An Investigation of the Lead-Free Surface Mount Soldering Process: Solder Joint Evaluation and Process Optimisation

2004 ◽  
Author(s):  
Claire Ryan ◽  
Jeff M. Punch ◽  
Bryan Rodgers ◽  
Greg Heaslip ◽  
Shane O’Neill ◽  
...  
Keyword(s):  
Screen Printing ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Surface Mount ◽  
Snagcu Solder ◽  
Soldering Process ◽  
Free Process ◽  
Free Solder

A European Union ban on lead in most electrical and electronic equipment will be imposed as of July 1st 2006. The ban, along with market pressures, means that manufacturers must transfer from a tin-lead soldering process to a lead-free process. In this paper the implications on the surface mount (SMT) soldering process are presented. A set of experiments was conducted to investigate the screen-printing and reflow steps of the SMT process using a tin-silver-copper (95.5Sn3.8Ag0.7Cu) solder and a baseline of standard tin-lead (63Sn37Pb). 10×10 arrays of micro Ball Grid Array (micro-BGA) components mounted on 8-layer FR4 printed wiring boards (PWBs) were used. The screen-printing experiment addressed the deposition of the solder paste on the board. The parameters used in the investigation were print speed, squeegee pressure, snap-off distance, separation speed and cleaning interval, with the responses being measurements of paste height and volume. Optimum screen-printer settings were determined which give adequate paste volume and height and a good print definition. The reflow experiment investigated the following parameters of the temperature profile: preheat, soak, peak and cool down temperatures, and conveyor speed. The resulting solder joints were evaluated using cross-section analysis and x-ray techniques in order to determine the presence of defects. A mechanical fatigue test was also carried out in order to compare the strength of the solder joints. The overall quality of the lead-free solder joints was determined from these tests and compared to that of tin-lead. The outcome is a set of manufacturing guidelines for transferring to lead-free solder including optimum screen-printer and reflow oven settings for use with an SnAgCu solder.

Thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components: a review

2016 ◽  
Vol 28 (2) ◽  
pp. 41-62 ◽  
Author(s):  
Chun Sean Lau ◽  
C.Y. Khor ◽  
D. Soares ◽  
J.C. Teixeira ◽  
M.Z. Abdullah
Keyword(s):  
Solder Joints ◽  
Simulation Modelling ◽  
Lead Free ◽  
Lead Free Solder ◽  
Reflow Process ◽  
Reflow Soldering ◽  
Content Type ◽  
Surface Mount ◽  
Soldering Process ◽  
Free Solder

Purpose The purpose of the present study was to review the thermo-mechanical challenges of reflowed lead-free solder joints in surface mount components (SMCs). The topics of the review include challenges in modelling of the reflow soldering process, optimization and the future challenges in the reflow soldering process. Besides, the numerical approach of lead-free solder reliability is also discussed. Design/methodology/approach Lead-free reflow soldering is one of the most significant processes in the development of surface mount technology, especially toward the miniaturization of the advanced SMCs package. The challenges lead to more complex thermal responses when the PCB assembly passes through the reflow oven. The virtual modelling tools facilitate the modelling and simulation of the lead-free reflow process, which provide more data and clear visualization on the particular process. Findings With the growing trend of computer power and software capability, the multidisciplinary simulation, such as the temperature and thermal stress of lead-free SMCs, under the influenced of a specific process atmosphere can be provided. A simulation modelling technique for the thermal response and flow field prediction of a reflow process is cost-effective and has greatly helped the engineer to eliminate guesswork. Besides, simulated-based optimization methods of the reflow process have gained popularity because of them being economical and have reduced time-consumption, and these provide more information compared to the experimental hardware. The advantages and disadvantages of the simulation modelling in the reflow soldering process are also briefly discussed. Practical implications This literature review provides the engineers and researchers with a profound understanding of the thermo-mechanical challenges of reflowed lead-free solder joints in SMCs and the challenges of simulation modelling in the reflow process. Originality/value The unique challenges in solder joint reliability, and direction of future research in reflow process were identified to clarify the solutions to solve lead-free reliability issues in the electronics manufacturing industry.

The Effect of Multiple Reflow Times on Lead-Free Solder Joint Microstructure

2003 ◽  
Author(s):  
Sami T. Nurmi ◽  
Janne J. Sundelin ◽  
Eero O. Ristolainen ◽  
Toivo K. Lepisto¨
Keyword(s):  
Solder Joint ◽  
Solder Joints ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Snagcu Solder ◽  
Silver Copper ◽  
Free Solder ◽  
Tin Silver Copper ◽  
Lead Free Solders

As environmental issues are raising more interest and are becoming crucial factors in all parts of the world, more and more environmental-friendly electronics products are emerging. Usually this means the introduction of products with lead-free solders. However, the reliability of lead-free solders is still a serious concern despite the vast research done in this field. This paper will describe the interconnect reliability of three kinds of solder joints respectively prepared with lead-free solder paste and lead-free PBGA components, lead-free solder paste and tin-lead-silver PBGA components, and tin-lead solder paste and tin-lead-silver PBGA components. Lead-free and tin-lead solders were composed of eutectic tin-silver-copper and tin-lead, respectively. In addition, the study also presents the effect of multiple reflow times. The study focuses on the microstructures of different assemblies. The particular interest is on the assemblies soldered with lead-free solder paste and tin-lead-silver PBGA components, since the SnPbAg solder on the bumps of the PBGA components were exposed to the reflow profile meant for the lead-free SnAgCu solder. Thus, these SnPbAg solder bumps were in the molten state almost twice as long as the rest of the solders. This had a notable effect on the reliability of these solder joints as we will be showing later in this paper. The test boards were temperature-cycled for 2500 cycles between −40 and +125°C (a 30-minute cycle). PBGA solder joint failures were monitored with a real time monitoring system. Optical and scanning electron microscopy was used to inspect the broken solder joints and their microstructure. The results of tests indicate that the number of reflow times can significantly affect the lifetime of PBGA solder joints. The most notable changes can be seen in the solder joints made with tin-lead-silver PBGA components and tin-silver-copper solder paste soldered with a lead-free reflow profile. The general trend was that the reliability of the solder joints increased in proportion to the number of reflow times. Mainly two factors are believed to have the major effect on the reliability of PBGA solder joints, voids, and microstructural changes in solder.

A Comparative Study of Soldering Temperatures and Materials on the Reliability of Photovoltaic Modules

2012 ◽  
Vol 562-564 ◽  
pp. 188-191
Author(s):  
Keh Moh Lin ◽  
Yang Hsien Lee ◽  
Wen Yeong Huang ◽  
Po Chun Hsu ◽  
Chin Yang Huang ◽  
...  
Keyword(s):  
Comparative Study ◽  
Lead Free ◽  
Automatic Process ◽  
Lead Free Solder ◽  
Snagcu Solder ◽  
Photovoltaic Modules ◽  
Soldering Process ◽  
Different Temperatures ◽  
Free Solder

To find out the important factors which decisively affect the soldering quality of photovoltaic modules, solar cells were soldered under different conditions (different temperatures, PbSn vs. SnAgCu solder, manual vs. semi-automatic). Experimental results show that the soldering quality of PbSn under 350°C in the semi-automatic soldering process was quite stable while the soldering quality of lead-free solder was generally unacceptable in the manual or semi-automatic process under different temperatures. This result indicates that the soldering process with lead-free solder still needs to be further improved. It was also found that most cracks were formed on the interface between the solder and the silver paste and then expanded outwards.

Quantitative Evaluation of Voids in Lead Free Solder Joints

2015 ◽  
Vol 772 ◽  
pp. 284-289 ◽  
Author(s):  
Sabuj Mallik ◽  
Jude Njoku ◽  
Gabriel Takyi
Keyword(s):  
Solder Bump ◽  
Solder Joints ◽  
Void Formation ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
X Ray ◽  
Size And Shape ◽  
Solder Bumps ◽  
Free Solder

Voiding in solder joints poses a serious reliability concern for electronic products. The aim of this research was to quantify the void formation in lead-free solder joints through X-ray inspections. Experiments were designed to investigate how void formation is affected by solder bump size and shape, differences in reflow time and temperature, and differences in solder paste formulation. Four different lead-free solder paste samples were used to produce solder bumps on a number of test boards, using surface mount reflow soldering process. Using an advanced X-ray inspection system void percentages were measured for three different size and shape solder bumps. Results indicate that the voiding in solder joint is strongly influenced by solder bump size and shape, with voids found to have increased when bump size decreased. A longer soaking period during reflow stage has negatively affectedsolder voids. Voiding was also accelerated with smaller solder particles in solder paste.

Practical Application and Analysis of Lead-Free Solder on Chip-On-Flip-Chip SiP for Hearing Aids

2017 ◽  
Vol 2017 (1) ◽  
pp. 000201-000207 ◽  
Author(s):  
Youngtak Lee ◽  
Doug Link
Keyword(s):  
Hearing Aids ◽  
Flip Chip ◽  
Failure Modes ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Practical Application ◽  
Surface Mount ◽  
Free Solder ◽  
On Chip

Abstract Due to rapid growth of the microelectronics industry, packaged devices with small form factors, low costs, high power performance, and increased efficiency have become of high demand in the market. To realize the current market development trend, flip chip interconnection and System-in-Package (SiP) are some of the promising packaging solutions developed. However, a surprising amount of surface mount technology (SMT) defects are associated with the use of lead-free solder paste and methods by which the paste is applied. Two such defects are solder extrusion and tombstoning. Considerable amount of defects associated with solder overflow are found on chip-on-flip-chip (COFC) SiP in hearing aids. Through the use of design of experiments (DOE), lead-free solder defect causes on hearing aids application can be better understood and subsequently reduced or eliminated. This paper will examine the failure modes of solder extrusion and tombstoning that occurred when two different types of lead-free solders, Sn-Ag-Cu (SAC) and BiAgX were used within a SiP for attachment of surface mount devices (SMD) chip components for hearing aid applications. The practical application and analysis of lead-free solder for hearing aids will include the comprehensive failure analysis of the SMD components and compare the modeling and analysis of the two different solder types through the DOE process.

Comparative Modeling and Analysis of Lead-Free Solder Extrusion for the Design of Reliability

2016 ◽  
Vol 2016 (1) ◽  
pp. 000111-000116
Author(s):  
Youngtak Lee ◽  
Doug Link
Keyword(s):  
Design Of Experiments ◽  
Flip Chip ◽  
Failure Modes ◽  
Form Factors ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Modeling And Analysis ◽  
Surface Mount ◽  
Free Solder

Abstract Due to rapid growth of the microelectronics industry, packaged devices with small form factors, low costs, high power performance, and increased efficiency have become of high demand in the market. To realize the current market development trend, flip chip interconnection and System-in-Package (SiP) are some of the promising packaging solutions developed. However, a surprising amount of surface mount technology (SMT) defects are associated with the use of lead-free solder paste and methods by which the paste is applied. Two such defects are solder extrusion and tombstoning. Through the use of design of experiments (DOE), lead-free solder defect causes can be better understood and subsequently reduced or eliminated. This paper will examine the failure modes of solder extrusion and tombstoning that occurred when two different types of lead-free solders, Sn-Ag-Cu (SAC) and BiAgX were used within a SiP for attachment of surface mount devices (SMD) chip components. The systematic investigation will include the comprehensive failure analysis of the SMD components and compare the modeling and analysis of the two different solder types utilizing the design of experiments methods.

SAC–xTiO2 nano-reinforced lead-free solder joint characterizations in ultra-fine package assembly

2018 ◽  
Vol 30 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Fakhrozi Che Ani ◽  
Azman Jalar ◽  
Abdullah Aziz Saad ◽  
Chu Yee Khor ◽  
Roslina Ismail ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Solder Joint ◽  
Solder Joints ◽  
Ion Beam ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Content Type ◽  
X Ray ◽  
Free Solder

Purpose This paper aims to investigate the characteristics of ultra-fine lead-free solder joints reinforced with TiO2 nanoparticles in an electronic assembly. Design/methodology/approach This study focused on the microstructure and quality of solder joints. Various percentages of TiO2 nanoparticles were mixed with a lead-free Sn-3.5Ag-0.7Cu solder paste. This new form of nano-reinforced lead-free solder paste was used to assemble a miniature package consisting of an ultra-fine capacitor on a printed circuit board by means of a reflow soldering process. The microstructure and the fillet height were investigated using a focused ion beam, a high-resolution transmission electron microscope system equipped with an energy dispersive X-ray spectrometer (EDS), and a field emission scanning electron microscope coupled with an EDS and X-ray diffraction machine. Findings The experimental results revealed that the intermetallic compound with the lowest thickness was produced by the nano-reinforced solder with a TiO2 content of 0.05 Wt.%. Increasing the TiO2 content to 0.15 Wt.% led to an improvement in the fillet height. The characteristics of the solder joint fulfilled the reliability requirements of the IPC standards. Practical implications This study provides engineers with a profound understanding of the characteristics of ultra-fine nano-reinforced solder joint packages in the microelectronics industry. Originality/value The findings are expected to provide proper guidelines and references with regard to the manufacture of miniaturized electronic packages. This study also explored the effects of TiO2 on the microstructure and the fillet height of ultra-fine capacitors.

Reliability Analysis of Lead-Free Solder Joints with Solder Doping on Harsh Environment

2016 ◽  
Vol 2016 (1) ◽  
pp. 000117-000122 ◽  
Author(s):  
Cong Zhao ◽  
Thomas Sanders ◽  
Zhou Hai ◽  
Chaobo Shen ◽  
John L. Evans
Keyword(s):  
Surface Finish ◽  
Isothermal Aging ◽  
Electroless Nickel ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Paste ◽  
Surface Mount ◽  
Surface Finishes ◽  
Free Solder ◽  
Immersion Silver

Abstract This paper investigates the effect of long term isothermal aging and thermal cycling on the reliability of lead-free solder mixes with different solder compositions, PCB surface finishes, and isothermal aging conditions. A variety of surface mount components are considered, including ball grid arrays (BGAs), quad flat no-lead packages (QFNs) and 2512 Surface Mount Resistors (SMRs). 12 lead-free solder pastes are tested; for BGA packages these are reflowed with lead-free solder spheres of SAC105, SAC305 and matched doped solder spheres (“matched” solder paste and sphere composition). Three surface finishes are tested: Organic Solderability Preservative (OSP), Immersion Silver (ImAg), and Electroless Nickel Immersion Gold (ENIG). All test components are subjected to isothermal aging at 125°C for 0 or 12 months, followed by accelerated thermal cycle testing from −40°C to 125°C. Data from the first 1500 cycles is presented here, with a focus on the effect of surface finish on package reliability. Current results demonstrate that the choice of surface finish has a strong effect on reliability. However, different solder materials appear to show different reliability trends with respect to the surface finishes, and the reliability trends of BGA and SMR packages also diverge.

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