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The Ni-P alloy [or Ni(P)] with a 6-13 wt.% P content is a very common surface finishing material used in microelectronic packages. When a high P-content Ni(P) finish (≃13 wt.%) was jointed to the Sn-based solders, there are several possible P-containing intermetallics, e.g., Ni2SnP, Ni2P, Ni12P5, and Ni3P, can form at the interface. Among these intermetallics, the Ni2SnP layer played a major role...
Because of the relatively low reactivity with solders, Ni-based materials are the most commonly used diffusion barrier layer materials in flip chip packaging technology for Al metallization integrated circuits. However, due to the high diffusivity of Cu, the diffusion barrier materials need to be re-evaluated for Cu/low k integrated circuits. Some literatures had indicated that Co is with superior...
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...
This study aimed to evaluate the drop reliability using Ag content and metal additives in a Sn-Ag-Cu system composition. In this study, the main compositions of the solder ball were Sn1.0Ag0.5Cu and Sn0.5Ag0.5Cu, respectively, and Ni and Co elements were additions a additive element. The PCB plating was used Cu-OSP, immersion Sn, electroplated Ni/Au, and ENEPIG (electroless Ni electroless Pd immersion...
To satisfy the requirements of the newest mobile product, smaller solder ball is needed for electronic packages such as chip scale package (CSP). The purpose of this study was to investigate the effect of solder ball size on the interfacial reaction. In this study, 400, 300, and, 200 ??m diameter solder balls of 98.5 wt.% Sn, 1 wt.% Ag, and 0.5 wt.% Cu(SAC105) were formed on the Cu/OSP and electroplated...
Intermetallic compounds (IMCs) properties play a significant role in determining the reliability of solder joints in service. IMCs and their evolution become more important for devices with micro- or nano-scale joints used in cryogenic applications. In this study, the interfacial reactions of In/Cu and In/Ni/Cu due to low-temperature cycling are investigated. The results illustrate that the character...
Electromigration of flip-chip solder joints has been studied extensively in recent years. It was investigated in plenty of studies that the current crowding effect takes place at the corner near the traces due to huge differences of dimensions between traces and solder joint. The local high current density, which has been known as a serious reliability issue, causes the failure such as void formation...
In this study, lead free (Sn-4Ag-0.5Cu (SAC)) and lead (62Sn-36Pb-2Ag (SP)) solder joint on various 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) was investigated by its interface morphology and its physical properties. To evaluate the mechanical and physical properties of BGA pad with...
A complete halogen-free test vehicle was achieved by assembling five ball grid array (BGA) components with daisy-chain on an 8-layer high density interconnection (HDI) printed circuit board with a low-halide Sn1.0Ag0.5Cu (SAC105) Pb-free solder pastes for reducing the formation of Ag3Sn. Afterward a board-level cyclic bending test was enforced on the as-reflowed assemblies according to the JESD22-B113...
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...
Flash gold with nickel and gold plating is a low-cost technique in PCB finishing, frequently used in the production of toys. The quality of plating has become one of the concerns for the performance and reliability of solderability. This study investigates the solderability of PCB produced by flash gold finish and traditional nickel and gold plating finish. For this purpose, solderability tests have...
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...
Flip chip solder joints made with Cu and Ni underbump metallurgy (UBM) on the chip under current stressing were studied. The effects of material and various thicknesses (5, 10, 15, and 20 mum) of UBM on reliability were investigated. The solder material used was lead-free (Sn4.0Ag0.5Cu). Time to failure of both cases (Cu and Ni UBMs) was forecasted through the physical damage occurring at the bump...
Two commonly used Pb-free solders, SnAg and SnCu, are studied for electromigration (EM) reliability. Two major EM failure mechanisms are identified in Sn-based Pb-free solders, which is mainly due to the differences in microstructures and Sn-grain orientation. In general, the EM damage in SnCu solder is driven by the fast interstitial diffusion of Ni and Cu away from solder/UBM interface and leads...
Significant innovations in Pb-free solder alloy compositions are being driven by volume manufacturing and field experiences. As a result, the industry has seen an increase in the number of Pb-free solder alloy choices beyond the common near-eutectic Sn-Ag-Cu (SAC) alloys. The increasing number of Pb-free alloys provides opportunities to address shortcomings of near-eutectic SAC, such as the poor mechanical...
There is an ongoing demand for low cost high performance RF components for high frequency applications. Current packages for this domain use plastic packages based on wirebonding. The RF performance is limited by parasitic effects due to the RLC network between the wirebond from the dies to the leadframe. One of the best ways to reduce these effects is the use of flip chip technology. Flip chip interconnections...
Observations from assorted current stressing experiments on flip-chip solder joints imply that the Cu content in a solder joint system plays a dominant role in its electromigration reliability. In this paper, electromigration reliability of various flip-chip solder joint systems including different substrate pad finishes and solder compositions is summarized to demonstrate the effect of the Cu content...
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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