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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...
Tin-plated copper structure was widely applied in the electronic products. With the development of the electronics industry, the integration degree increased and the component size reduced obviously. The conventional tin plating technology met the micro-structure challenge; it may not be used in advanced electronic packaging process. The electroless tin plating technology could solve this problem...
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 this paper, tin whisker behaviour of electroplating tin coating was studied in different environments. Different thickness of electroplating tin coating on copper substrate had been tested. Two different environmental conditions had been applied :one temperature tests (70 °C)and one external force tests(70 °C /17.5N). The growth of tin whisker was studied by using scanning electron microscopy (SEM)...
The copper substrates with different preferred orientations (200) and (220) were prepared and the interfacial reactions of the Cu(200)/Sn and Cu(220)/Sn diffusion couples were studied after annealing at 423K. The thickness and morphology of the intermetallic compounds were investigated. The appearance of the Cu3Sn was observed at Cu(220)/Sn interface after aged for 4 hours and then the thickness of...
The effect of thermal aging temperature and external tension on the formation and growth of tin whisker from Sn electroplating coating was studied by use of scanning electron microscopy(SEM)in this article. It is shown that the unbiased temperature accelerates the formation and growth of tin whisker. However external tension do not obviously promote the formation and growth of tin whisker. After coating...
The effect of thermal aging temperature and external tension on the formation and growth of tin whisker from Sn electroplating coating was studied by use of scanning electron microscopy(SEM)in this article. It is shown that the unbiased temperature accelerates the formation and growth of tin whisker. However external tension do not obviously promote the formation and growth of tin whisker. After coating...
The copper substrates with different preferred orientations (200) and (220) were prepared and the interfacial reactions of the Cu(200)/Sn and Cu(220)/Sn diffusion couples were studied after annealing at 423K. The thickness and morphology of the intermetallic compounds were investigated. The appearance of the Cu3Sn was observed at Cu(220)/Sn interface after aged for 4 hours and then the thickness of...
In this paper, tin whisker behaviour of electroplating tin coating was studied in different environments. Different thickness of electroplating tin coating on copper substrate had been tested. Two different environmental conditions had been applied :one temperature tests (70 °C)and one external force tests(70 °C /17.5N). The growth of tin whisker was studied by using scanning electron microscopy (SEM)...
Electroless nickel-phosphor (Ni-P) plating has been extensively used as a diffusion barrier layer in printed circuit board applications. However, the interfacial reactions between electroless Ni-P and lead (Pb)-free Sn solders during high temperature reflow are known to dissolve Ni-P excessively into Sn leaving behind a brittle Ni3P compound at the interface. This often causes various reliability...
Electroplated Ni/Au over Cu is a popular metallization for printed circuit board (PCB) finish as well as for component leads, especially for wire-bondable high frequency packages, where the gold thickness requirement is high (≥ 20 µinches) for wire bonding. This study examines the effect of redeposition of bulk AuSn4 IMC as a function of varying gold content (2–5 nominal weight-%) in the solder joint...
Microstructure evolutions of as-reflowed and aged electroplated Cu/Sn/Cu sandwich structure with 20 or 40μm Sn layer have been investigated. Cu3Sn was observed at lower side of Cu/Sn/Cu structure with 40μm Sn layer after isothermal aging treatment for 24 hours, as for that structure with 20μm Sn layer, Cu3Sn appeared after aging for 48 hours. Regardless of Sn volume, the thickness of the blanket Cu...
In this paper, the effect of Ni-W alloy barrier layer on copper pillar/Sn IMCs evolution has been investigated. Additive W weight content of Ni-W alloy ranged from 16 to 18 at. %. Controlled thickness of barrier layer was prepared on Cu substrate. Then, excessive matte Sn electroplated on as-deposited Ni-W layer. Ni-W had compact microstructure in state of FCC solid solution, which means it had good...
Dimensional stability is critically important to various applications for which the functions are sensitive to dimensional change and internal strain. Due to the variation of densities of materials in solder, pad metal and formed IMCs, the total volume and dimensions of solder joint could varies with time of aging or service. This paper theoretically analyzed the change in volume of tin/copper solder...
In this investigation, Cu-Sn lead-free solder microbumps on 10- pads with a 20- pitch are designed and fabricated. The chip size is 5 5 mm with thousands of microbumps. A daisy-chain feature is adopted for the characterization and reliability assessment. After pattern trace formation, the microbump is fabricated on the trace by an electroplating technique. A suitable...
3-D integration provides a pathway to achieve high performance microsystems through bonding and interconnection of best-of-breed materials and devices. Bonding of device layers can be accomplished by dielectric bonding and/or metal–metal interconnect bonding with a number of metal–metal systems currently under development. RTI has been investigating Cu–Cu and Cu/Sn–Cu interconnect processes for high...
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...
Joint properties of Au stud bumps joined with Sn-3.5Ag solder by flip chip bonding were investigated. Au stud bumps were bonded on SOP (solder on pad) at bonding temperature of 260°C and 300°C for 10sec, respectively. Aging treatment was carried out at 150°C for 100 and 300 hrs. After flip chip bonding, intermetallic compounds (IMCs) of AuSn, AuSn2, and AuSn4 were formed at interface between Au stud...
In this study, two kinds of microscale solder joints, Sn-0.3Cu/Cu and Sn-0.5Cu/Cu, were studied. The element diffusion behavior at the soldering interface was investigated as the bulk solder size various from 5μm to 100μm during HTS (High Temperature Storage) aging. Experimental results indicated that the size and shape of solder joints have a significant effect on the element concentrations at the...
Lead free soldering has been the main stream of industry since 2006, with eutectic SnPb system phased out by SnAgCu system. However, development of lead-free alternatives for high melting high lead solder alloys is still struggling, thus hampering the completion of full lead-free conversion. BiAg alloy exhibits acceptable bulk strength but very poor ductility and wetting on copper, therefore is not...
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