Contact Angle Measurement of Melting SnAgCu Solder Paste Mix with Carbon Allotropes Using In-Line Digital Holography Technique

In this research we investigated the contact angle of commercial SnAgCu solder paste mixing with some carbon allotropes such as graphite, graphene quantum dots, and fullerene of varying concentrations with melting temperature, wettability, interfacial microstructure. The wettability was assessed in terms of the contact angle. The in-line digital holography was used for determining the contact angle and morphological of samples at each temperature which the samples have been heating from room temperature until the melting temperature. In the experiment, only one beam was used as the object and reference beams which recorded by a CMOS camera. The recorded image was reconstructed by the angular spectrum digital holography numerical programing. Using the reconstructed images of our results, the shape and contact angle of solder pastes can be investigated.

Low Temperature Material Characterization of Lead-Free SAC Solder Alloy at High Strain Rate After Prolonged High Temperature Storage

During operations, handling, and storage in extreme environmental applications including aerospace, defense and automotive, the electronics may be exposed to high and low operating temperatures. In automotive underhood applications, the temperature can vary especially from −65 to +200 °C. Under prolonged storage, SnAgCu solder materials have been shown to continually evolve in the mechanical properties. New doped SAC solder alloys have recently been introduced with the addition of Ni, Co, Au, P, Ga, Cu and Sb to SAC solder alloy to increase the robustness under prolonged thermal exposure. High strain-rate data on SAC solder alloys after prolonged storage operating at low operating temperatures is not available in published literature. In this paper, materials characterization of SAC (SAC105 and SAC-Q) solder after prolonged storage at low operating temperatures (−65°C–0 °C) and at high strain rates (10–75 per sec) has been studied. The fabricated SAC leadfree solder specimens were isothermally aged up to 12 months at 50°C before testing. Anand Viscoplastic model has been used to compute 9 anand parameters from measured Tensile data to describe the material constitutive behavior. The computed 9 anand parameters were used to verify the accuracy of the Anand model. A good correlation was found between experimental data and Anand predicted data.

Strength and Isothermal Fatigue Resistance of Snbi/snagcu Joints Reflowed At Low Temperatures

Soldered microelectronics assemblies may have to survive a variety of mechanical loads in repeated drops, cyclic bending, or vibration. A very large body of work has addressed the isothermal fatigue performance of SnAgCu solder joints. The present work offers a general assessment of the achievable performance of so-called hybrid solder joints formed by soldering with eutectic SnBi or SnBiAg to SnAgCu bumps on area array components. This allows for soldering at much lower temperatures than with SnAgCu alone, but the deformation and damage properties of the resulting structures depend strongly on details of the design and process. A peak reflow temperature of 175C was shown to be sufficient to ensure that the life of the joints remains limited by fatigue of the unmixed SnAgCu near the component. However, a higher effective stiffness of the mixed region near the substrate means that the life will be lower by 45%.