Addition of Al into SAC alloys reduces the number of hard Ag3Sn and Cu6Sn5 IMC particles,and forms larger,softer non-stoichiometric AlAg and AlCu particles. This results in a significant reduction in yield strength,and also causes some moderate increase in creep rate. For high Ag SAC alloys,adding Al 0.1-0.6% to SAC alloys is most effective in softening,and brings the yield strength down to the level of SAC105 and SAC1505,while the creep rate is still maintained at SAC305 level. Addition of Ni results in formation of large (Ni,Cu)3Sn4 IMC particles and loss of Cu6Sn5 particles. This also causes softening of SAC alloys,although to a less extent than that of Al addition. Addition of Al also drives the microstructure to shift from near-ternary SnAgCu eutectic toward combination of eutectic SnAg and eutectic SnCu. Addition of Ni drives shifting toward eutectic SnAg. For SAC+Al+Ni alloys,the pasty range and liquidus temperature are about 4?C less than that of SAC105 or SAC1505 if the addition quantity is less than about 0.6%. Addition of Al and Ni also results in a slight decrease in modulus and elongation at break,although the tensile strength is not affected.

It is known that pure tin will undergo an allotropic transformation below 13°C where it becomes a semiconductor with a 26% volume increase,and in appearance turns from a bright shiny metallic material,white ß tin,to a dark blue/grey dust,a tin. Such a transformation for an electrical interconnect is disastrous,if it were to occur in any of the high tin lead-free alloys it would be a catastrophe. The elimination of lead,one of the best elements to arrest the transformation process,has resulted in a number of high tin content alloys about which the potential to transform is unknown. Environmental factors that may enhance or arrest the rate and the incubation period of the transformation processes are also unknown.
An analysis based on the lattice parameter of a tin to find similar materials was substantiated and was used to select inoculators to minimize the incubation period. Following which a number of experiments were conducted using CdTe. To further the study the transformation process was videoed using time lapse photography with the sample held at –35°C in vacuum system. The transformation progressed radically from the inoculation point,starting at the surface. Propagation into the bulk occurred by peeling; with the external layers tending to “roll out” due to the volume expansion of the internal layers. In the meantime,cracks parallel to the propagation direction formed. Typically a sample would completely transform in just over 24 hours.
Further work is now looking at the effect of cubic ice,temperature on the transformation and the effect of alloying additions in influencing the transformation process.
The roll of this particular lattice form of ice is a worrying aspect,since it can commonly occur under the relevant temperatures. Experiments have shown that ice can act as the inoculators,seeding the transformation,particularly when other inoculators are in the vicinity.

Flux technology for lead-free alloys differs considerably from that for eutectic Sn/Pb solder systems,mainly for soldering and cleaning purpose. For most of the lead-free solders,paste handling is not an issue. Although dust has not settled yet,it becomes clear that the flux needed should have higher flux capacity,higher oxygen barrier capability,and higher thermal stability. Halide-free fluxes are placing greater challenge on cleaning due to the lower flux efficiency per unit flux volume than halide-containing fluxes. The oxygen barrier capability can be reduced if inert reflow atmosphere is available. RMA flux,no-clean flux with high solid content,and water washable systems exhibit a greater prospect to be upgraded for lead-free applications. For 58Bi/42Sn solder,flux with low activation temperature is needed. For Sn/Zn/Bi solders,the demand on flux capacity and oxygen barrier capability is even greater than other lead-free solder systems. In addition,the fluxes should be stable enough to retard the reaction with Zn. Cleaning flux residue of lead-free solder pastes is more challenging than that of Sn/Pb systems. This is primarily due to (1) higher reflow temperature,(2) higher flux capacity,therefore higher flux-induced side reactions,(3) more tin-salts formation. The cleanability decreases from no-clean soft-residue fluxes to water washable fluxes to no-clean hard residue fluxes. Improvement in cleanability may link to improvement in thermal stability of fluxes. Semi-aqueous and/or aqueous solvent sprayable cleaners yield the best cleaning efficiency,if the solvent is selected properly. Spray is the most critical mechanical agitation,regardless whether it is spray-in-air or spray-under-immersion. Ultrasonic aid also imparted a significant positive effect. Saponified aqueous spray is one of the top choices for cleaning water washable residues. Better solvency and spray are the directions for further improving cleaning. Improvement in flux thermal stability will help both soldering and cleaning.

Companies seeking sales or suppliers in the global marketplace must proceed with caution. This presentation provides an overview of U.S. regulation of import and export transactions. Importers must exercise “reasonable care” to ensure that accurate information is provided to U.S. Customs & Border Protection regarding the nature,value,and origin of imported merchandise. Reliance on third parties or suppliers for that information does not protect the importer from liability. Further,importers must establish and maintain compliance programs consistent with the customs laws and regulations. On the export side,companies seeking new markets for their products must ensure compliance with U.S. export controls,economic sanctions,and embargoes. This presentation will give companies insight into how to manage these risks while employing legal tools to reduce costs in international trade.

•Rewards businesses with a dollar for dollar reduction of tax
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•Federal tax benefit can be as high as 6.5% of investment in new products and processes
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Various forms of contamination on the surface of hydrocarbon ceramic dielectric PWBs have been observed following component population. Although contamination is occasionally observed on PWBs fabricated from other dielectric materials,the light color of hydrocarbon ceramic substrates increases the frequency of detection,and consequently increases the number of investigations into possible contamination causes and impacts to reliability. Three contamination types are evaluated: staining due to rework of gold plated surfaces,discoloration due to flux application,and the resulting anomalies due to the effects of multiple chemical processing steps. The causes of the anomalies,quantitative analysis of residues,and impacts to reliability for each of these contaminants are discussed.

All things corrode,and the rate of corrosion among electronics devices is accelerating. Electronic devices are being used in more places than ever before. They are finding more uses,they're more portable,and they're increasingly used in polluted areas. Worldwide industrialization has produced more sulfur,chlorine and nitrogen compounds that aggressively attack electronics. The initiatives to eliminate lead (Pb) in electronics reduced the ability for circuitry to resist corrosion. To replace thick tin-lead deposits more circuits employ thin,easily corroded surface finishes on the PCB,connectors,and component leads. There is a need for better prediction of service-life corrosion,yet there is a lack of adequate test methods. Environmental testing rarely progresses beyond thermal cycling or heat/humidity. Mixed flowing gas testing uses standardized pollutants as a stress to electronics,but has limited success in reproducing all corrosion failures. An elevated rate in the observation of one type of failure,termed creeping corrosion,motivated the electronics industry to review corrosion test methods. As part of the IPC 3-11g committee,a number of OEM's,EMS providers,PCB fabricators,material suppliers,universities,and testing laboratories joined forces to address the need for better corrosion prediction.
The project conducted experiments using environmental pollutants and various levels of exposure to moisture to form corrosion salts from copper circuitry. A main objective of the testing was to create a standardized method for inducing corrosion. Test results will show the ability to recreate creep corrosion at the participating laboratories. As a project summary,this paper will review the many attributes of a PCB surface finish,the ways that each finish can fail under environmental contamination,the mechanism of creeping corrosion,and new ways to interrupt the corrosion mechanism while preserving other surface finish attributes. The summary contained herein had been intended to include the latest corrosion results from the IPC 3-11g team; however,the testing was not complete by the time of publication. This review will detail the status of the team’s findings to date,provide references to newly collated data,and chart the team’s forward direction.

Electronics,especially mobile electronic items,are subjected to unintentional abuse by having various beverages spilled onto or into them. Ion Chromatography and emission spectroscopy were used to identify the common inorganic ions in various carbonated drinks,coffee,tea,milk,juices,beer,wine,hot chocolate and a well-known sports drink. Except for the carbonated drinks,the others were then intentionally spilled onto clean circuit boards,dried,extracted and re-analyzed. The results show that there is generally little change from the virgin materials using the IPC extraction method and thus a library of “usual suspects” can be accumulated for comparison purposes for electronic products that come back from the field.

Printing technologies provide a simple solution to build electronic circuits on low cost flexible substrates. Nanocomposites will play important role for developing advanced printable technology. Advanced printing is relatively new technology and need more characterization and optimization for practical applications. In the present paper,we examine the use of nanocomposites or materials in the area of printing technology. A variety of printable nanomaterials for electronic packaging have been developed. This includes nano capacitors and resistors as embedded passives,nano magnetic materials,multifunctional materials,etc. Nanocomposites can provide high capacitance densities,ranging from 5nf/inch2 to 25 nF/inch2,depending on composition,particle size and film thickness. The electrical properties of capacitors fabricated from BaTiO3-epoxy nanocomposites showed a stable capacitance and low loss over a temperature range from 25 0C to 100 0C. A variety of printable discrete resistors with different sheet resistances,ranging from 1 ohm to 120 Mohm,processed on large panels (19.5 inches x 24 inches) have been fabricated. Low resistivity nanocomposites,with volume resistivity in the range of 10-4 ohm-cm to 10-6 ohm-cm depending on composition,particle size,and loading can be used as conductive joints for high frequency and high density interconnect applications. Thermosetting polymers modified with ceramics can produce low k dielectrics with k value in the range between 5.41 and 3.59. Similarly,low loss dielectric materials can be produced form mixing epoxy with silica or other low loss fillers. Reliability of the nanocomposites was ascertained by IR-reflow,thermal cycling,pressure cooker test (PCT),and solder shock. Change in capacitance after 3X IR-reflow and after 1000 cycles of deep thermal cycling (DTC) between -55oC and 125oC was within 5%. Most of the nanocomposites in the test vehicle were stable after IR-reflow,PCT,and solder shock.

Following the implementation of WEEE legislation,there will be an increasing interest in adopting more sustainable manufacturing processes and materials as targets are increased,and must be achieved without a loss in performance. These innovations may well lead to alternative failure modes. This work studies the performance of specific favoured materials to qualify the failure mechanisms and the effective stress screening regimes,and hence put in place the underpinning work for developing a test method for characterising these materials.
Three systems are evaluated; thermoplastic printed circuit assemblies based on copper-clad polyetherimide,polymer thick film on PET,and direct write copper on PET,were assembled using electrically conductive adhesives and tested using damp heat,dry heat and thermal cycling. All combinations showed very good reliability during the arduous testing. Chip resistor components generally showed less than 5% failures due to increased joint resistance after 1000 hours at 85°C/85%RH or 1000 thermal cycles from –55°C to +125°C. Results from gull-wing SOIC components were less promising but current work is investigating assembly methods to improve reliability of these components. Results were found to be conductive adhesive dependent,but results show that if the right combination of materials is chosen,thermoplastic substrates can be reliable for a wide range of electronics applications. The thermoplastic substrate technology offers great flexibility,for example 3D manufacturing or using the housing as the circuit board are all feasible. The lower energy and cost of manufacture and the improved potential for recycling indicate the value of further work.