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Aluminium is widely used as conductor material for power cables, but corrosion taking place under specific circumstances can have impact on its reliability. Aluminium corrosion under the influence of an alternating current was studied experimentally. Submerged cable segments with inflicted damage exposing the conductors resulted in a continuous corrosion of the conductor material. Effects of temperature...
Sintered Ag has gained attention as a replacement for high lead applications due to its high thermal, electrical and reliability performance. Today, the temperature requirements for certain business units require higher levels of capability. Coupled with the pressures of converting to lead free, a feasible solution needs to be reached soon. This led to the formation of the DA5 (die attach 5) consortium...
In this paper, wet cleaning solution compatible with cobalt are investigated to achieve low Co etching rate on blankets film and no film attack on patterned 14nm wafer after line and via etching. Proposed solutions are compared to conventional wet cleaning solutions [5],[6].
Cloud computing and storage now are more important for people's life. Data center set-up is more popular all over the world. For the cooling of the computing server, a lot of data center choose the natural air circulation method replacing traditional one to save the power consumption. So from the natural air circulation, more reliable issue will come from the quality of air depending on which place...
Fine pitch copper wire bonding presents challenges to both first and second bond processes. Corrosion of the first bond copper-aluminum (Cu-Al) intermetallic compound bond interface layer can be induced by mobile chlorine in the epoxy mold compound, and the second bond process window can be narrower than with gold wire. Palladium-coated copper wire is believed to overcome these two problems, however,...
Understanding the moisture-induced corrosion mechanism of copper wire bonding is crucial for achieving longer life reliability of copper bonding. While the formation of Al-Cu intermetallic compound (IMC) is found to dominate the bond reliability, the mechanism remains unclear despite considerable efforts by experiments. Pourbaix (Eh-pH) diagrams have long been used to evaluate the theoretical activity...
Cu wirebonding become a great interest of industry in recent years due to its cost effectiveness and electrical and mechanical properties. However, several Cu wire bond reliability challenges are the key concerns in Cu wire deployment in semiconductor packaging. These include Cu wire oxidation and CuAl interface corrosion post HAST or UHAST reliability test. Bond reliability at a Cu wire bond under...
One critical obstacle to preparing highly reliable isotropically conductive adhesives (ICAs) filled with Ag-coated Cu flakes is the oxidation and corrosion of Ag-coated Cu fillers, which cause the degradation of electrical properties of the ICAs at elevated temperatures and relative humidity (RH) during long-term reliability tests. Various organic compounds could be used for corrosion prevention of...
This paper describes the challenges of a 17.5um thin bare Cu wire bonding on aluminum bond pads for a fragile low-k wafer technology, on a BGA package. Previous evaluations have so far focused on 20um and 25um bare Cu wires as a suitable low cost replacement for Au wires. To improve performance, more fragile low-k wafer technology is being developed. In the past, some key technical challenges experienced...
Alternative solutions for Au wire are high in demand as a result of increasing gold price and high demand for lower cost packages. Copper wire has been the natural low cost alternative but concerns on corrosion susceptibility and package reliability have driven the industry to look for better alternative wire materials while maintaining substantial material cost savings. PdCu wire is supposed to close...
Copper (Cu) wire has been highlighted as a low cost material for use in thermo sonic ball bonding for various package (PKG) groups. This wire has already been applied in high-end PKGs such as BGA, QFP and QFN in mass production, and the volume is feasible. Not only the advantage of a low cost material, but Cu wire has other merits which include higher electrical conductivity and a much slower intermetallic...
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...
A detailed description of the Cu-Al wire bond interface is presented, which can possibly explain the often observed corrosion failures in humidity reliability tests. Using micro-structural analysis techniques, it is shown that the unstressed interface contains up to three intermetallic phases, where the Cu-rich phases are located at the Cu-ball interface. Upon humidity stress test only the high-Cu...
Wire bonding has been the dominant mode of chip to substrate interconnection for many decades. The most common metal used has been gold which is rather malleable and very resistant to oxidation and corrosion. The surge in commodity prices over the last few years has prompted the introduction of copper as a lower cost alternative. While copper has some advantages electrically, thermally and mechanically,...
For automotive applications, the mechanical behaviour of the contact area under vibrations is one of the key factors for connector reliability. Such vibrations are typically in the range of 10-2000 Hz and result in displacements of only a few microns, at the contact interface. In the present study, a bench test has been developed to control more representative motions down to 1 μm. The objective is...
Creep corrosion failures have recently been seen on all surface finishes. The increase in occurrence of this phenomenon is a result of the convergence of alternative surface finishes, developed to support RoHS compliant, lead-free, fine-pitch technology and an overall increase in the use of electronics in harsh environments. It has taken time and extensive investigation to understand the root cause...
The influence of EMC (Epoxy Molding Compound) and reliability with fine Cu wire was studied. It is found that the failure mode was corrosion at the intermetallic layer of the wire bonding part by failure analysis after HAST (Highly Accelerated Temperature & Humidity Stress Test). Al elution and Cl ion was observed at the intermetallic layer. EMC with lower Cl ion content and Al inhibitor of corrosion...
In plastic power devices, the interfaces of Cu/EMC are most likely to delaminate under thermal loading, especially when moisture diffuses into the interface through EMC. In this work, the bare die samples were fabricated in standard commercial process. Shear test of Cu/EMC interface was designed to measure the strength of the interface with different lead-frame oxidation and moisture absorption time...
This paper presents an investigation on field returned open and short failures related to printed circuit board (PCB), including via hole crack, prepreg crack and insufficient circuit etching. After an experimental study with cross section, time domain reflectometry (TDR), and finite element (FE) modelling, it was found that weak plating and corrosion induced via hole crack was a major root cause...
This study focuses on a method of reliability assessment for creep corrosion on immersion silver-finished PCBs utilizing the mixed flow gas (MFG) test and clay test. Four kinds of locations were defined to conveniently describe the location from which the dendrite corrosion products were growing: IL refers to the location that corrosion products grew from a hole or pad edge with solder mask; IIL refers...
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