mechanical properties of SAC105-xTi (x = 0.1, 0.2, 0.3, 0.4, 0.5 wt%) composite solder were systematically investigated. The results showed that adding Ti NPs improved the wettability of SAC105 solder, in which the wetting angle of SAC105-0.3Ti solder was 19.51°. Additionally, Ti NPs helped to refine the microstructure and inhibited the growth of interfacial intermetallic compounds (IMC). The shear strength of SAC105/Cu joints increased and then decreased with increasing Ti NPs content, and the optimum shear strength was obtained for SAC105-0.3Ti/Cu joints at 27.98 MPa. The strength of the solder matrix and the IMC layer was altered by adding Ti NPs, resulting in a modification of the fracture path of the joint, bringing it closer to the IMC layer. Excessive addition of Ti NPs could lead to their agglomeration within the joints and result in damage to the mechanical properties of the joints. Furthermore, adding Ti NPs increased the microhardness of SAC105 solder.

Tuning the growth of intermetallic compounds at Sn-0.7Cu solder/Cu substrate interface by adding small amounts of indium

The void defect in intermetallic compounds (IMCs) layer at the joints caused by inhomogeneous atomic diffusion is one of the most important factors limiting the further development of Sn-based solders. In this work, the thermodynamic stability of IMCs (high-temperature η-Cu6Sn5 and o-Cu3Sn phases) was improved by adding small amounts of indium (In), and the IMCs layers with moderate thickness, low defect concentrations and stable interface bonding were successfully obtained. The formation order of compounds and the interfacial orientation relationships in IMCs layers, the atomic diffusion mechanism, and the growth tuning mechanism of In on η-Cu6Sn5 and Cu3Sn, after In adding, were discussed comprehensively by combining calculations and experiments. It is the first time that the classic heterogeneous nucleation theory and CALPHAD data were used to obtain the critical nucleus radius of η-Cu6Sn5 and Cu3Sn, and to explain in detail the main factors affecting the formation order and location of IMCs at joints during the welding process. A novel and systematic growth model about IMCs layers in the case of doping with alloying elements was proposed. The growth tuning mechanism of In doping on η-Cu6Sn5 and Cu3Sn was further clarified based on the proposed model using first-principles calculations. The growth model used in this study can provide insights into the development and design of multielement Sn-based solders.

Reliability improvement of SnAgCu interconnections under extreme temperature condition by TiO2 nanoparticles doping: Experiments and first principles calculations

Electronic components of the spacecraft during their service may endure intricate and extreme temperature environments. In this study, the interfacial microstructure evolution and reliability of Cu/Sn-3.0Ag-0.5Cu (SAC305)/Ni and Cu/Sn-3.0Ag-0.5Cu-0.05TiO2 (SAC305–0.05TiO2)/Ni interconnections under thermal shock from −196 °C to 150 °C are investigated. Short-column-type (Cu,Ni)6Sn5 intermetallic compounds (IMCs) are developed at the solder/Ni interface for both interconnections after the reflow process, and their morphology changes to long-rod type after 200 cycles. Extremely thin and discontinuous (Ni,Cu)3Sn4 phases are generated between (Cu,Ni)6Sn5 and Ni only in SAC305 interconnections after 200 cycles. The rate of interfacial IMCs growth in SAC305–0.05TiO2 interconnections is slower than that in the SAC305 interconnections. Cracks are formed in the IMC layer of the SAC305 interconnection after 200 cycles, which propagate through the whole IMC layer after 250 cycles. While for the SAC305–0.05TiO2 interconnection, no crack is observed until after 250 cycles. TiO2 nanoparticles doping could suppress the interfacial IMC growth, leading to an enhancement in the interconnection reliability under thermal shock. First-principles calculations are performed to further understand the mechanism for phase transformation of Ni-Cu-Sn IMCs and the reliability improvement of interconnections.

Effect of non-standard SnAg surface finishes on properties of solder joints

In this study, the effects of nonstandard near-eutectic SnAg surfaces on the wettability, intermetallic compound growth and mechanical properties of solder joints were investigated. Four types of surface finishes based on near-eutectic SnAg alloys with different compositions and numbers of layers were analyzed. Design/methodology/approachThe effect of surface-finishes SnAg5NiP and SnAg7NiP, which were prepared with and without a Ni-P diffusion barrier, was tested. The Ni-P layer was produced either chemically or electrochemically. The effect of the SnAg surface finish on wettability, formation, and growth of intermetallic compound in the solder joint was analyzed. We further explored the impact of different PCB finishes on the quality of soldered joints. This investigation involved a comparative analysis of the behavior of SnAg finishes in comparison to pure copper, as well as the commonly employed HASL, ENIG, and ImSn finishes. FindingsIt was found that SnAg surface finishes with a Ni-P diffusion barrier are wetted by molten solder faster than surface finishes without a diffusion barrier. The mechanical properties of the joints on both surfaces are comparable to those on ENIG. SnAg that include a chemically created Ni-P diffusion layer is characterized by the formation of more thermally stable ternary intermetallic compounds based on (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4. On the contrary, the electrochemically formed Ni layer supports the increase in the rate of intermetallic compound formation, which affects the properties of the soldered joints. OriginalityNonstandard near-eutectic SnAg finishes, which contains a Ni-P diffusion layer can be used as promising replacement of ENIG or other standard finishes.

Phase Equilibria of the Ag-Al-Au Ternary System and Interfacial Reactions in the Au-xAg/Al Couples at 450 °C.

The phase equilibria of the Ag-Al-Au ternary system and the solid-state reaction couple for the Au-xAg/Al system were investigated isothermally at 450 °C. By investigating the Ag-Al-Au ternary system and its isothermal section, this study aims to provide a clearer understanding of the phase stability and interfacial reactions between different phases. This information is crucial for designing materials and processes in electronic packaging, with the potential to reduce costs and improve reliability. There were seven single-phase regions, thirteen two-phase regions, and six three-phase regions, with no ternary intermetallic compound (IMC) formed in the isothermal section of the Ag-Al-Au ternary system. When the Au-25 wt.% Ag/Al couple was aged at 450 °C for 240-1500 h, the AuAl2, Au2Al, and Au4Al phases formed at the interface. When the Ag contents increased to 50 and 75 wt.%, the Ag2Al, AuAl2, and Au4Al phases formed at the interface. When the aging time increased from 240 h to 1500 h, the total IMC thickness in all Au-xAg/Al couples became thicker, but the types of IMCs formed at the interface did not change. The total IMC thickness also increased with the increase in the Ag content. When the Ag content was greater than 25 wt.%, the Au2Al phase was converted into the Ag2Al phase. The IMC growth mechanism in all of the couples followed a reaction-controlled process.

Growth of intermetallic compounds and their reinforcement on CrCoNi/Au80Sn20 soldering interfaces

To broaden the utility of the CrCoNi medium entropy alloy in engineering applications, it is imperative to conduct a comprehensive investigation into its soldering capabilities. This study is centered on a detailed examination of the microstructure and mechanical properties of solder joints formed between Au80Sn20 and CrCoNi through vacuum soldering. Nonetheless, the interaction between the solder and the alloy leads to the formation of an intermetallic compound layer with a specific thickness. Raising the soldering temperature results in an expanded contact area and an increase in the shear strength of the joints. This can be attributed to the enhanced diffusion and atom migration at elevated temperatures.Moreover, the hardness of the intermediate layer exceeds that of both the medium entropy alloy and the Au80Sn20 alloy. This is primarily due to the strengthening effects brought about by the presence of Ni and Co in the alloy. This study underscores the importance of thoroughly investigating soldering techniques for the medium entropy alloy. It also provides valuable insights into the mechanical characteristics and microstructure of the resulting solder joints.

The design of low-temperature solder alloys and the comparison of mechanical performance of solder joints on ENIG and ENEPIG interface

In recent years, in order to adapt to the trend of low-temperature assembly and integration, low-temperature hybrid solders with multiple elements added to the tin solder matrix have been investigated. In this regard, the morphology and size of intermetallic compounds (IMCs) are altered by adding some alloying elements, and the strength of solder joints is improved to some extent. Different pad surface treatments affect the growth of IMC, which leads to various failure modes in interconnect solder joints. Therefore, it is necessary to study the interfacial reaction, microstructure and mechanical properties of hybrid solder and different metal pads to explore the growth mechanism of IMC and the failure modes of solder joints. In this paper, mixed Sn–3Ag-0.5Cu/Sn–58Bi low-temperature solder joints on Au/Ni/Cu (ENIG) and Au/Pd/Ni/Cu (ENEPIG) substrates are investigated. The results show that the addition of palladium element can change the IMC morphology, refine the grain size of the hybrid solder joints, and affect the fracture failure mode of the solder joints under shear force. The average shear strength is significantly higher than that of solder joints with ENIG surfaces under different process parameters. Thermodynamic calculations of enthalpy change and the effect of Jackson's parameter α value on IMC morphology are also investigated in this paper. The addition of palladium elements increases the α value and is more favorable to the formation of columnar grains. This provides guidance for the grain growth of IMC in hybrid solder joints with added alloying elements.

Wettability of Sn-3.0Ag-0.5Cu Solder Reinforced with TiO2 and Al2O3 Nanoparticles at Different Reflow Times.

This study investigated the influence of reinforcing 0.50 wt.% of titanium oxide (TiO2) and aluminium oxide (Al2O3) nanoparticles on the wettability performance of a Sn-3.0Ag-0.5Cu (SAC305) solder alloy. The thermal properties of the SAC305 nanocomposite solder are comparable with thos of an SAC305 solder with a peak temperature window within a range of 240 to 250 °C. The wetting behaviour of the non-reinforced and reinforced SAC305 nanocomposite solder was determined and measured using the contact angle and spreading area and the relationships between them were studied. There is an increment in the spreading area (5.6 to 7.32 mm) by 30.71% and a reduction in the contact angle (26.3 to 18.6°) by 14.29% with an increasing reflow time up to 60 s when reinforcing SAC305 solder with 0.50 wt.% of TiO2 and Al2O3 nanoparticles. The SAC305 nanocomposite solder has a better wetting performance compared with the SAC305 solder. As the reflow time increased, the spreading area increased and the contact angle decreased, which restricted intermetallic compound growth and thus improved wettability performance.

Improvement of weldability and fracture behavior of mild steel and A7075 aluminum alloy dissimilar friction stir welded joints by increasing welding speed

In this study, dissimilar friction stir welding of mild steel and A7075 aluminum alloy was conducted at a constant tool rotational speed (900 rpm) and different welding speeds of 100–400 mm/min with an interval of 100 mm/min. A thermocouple was employed to record the thermal cycle and the maximum reached temperatures of the A7075/steel interface during the joining process. The higher the welding speed, the lower the maximum temperature recorded during the joining process. Conducting the joining process at a high welding speed also enhanced the cooling rate and, thus, effectively contributed towards eliminating the thermal residual stresses and suppressing the interfacial intermetallic compounds growth. As a result, 100% joint efficiency with a steel base metal fracture was obtained for the joints fabricated at the welding speeds of 300 and 400 mm/min.

Crack initiation and propagation behavior of dissimilar interface with intermetallic compound layer in Al/steel joint using coupled multiscale mechanical testing

We demonstrate multiscale mechanical testing using miniature and microscale tensile tests to elucidate the crack initiation and propagation behaviors corresponding to interfacial nanostructures in dissimilar joints of 6061 aluminum alloy and 304 stainless steel. The initial nucleation and subsequent growth of intermetallic compounds (IMCs) can be controlled by heat treatment after friction stir lap welding. The miniature tensile tests exhibited the relationship between the joint strength and IMC layer thickness with changes in the fracture location. Microscale tensile testing using a single edge-notch tension geometry initiates the crack and subsequent propagations near the interface, which helps identify the crack initiation site and understand the dependence of the local strength on the type of IMCs. Crack deviation behavior toward the Al side, attributed to the difference of local strength, is confirmed by in situ observations, which indicated that continuous failure can easily occur within the grown IMCs, particularly in macroscale joints. It was concluded that the crack propagation is controlled by the local crack deviation toward metal matrix, which tends to occur for the dissimilar interface with thin IMC layer. This miniature/microscale tensile testing approach is expected to clarify the essential relationship between the interfacial microstructure and the fracture behavior.

Comprehensive analysis of Sn58Bi/Cu solder joints reinforced with Mg particles: Wettability, thermal, mechanics, and microstructural characterization

In this study, the Sn58Bi-xMg (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) composite solders were synthesized to explore the impact of Mg particles. The study examined the wettability, thermal properties, mechanical properties, microstructure, and growth of interfacial IMC (intermetallic compound) of composite solder. Experimental results showed that adding Mg particles had no significant impact on the melting point of Sn58Bi solder. However, increasing the Mg content increased the undercooling of the solder. Moreover, the incorporation of Mg particles resulted in a consistent rise in the coefficient of thermal expansion (CTE) of the composite solder, ranging from 11.4 × 10−6/°C to 15.6 × 10−6/°C. It was worth noting that including Mg particles enhanced the wetting ability of Sn58Bi alloy on Cu substrates. With a 0.4 % addition of Mg particles, the wetting area could be increased by 60.14 %, and the lowest wetting angle was approximately 10.43°. Adding Mg particles resulted in an amelioration in the brittleness of the Bi-rich phase within the solder matrix, coupled with a decrease in both the thickness of IMC and the grain size at the joint interface. Compared to the joints without mixed Mg particles, the shear strength of Sn58Bi-0.4Mg solder joints and the microhardness of the alloy increased by 30 % and decreased by 10 %, respectively. Also, the presence of dimples within the fracture indicated a rise in the ductility of the solder joints. Overall, adding 0.4 wt% Mg particles in this experiment resulted in a more effective modification of the Sn58Bi solder comprehensive properties.

Effect of the addition of Cu6Sn5 nanoparticles on the growth of intermetallic compounds at the interfaces of Sn3.0Ag0.5Cu solder joints

To solve the issue of overgrowth of intermetallic compounds (IMCs) at the interfaces of solder joints in electronic devices, this study has focused on the modification of Sn3.0Ag0.5Cu (SAC305) solder by adding Cu6Sn5 nanoparticles (NPs). It was found that Cu6Sn5 NPs would adsorb on the surfaces of the interfacial IMCs due to the high surface energy in solid–liquid reactions and resulted in a peculiarly ordered growth pattern of the new grains. In addition to this, a combined growth mechanism involving encapsulated and engulfed crystal growth of the interfacial IMCs was identified. The addition of Cu6Sn5 NPs was also calculated to increase the activation energy associated with interfacial IMCs growth during high-temperature service, thereby effectively inhibiting the overgrowth of interfacial IMCs. When the mass fraction of Cu6Sn5 NPs was 0.6 wt%, the activation energy for interfacial IMCs growth was the highest (31.9 kJ/mol).

Current-induced solder evolution and mechanical property of Sn-3.0Ag-0.5Cu solder joints under thermal shock condition

Solder joint reliability suffers great challenges due to high current density and miniature solder bump diameter of electronic packages at cryogenic temperature. To tackle these issues, the solder microstructure evolution and the corresponding failure mechanism should be emphasized. In this study, the current-induced microstructure characteristics and mechanical behavior of Sn-3.0Ag-0.5Cu (SAC305) solder joints during thermal shock process was thoroughly addressed over cycles by combining diffusional, electrical, thermal and mechanical features. This result verified that the combining method of thermal shock and electromigration (EM) contributed to the atom diffusion and high thermal stress formation, further causing intermetallic compound (IMC) growth, the repaid dissolution of Cu pad and high thermal stress of the solder joints. High stress induced by either the thermal expansion mismatch of different component, large temperature change (ΔT =346 ℃) and severe lattice distortion became the direct reason for twins and cracks formation of SAC305 solder joints. The combination of crack propagated along the interface and the quick dissolution of Cu substrate at the corner accelerated the eventually failure of the solder joints. Moreover, as the thermal chock cycles was extended, the initiation and propagation of cracks at the cathode side weaken the cathodic shear strength. High stress-induced twin formation at the interface effectively moderated the shear strength degradation due to anode IMC growth after 9 cycles. This study contributed to thoroughly grasp the failure mechanism of the solder joints and design the twin-strengthened Sn-based solder joints under the coupling effects of extreme temperature variation and current stressing.

Oxidation behavior and intermetallic compound growth dynamics of SAC305/Cu solder joints under rapid thermal shock

Oxidation behavior of SAC305/Cu solder joints and kinetics of intermetallic compound (IMC) growth were investigated using an electromagnetic induction heating device. The results show that the solder joint undergoes oxidation when subjected to rapid thermal shock. The oxidation behavior of the solder joint itself is the main factor, which is exacerbated by the presence of the internal Cu6Sn5 IMC. The growth of the Cu6Sn5 layer is controlled by grain boundary diffusion, while that of the Cu3Sn layer is controlled by bulk diffusion. The dissolved Cu of the substrate diffuses mainly into the interfacial IMC and the interior of the solder. Under rapid thermal shock, the shear strength of the solder joint decreases substantially, by 49.2% after 72 h. The fracture mechanism changes from ductile fracture to mixed tough−brittle fracture and finally, to brittle fracture.

Zn additions modifying microstructure, thermal parameters and cytotoxicity of Sn-0.7Cu eutectic solder alloys

Alloys from the SnCu systems have superior properties as compared to the SnPb alloys, such as mechanical and corrosion resistance. However, SnCu alloys still exhibit low oxidation resistance, poor wettability and low reliability. One way to optimize such properties is by adding alloying elements, such as zinc. Zn is generally used in Pb-free solder alloys to minimize intermetallic compound growth in soldered joints, refine the microstructure and increase mechanical strength, in addition to reducing the final cost. The addition of Zn is motivated by the effects it promotes such as microstructural refining, suppression of intermetallics in the substrate/alloy reaction layer, increase in fluidity and mechanical properties. Therefore, this study aims to understand the effects of Zn additions (0.2 and 0.5 in wt%) on solidification thermal parameters (growth rate-V and cooling rate-Ṫ), macrostructure, microstructure, phase transformation, macrosegregation and cytotoxicity in directionally solidified eutectic Sn-0.7wt.%Cu alloy under transient heat flow regime of solidification in copper sheet. Thus, the samples have been characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD). The CALPHAD (CALculation of PHAse Diagrams) method by Thermo-calc software was used to generate property diagrams and isopleths. Cytotoxicity analysis was performed based on cell viability with incubation periods of 15 and 30 days for the alloys, with subsequent exposures of the extracts for 24 and 48 h. The Zn additions caused slight changes in the phase transformation temperatures of the Sn-Cu-Zn alloys. Macrostructures exhibiting columnar-to-equiaxed transition (CET) were observed for the Sn-Cu-Zn alloys. The microstructures of the Sn-Cu-Zn alloys were predominantly dendritic with a matrix rich in tin (β-Sn) surrounded by a eutectic mixture of the β-Sn + Cu6Sn5 + CuZn phases. After CET on Sn-Cu-Zn castings, low velocity eutectic cells have been observed. Moreover, Zn additions refined and did not change the dendritic arrangement of the Sn-Cu-Zn alloys, when compared to the Sn-0.7wt.%Cu alloy. However, increasing the Zn content did not affect the microstructural scale in the ternary alloys when compared to each other. The variations in the microstructural scale did not influence the toxicity of the examined alloys, but factors such as incubation time and chemical composition did. In general, Zn improved the cell viability of the Sn-Cu-Zn alloys, but still with moderate cytotoxic levels.

Study on inhibition of interfacial compounds and improvement of joint properties by low temperature and high-pressure process in diffusion bonding of Ti/Cu

The vacuum diffusion bonding of Ti/Cu under low temperature and high pressure was prepared to explore a suitable process to inhibit the formation of Ti–Cu intermetallic compounds and thus effectively improve the strength of Ti/Cu joints. The conventional diffusion bonding of Ti/Cu joint was also compared and analyzed. The diffusion process, especially the bonding temperature, significantly influences the morphology of the joint interface. At a lower diffusion temperature (550–580 °C) and a larger bonding pressure (30∼40 MPa), the effective bonding of Ti/Cu was realized. Low temperature inhibited the nucleation and growth of intermetallic compounds, and the types and thicknesses of intermetallic compounds at the interface decreased significantly. The interface of the Ti/Cu joint prepared at 550°C- 40 MPa formed an amorphous transition layer with a width of approximately 10 nm, rather than a brittle intermetallic compound layer. The grain size of the transition layer was mainly concentrated in the range of 0.25–1.05 μm. The hardness distribution of the sample did not show an obvious increase. The shear strength of the Ti/Cu joint at 580°C-30MPa reached 181 MPa.

Interfacial reactions in the Sn-9.0 wt.% Zn/Cu-Ti alloy (C1990 HP) couple

PurposeThe purpose of this study was to examine the influence of adding a small amount of Ti to a Cu-based alloy, specifically the commercial Hyper Titanium Copper alloy (C1990 HP), which contains Cu-3.28 wt.% Ti, on its interfacial reaction with Sn-9.0 wt.% Zn (SnZn) solder, using the liquid/solid reaction couple technique.Design/methodology/approachThe SnZn/C1990 HP couples were subjected to a reaction temperature of 240–270°C for a duration of 0.5–5 h. The resulting reaction couple was characterized using a scanning electron microscope, energy dispersive spectrometer, electron probe microanalyzer and X-ray diffractometer.FindingsIt was observed that the scallop-shaped CuZn5 and planar Cu5Zn8 phases were formed in almost all SnZn/C1990 HP couples. With increased reaction duration and temperature, the Cu-rich intermetallic compound (IMC)-Cu5Zn8 phase became a dominant IMC formed at the interface. The total thickness of the IMCs was increased with the increase in the reaction duration and temperature. The IMC growth obeyed the parabolic law, and the IMC growth mechanism was diffusion controlled. The activation energy of the SnZn/C1990 HP couple was 64.71 kJ/mol.Originality/valueThis article presents an analysis of the IMC thickness in each sample using ImageJ software, followed by kinetic analysis using Origin software at various reaction temperatures of SnZn/C1990 HP in liquid/solid couples. The study also includes detailed reports on the morphology, interface composition and X-ray diffraction analysis, as well as the activation energy. The findings can serve as a valuable reference for electronic packaging companies that utilize C1990 HP substrates.