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As the electronic packaging density continues to increase, flip chip or stacked packaging via bump bonding is gradually replacing traditional wire bonding and will become the mainstream packaging form in the future. For copper bumps, this new type of electronic interconnection has not yet been fixed by industry standards. Therefore, this paper has made a preliminary study on the reliability of this...
Sn whisker has been found since 1940s.[1] The formation mechanism of whiskers was controversial. There were two possible mechanisms. Some scientists thought whisker formation were the result of recrystallization or abnormal grain growth, however others suggested that the atomic migration of Cu caused by compressive stress gradient were the main driving force of whisker formation. In latest study,...
In recent years, Ag alloy wire has attracted great interest as a novel bonding material to replace the conventional Au wire bonding. Ag wire has the advantages of great workability, high electrical conductivity and low growth rate of intermetallic compound at bonding interface. However, in literatures, studies on mechanisms of the growth of Ag-Al intermetallic compounds and their impact on bonding...
Gold wire bonding has been widely used as the first-level interconnect in semiconductor packaging. The increase in the gold price has motivated the industry search for an alternative to the gold wire used in wire bonding and the transition to a copper wire bonding technology. Potential advantages of transition to a Cu–Al wire bond system include low cost of copper wire, lower thermal resistivity,...
Gold wire bonding has been widely used as first-level interconnect in semiconductor packaging. The increase in the gold price has motivated the industry search for alternative to the gold wire used in wire bonding and the transition to copper wire bonding technology. Potential advantages of transition to Cu-Al wire bond system includes low cost of copper wire, lower thermal resistivity, lower electrical...
Gold wire bonding has been widely used as first-level interconnect in semiconductor packaging. The increase in the gold price has motivated the industry search for alternative to the gold wire used in wire bonding and the transition to copper wire bonding technology. Potential advantages of transition to Cu-Al wire bond system includes low cost of copper wire, lower thermal resistivity, lower electrical...
Large scale conversion of gold to copper wiring in microelectronics can only become successful when all the failure mechanisms that can be encountered during reliability testing, or during product application life are understood. One of these mechanisms is corrosion of the contact between the copper (Cu) ball and the aluminum (Al) bond-pad, consisting of various intermetallic compounds (IMCs), which...
Wire bonding using bare Cu wire and Pd coated Cu (PdCu) wire has been adopted rapidly as a mainstream packaging technology as an alternative to Au wire bonding. The interfacial characteristics of both Au and Cu wire bonds are well understood as a result of extensive research. However, the interfacial feature and its evaluation in connection with Pd coated Cu wire bonds have not been investigated in...
The formation and growth characteristics of intermetallic compounds (IMC) at the interfaces in nanoscale and microscale thickness Cu-Sn-Cu sandwich structure (with different solder layer thicknesses of 130nm, 400nm and 1.5µm) during reflow soldering and aging were studied. The sandwich structure samples were fabricated by electro-plating, and followed by reflow and aging process. It was found that...
Although lead free soldering has been the main stream of industry since 2006, with the replacement of eutectic SnPb system by SnAgCu system, the development of drop-in lead-free alternatives for high melting high lead solder alloys is still far from mature. BiAg alloy exhibits acceptable bulk strength but very poor ductility and wetting, therefore is not acceptable as an option. In current work, a...
The aim of this research is to examine the effect of annealing and recrystallization of electroplated tin layers on mitigating the growth of tin whiskers. Electroplated tin on copper substrate has been tested. Three different groups of samples have been investigated: a reference, an annealed and a recrystallized. Three types of aging were being used to accelerate the whisker appearance; two life-like...
Nowadays, nanoelectroctronic, electro-nanotechnologies environmental friendly products become the roadmap in industry. Hence, nanoscale of reinforcement into lead-free solder becomes more popular rather than the micro size of reinforcement. In this paper, Cobalt nanoparticles-reinforced Sn-Ag-Cu composite solders were prepared by thoroughly blending 0.75 wt% of cobalt nanoparticles with near eutectic...
In this study, varying amounts of Ni-CNTs were incorporated into the Sn-Ag-Cu matrix to form the composite solders. The interfacial intermetallic thickness formed on the Ni/Au metallized Cu substrate was determined under the as-soldered and isothermally aged (at 150°C for up to 42 days) conditions. The results of the interfacial intermetallic thickness showed that for the case of the unreinforced...
Gold and copper ball bonds were isothermally aged under moist conditions (85°C and 85% relative humidity (RH)) and wet conditions (85°C in DI water with and without NaCl) in an effort to better understand the corrosion mechanisms that operate under moist and wet conditions. The objective of this work is to undertake and report on the initial stages of a research project that aims to compare the performance...
For high temperature automotive application, IC products are required to pass stringent high temperature storage stress test (e.g. 5000hrs at 150 deg C), hence requires reliable wire bonds. Such requirement is especially challenging with fine pitch Au & Cu wire bond (e.g. bond pad pitch <; 70um and bonded ball diameter <; 58um), more-so on low k wafer technology with bond-over-active requirement...
High gold prices have led to renewed interest in replacing gold with copper in existing packages and new packages in order to save costs. Although reliability is often cited as a reason for using copper, the main driving force for its use is undoubtedly cost. Perceptions that copper wire is more reliable are based on the notion that the intermetallics grow more slowly and that thinner intermetallics...
The Ni/95Pb5Sn/Cu ternary diffusion couples were used to investigate the cross-interaction between Ni and Cu across a layer of 95Pb5Sn solder. High-lead solder layers with thickness of 100 or 400 μm was electroplated over Cu foils. A pure Ni layer (20 μm) was then deposited over the as-deposited high-lead solder surface. The diffusion couples were then aged at 150 to 250°C for different periods of...
Intermetallic compounds (IMCs) that grow on the interface between the solder alloy and its bonding pads play a crucial role in the reliability of solder joints. It has been identified that the cracking around the IMC layer is the primary failure mode in lead-free solder joints. Therefore the mechanical behavior of the IMC has attracted great attentions. In this paper, mechanical properties of two...
Copper and gold ball bonds were bonded on 1.2 μm thick Al-0.5%Cu-1%Si. One set of devices was aged at 175°C up to 1000 hours. A second set of devices was pre-conditioned for 168 hours at 85°C and 85% relative humidity followed by ageing at 175°C up to 1000 hours. No cratering was found with either wire in as-bonded devices but devices bonded with copper developed cratering after ageing. Neck and stitch...
Copper (Cu) wire bonding is getting more common as interconnections on aluminium (Al) bond pad metallization in microelectronics due to lower cost compared to gold wire bonding. The Cu-Al intermetallic compounds (IMC) growth in Cu ball bonds has been investigated by many researches but the understanding of the IMC phases is still incomplete and the impact to bond reliability know-how is limited. This...
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