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Lead-free reflow soldering techniques applying AuSn as well as SnAg electroplated bumps were chosen for the evaluation of the flip-chip-bonding process for X-ray pixel detectors. Both solders can be used in pick-and-place processes with a subsequent batch reflow suitable for high-volume production. AuSn solder was selected because of its fluxless bondability, good wettability, and self-alignment process...
This paper presents the effect of the reflow oven type to the intermetallic (IMC) formation and solders joint reliability for the wafer level packages (WLPs). Two common used reflow oven in electronic manufacturing industry which are conduction and convection oven have been studied. Four reflow profiles with same peak temperature and wetting time for both ovens were developed. In this study, two low...
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...
This paper presents the assembly optimization and characterization of through-silicon vias (TSV) interposer technology for two 8 ?? 10mm2 micro-bumped chips. The two micro-bumped chips represent different functional dies in a system-in-package (SiP). In the final test vehicle, one of the micro-bumped chips had 100??m bump pitch and 1,124 I/O; the other micro-bumped chip had 50??m bump pitch and 13,413...
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...
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,...
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...
Ball grid array (BGA) solder interconnecting is one of the key technologies in electronic packaging and assembly. Legislation of lead-free process has made the application of lead-free solder become wider in electronic products. Compared to the lead-tin solder, the relatively higher melting points of most lead-free solders call for a higher reflow temperature. Thus conventional integral-heating process...
PoP structures have been used widely in digital consumer electronics products such as digital still cameras and mobile phones. However, the final stack height from the top to the bottom package for these structures is higher than that of the current stacked die packages. To reduce the height of the package, a flip chip technology is used. Since the logic chips of mobile applications use a pad pitch...
The electronics industry has successfully transitioned to lead free soldering for computer and consumer products while in the automotive industry due to the very high reliability requirements this step is still in an ongoing process. In order to ensure or even to enhance the reliability of electronics the improvement of lead free solder joints based on Sn-Ag-Cu (SAC) solder has been the focus of many...
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...
Material parameters has to be determined with regard to the influence of the solder volume and the crystal orientation to understand the thermo-mechanical properties and therefore the reliability of small lead free solder joints in microelectronics. The influence of crystal orientation to the reliability is very important because a small solder joint of a 0201 or a 01005 electronic device consists...
The work presented in this paper focuses on the role of 3 wt.% Bi in the base Sn-9%Zn solder on the shear strengths and the interfacial reactions with Au/Ni/Cu pad metallization in ball grid array (BGA) applications. Sn-Zn based Pb-free solder alloys were kept in molten condition (240degC) on the Au/electrolytic Ni/Cu bond pads for different time periods ranging from 1 minute to 60 minutes. Cross-sectional...
We report in this work the effect of multiple reflow cycles on ball impact test (BIT) responses and fractographies obtained at an impact velocity of 500 mm/s on Sn-4Ag-0.5 Cu solder joints. Solder balls were mounted on Cu substrate pads with immersion tin surface finish, supplied by two vendors. For these particular test vehicles and test conditions, fracture near the interface between the interfacial...
In this paper, the behavior of BGA solder joints microstructures was studied as a function of Ni doping in SAC solder. Three kinds of solder compositions were selected including Sn3.0Ag0.5Cu, Sn1.0Ag0.5Cu and Sn1.0Ag0.5Cu0.02Ni to value the influence the effect of Ni doping, OSP and Au/Ni pad was employed on the PCB side. Emphasis was placed on studying the effect of low level doping with Ni on the...
With the increasing connection density of ICs, the bump pitch is growing smaller and smaller. The limitations of the conventional solder bumps are becoming more and more obvious due to the spherical geometry of the solder bumps. A novel interconnect structure - copper pillar bump with the structure of a non-reflowable copper pillar and a reflowable solder cap is one of the solutions to the problem...
We recently developed Cu-Zn alloy wetting layer for the SAC solder balls to improve the reliability. In this paper, IMC formation and solder joint reliability have been investigated in the solder joint between SAC solder balls and Cu-Zn alloy pads, and Cu pads were also used as a reference. Sn-4.0Ag-0.5 Cu solder balls were used and the substrates were Cu and 80 wt% Cu-20 wt% Zn pads which were defined...
This study investigated the reaction and mechanical properties of a In added quaternary composition solder alloy having low Ag content, i.e. Sn-xAg-0.5Cu-yIn to replace the Sn-3.0Ag-0.5Cu composition used widely as a representative Pb-free solder alloy. We found that the In addition of small amount did significantly improve a wettability of the solder at the reflow temperature of 230~240degC. Moreover,...
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