Soldering Temperature Research Articles

Influence of pH on Indium Deposition Rates: A Comprehensive Electrochemical Analysis

Abstract Binary indium-tin (In-Sn) and ternary indium-tin-bismuth (In-Sn-Bi) alloys hold significant promise for reducing soldering temperatures in electronic assembly. However, traditional metallurgical methods are unsuitable for fabricating micro-solder joints, making alloy electroplating essential for fine-pitch interconnects. The co-electroplating of alloy constituents is often hindered by substantial differences in reduction potentials. Therefore, sequential electroplating followed by high-temperature reflow emerges as a more practical solution. Nonetheless, challenges persist, particularly due to the limited understanding of indium (In) deposition kinetics and its strong dependence on pH. This study investigates the influence of pH on In plating rates and overall deposition kinetics. The thickness and cross-sectional morphology of electroplated In films are analyzed across a pH range of 2.2–3.3, with plating conditions optimized to identify the most effective parameters. Structural properties, uniformity, and potential oxide inclusions in the electroplated films are assessed using X-ray diffraction and differential scanning calorimetry. Plating at pH 2.9 in a solution of 0.12M In₂(SO₄)₃ and 0.70M Na₂SO₄ produces the highest deposition rate and the most structurally homogeneous layers. Deviations from this optimal pH inevitably promote side reactions that markedly reduce deposition rates and compromise film quality.

Effects of Ni addition on wettability and interfacial microstructure of Sn-0.7Cu-xNi solder alloy

Purpose This paper aims to study the effect of different Ni content on the microstructure and properties of Sn-0.7Cu alloy. Then, the spreading area, wetting angle, interface layer thickness and microstructure of the soldering interface was observed and analyzed at different soldering temperatures and times. Design/methodology/approach Sn-0.7Cu-xNi solder alloy was prepared by a high-frequency induction melting furnace. Then Sn-0.7Cu-xNi alloy was soldered on a Cu substrate at different soldering temperatures and times. Findings It was found that Ni made the intermetallic compounds in the Sn-0.7Cu solder alloy gradually aggregate and coarsen, and the microstructure was refined. The phase compositions of the solder alloy are mainly composed of the ß-Sn phase and a few intermetallic compounds, Cu6Sn5 + (Cu, Ni)6Sn5. The maximum value of 12.1 HV is reached when the Ni content is 0.1 Wt.%. When the Ni content is 0.5 Wt.%, the wettability of the solder alloy increases by about 15%, the interface thickness increases by about 8.9% and the scallop-like structure is the most refined. When the soldering time is 10 min and the soldering temperature is 280 °C, the wettability of Sn-0.7Cu-0.2Ni is the best. Originality/value It is groundbreaking to combine the change in soldering interface with the soldering industry. The effects of different soldering temperatures and times on the Sn-0.7Cu-xNi alloy were studied. Under the same conditions, Sn-0.7Cu-0.2Ni exhibits better wettability and more stable solder joint stability.

Effects of soldering temperatures and composition on the microstructures and shear properties of Sn58Bi-xSAC0307/ENIG solder joints

PurposeThis paper aims to systematically study the effects of reflow temperature and SAC0307 (SAC) content on the micromorphology and mechanical properties of Sn58Bi-xSAC0307 composite solder joints to meet the requirements of high integration and low-temperature packaging of devices and provide references for the application of composite solder joints.Design/methodology/approachSn58Bi and SAC0307 solder paste was mechanically mixed in different proportions to prepare Sn58Bi-xSAC0307/ENIG solder joints. The thermal properties, microstructure and mechanical properties of the composite solder joints were studied.FindingsAs SAC content in the solder increases, the balling temperature of SnBi-SAC solder gradually increases. The addition of SAC alloy reduces the grain size of large Bi-rich phase, and there are small-sized dispersed Bi and Ag3Sn particles in the bulk solder. The intermetallic compounds composition of the SnBi-xSAC/ENIG solder joint changes from Ni3Sn4 to (Ni, Cu)3Sn4 and (Cu, Ni)6Sn5 with SAC increasing. As the soldering temperature increases, the strength of all solder joints shows a rising trend. Among them, the shear strength of SnBi-20SAC solder joints at a reflow temperature of 150°C is approximately 37 MPa. As the reflow temperature increases to 250°C, the shear strength of solder joints increases to approximately 67 MPa.Originality/valueThis study provides a reference for the optimization of low-temperature solder composition and soldering process under different package designs.

Investigation of the Impacts of Solder Alloy Composition and Temperature Profile on Fatigue Life of Ball Grid Array Solder Joints Under Accelerated Thermal Cycling

Abstract This study investigated the thermal fatigue reliability of ball grid array (BGA) solder joints under accelerated thermal cycling, considering the impacts of solder alloy and temperature profile. Applying the Darveaux solder joint reliability assessment, simulations consider lead-based (63Sn37Pb and 62Sn36Pb2Ag) and lead-free (SAC105, SAC305, and SAC405) solder alloys under temperature profiles: 0°C (Tmin) to 100°C (Tmax), −40°C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C. Results indicate that SAC305 exhibited the highest equivalent stress, while 63Sn37Pb demonstrated the highest plastic strain and creep strain energy density. SAC105 displayed the lowest stress and strain parameters. Moreover, increasing the thermal cycling temperature range intensifies stress, strain, and damage parameters, with −40 °C to 150 °C showing the highest magnitudes. SAC405 exhibited superior thermal fatigue life compared to other alloys, with its cycles to failure outperforming 63Sn37Pb, SAC105, 63Sn36Pb2Ag, and SAC305 by 16832, 11992, 6218, and 3601 cycles, respectively. Lower temperature ranges enhance thermal fatigue life, with 0 °C to 100 °C recording 8%, 33%, and 53% higher life than −40 °C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C, respectively. Notably, higher silver content and lower temperature ranges were associated with increased thermal fatigue life, providing valuable insights for BGA solder joint reliability enhancement.

Effects of soldering temperature and preheating temperature on the properties of Sn–Zn solder alloys using wave soldering

Purpose This study aims to address the problem of low-temperature wave soldering in industry production with Sn-9Zn-2.5 Bi-1.5In alloys and develop qualified process parameters. Sn–Zn eutectic alloys are lead-free solders applied in consumer electronics due to their low melting point, high strength, and low cost. In the electronic assembly industry, Sn–Zn eutectic alloys have great potential for use. Design/methodology/approach This paper explored developing and implementing process parameters for low-temperature wave soldering of Sn–Zn alloys (SN-9ZN-2.5BI-1.5 In). A two-factor, three-level design of the experiments experiment was designed to simulate various conditions parameters encountered in Sn–Zn soldering, developed the nitrogen protection device of waving soldering and proposed the optimal process parameters to realize mass production of low-temperature wave soldering on Sn–Zn alloys. Findings The Sn-9Zn-2.5 Bi-1.5In alloy can overcome the Zn oxidation problem, achieve low-temperature wave soldering and meet IPC standards, but requires the development of nitrogen protection devices and the optimization of a series of process parameters. The design experiment reveals that preheating temperature, soldering temperature and flux affect failure phenomena. Finally, combined with the process test results, an effective method to support mass production. Research limitations/implications In term of overcome Zn’s oxidation characteristics, anti-oxidation wave welding device needs to be studied. Various process parameters need to be developed to achieve a welding process with lower temperature than that of lead solder(Sn–Pb) and lead-free SAC(Sn-0.3Ag-0.7Cu). The process window of Sn–Zn series alloy (Sn-9Zn-2.5 Bi-1.5In alloy) is narrow. A more stringent quality control chart is required to make mass production. Practical implications In this research, the soldering temperature of Sn-9Zn-2.5 Bi-1.5In is 5 °C and 25 °C lower than Sn–Pb and Sn-0.3Ag-0.7Cu(SAC0307). To the best of the authors’ knowledge, this work was the first time to apply Sn–Zn solder alloy under actual production conditions on wave soldering, which was of great significance for the study of wave soldering of the same kind of solder alloy. Social implications Low-temperature wave soldering can supported green manufacturing widely, offering a new path to achieve carbon emissions for many factories and also combat to international climate change. Originality/value There are many research papers on Sn–Zn alloys, but methods of achieving low-temperature wave soldering to meet IPC standards are infrequent. Especially the process control method that can be mass-produced is more challenging. In addition, the metal storage is very high and the cost is relatively low, which is of great help to provide enterprise competitiveness and can also support the development of green manufacturing, which has a good role in promoting the broader development of the Sn–Zn series.

Impact of hot air gun soldering process parameters on the electromechanical properties of electronic yarn

Researchers now confirm that the market for electronic textiles, or ‘E-textiles,’ will rise rapidly. One method of creating e-textiles is the integration of electronics with textiles. Several techniques were used to combine electronics with conductive textile. One of the best methods for connecting electronics to conductive textile fabrics is soldering. Because of this, it is important to look into how the soldering process parameter affects the developed e-textile’s characteristics. In the research paper presented, the effects of temperature, speed of hot air, and amount of paste size of hot air gun re-flow soldering parameters on the electromechanical properties of surface mount device (SMD) embedded electronic yarn were examined. Three main soldering parameters at four different levels were selected based on the preliminary test results involving the soldering of the tiny SMD into CLEVERTEX electrically conductive hybrid yarn. The result shows that soldering of SMD into CLEVERTEX electrically conductive hybrid yarn provided a higher conductivity with 10-ohm DC resistance. Statistical analyses were also carried out to prove the significant effect of the temperature on changing electrical resistance at, α = 0.5, with an F-value of 0.27 and a p value of .036. While the effects of different amounts of solder paste size on the electrical resistance were not statistically significant at α = 0.5, with an F-value of 0.27 and a p value of .84. Moreover, the tensile strength of the developed e-yarn was affected by the hot air soldering parameters. Furthermore, the developments of e-yarn using hot air gun soldering was pronounced in more extreme process conditions, which revealed that there was a strong interaction between the solder temperature, solder paste volume and solder speed. Furthermore, this approach made it easier to generate the optimum quality of e-yarn needed to continue creating prototype electronic textiles.

Thermal and compositional fields to maneuver Cu6Sn5 intermetallic growth on (111) nanotwinned copper substrate

The microstructure of the Cu6Sn5 phase plays a pivotal role in the functionality of microbumps utilized in 3D packaging. In this study, we present an experimental methodology aimed at maneuvering the orientation and morphology of Cu6Sn5 grains formed on (111) nanotwinned Cu substrate, achieved through variations in reflow temperatures (260∘C and 300∘C) and initial Cu proportion in solder (ranging from 0 to 3.0 wt%). At 300∘C and lower initial Cu concentrations (0 and 0.7 wt%), irregularly arranged roof-type Cu6Sn5 grains exhibiting a pronounced {21¯1¯0} texture were observed. Conversely, typical scallop-type Cu6Sn5 grains displaying a specific preferential {21¯1¯3} texture were identified at this temperature for Cu concentrations of 1.5 and 3.0 wt% At 260∘C, the scallop-type morphology was solely present at all Cu composition variants. The differing rates of solute controlled intermetallic phase clustering mechanism at altered solubility limits and magnitudes of thermodynamic driving force for different temperatures, can decide the relative loss of interface coherency and subsequently change the preferred orientation direction of evolving interfacial structures. Our findings demonstrate that the precise control over soldering temperature, solder Cu composition, and the microstructure of Cu UBM can enable the attainment of Cu6Sn5 microstructure with a designated orientation and morphology.

A novel packaging method for FBG temperature sensors based on ultrasonic-assisted soldering technology

The packaging technology of fiber Bragg grating (FBG) sensors is the key to determining their operational performance. A method for encapsulating FBG temperature sensors using ultrasonic-assisted soldering technology has been proposed and attempted. This packaging method is based on the successful connection between SiO2 quartz glass and Invar alloy. Implementing this soldering connection depends on the active components in the solder, which are dispersed into SiO2 and metal alloys to form more stable substances. The FBG with the removed coating is reliably connected to the metal capillary through ultrasonic soldering. The fragile FBG is adequately protected in the capillary. Sn-based solder with a melting point of 297 ℃ has been selected. The soldering temperature of 330 ℃ avoids significant residual stress caused by the difference in the thermal expansion coefficient of the material at the joint. Excellent bonding strength between optical fibers, solder, and capillaries is necessary for encapsulating sensors. Compared to adhesive, solder packaging is no longer affected by the creep of the sealant. The results show that the working range of FBG temperature sensors encapsulated in epoxy resin is −25 ℃ −115 ℃, while temperature sensors encapsulated by welding can operate stably at −50 ℃ −280 ℃. Sensors packaged using ultrasonic-assisted soldering technology have the potential to be embedded in metal substrates, creating favorable conditions for the development of intelligent electromechanical components.

A temperature control method of hot-bar soldering based on extended Kalman filter

PurposeThis study aims to introduce a novel technique for nonlinear sensor time constant estimation and sensor dynamic compensation in hot-bar soldering using an extended Kalman filter (EKF) to estimate the temperature of the thermocouple.Design/methodology/approachTemperature optimal control is combined with a closed-loop proportional integral differential (PID) control method based on an EKF. Different control methods for measuring the temperature of the thermode in terms of temperature control, error and antidisturbance are studied. A soldering process in a semi-industrial environment is performed. The proposed control method was applied to the soldering of flexible printed circuits and circuit boards. An infrared camera was used to measure the top-surface temperature.FindingsThe proposed method can not only estimate the soldering temperature but also eliminate the noise of the system. The performance of this methodology was exemplary, characterized by rapid convergence and negligible error margins. Compared with the conventional control, the temperature variability of the proposed control is significantly attenuated.Originality/valueAn EKF was designed to estimate the temperature of the thermocouple during hot-bar soldering. Using the EKF and PID controller, the nonlinear properties of the system could be effectively overcome and the effects of disturbances and system noise could be decreased. The proposed method significantly enhanced the temperature control performance of hot-bar soldering, effectively suppressing overshoot and shortening the adjustment time, thereby achieving precise temperature control of the controlled object.

Reducing anisotropy of rhombohedral Bi-rich phase for high-performance Ag-alloyed Sn–Bi low-temperature solders

The rhombohedral structure is with anisotropic properties, leading to brittle mechanical properties. However, it is one of the major constituent phases, the (Bi) phase, in the Sn–Bi-based low-temperature solders, which is demanding in the electronic industry for reducing the soldering temperature and alleviating the warpage in high-density fine-pitch electronic packaging. Herein, we proposed a high-performance Ag-alloyed Sn–Bi (SBA) low-temperature solder by reducing the fraction and, more importantly, the anisotropy of the (Bi) phase. We found that the (Bi) phase exhibited considerable solubility for Ag and Sn, even after thermal aging, without any nanoprecipitates as confirmed with both CALPHAD-type thermodynamic modeling and high-resolution TEM. The solution effects of Ag and Sn in the (Bi) phase is elaborated based on in situ nano-indentation, EPMA compositional analyses, EBSD characterizations, and ab initio calculations. The presence of Ag and Sn in the (Bi) phases resulted in both solid solution hardening and softening effects, depending on the Schmid factor of the grain. As a result, in (Bi) polycrystals, alloying could effectively mitigate the anisotropic mechanical properties of the (Bi) phase and facilitated a more uniform dispersion of forces exerted among (Bi) grains in all orientations. Consequently, the designed SBA solder exhibited superior mechanical properties, e.g., an ultimate tensile strength (UTS) of 55 MPa, elongation of 46%, and toughness of 20.6 × 106 J/m3 at a strain rate of 0.0005 s−1. This understanding opens the door for enhanced rhombohedral phase in alloy design for various applications.

Process Window of Mini-LED Display Panel Packaging using Laser Assisted Bonding Technology

For high-resolution display panels using mini-LEDs, high alignment accuracy and high yield of LED transfer and bonding technology are very important parameters of packaging technologies. These parameters of packaging technologies are highly dependent on the interconnection material and bonding process. The use of laser assisted bonding (LAB) technology and epoxy-based interconnection materials has been introduced in mini-LED display panel packaging to improve bonding accuracy and yield. The bonding process of the entire display panel was performed by a tiling SITRAB process because the laser irradiation area is smaller than the LED bonding area on the substrate. For the SITRAB process, an epoxy-based SITRAB material to remove oxide on the surface of solder bump has been developed as a solvent free material. For good wetting of the solder bump during the SITRAB process, the temperature of the solder bumps must be higher than the melting temperature of solder. In general, the stage temperature of the laser process is determined to be around 100C in order to minimize the laser power. However, if the stage temperature is high, the initial properties of the SITRAB material (such as low viscosity and deoxidation function) may be lost due to the high temperature. In this study, the process window of the SITRAB material was determined for a stable SITRAB process. The process window was identified according to three different pot lifes: room temperature pot life (RPL), stage pot life (SPL), and laser pot life (LPL).

Ceramic-to-metal bonding using rare-earth containing Sn–Bi solder

With the increasing miniaturization and power of optoelectronic devices, direct bonding of optical substrates like semiconductors and ceramics to metal heat sinks using low melting-point solder has gained significant interest. In this study, we demonstrated the bonding of glass to copper using Sn-58 wt% Bi solder (SB solder) doped with a small amount of rare earth (RE) elements. The RE elements act as active agents that facilitate the bonding to glasses without glass metallization. By optimizing the bonding parameters, such as reflow temperature and time, and employing an inert gas atmosphere to prevent solder or RE oxidation, we successfully achieved the highest shear strength in glass-copper solder joints using SB-RE solder, without the need for ultrasonic-assisted soldering (UAS). These results demonstrate the potential of using RE-containing solder for bonding unmetallized glass and ceramics in optoelectronic devices with metals at low soldering temperatures (< 200 °C). Furthermore, analysis of the shear strength and failure morphology of solder joints revealed only small degradation, primarily originating from the bulk solder region rather than the solder-glass interface, after both thermal aging (100 h) and cycling tests (100 cycles). The establishment of low-melting point RE-containing solders opens the possibility of direct jointing ceramic optoelectronic substrates to metal heat sinks for more efficient heat dissipation. In the meantime, our work also suggests that further optimization studies are necessary to explore its performance under more extreme working conditions.

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.

Rapid ultrasonic soldering Cf/Al at low temperature

Carbon fiber reinforced aluminum matrix composites (Cf/Al) are widely used in various industries. But they are difficult to join because it is hard to realize the wetting and continuity of the carbon fiber in joint. To solve this problem, Cf/Al are joined by ultrasonic soldering in this work. Results show that the Cf/Al can be wetted within 5 s under ultrasonic. Transmission electron microscope result shows that the surface of the wetted carbon fiber is covered by an amorphous-nanocrystalline layer, which is formed due to the high solder velocity, temperature and pressure caused by cavitation. Carbon fibers flow into the solder after the Al matrix is eroded, guaranteeing its continuity in the joint. Limited carbon fibers flow into the joint at low ultrasonic power of 333.3 W, while a fully carbon fiber reinforced composite joint is obtained at 1000 W. The soldered joints have higher strength than the Cf/Al substrate, and its formation mechanism is discussed.

Preventing formation of intermetallic compounds in ultrasonic-assisted Sn soldering of Mg/Al alloys through pre-plating a Ni coating layer on the Mg substrate

Magnesium and aluminum alloys are widely used in various industries because of their excellent properties, and their reliable connection may increase application of materials. Intermetallic compounds (IMCs) affect the joint performance of Mg/Al. In this study, AZ31 Mg alloy with/without a nickel (Ni) coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu (SAC) filler. The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated. The Ni coating layer had a significant effect on formation of the Mg2Sn IMC and the mechanical properties of Mg/Al joints. The blocky Mg2Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer. The content of the Mg2Sn IMC increased with increasing soldering temperature, but the joint strength decreased. The joint without a Ni coating layer fractured at the blocky Mg2Sn IMC in the solder, and the maximum shear strength was 32.2 MPa. By pre-plating Ni on the Mg substrate, formation of the blocky Mg2Sn IMC was inhibited in the soldering temperature range 240–280 °C and the joint strength increased. However, when the soldering temperature increased to 310 °C, the blocky Mg2Sn IMC precipitated again in the solder. Transmission electron microscopy showed that some nano-sized Mg2Sn IMC and the (Cu, Ni)6Sn5 phase formed in the Mg(Ni)/SAC/Al joint soldered at 280 °C, indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280 °C. The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280 °C, which was 80.7% higher than that of the Mg/SAC/Al joint, and the joint was broken at the Mg(Ni)/SAC interface. Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.

Metallurgical pathways of lead leaching from brass

Leaded (Pb) brass components used in water pipeworks are prone to lead leaching following soldering or brazing during installation. Synchrotron radiation X-ray imaging shows that in the initial state of potable-water grade brass samples, Pb exists mainly as isolated or linked-together particles from sub-micron to several microns large. On heating to the usual soldering temperature of ~200 °C, the Pb contents surface rapidly via diffusion pathways involving an interpenetrating Pb–brass structure with orientation relationship (11bar{1})α-brass//(220)Pb; [011]α-brass//[bar{1}13]Pb. On heating to the usual brazing temperature of 700 °C, the Pb particles melt and expand in volume, with the Pb content forced into the brass lattice preferentially along {101}α-brass planes, forming Pb phase of low sphericity or even large sheets. On immersion in water, the surfaced Pb particles are oxidized to form PbO needles along the normal direction of {bar{2}bar{2}2}PbO planes, which are then easily washed away to cause Pb leaching.

High-strength joining of silica glass and 2024 aluminum alloy by ultrasonic-assisted soldering with Sn-Bi low temperature solder

To alleviate the problem of residual stress in silica glass/2024Al soldered joints, ultrasonic-assisted soldering of silicon glass and 2024Al was carried out using SnBi low-temperature solders. The impact of the soldering temperature and Bi content of the solder on the soldered joints were studied. Powder-reinforced solders were utilized to further improve the joint shearing strength, and the stirring time of the composite solder was also researched. The results showed that the joint strength stabilized after the soldering temperature reached 260 °C. For solders with different Bi content, the highest joint strength (27.3 MPa) was achieved with Sn28Bi solder. The composite solder could further increase the joint strength to 32.1 MPa. In addition, 10 min of ultrasonic vibration and mechanical stirring were recommended to obtain a high-quality composite solder.

Study on the transport current of FeSe0.5Te0.5 coated conductor with different stabilizing layers and solders

The analysis of the influence of different stabilizing layers and solders on the transport current is very necessary for the engineering application of FeSe0.5Te0.5 coated conductors. The soldering temperature and thermal stress caused by cooling from room temperature to liquid helium can affect the critical current values of the superconducting tapes. For this, FeSe0.5Te0.5 coated conductors with four types of stabilizing layers and three types of solders were prepared. The stabilizing layer includes the copper layer with a thickness of 0.02 mm, 0.05 mm, 0.1 mm, and the silver layer with a thickness of 0.1 mm. The solders are respectively Bi50Pb25Sn12.5Cd12.5, Bi51.2Pb30.6Cd18.2, and Sn63Pb37. The experimental results show that the critical current of the tape encapsulated by the 0.02 mm thick copper layer and Bi50Pb25Sn12.5Cd12.5 is about 400 A at self-field and about 25 A at 10 T, which is superior to other samples. The details of the fabrication process and performance test results were presented in this paper.

New Solder Based on the Sn-Zn Eutectic with Addition of Ag, Al, and Li

New solder, based on Sn-Zn, with the addition of 1 at.% Ag, 1 at.% Al, and 0.5 at.% Li (SZAAL) was prepared. The influence of alloying elements on mechanical and electrical properties, microstructure, and melting point was investigated. The tensile test showed enhanced mechanical properties of SZAAL alloy compared to Sn-Zn eutectic and Sn-Zn-Ag. Investigated Al and Li additions improve the mechanical properties of the alloy, tensile strength and solder plasticity. Another positive effect is that those elements caused a decrease in the melting point, compared to Sn-Zn with 1 at.% Ag. Microstructural investigation revealed a fine Sn-Zn eutectic structure with the present epsilon phase (AgZn3). The addition of lithium and silver decreased the coefficient of linear expansion of the tested alloys. Li addition reduced significantly both the surface and interfacial tension, which translates into improved solder wettability. The surface tension of all solders decreased with temperature, but the interfacial tension increased with temperature. That is due to the weakening effect of the flux. Thus, the soldering temperature in the presence of the ALU33® flux should not exceed 250 °C.

OPTIMIZATION OF HOT AIR SOLDER LEVELING (HASL) MACHINE FOR A ROBUST SURFACE FINISH IN SOLDERING APPLICATIONS

Hot Air Solder Leveling (HASL) is one of the most commonly used surface finishes in the industry. HASL is also one of the least expensive types of PCB surface finishes available. This study aims to examine the influence on the solder joint microstructure of dipping time and solder temperature. During soldering process, the temperature that used were 300°C and 400°C. The dipping time was split into three batches which is 20s, 60s, and 100s. The Sn-0.7Cu-0.05Ni solder alloy was used in this analysis to shape the solder coating microstructure. In this analysis, an Optical Microscope (OM) was used to determine the microstructure of the shape of the solder coating microstructure. As dipping time and dipping speed increased, the interfacial IMC thickness was found to increase, grown up and getting thicker. This outcome results can be used as the basis in order to improve the solder joint properties.