Development of lead-free Sn-3.5Ag/SnO2 nanocomposite solders

Scopus: "In the present study, feasibility of using SnO2 as reinforcement in Sn-3.5Ag is assessed. Energy-efficient microwave assisted powder metallurgy route was used for synthesis of materials. Characterization results revealed that best combination of hardness and tensile strength was realized with 0.7 vol% of SnO2 in solder matrix. An attempt is made to correlate mechanical properties of Sn-3.5Ag with the increasing presence of SnO2 particulates at the nanometer length scale."

National University of Singapore

Reactive nanometer multilayers as tailored heat sources for joining

Scopus : "The use of traditional joining techniques like soldering or brazing for heat sensitive microstructures often results in damaging or stress induced deformation of the components. Therefore a technology would be desirable, where heat is produced locally and only for a short time. 

A very promising approach is the application of socalled reactive nanometer multilayers. Reactive nanometer multilayers consist of several hundreds or a few thousands of alternating layers with thicknesses in the nanometer range that can exothermic react with each other. After a local activation of the chemical reaction by an electrical spark or a laser pulse, a selfsustaining reaction starts, which propagates parallel to the multilayer surface resulting in a stable intermetaliic single layer. The peak temperature of the reaction can be above 1000 'C, but the maximum temperature is only reached for several ten milliseconds. Therefore, the heat remains localized in the vicinity of the solder layers surrounding the reactive multilayer. During the entire process the components to be joined exhibit temperatures close to room temperature. We will show new results concerning the fabrication of reactive nanometer multilayers by magnetron and ion beam sputter deposition and the fabrication of free standing nanometer multilayers"

Fraunhofer-Institut, Dresden, Germany

Effects of cerium on Sn-Ag-Cu alloys based on finite element simulation and experiments

Scopus: "Effect of small addition of rare earth on Sn-Ag-Cu solder was investigated by finite element method based on creep model of low stress and high stress and experiments respectively. It was found that addition of rare earths evidently improved the resistance to creep deformation of the solder, so that the reliability of Sn-Ag-Cu-Ce solder joint could be improved remarkably."

The influence of stress on creep behavior of Ag particle enhancement SnCu based

Scopus: "Single shear lap creep specimens were developed using Ag particle-enhancement SnCu based composite solder to examine the influence of stress on creep behavior of the composite solder in this paper. 

Results show that the creep resistance of solder joints of particle enhancement 99.3Sn0.7Cu based composite solder is superior to that of 99.3Sn0.7Cu solder joints. At the same time, the creep rupture lifetime of the solder joints of the composite solders was decreased with the increasing of stresses and felt down faster than those of 99.3Sn0.7Cu solder joints."

Henan Key Lab of Advanced Non-Ferrous Metals, China

China Shipping Heavy Industry Group, China

Reliability of Lead-Free Solder Interconnections in Thermal and Power Cycling Tes

Scopus: "Lead-free solder interconnection reliability of thin fine-pitch ball grid array (BGA) lead-free packages has been studied experimentally as well as with finite-element (FE) simulations. The reliability tests were composed of the thermal shock test, the local thermal cycling test (resistors embedded in the board around the package), and the power cycling test (heat generation in the die). A 3-D board-level finite-element analysis (FEA) with local models was carried out to estimate the reliability of the solder interconnections under various test conditions."

Helsinki University, Finland

Creep behavior of lead-free Sn-Ag-Cu Ni-ge solder alloys

Scopus: "We developed a new lead-free solder alloy, an Sn-Ag-Cu base to which a small amount of Ni and Ge is added, to improve the mechanical properties of solder alloys. We examined creep deformation in bulk and through-hole (TH) form for two lead-free solder alloys, Sn-3.5Ag-0.5Cu-Ni-Ge and Sn-3.0Ag-0.5Cu, at elevated temperatures, finding that the creep rupture life of the Sn-3.5Ag-0.5Cu-Ni-Ge solder alloy was over three times better than that of the Sn-3.0Ag-0.5Cu solder at 398 K. Adding Ni to the solder appears to make microstructural development finer and more uniform. 

The Ni added to the solder readily combined with Cu to form stable intermetallic compounds of (Cu, Ni) 6Sn5 capable of improving the creep behavior of solder alloys. Moreover, microstructural characterization based on transmission electron microscopy analyses observing creep behavior in detail showed that such particles in the Sn-3.5Ag-0.5Cu-Ni-Ge solder alloy prevent dislocation and movement."

Fuji Electric, Japan

Tokyo Metropolitam University, Japan

Solder-free connectors using buckled pillars

Scopus: "The innovative use of stud bumping machine has lead to the development of buckled pillar connectors for three-dimensional (3D) electronic assemblies that are put together with screws rather than solder. These screws work against spacers to provide exactly the right amount of compression that is enough to buckle the pillars by a few percent in length, making the bonding wire material not stressed above its elastic limit."

Fjelstad to Present on the Occam Process at Stanford

PCB007: "Then, the terminations are interconnected, e.g. by copper plating. Eliminating the solder bumps that have connected chips to systems boards solves the problems of lead-free solder materials; the new process also offers many other benefits, including reduced total energy requirements for the manufacturing and assembly process. 

Moreover, solder-less assembly technology is expected to be low cost. This presentation will describe the process and review some of the various process variations."

Fluxless hermetic lid sealing using electroplated Sn-rich solder

Scopus: "A thick Sn layer is plated over the Cr/Au patterned glass wafer, followed immediately by thin Au layer. This outer Au layer prevents the inner Sn from oxidation. In bonding, the glass lid is placed over the package rim which has a metallization structure of W/Ni/Au. The fluxless sealing process is performed in vacuum (50 millitorrs) to suppress tin oxidation. Compared to bonding in air, the oxygen content is reduced by a factor of 15200. Fluxless bonding is valuable in many hermetic sealing applications such as microelectromechanical systems (MEMS), sensors, photonic devices, and imaging devices. Nearly void-free sealed joints are achieved"

Creep and fatigue behavior of SnAg solders with lanthanum doping

Scopus: "It is found that La doping increases the fatigue life by about five times. The optimal doping level for better fatigue performance is around 0.1%"

Numerical investigation of underfill failure due to phase change of Pb-free flip

Scopus: "Most of the current Pb-free solder candidates are based on Sn and their melting temperatures are in the range of 220 'C-240 'C. Thus, Pb-free flip chip solders melt again during subsequent board-level interconnect (BGA) reflow cycle. Since solder volume expands as much as 4% during the phase change from solid to liquid, the volumetric expansion of solder in a predefined volume by chip, substrate, and underfill creates serious reliability issues."

Effect of the addition of In on the microstructural formation of Sn-Ag-Zn lead-free solder

Scopus: "Clearly, the addition of In into the explored Sn-Ag-Zn solder promotes the formation of rod-like IMCs for the reason that the growth competition of the Ag3Sn and AgZn IMCs was destroyed by the selective adsorption of In atoms on a certain preferable crystalline planes of the separated IMCs. 

The change in the morphology of the formed IMCs leads to a great difference in the mechanical performances, for example, the measured microhardness of the investigated solders evolves from 16.95 HV to 21.35 HV with the increase of In content."

Cookson 2008: Electronics: Assembly Materials.

Factiva: "For its fiscal 2008, the Assembly materials segment of the Electronics division of Cookson Group pc has reported revenue of GBP 382 M ( 5% on its fiscal 2007). Assembly Materials is a leading global supplier of materials to assemblers of printed circuit boards (PCBs), the semi-conductor packaging industry and to certain non-electronics markets such as plumbing, automotive and water treatment under the trade names of Alpha and Fry."

A number of new products have been launched during the year including a 1% silver lead-free solder alloy, SACX solder paste and an expanded range of environmentally friendly Greenline products, which are halogen-free and contain low, or no, volatile organic compounds. 

The business has also benefited from the continued growth, stimulated by high metal prices, in the reclaim business in the US, in which scrap solder generated by customers' production processes is reclaimed for processing back into solder alloys for sale to third parties or for reuse within the business. A similar reclaim business has been set up in Guangxi Province, China, which became operational at the end of 2008. In Feb 2008, the transfer of solder paste production from Ashford, UK to Hungary was announced for completion in 1H 2009. This initiative will result in annualised savings of GBP 1 M from the middle of 2009. 2008 also benefited from the full year effect of the transfer of Assembly Materials' manufacturing operations within NAFTA from the US to Mexico, which was completed towards the end of 2007.

BERR publishing consultation to revise the WEEE and ROHS directives

RECYCLINGPORTAL: "Commenting on the proposals a BERR spokesperson said: 'The UK welcomes the Commission's intention to strengthen the Directives, with further steps to limit the environmental impact of waste equipment. However, we are concerned that the WEEE proposals in particular do present some significant challenges for British businesses.

'Our consultation paper will give the electronics and ICT industries, the waste management sector, consumers and other interested parties the opportunity to inform the UK government's understanding of the impact the changes will have, ahead of the formal negotiations in Brussels.'

Responses to the consultation are sought by 13 May 2009."

Bottom-up nanoconstruction by the welding of lndividual metallic nanoobjects using nanoscale solder

Scopus: "We report that individual metallic nanowires and nanoobjects can be assembled and welded together into complex nanostructures and conductive circuits by a new nanoscale electrical welding technique using nanovolumes of metal solder. 

At the weid sites, nanoscale volumes of a chosen metal are deposoted usong a sacrificial nanowire, which ensures that the nanoobjects to be bonded retain their structural integrity. We demonstrate by welding both similar and dissimilar materials that the use of nanoscale seider is clean, controllable, and reliable and ensures both mechanically streng and etectrically conductive contacts. Nanoscale weld resistances of just 20Ω are achieved by using Sn solder."

IPC lead-free share figures March 2009

evertiq.com: "According to a study made by US Electronics Trade Organization IPC, 62% of all solder sold during the fourth quarter in 2008 was lead free. In Europe 46% percent of the EMS providers still consumes standard solder in their production. 61% in the US, 31% in Japan, 26% in China and 29% in the rest of Asia. The rest is lead free solder."

A new Zn solder wetting layer for Pb-free solders

Scopus: "We developed a new Cu-Zn wetting layer for Pb-free solders. By adding Zn to the wetting layer, intermetallic growth in the Sn-Ag-Cu (SAC) solder interfaces was delayed. Cu3Sn intermetallic compounds and microvoids were not observed in the SAC/Cu-Zn interfaces after aging. The drop reliability of the SAC solder/Cu-Zn joints was excellent"

US Navy Selects DfR Solutions for Pb-Free Solder Reliability Research

News Blaze: "DfR Solutions today announced it has been chosen by the United States Navy to perform a study on the reliability of Pb-free solder when exposed to vibration and mechanical shock. The Navy chose DfR Solutions because of the firm's proven reputation as an industry leader in Pb-free solder research.

The pressure to move to Pb-free has intensified within the supply chain. However, Pb-free electronics have a history of poor performance when exposed to vibration or mechanical shock. This poor performance has led to concerns within the military community about the reliability of Pb-solder.

'We are proud to be recognized as a Pb-free center of excellence by the Department of Defense,' said Dr. Nathan Blattau, Chief Scientist of DfR Solutions. 'We see a real opportunity to quantify the reliability of Pb-free solder under complex mechanical loads and take some of the uncertainty out of Pb-free in military applications. Companies that partner with us on this activity will have access to data and analysis critical for a successful Pb-free transition.'"

Low temperature chip bonding from ThreeBond‏

EMSNow‏: "The TB2217H low temperature cure chip bonder from ThreeBond offers curing at 80'C and addresses an array of chip bonding issues for manufacturers and rework facilities. This single component epoxy offers ease of handling by syringe and full compatibility with automated dispensing systems to enable chip retention on pcb's going through multi-station lines and wave
soldering equipment.

By offering a very low cure temperature of 80'C with a 220 sec cure time, TB2217H can eliminate possible damage to heat sensitive components while at the same time offering a high speed snap cure of 60 seconds at 150'C where needed."

Air Force Awards Optomec Project to Eliminate Solder in Electronics and Reduce E-Waste

Consumer Electronics net: "Optomec announced today that the company, along with a major Aerospace OEM, was awarded a project to eliminate solder from the manufacture of electronics. The $300,000 proof of concept project is structured as a one-year feasibility study. Follow-on awards are anticipated based on initial project results."

The main goal of the Solder Free project is to demonstrate the fabrication of functional circuits without solder. To accomplish this goal, a leading Aerospace/Defense company will design multiple test circuits, including a Twin-T notch filter circuit and an inverter circuit that will then be completely printed using an Aerosol Jet system. All elements of these test circuits, which include resistors, capacitors, transistors and interconnects, will be fully printed by an Aerosol Jet system and will demonstrate its ability to precisely deposit a variety of conductor, semiconductor, resistor and dielectric materials. Performance and cost data will be gathered to demonstrate the potential savings of using Aerosol Jet compared to traditional manufacturing processes for military printed electronics applications.

oth the Lead Solder process and the Lead-Free Solder process exhibit many problems and challenges for current day electronics manufacturers, all of which can be avoided when the Aerosol Jet process is employed. The Lead Solder process poses e-waste hazards worldwide and many countries have taken measures to prevent the use of lead and other harmful materials in manufacturing. The use of Lead-Free solders in the fabrication process introduces reliability challenges, including the growth of tin whiskers, solder cracking and voids. The Aerosol Jet deposition process, however, can print the entire circuit board, including interconnects, and active and passive components. No soldering is required, hence environmental and reliability concerns are eliminated. Other key benefits of the Aerosol Jet process include reduced cycle time and reduced cost for low volume production.