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For a limited solder volume interconnect structure, bump interconnect reliability is more sensitive to the growth behavior of the interfacial intermetallic compounds(IMCs). The study of the effect of solder cap thickness on the interfacial diffusion reaction is of great importance to the application of copper pillar bump. Here, we investigated the effect of different solder cap thicknesses on IMCs...
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...
The wide band-gap semiconductor devices, such as SiC, GaAs power devices, provide great opportunities to develop power electronic systems with increased power densities, high reliability in extreme environments and higher integration density. High-temperature resistance is needed for the thermal interface materials. In this work, the intermetallic joints consisted of nearly sole Ni3Sn4 during die...
Ag finish is a low cost and low resistant solution comparing with Au finish in electronic packaging. For the sake of application of Ag finish, the solder joint reliability with broad silver finish designs on PCB of packaging is studied. It is found that both finish structure and process affect the reliability. Electro-less Ni/Pd/immerging Ag (ENEPIS) has the best integrated solder joint performance...
In this study, the formation mechanisms of Kirkendall voids in Sn3Ag0.5Cu/Cu and Ni/Sn3Ag0.5Cu/Cu joints were investigation, and the coupling effect of joint size and Kirkendall voids on the fracture features of Ni/SnAgCu/Cu joints were also studied. It was found that the size effect had a significant influence on the formation of Kirkendall voids at Cu side in Sn3Ag0.5Cu/Cu and Ni/Sn3Ag0.5Cu/Cu joint,...
Ag finish is a low cost and low resistant solution comparing with Au finish in electronic packaging. For the sake of application of Ag finish, the solder joint reliability with broad silver finish designs on PCB of packaging is studied. It is found that both finish structure and process affect the reliability. Electro-less Ni/Pd/immerging Ag (ENEPIS) has the best integrated solder joint performance...
In this study, the formation mechanisms of Kirkendall voids in Sn3Ag0.5Cu/Cu and Ni/Sn3Ag0.5Cu/Cu joints were investigation, and the coupling effect of joint size and Kirkendall voids on the fracture features of Ni/SnAgCu/Cu joints were also studied. It was found that the size effect had a significant influence on the formation of Kirkendall voids at Cu side in Sn3Ag0.5Cu/Cu and Ni/Sn3Ag0.5Cu/Cu joint,...
Epoxy-based flux has been developed to improve the impact reliability of the lead-free solder ball joint. The improvement effect of impact properties of the solder ball joint with epoxy-based flux was examined. Residue of epoxy-based flux is left around the solder ball joint and reinforces the joint. Thus interfacial fracture is inhibited and solder fracture increases. The solder ball joint with epoxy-based...
Recently, the demand on the 3-D integration using through-silicon vias (TSVs) and micro-bumps has been increasing for better electrical performance and smaller form factor. However, lots of doubtful concerns on the reliability of 3-D stacked chips still exist, which are Cu TSV expansion, transistor degradation or open failures on Cu contamination, micro-bump stress, and so on. In this study, we investigated...
Short time interfacial reactions between Sn-3Ag-0.5Cu solder balls and ENEPIG pads at 250 °C were investigated. Transitions in morphology and type of the interfacial intermetallic compounds (IMCs) with reaction time were revealed. It was found that the transition rate of the interfacial IMCs in smaller solder joints was faster than that of larger ones. For 200 µm solder joint, dodecahedron type (Cu,Ni)...
Reliability issues of Pb-free solder joints used in microelectronic interconnects, such as BGA, flip-chip, or even 3D-IC, are becoming more critical recently when high performance electronic systems demand more rigorous reliability requirements. The selection of new solder materials has been an important topic in order to enhance the reliability of Pb-free solder joints. In the past few years, numerous...
Electromagnetic interference (EMI) is considered as a crucial environmental and reliability issue in electronic information industries, especially with the rapid development of information technology. Since electromagnetic signals are prone to be interfered by external electromagnetic radiation, it is urgent to take effective measures to reduce, or ultimately eliminate the electromagnetic interference...
In this work, IMC (Inter metallic compound) of lead free (Sn-Ag-Cu (SAC)) and lead (62Sn-36Pb-2Ag (SP)) solder joint on the four kinds of surface finished of ball grid array (BGA) pad, such as Immersion Tin (ImSn), Organic solderability preservatives (OSPs), Ni-P/Pd/Au (ENEPIG), and Ni-P/Au (ENIG) were investigated by Focus Ion Beam microscope (FIB). Sample after failure ageing conditions (Baking...
The η-η' transformation of interfacial Cu6Sn5 in solder joints was studied. Two cooling rates were selected to obtain different grain sizes of intermetallic compounds (IMCs). In the case of air cooling, the compounds were tiny and no η-η transformation was detected in the as-soldered state. Under furnace cooling, however, thick and coarse interfacial IMCs were obtained and η was still stable. After...
It is of importance for the reliability of lead-free and lead-bearing solder joints to have better understanding and control of the solder/metallization interactions during soldering. In the reactions between solders and Cu substrate, the formation of micro voids within the Cu3Sn layer had been report by many research groups. Because the Cu3Sn growth had been linked to the formation of micro voids,...
This paper deals with presentation of some new aspects of solder ternary alloy 96.5Sn3Ag0.5Cu (wt.%) - SAC305, in order to determine variations in mechanical properties and microstructure caused by treatment in vapour phase soldering (VPS) as well as by accelerated isothermal aging. These specimens have been melted and solidified on HASL (hot air solder levelling) and Ni/Au (ENIG) PCB (printed circuit...
The objective of this study is to investigate the alloying effects of Fe, Co, and Ni on the interfacial reactions between solder and Cu. Emphasis is placed on a systematic comparison study on the effect of Fe, Co, and Ni additions. Solders with simultaneous Fe and Ni addition as well as simultaneous Co and Ni addition are also prepared in order to investigate whether there is any interaction between...
The conversion to Pb-free solders has already been implemented in the consumer market. However, the transition to Pb-free solders in the high performance, mission critical networking/server industry has not yet been fully implemented. A significant factor in the slow transition to Pb-free solders is the absence of industry accepted Pb-free acceleration transforms that can translate lab test results...
SiC power devices were die bonded to a AlN/Cu/Ni(Au) direct bonded copper (DBC) substrate with a Au-Ge eutectic solder in a vacuum reflow system. The long term joint reliability of the bonded chips was evaluated at 330degC in air for up to 1600 hours. The bonded samples were inspected with a micro focus X-ray TV system. The microstructure of the samples was observed and analyzed by the scanning electron...
Sn-Ag-Cu (SAC) solders are susceptible to appreciable microstructural coarsening during storage or service, resulting in evolution of joint properties, and hence reliability, over time. Although the problem of microstructural coarsening in joints has been studied extensively, the effect of joint scale on aging kinetics has never been investigated. Understanding the scale dependence of aging is particularly...
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