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Microelectronic integrated circuits experience nonuniform high temperatures during normal operation. Thermal expansion mismatch among the different materials comprising the device lead to a large tensile stress after high temperature cycles. Voiding and open-circuit failure from cracking of interconnects are often observed during isothermal aging and thermal fatigue tests with or without electric...
One of the main drawbacks of silver-filled isotropically conductive adhesives (ICAs) is the high cost of silver fillers, while low cost copper-filled ICAs are not reliable due to the oxidation of copper fillers. In this paper, we develop highly conductive, highly reliable, and low cost ICAs filled with silver-coated copper (Ag-coated Cu) flakes, i.e. an anhydride-cured ICA filled with Ag-coated Cu...
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...
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...
Effect of Cu substrates and solder alloy on the formation of kirkendall voids in the solder joints during thermal aging was investigated. Solder joints with three types of Cu bonding pads (electroplated Cu, polycrystalline Cu and single-crystal Cu) and Sn-based solders (Sn-3Ag-0.5Cu and Sn-37Pb) were prepared, and subsequently the samples were aged at 150°C and 175°C, Under the same aging conditions,...
Despite the fact that epoxy has continuously used as encapsulant in electronic packaging, its joint with copper-based substrate is prone to delaminate during reliability test. A prime reason is the lack of adhesion between Cu and epoxy compound. To solve the problem, self-assembly molecular structure (SAM) is adopted to improve adhesion of epoxy-copper system. In seeing that hydrophobic behaviour...
The formation and growth of intermetallic compound layer thickness is one of the important issues in search for reliable electronic and electrical connections. Intermetallic compounds (IMCs) are an essential part of solder joints. At low levels, they have a strengthening effect on the joint; but at higher levels, they tend to make solder joints more brittle. If the solder joint is subjected to long-standing...
Porous low-k dielectrics reliability in interconnect is a major concern for sub 45 nm technology nodes. Low-k dielectric ageing characterization during stress is becoming a key point to improve low-k interconnect robustness. In this context, the leakage and especially the capacitance shifts under electrical stress are analyzed in this paper. Four dielectric ageing mechanisms potentially responsible...
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 morphological features and growth kinetics of interfacial IMCs have shown significant effect on the mechanical properties, and hence, on the reliability of lead free solder joints. The growth behavior of the interfacial IMCs of SnAgCu/Cu solder joint, in reflow and thermal cycling, was investigated with the focus on the influence of reflow dwell time and the cyclic parameters on the growth kinetics...
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 demand for more complex and multifunctional microsystems with enhanced performance characteristics is driving the electronics industry toward the use of best-of- breed materials and device technologies. Three-dimensional (3-D) integration enables building such high performance microsystems through bonding and interconnection of individually optimized device layers. Bonding of device layers can...
The excessive growth of intermetallic compound (IMC) and the formation of microvoids in the interface between Sn-Ag-Cu (SAC) solder and Cu substrate have been a serious problem which may degrade the solder joints reliability. Recently, a new Cu-Zn alloy solder wetting layer for the Pb-free solders has been developed to reduce the IMC growth rate. In this paper, the kinetics of IMC growth and the shear...
Sn-8Zn-3Bi solder balls with different weight percentages of Sn-Ag-Cu addition were bonded to Au/Ni metallized Cu pads, and the effect of multiple reflow and aging on impact reliability was investigated. In the Sn-Ag-Cu content Sn-Zn-Bi solder joints, the AgZn3 intermetallic compound layer was clearly observed at the interfaces and its thickness increased with an increase the number of reflow cycles...
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...
This study utilized out high speed lap-shear tests at various strain rates (0.01 mm/s ~ 500 mm/s) for Sn-37Pb/Cu and Sn-37Pb/ENIG solder joints to evaluate the drop reliability. The samples aged for 120 h at different temperatures (150??C and 170??C) were also tested to examine the effects of aging on the drop reliability. We thoroughly analyzed the stress-strain curves obtained from the lap-shear...
Thermosonic copper ball bonding is an interconnection technology that serves as a viable and cost-saving alternative to gold ball bonding. However, the reliability of copper bonds remains to be ascertained. Intermetallic compounds (IMCs) and possible voids and cracks may grow and propagate at the interface of bonds during their service. The proper IMCs formation is beneficial to bonding strength but...
The reliability of lead free electronic devices depends strongly on the reliability of the soldered joints while the later one was controlled, mainly, by the formation and growth of the interfacial intermetallic compounds (IMCs) between the solder matrix and the substrates. The morphological features, microstructural evolutions and growth kinetics of the IMCs on the interfacial of SnAgCu/Cu soldered...
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