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It is well known that during service the layer of Cu6Sn5 intermetallic at the interface between the solder and a Cu substrate grows but the usual concern has been that if this layer gets too thick it will be the brittleness of this intermetallic that will compromise the reliability of the joint, particularly in impact loading. There is another level of concern when the Cu-rich Cu3Sn phase starts to...
Sintered silver is being increasingly recognized as an ideal method of joining in situations where a relatively low temperature process is required to form a bond that can survive service at elevated temperatures, e.g. in the mounting of power semiconductor dies. In the optimization of this process much consideration is given to the parameters of the sintering stage but the integrity and reliability...
Thermal fatigue is a major source of failure of solder joints in surface mount electronic components and it is critically important in high reliability applications such as telecommunication, military, and aeronautics. The electronic packaging industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu alloys first established as replacements...
The commercial success as Pb-free solders of alloys based on a trace addition of Ni to Sn-0.7Cu and the academic recognition of the metallurgical effects that deliver the excellent performance in soldering processes and in service, means that Sn-Cu-Ni is now well established as one of the main alloy systems on which the electronics industry depends for the assembly of reliable circuitry. One important...
Thermal fatigue and room temperature isothermal mechanical performance of various Pb-free and SnPb solder joints were examined. Various solder alloys doped with Ni (SN100C) and Mn (SAC105-Mn and SACM) were evaluated and compared to SAC105, SAC 205 SAC 305 and SAC 405 and eutectic SnPb alloys. Solder spheres ranging from 10 to 20 mils were reflowed on various printed circuit board (PCB) surface finishes...
This study explores the effect of a nickel (Ni) microalloy addition on the thermal fatigue performance and microstructure of two low Ag content, Pb-free solder alloys, Sn-1.0Ag-0.5Cu (SAC105) and Sn-2.0Ag-0.5Cu (SAC205). The alloy performance was evaluated using two different area array component test vehicles, an 84-pin chip scale package (CSP) and a 192-pin fine pitch ball grid array (BGA). The...
Tin is the main component of contemporary lead-free solders. Under equilibrium conditions, tin exists as either a tetragonal β-Sn) or cubic (α-Sn) allotrope at temperatures above and below approximately 13°C, respectively. The transformation from β to α, often referred to as ‘tin-pest’ is poorly understood, despite the phenomena being documented over 100 years ago. Possibly because the high lead content...
Different surface appearances were detected on printed circuit board (PCB) pads with a lead-free (Pb-free) Hot Air Solder Leveled (HASL) surface finish although all were processed in the same solder machine at the same time. The appearance of these HASL finished pads could be categorized into two main groups: shiny surface and dull surface. A useful feature of the HASL finish that distinguishes it...
Significant innovations in Pb-free solder alloy formulations are being driven by volume manufacturing and field experiences. As a result, the industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu (SAC) alloys first established as replacements for Sn-37Pb. The increasing number of Pb-free alloys provides opportunities to address shortcomings...
Recently, the industry has seen an increase in the number of Pb-free solder alloy choices beyond the common neareutectic Sn-Ag-Cu (SAC) alloys. The increasing number of Pb-free alloys provides opportunities to address important issues, such as the poor drop/shock performance, alloy cost, copper dissolution, and poor mechanical behavior in bend/flex. Most recently, investigations into new solder paste...
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