Solder Joint Reliability of Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys Solidified on Copper Substrates with Different Surface Roughnesses

2015 ◽  
Vol 830-831 ◽  
pp. 265-269
Author(s):  
Satyanarayan ◽  
K.N. Prabhu
Keyword(s):  
Solder Joint ◽  
Solder Matrix ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Cu Substrate ◽  
Cu Substrates ◽  
Free Solder ◽  
Substrate Surfaces ◽  
Lead Free Solders

In the present work, the bond strength of Sn-0.7Cu, Sn-0.3Ag-0.7Cu, Sn-2.5Ag-0.5Cu and Sn-3Ag-0.5Cu lead free solders solidified on Cu substrates was experimentally determined. The bond shear test was used to assess the integrity of Sn–Cu and Sn–Ag–Cu lead-free solder alloy drops solidified on smooth and rough Cu substrate surfaces. The increase in the surface roughness of Cu substrates improved the wettability of solders. The wettability was not affected by the Ag content of solders. Solder bonds on smooth surfaces yielded higher shear strength compared to rough surfaces. Fractured surfaces revealed the occurrence of ductile mode of failure on smooth Cu surfaces and a transition ridge on rough Cu surfaces. Though rough Cu substrate improved the wettability of solder alloys, solder bonds were sheared at a lower force leading to decreased shear energy density compared to the smooth Cu surface. A smooth surface finish and the presence of minor amounts of Ag in the alloy improved the integrity of the solder joint. Smoother surface is preferable as it favors failure in the solder matrix.

Wetting and Intermetallic Study between Sn-3.5Ag-1.0Cu-xZn Lead-Free Solders and Copper Substrate (x = 0, 0.1, 0.4, 0.7)

2012 ◽  
Vol 501 ◽  
pp. 150-154 ◽  
Author(s):  
Ramani Mayappan
Keyword(s):  
Copper Substrate ◽  
Electronics Industry ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Spreading Area ◽  
Cu Substrate ◽  
Soldering Time ◽  
Free Solder ◽  
Lead Free Solders

The development of lead-free solders has been an essential task in the electronics industry because of the restriction of lead use by legislation. Among the candidates, Sn-Ag-Cu group of solder alloys have great advantages to replace the conventional Sn-Pb solder. In this study, the wetting and intermetallic study between Sn-3.5Ag-1.0Cu-xZn lead-free solder reacting on copper substrate were investigated under different soldering conditions. The addition of 0.7wt% of Zn improved the wettability on Cu substrate since it has the highest spreading area at 310°C. The Cu6Sn5 and Cu3Sn phases are the main interface intermetallic formed and these intermetallics increased in thickness with time and temperature. At 270°C, the addition of 0.7wt% Zn retarded the growth of Cu3Sn intermetallic until 10 min of the soldering time. Generally the addition of Zn was beneficial in retarding the total intermetallic thickness.

Nanoindentation Characterization of Lead-free Solders and Intermetallic Compounds under Thermal Aging

2010 ◽  
Vol 2010 (1) ◽  
pp. 000314-000318
Author(s):  
Tong Jiang ◽  
Fubin Song ◽  
Chaoran Yang ◽  
S. W. Ricky Lee
Keyword(s):  
Mechanical Properties ◽  
Thermal Aging ◽  
Solder Joints ◽  
Lead Free ◽  
Small Range ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Aging Test ◽  
Free Solder ◽  
Lead Free Solders

The enforcement of environmental legislation is pushing electronic products to take lead-free solder alloys as the substitute of traditional lead-tin solder alloys. Applications of such alloys require a better understanding of their mechanical behaviors. The mechanical properties of the lead-free solders and IMC layers are affected by the thermal aging. The lead-free solder joints on the pads subject to thermal aging test lead to IMC growth and cause corresponding reliability concerns. In this paper, the mechanical properties of the lead-free solders and IMCs were characterized by nanoindentation. Both the Sn-rich phase and Ag3Sn + β-Sn phase in the lead-free solder joint exhibit strain rate depended and aging soften effect. When lead-free solder joints were subject to thermal aging, Young's modulus of the (Cu, Ni)6Sn5 IMC and Cu6Sn5 IMC changed in very small range. While the hardness value decreased with the increasing of the thermal aging time.

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.

How Silver Powder Metallurgy Affects the Physical Properties of Low Temperature Firing Silver Conductor

2011 ◽  
Vol 2011 (1) ◽  
pp. 000099-000106 ◽  
Author(s):  
Samson Shahbazi ◽  
Mark Challingsworth
Keyword(s):  
Powder Metallurgy ◽  
Thick Film ◽  
Silver Powder ◽  
Lead Free ◽  
Lead Free Solder ◽  
Pure Silver ◽  
Solder Alloys ◽  
Film Conductor ◽  
Free Solder ◽  
Lead Free Solders

With the implementation of RoHS (the Restriction of Hazardous Substance) Directive banning the use of Lead, Cadmium, Mercury and Hexavalent Chromium, hybrid microelectronic manufacturers are globally embracing the lead free movement. These manufacturers must not only understand the implications of their material choice but must be aware of the interaction between lead free solder alloys and their RoHS compliant thick film materials. It is commonly known that lead free solder alloys process at much higher reflow temperatures than lead containing solder which can directly impact the fired film leach resistance and the loss of adhesion. There are also other concerns; lead free solders alloys generally require a different organic flux system to promote wetting and reflow, but this change may cause a fired film conductor to leach more easily than the flux used in the lead containing solders. The use of lead free solders such as SAC305, SAC405 or 95/5 on a low firing (550–570 °C) pure silver conductor has the tendency of leaching the fired film more readily than conductors containing small amounts of palladium or platinum. Many of these situations provide new challenges for the hybrid circuit manufacturer. There is little information available regarding the effects of the lead free solders on low firing silver thick film conductors. This paper discusses the results of a newly developed Pb and Cd free silver thick film conductor paste with a modified silver powder metallurgy to improve the leach resistance, solder acceptance and adhesion using lead free solder. In addition, the pure silver conductor was fired on top of a low temperature dielectric paste. This conductor was evaluated by comparing lead free solder alloys to traditional tin-lead-silver solder alloys. This study included evaluations based on SEM photos, solderability, leach resistance, and initial and long term adhesions. Results are published describing the difference in behavior between the different solder alloys in conjunction with the different silver powder metallurgy.

Effect of Isothermal Aging on the Growth and Morphology of the Intermetallic Compounds Formed at the Solder/Cu Interface of the Lead - Free Solder Joint

2007 ◽  
Vol 561-565 ◽  
pp. 2115-2118
Author(s):  
Yun Fu ◽  
Qi Zhang ◽  
Feng Sun ◽  
Hao Yu Bai
Keyword(s):  
Solder Joint ◽  
Intermetallic Compounds ◽  
Aging Time ◽  
Isothermal Aging ◽  
Lead Free ◽  
Intermetallic Compound Layer ◽  
Lead Free Solder ◽  
Cu Substrate ◽  
Cu6sn5 Layer ◽  
Free Solder

The growth and morphology of the intermetallic compounds (IMC) formed at the interface between the solder ( Sn–3.5Ag–0.5Cu ) and the Cu substrate of the lead - free solder joint have been investigated by means of isothermal aging at 125°C. The scalloped Cu6Sn5 intermetallic compound layer was formed at the interface between the solder and Cu substrate upon reflow. The thickness of Cu6Sn5 layer increased with aging time. Cu3Sn appeared between Cu6Sn5 layer and Cu substrate when isothermally aged for 100 hours. Compare to Cu6Sn5 , the thickness of Cu3Sn was rather low, and nearly did not increase with aging time. In this paper, the comparison was made among the Sn-Pb and the Sn-Ag-Cu(SAC) solders which were pre-treated differently before soldering.

Aging Induced Mechanical Property Degradation and Microstructure Evolution of SAC+X Lead Free Solder Alloys

2013 ◽  
Author(s):  
Zijie Cai ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall ◽  
Michael J. Bozack
Keyword(s):  
Thermal Cycling ◽  
Aging Time ◽  
Aging Temperature ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Stress Strain ◽  
Free Solder ◽  
Effects Of Aging ◽  
Lead Free Solders

The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. In our prior work on aging effects, we have demonstrated that large degradations occur in the material properties (stiffness and strength) and creep behavior of Sn-Ag-Cu (SAC) lead free solders during aging. These effects are universally detrimental to reliability and are exacerbated as the aging temperature and aging time increases. Conversely, changes due to aging are relatively small in conventional Sn-Pb solders. In our current work, we are exploring several doped SAC+X alloys in an attempt to reduce the aging induced degradation of the material behavior of SAC solders. The doped materials are lead free SAC solders that have been modified by the addition of small percentages of one or more additional elements (X). Using dopants (e.g. Bi, In, Ni, La, Mg, Mn, Ce, Co, Ti, Zn, etc.) has become widespread to enhance shock/drop reliability, wetting, and other properties; and we have extended this approach to examine the ability of dopants to reduce the effects of aging and extend thermal cycling reliability. In this paper, we concentrate on presenting the results for SAC+X (X = Zn, Co, Ni). The enhancement of aging resistance for the doped lead free solders was explored. Comparisons were made to the responses of non-doped SAC lead free solder alloys. The effects of aging on mechanical behavior have been examined by performing stress-strain and creep tests on solder samples that were aged for various durations (0–6 months) at elevated temperature (100 °C). Variations of the mechanical and creep properties (elastic modulus, yield stress, ultimate strength, creep compliance, etc.) were observed and modeled as a function of aging time and aging temperature. Our findings show that the doped SAC+X alloys illustrate reduced degradations with aging for all of the aging temperatures considered. Also, the stress-strain and creep mechanical properties of doped solders are better than those of reference solders after short durations of aging. After long term aging, doped solder alloys were found to have more stable behaviors than those of the standard SAC alloys. A parallel microstructure study has shown that less degradation and coarsening of the phases occurs in doped solder materials relative to non-doped solders after severe aging.

Bismuth-Antimony as an Alternative for High Temperature Lead Free Solder

2012 ◽  
Vol 476-478 ◽  
pp. 1163-1168 ◽  
Author(s):  
M.Z. Shahrul Fadzli ◽  
M.A. Azmah Hanim ◽  
T. Sai Hong ◽  
A. Aidy ◽  
R. Rohaizuan
Keyword(s):  
High Temperature ◽  
Solder Alloy ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Bulk Analysis ◽  
Rich Phase ◽  
Solder Bulk ◽  
Free Solder ◽  
Lead Free Solders

The development works on high temperature lead free solder are mostly discussed nowadays. To replace the current high temperature lead free solders, further research need to be done. A great deal of effort has been put into the development of lead free solder alloys. Bi (Bismuth) and Sb (Antimony) solder system proved as one of the promising candidates for electronic assembly. Melting temperature of three Bi-Sb solder alloys studied in this research enhanced their potential as the alternative solder candidates for high temperature lead free solder. At interface, Cu3Sb IMC layer was formed for 95Bi-5Sb solder alloy. Spallation of Cu3Sb IMC layer took placed with the results of Cu3Sb IMC also found in the solder bulk. Analysis of 97.5Bi-2.5Sb solder alloy classified as no metallurgical reaction at the interface and only the mechanical joining existed at the interface. The dissolution of Cu from subtrate affected the formation of Cu rich phase and the unstable Bi-Cu rich phase phenomena act as the isothermal product found in solder bulk. Mechanical grain boundary grooving observed in 98.5Bi-1.5Sb solder alloys at interface. Different compositions of Bi-Sb solder alloys resulted in different types of microstructures at interface and in solder bulk after reflow.

Properties of Two Lead-Free Solder Alloys and Comparison with Sn37Pb

2010 ◽  
Vol 154-155 ◽  
pp. 540-544
Author(s):  
Tian Han Xu ◽  
Mai Qun Zhao ◽  
Dang Hui Wang
Keyword(s):  
Ductile Fracture ◽  
Cleavage Fracture ◽  
Fracture Mechanism ◽  
Tensile Specimen ◽  
Lead Free ◽  
Lead Free Solder ◽  
Solder Alloys ◽  
Cu Substrate ◽  
Free Solder ◽  
Sn37pb Solder

The microstructures and properties of Sn3Ag2.8Cu and Sn3Ag2.8Cu-0.1Ce solder alloys were investigated by means of OM, SEM and EDX and compared to that of Sn37Pb. The results show that the wettability of Sn3Ag2.8Cu-0.1Ce is more favorable, Sn3Ag2.8Cu exhibits poorer wetting behaviour compared to that of Sn37Pb solder; the conductivities of Sn3Ag2.8Cu-0.1Ce and Sn3Ag2.8Cu soldesr are almost 20 percent and 8 percent higher than that of Sn37Pb respectively; the fractography of tensile specimen of Sn3Ag2.8Cu is smooth and light, and is a quasi-cleavage fracture mechanism, whereas that of Sn3Ag2.8Cu-0.1Ce is dark and rough, and has a fibrous pattern, and is a ductile fracture mechanism; the fractography of Sn3Ag2.8Cu-0.1Ce includes more compact and more uniform dimples than that of Sn3Ag2.8Cu, this is cause of the trace amounts of Ce refining the microstructure; brazing with the Cu substrate, the diffusion layer of Sn3Ag2.8Cu solder with Cu substrate includes more irregular IMC compared to Sn3Ag2.8Cu-0.1Ce and Sn37Pb..

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.

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