Lead-free Technology Research Articles

The effect of pre-existing voids on solder reliability at different thermomechanical stress Levels: Experimental assessment

After lead-free technology, pre-existing voids in Power-MOSFET device solder connections have been a hot topic. Previous studies have examined the mechanical performance of solders with manufacturing-induced voids typically by generating excessive voids intentionally using simulation analysis without/insufficient experimental results. Electronic assembly standards such as IEC 61191-2, J-STD-001G, and IPC-A-610G do not cover voiding due to conflicting opinions and insufficient experimental evidence. In this context, comprehensive experimental results are needed to verify simulation results and assist in setting the standard. Silicon-based Power MOSFET packages with different locations, sizes, and patterns of pre-existing voids with nearly the same percentage of voids (30–33%) have been chosen to address this critical issue. The Power MOSFET test samples underwent power cycling-based accelerated degradation testing at various stress levels and monitored the location and rate of solder degradation at specific time intervals. It is found that small dispersive voids in solder life are useful, but clusters can accelerate damage propagation. Contrary, large dispersive voids at the edges initiate solder damage, reducing solder life. Our experimental investigation findings indicate that pre-existing voids' positions, sizes, and patterns should be considered when establishing solder void inspection standards. This would improve power devices' reliability for end-user power supply and control.

Electrochemical deposition of tin-copper alloy coatings

Solderable tin-base alloy coatings are widely used when assembling electronic products. The reorientation of production to lead-free technologies sets the task of developing new technological processes for the formation of coatings for electrical contacts with stable electrical properties, high soldering ability, which lasts for a long time. The features of the process of electrodeposition of coatings with a tin-copper alloy were experimentally investigated and the regularities of the influence of the electrolyte composition, current density, and ultrasound intensity on the cathode current efficiency of the alloy, the deposition rate, elemental composition, structure and functional properties of the precipitation were established. For sonochemical treatment an experimental setup developed at Research Laboratory 5.2 of BSUIR, which makes it possible to vary the intensity of ultrasonic vibrations in the range of 0.058– 1.7 W/cm2 , was used. It has been established that the use of ultrasound changes the formation mechanism of the electrochemical alloy, reduces cathodic polarization, increases the value of the limiting current and makes it possible to control the composition and structure of the precipitates. With an increase in the intensity from 0.12 to 0.95 W/cm2 the amount of copper in the coating increases by 4.5 times. The spreading coefficient of the solder is 92.59–98.44 %.

Methods for analyzing the reliability of mounting microelectronic radio components

According to modern standards of the radio-electronic industry, manufacturers have to use more and more lead-free technology for soldering nodal joints in produced electronic equipment for various purposes. But with the use of lead-free solders, the question arose about their reliability in comparison with their lead counterparts. It is just about the study of the reliability of lead-free solders that is described in this article. For these purposes, such brands of lead-free solders were investigated as SAC 0107, SAC 0307, SAC 0807, SAC 105, SAC 263, SAC 305, SAC 405, SAC 387, SAC 396. The main differences between linear regression analyses of the reliability of lead-free solder based on the characteristics of the solder and under the influence of thermal cycles based on the Weibull distribution are substantiated. The results of the research are presented at the end of the article in the form of graphical figures and tables.

Characteristic morphologies that cause failure of Au80Sn20/AlN substrate solder joint under combined temperature cycle and current switch cycle tests

With the requirement of lead-free soldering technology in electronic industry for manufacturing lead-free electronic devices, Au80Sn20 solder has been developed and applied in high-power devices due to its excellent physical and chemical properties. However, the application of new type of chip in high-power devices leads to the exposure of the Au80Sn20 solder joints to the complex environment of temperature cycle and current switch cycle, which seriously affects the reliability of solder joints in practical applications. In this study, the solder joint structure and simulation platform were designed independently. The failure mechanism of Au80Sn20/AlN substrate solder joint under temperature cycle and current switch cycle was studied by analyzing the changes in morphological characteristics of solder joint and composition in different working times. It was found that the failure process of solder joint involved the generation of steps along the grain boundary and phase boundary, and the failure was caused by the gradual expansion of steps. Owing to the uneven distribution of Cu and Ni in Au5Sn and AuSn phases, the volume difference among different phases was generated, which promoted the formation of phase boundary steps. The grain boundary steps were formed due to the formation of Au3Cu phase at the grain boundary, resulting in the volume difference between grain boundary and grain. Based on the research results, the idea of improving solder joint reliability by adjusting microstructure of Au80Sn20 solder is put forward, which plays a theoretical guiding role in the optimization of targeted performance of Au80Sn20 solder.

A reliability assessment guide for the transition planning to lead-free electronics for companies whose products are RoHS exempted or excluded

While a majority of electronic manufacturers have transitioned to lead-free materials and processes, both to comply with government legislation and to be compatible with the evolving supply-chain infrastructure, there are still many electronic manufacturers who are not using lead-free technologies, because they produce products that are either currently exempted or excluded from the government-imposed restrictions. Nevertheless, at some time, these manufacturers will need to have a lead-free transition plan, which includes compliance identification of the materials used, supplier compliance, process updates, and reliability assessment and qualification to the targeted application. This paper first briefly overviews the state of the knowledge as it relates to the reliability of lead-free solders. Then the paper provides a guide to help the planning team to assess the reliability issues needed for scheduling and resource identification to ensure a cost-effective and timely transition to lead-free products. The focus is on a risk matrix developed to help companies determine the general category of risk that they will encounter if they are currently exempt or excluded from making lead-free electronics.

Materials and soldering challenges in lead-free Package-on-Package (PoP) technology

Purpose– The purpose of this paper is to present challenges met during package-on-package (PoP) technology implementation in real surface-mount technology assembly processes.Design/methodology/approach– The properties and behavior of different combinations of soldering materials, PoP components and soldering profiles were investigated, both in the laboratory and during production trials. The purpose of such an approach was identification of existing problems and challenges in lead-free PoP systems assembly as well as checking which soldering material designed to PoP is more suitable for this technology.Findings– Technological trials are needed to select adequate soldering materials for PoP systems assembly, as laboratory tests of materials alone were not sufficient. The challenges of PoP technology were associated with the equipment utilized, the soldering materials, operational parameters and the soldering profile used for assembly. The localization of defects in PoP systems is very difficult and, in many cases, destructive methods have to be used on solder joints for the assessment and confirmation of failures.Originality/value– This paper shows main materials and soldering challenges in lead-free PoP technology. In particular, the problem related with selection of soldering materials and soldering profiles for PoP was presented. Moreover, the issues that have to be taken into consideration during the planning of a PoP system assembly procedure are presented.

Analysis of the Research Status of Tin Whisker's Influence on Lead-Free Soldering

Strengthening the study on whiskers influence on the reliability of lead-free soldering can improve welding technology and contribute to the overall development of the electronics industry. This paper provides an overview of the study on lead-free solder technology and development, summaries the materials, processes and other reliability issues and welding reliability problems of lead-free solder, finally gives an overview of the research status of whiskers formation mechanism and reliability.

Characterizing Corrosion Effects of Weak Organic Acids Using a Modified Bono Test

To meet environmental requirements and achieve benefits of cost-effective manufacturing, no-clean fluxes (NCFs) or low-solids fluxes have become popular in present electronic manufacturing processes. Weak organic acids (WOAs) as the activation ingredients in NCFs play an important role, especially in the current lead-free and halogen-free soldering technology era. However, no standard or uniform method exists to characterize the corrosion effects of WOAs on actual metallic circuits of printed wiring boards (PWBs). Hence, the development of an effective quantitative test method for evaluating the corrosion effects of WOAs on the PWB’s metallic circuits is imperative. In this paper, the modified Bono test, which was developed to quantitatively examine the corrosion properties of flux residues, is used to characterize the corrosion effects of five WOAs (i.e., abietic acid, succinic acid, glutaric acid, adipic acid, and malic acid) on PWB metallic circuits. Experiments were performed under three temperature/humidity conditions (85°C/85% RH, 60°C/93% RH, and 40°C/93% RH) using two WOA solution concentrations. The different corrosion effects among the various WOAs were best reflected in the testing results at 40°C and 60°C. Optical microscopy was used to observe the morphology of the corroded copper tracks, and scanning electron microscopy (SEM) energy-dispersive x-ray (EDX) characterization was performed to determine the dendrite composition.

Laser Irradiation on Tin Electroplating and Whisker Suppressibility

Tin electroplating with its excellent solderability and low cost performance is garnering attention as a lead-free technology. However, tin electroplated film is plagued with the issue of whisker formation. In this research, in order to suppress the whisker formation, the effect of laser irradiation on tin electroplated film onto a phosphor bronze substrate was studied by scanning electron microscopy and focused ion beam microscopy. Whiskers and nodules were generated on the surface of the tin electroplated film for a short time after electroplating. However, laser irradiated specimens showed no whiskers as well as nodules. This whisker suppression is attributable to the formation of thinly uniform intermetallic compound layer. Moreover, the solderability of the laser irradiated specimen was superior to that of the reflow specimen. These results demonstrated the effectiveness of laser treatment.

Reliability of Lead-Free BGA Assembly: Correlation Between Accelerated Ageing Tests and FE Simulations

In 2006, lead was banished in electrical and electronic equipment in Europe, but the reliability of lead-free technology is not yet well known. This paper describes a methodology using experiments and FE simulations that allow us to assess acceleration coefficients (ACs) and to predict assembly lifetimes. Two accelerated ageing tests have been conducted on lead-free ball grid array (BGA) assemblies. During the ageing test, cycles-to-failure have been accurately determined by an event detector from AnaTech. The 3-D nonlinear finite-element model of the BGA assembly has been designed and built using ANSYS software. Thermomechanical simulations have been carried out on this model to compute the strain energy density (SED) that dissipated in the solder joints during the thermal cycles. Then, the correlation between the experimentations and the simulations has allowed us to assess the ACs of two different kinds of thermal cycles and, thus, the cycles-to-failure for another test.

Lead-free solders: Reliability and other issues a year after the legislation

July 1, 2006 is in the rearview mirror and the legislated implementation of a ban on lead in electrical and electronic equipment throughout the European Union according to the directives of Restriction of the use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS) is almost a year old. Although legislation in Europe was implemented according to the plan, a number of questions remain regarding lead-free technology as the drop-in replacement for lead-bearing alloys. To compound the confusion, China is only in the drafting stage of its “Management Methods for Prevention and Control of Pollution from Production of Electronic and Information Products,” and with the exception of California, the United States has yet to legislate lead-free solders in electronics. In light of this legislation many electronic products manufacturers are making haste to implement lead-free solders and to market reliable green products. Thus, in response to growing interest and want of technical information on lead-free solders, the Electronic Packaging and Interconnection Materials Committee of the TMS Electronic, Magnetic & Photonic Materials Division organized a series of successful symposia on lead-free and lead-bearing solders in the past few years. The symposia were held at TMS annual and fall meetings and results were published. Continuing the trend, the recent “Pbfree Electronic Solders: Alloy Design, Characterization and Service Reliability” symposium held from February 25 to March 1, 2007 at the TMS Annual Lead-Free Solders: Reliability and Other Issues a Year after the Legislation

Environment-Friendly Electronics: Lead-Free Technology

Environment-Friendly Electronics: Lead-Free Technology

Are you ready for lead-free electronics?

An expedient transition to lead-free electronics has become necessary for most electronics industry sectors, considering the European directives [The Waste of Electrical and Electronic Equipment (WEEE) directive requires manufacturers to reduce the disposal waste of electrical and electronic products by reuse, recycling, and other forms of recovery. The Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS) legislation restricts the use of lead, as well as cadmium, mercury, hexavalent chromium, and two halide-containing flame retardants, namely polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE), in eight of the ten product categories identified in the WEEE directive. Unlike for WEEE, whereby EU member states are free to set more severe national legislation satisfying the WEEE directive requirements, RoHS is a single market directive. Both the WEEE and RoHS directives will become effective on July 1, 2006] , other possible legislative requirements, and market forces , . In fact, the consequences of not meeting the European July 2006 deadline for transition to lead-free electronics may translate into global market losses. Considering that lead-based electronics have been in use for over 40 years, the adoption of lead-free technology represents a dramatic change. The industry is being asked to adopt different electronic soldering materials , component termination metallurgies, and printed circuit board finishes. This challenge is accompanied by the need to requalify component-board assembly and rework processes, as well as implement test, inspection, and documentation procedures. In addition, lead-free technology is associated with increased materials, design, and manufacturing costs. [The cost of implementing the RoHS directive in the EU has been estimated to be US$ 20Bn . Intel Corporation's efforts to remove lead from its chips have been estimated to cost the company over US$ 100 million so far]. The use of lead-free materials and processes has also prompted new reliability concerns , as a result of different alloy metallurgies and higher assembly process temperatures relative to tin-lead soldering. This paper provides guidance to efficiently implement the lead-free transition process that accounts for the company's market share, associated exemptions, technological feasibility, product reliability requirements, and cost. Lead-free compliance, part and supplier selection, manufacturing, and education and training are addressed. The guidance is presented in the form of answers to key questions.

ELFNET – a new era in European lead-free soldering technology

ELFNET – a new era in European lead-free soldering technology

Environmental-Friendly Electronics: Lead-Free Technology

Environmental-Friendly Electronics: Lead-Free Technology

Environmentally-friendly electronics: lead-free technology [Book Review

Environmentally-friendly electronics: lead-free technology [Book Review

Environment-friendly electronics: lead free technology

Environment-friendly electronics: lead free technology

Environment-friendly Electronics: Lead-free Technology

Environment-friendly Electronics: Lead-free Technology

Solders and Soldering

Solders and Soldering

Environment-Friendly Electronics: Lead-Free Technology [Book Review

Environment-Friendly Electronics: Lead-Free Technology [Book Review