Reliability of Lead-Free Solder Joints

2006 ◽  
Vol 128 (3) ◽  
pp. 297-301 ◽  
Author(s):  
John H. Lau
Keyword(s):  
Solder Joint ◽  
Hazardous Substances ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Joint Reliability ◽  
Joint Reliability ◽  
The World ◽  
The Future ◽  
Free Solder ◽  
Lead Free Solders

Reliability of the restriction of the use of certain hazardous substances in electrical and electronic equipment compliant products is investigated in this study. Emphasis is placed on the lead-free solder joint reliability. Solder is the electrical and mechanical “glue” of electronics assemblies. Will lead-free solders provide the characteristics necessary to allow the world to depend on it in the future? This paper cannot answer this question; however, it will help all participants in the soldering world better understand what needs to be done in order to answer this question and plan for the future.

scholarly journals Lead-free Solder Joint Reliability – State of the Art and Perspectives

2005 ◽  
Vol 2 (1) ◽  
pp. 72-83 ◽  
Author(s):  
Jianbiao Pan ◽  
Jyhwen Wang ◽  
David M. Shaddock
Keyword(s):  
Solder Joint ◽  
Electronics Industry ◽  
Lead Free ◽  
Lead Free Solder ◽  
Joint Failure ◽  
Solder Joint Reliability ◽  
Electronic Products ◽  
Joint Reliability ◽  
Free Solder ◽  
Lead Free Solders

There is an increasing demand for replacing tin-lead (Sn/Pb) solders with lead-free solders in the electronics industry due to health and environmental concerns. The European Union recently passed a law to ban the use of lead in electronic products. The ban will go into effect in July of 2006. The Japanese electronics industry has worked to eliminate lead from consumer electronic products for several years. Although currently there are no specific regulations banning lead in electronics devices in the United States, many companies and consortiums are working on lead-free solder initiatives including Intel, Motorola, Agilent Technologies, General Electric, Boeing, NEMI and many others to avoid a commercial disadvantage. The solder joints reliability not only depends on the solder joint alloys, but also on the component and PCB metallizations. Reflow profile also has significant impact on lead-free solder joint performance because it influences wetting and microstructure of the solder joint. A majority of researchers use temperature cycling for accelerated reliability testing since the solder joint failure mainly comes from thermal stress due to CTE mismatch. A solder joint failure could be caused by crack initiation and growth or by macroscopic solder facture. There are conflicting views of the reliability comparison between lead-free solders and tin-lead solders. This paper first reviews lead-free solder alloys, lead-free component lead finishes, and lead-free PCB surface finishes. The issue of tin whiskers is also discussed. Next, lead-free solder joint testing methods are presented; finite element modeling of lead-free solder joint reliability is reviewed; and experimental data comparing lead-free and tin-lead solder joint reliability are summarized. Finally the paper gives perspectives of transitions to totally lead-free manufacturing.

Solder Joint Reliability Improvement Using the Cold Ball Pull Metrology

2005 ◽  
Author(s):  
George F. Raiser ◽  
Dudi Amir
Keyword(s):  
Solder Joint ◽  
Electroless Nickel ◽  
Lead Free ◽  
Attractive Alternative ◽  
Lead Free Solder ◽  
Solder Joint Reliability ◽  
Solder Interconnect ◽  
Joint Reliability ◽  
Test Conditions ◽  
Free Solder

The various methods for improvement of package solder joint reliability (SJR) have centered on the broad categories of (i) reductions in the thermomechanical and mechanical stresses and strains applied to the joints, and (ii) strengthening of the solder interconnect interfaces and materials themselves. In practice, the success of the former depends first and foremost on the latter — an adequate and consistent interconnect ‘strength’ during the package development and production cycles. With the advancement of various pad-plating technologies (most notably ENIG – Electroless Nickel Immersion Gold), sphere chemistries, fluxes and processing conditions, each with their own stability issues, the interconnect strengths can easily undergo seemingly random drifts over time. The Dage™ Cold Ball Pull (CBP) technique, however, has emerged as an attractive alternative to the traditional ball-shear metrology as an interconnect strength monitor. The open issues preventing its adoption are related to identifying the best test conditions (e.g. aging time, pull speed, jaw pressure, etc...), all of which are addressed here. After identifying the best test conditions, we present a number of experimental results that highlight the powerful capability of this tool for optimizing and monitoring solder-joint strength. A full metrology characterization to demonstrate accuracy, repeatability and reproducibility has been performed. Moreover, interesting results have been obtained with respect to solder-aging, multiple-reflow, and time-above-liquidus effects on interconnect strength. Examples of direct correlation between CBP measurements and solder-joint shock performance are demonstrated. CBP is also shown to correlate well to other strength metrologies, such as three-point bend. Finally, CBP is used here to show how to strengthen interconnects by the proper selection of pad plating chemistries, sphere compositions, fluxes, reflow conditions, etc… Maintaining those strengths through development and production can be handled effectively using CBP as a monitor. Looking forward, CBP data presented here shows that certain material and processing choices can maximize lead-free solder interconnect strength and lead-free solder joint reliability.

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