Soldering Practices Are Insane | EE Times:
I think this would be an interesting article to include, perhaps paraphrasing & trying to induce some conversation?
He makes a number of interesting points. Perhaps also point out that Soldertec used to teach a course on the metallurgy of soldering at the onset of Lead free
'via Blog this'
Showing posts with label Fundamentals. Show all posts
Showing posts with label Fundamentals. Show all posts
Tuesday, August 27, 2013
Wednesday, June 26, 2013
SMTONLINE Surface Tension and Load-Carrying Capacities of Solder
SMTONLINE Surface Tension and Load-Carrying Capacities of Solder: "
Surface Tension and Load-Carrying Capacities of Solder"
Reflow soldering on both sides of a board is standard procedure in the SMT manufacturing process. When the second component side is soldered, the components hang upside-down on the PCB. When the reflow process reaches its peak range, the possibility of remelting previously finished solder joints cannot be ruled out, which leaves the component hanging directly from the molten solder.
Manufacturers count on the load-carrying capacity of molten solder millions of times a day. Figure 1 shows a component hanging from a drop of solder. Molten solder is entirely capable of bearing considerable component weight.
Read the full article here.
'via Blog this'
Surface Tension and Load-Carrying Capacities of Solder"
Reflow soldering on both sides of a board is standard procedure in the SMT manufacturing process. When the second component side is soldered, the components hang upside-down on the PCB. When the reflow process reaches its peak range, the possibility of remelting previously finished solder joints cannot be ruled out, which leaves the component hanging directly from the molten solder.
Manufacturers count on the load-carrying capacity of molten solder millions of times a day. Figure 1 shows a component hanging from a drop of solder. Molten solder is entirely capable of bearing considerable component weight.
Read the full article here.
'via Blog this'
Friday, October 12, 2012
How Lead-Free Solder (Mis)Behaves under Stress | Advanced Photon Source
How Lead-Free Solder (Mis)Behaves under Stress | Advanced Photon Source:
The reliability and longevity of electronics are critical to our interconnected world that is so dependent upon Internet and telecommunications technology. The computers, routers and switches, phones, and all the devices that link us together must be dependable down to the solder joints that connect integrated circuits to circuit boards, which can be an Achilles heel in an otherwise failure-free device.
Utilizing new synchrotron x-ray techniques and two synchrotron x-ray beamlines at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS), researchers from Cisco Systems, Inc.; Michigan State University; and the Max-Planck-Institut für Eisenforschung GmbH studied the beginnings of the thermal fatigue process in environmentally friendly, lead-free solder joints, as well as what happens toward the end of that process. These insights bring scientists a step closer to developing useful models for making reliability predictions about solder-joint failure in this new material.
"In electronic system failures, more than half are solder joint failures," said Thomas Bieler of Michigan State University, a coauthor of the two Journal of Electronic Materials articles based on these studies. "There are a lot of these connections, and a failure in any one of them could potentially kill the functionality of the entire system."
The first century of electronics used lead-based solder because it was cheap and easy to work with. Engineers thoroughly understood the electrical, thermal, and structural behavior of these solders and were able to accurately predict reliability. As the environmental dangers of lead became apparent, manufacturers looked for alternatives. In 2006, the European Union Restriction of Hazardous Substances Directive came into effect, banning lead-containing solders from all consumer electronics devices. But while protecting people and the environment, the ban created a new problem: How reliable were lead-free solders?
"Especially in the telecommunications industry, the expected lifetime of many products is long, and also a very low failure rate is needed," said coauthor Tae-Kyu Lee of the Component Quality and Technology Group at Cisco Systems. "Before 2006, the industry had a very large library of reliability data based on lead-containing material, so even if they didn't know the exact failure mechanism, they could still assess the lifetime of the product. But since we're now using a new material, we need to know more about how the material’s performance evolves."
The researchers in this study developed new techniques and employed them at the APS to track the development of the failure mechanism of lead-free solder joints in situ for the first time. Working at the X-ray Science Division 6-ID-D and 34-ID-E beamlines at the Argonne National Laboratory APS, they conducted experiments to demonstrate how synchrotron x-ray diffraction could reveal the evolution of crystal orientation and strain patterns during thermal cycling in tin-containing, lead-free solder joints, specifically in the commonly used tin-silver-copper alloy SAC 305 (Sn-3%Ag-0.5% Cu).
Older lead-tin solders tend to solidify as a polycrystal, delivering a solder joint that has a uniform microstructure, with reproducible properties. But lead-free solders usually solidify either as a randomly oriented single crystal or a tricrystal. "With the lead-free solders, the properties of solder joints are all over the map," Bieler said. "Some joints have hard orientations, others soft, some last forever, some fail at a very early time. That makes life difficult for electronics manufacturers when they have to think about warranty costs and when the first failure is going to happen."
Failures in lead-free solders don't always occur in areas where shear strains from thermal expansion mismatches are highest. This is a consequence of the non-cubic structure of tin and its highly anisotropic thermal expansion and stiffness. It is difficult to predict the strains that develop in an individual joint, given the random crystal orientation, so the prediction of damage is even more challenging. Furthermore, the crystal orientations evolve with thermal cycling. The experimenters examined SAC 305 joints both in a plastic ball grid array (PBGA) package sample and a wafer-level chip-scale package (WLCSP). Both types have been examined under thermal cycling, and the latter was studied in situ during melting, resolidification, and thermal cycling.
The advantages of the x-ray approach over the cross-sectional electron microscopy generally used to study solder joints were immediately apparent. "In a two-dimensional cross section, one does not necessarily know what has been removed or what is underneath the surface. With three-dimensional full illumination of the joint, we were able to prove that we did indeed primarily have single crystals in some joints and tricrystals in others," said Bieler.
"To clearly predict the lifetime of a certain joint,” said Lee, “we need to understand the failure mechanism. This study allowed us to see inside the joint while imposing thermal cycles in situ. Most of the earlier studies use destructive analysis to see the microstructure development after things happened. But the APS synchrotron lets us see the microstructure evolution during the event."
The x-ray diffraction measurements also provide a more dynamic picture of what happens inside the solder joint as it passes through different phases over time. For example, although there are only a few different tin crystal orientations in a given SAC lead-free solder joint, different orientations are always observed after melting and resolidification. Recrystallization behavior under thermal cycling also results in evolution of the tin crystal orientation.
Lee was surprised by "the overall tin material response to the external factors. I considered tin as a 'dead' material with a certain crystal structure, but the more you look into this material, it seems to react like a living thing."
“What the APS data has especially enabled us to do is get a comprehensive picture of the very beginning of the thermal fatigue process [on beamline 6-ID-D] and connect it with what happens toward the end [on beamline 34-ID-E]," Bieler said.
Observing how the x-ray diffraction peaks changed from initial solidification and proceeded to spread out over repeated thermal cycles, Bieler said, "really helped us get to the point where we could describe the sequential mechanism from the moment of solidification up to the first crack that forms. We are able to explain everything that happened and why it happened in these solder joints as a result of what we've been able to do at the APS. The APS has been very helpful for understanding the early stage as well as the stage just before cracks form."
These fresh insights into the failure mechanism of lead-free solder joints guide scientists in their development of models for making reliability predictions. Although it is too early to proclaim any definite remedy for improving reliability in lead-free solder joints, the work provides some important clues.
"To find the right mitigation, you need to find the right failure mechanism," Lee said. "Based on the study so far, we identified that the grain refinement in tin interconnects is bad for thermal cycling performance. But at the same time it is beneficial for resistance to mechanical shock. So there are no golden rules, but at least we are beginning to understand why."
As for next steps, Bieler said that "finding a reliable, automated way to index diffraction patterns from multi-crystal joints would greatly speed up our ability to mine the data we have more effectively. Analysis strategies to obtain stress and strain would naturally follow using established methods. Continuing in situ measurements in thermomechanical cycling specimens, and looking toward comparing the microstructure before and after shock conditions (or possibly in situ), could also be effective. Microbeam diffraction in solder bumps is also a desirable thing to do, as the volumes are small, and this method is well suited for exploring tiny places." — Mark Wolverton
http://www.aps.anl.gov/Science/Highlights/Content/APS_SCIENCE_20121008.php
'via Blog this'
The reliability and longevity of electronics are critical to our interconnected world that is so dependent upon Internet and telecommunications technology. The computers, routers and switches, phones, and all the devices that link us together must be dependable down to the solder joints that connect integrated circuits to circuit boards, which can be an Achilles heel in an otherwise failure-free device.
Utilizing new synchrotron x-ray techniques and two synchrotron x-ray beamlines at the U.S. Department of Energy Office of Science’s Advanced Photon Source (APS), researchers from Cisco Systems, Inc.; Michigan State University; and the Max-Planck-Institut für Eisenforschung GmbH studied the beginnings of the thermal fatigue process in environmentally friendly, lead-free solder joints, as well as what happens toward the end of that process. These insights bring scientists a step closer to developing useful models for making reliability predictions about solder-joint failure in this new material.
"In electronic system failures, more than half are solder joint failures," said Thomas Bieler of Michigan State University, a coauthor of the two Journal of Electronic Materials articles based on these studies. "There are a lot of these connections, and a failure in any one of them could potentially kill the functionality of the entire system."
The first century of electronics used lead-based solder because it was cheap and easy to work with. Engineers thoroughly understood the electrical, thermal, and structural behavior of these solders and were able to accurately predict reliability. As the environmental dangers of lead became apparent, manufacturers looked for alternatives. In 2006, the European Union Restriction of Hazardous Substances Directive came into effect, banning lead-containing solders from all consumer electronics devices. But while protecting people and the environment, the ban created a new problem: How reliable were lead-free solders?
"Especially in the telecommunications industry, the expected lifetime of many products is long, and also a very low failure rate is needed," said coauthor Tae-Kyu Lee of the Component Quality and Technology Group at Cisco Systems. "Before 2006, the industry had a very large library of reliability data based on lead-containing material, so even if they didn't know the exact failure mechanism, they could still assess the lifetime of the product. But since we're now using a new material, we need to know more about how the material’s performance evolves."
The researchers in this study developed new techniques and employed them at the APS to track the development of the failure mechanism of lead-free solder joints in situ for the first time. Working at the X-ray Science Division 6-ID-D and 34-ID-E beamlines at the Argonne National Laboratory APS, they conducted experiments to demonstrate how synchrotron x-ray diffraction could reveal the evolution of crystal orientation and strain patterns during thermal cycling in tin-containing, lead-free solder joints, specifically in the commonly used tin-silver-copper alloy SAC 305 (Sn-3%Ag-0.5% Cu).
Older lead-tin solders tend to solidify as a polycrystal, delivering a solder joint that has a uniform microstructure, with reproducible properties. But lead-free solders usually solidify either as a randomly oriented single crystal or a tricrystal. "With the lead-free solders, the properties of solder joints are all over the map," Bieler said. "Some joints have hard orientations, others soft, some last forever, some fail at a very early time. That makes life difficult for electronics manufacturers when they have to think about warranty costs and when the first failure is going to happen."
Failures in lead-free solders don't always occur in areas where shear strains from thermal expansion mismatches are highest. This is a consequence of the non-cubic structure of tin and its highly anisotropic thermal expansion and stiffness. It is difficult to predict the strains that develop in an individual joint, given the random crystal orientation, so the prediction of damage is even more challenging. Furthermore, the crystal orientations evolve with thermal cycling. The experimenters examined SAC 305 joints both in a plastic ball grid array (PBGA) package sample and a wafer-level chip-scale package (WLCSP). Both types have been examined under thermal cycling, and the latter was studied in situ during melting, resolidification, and thermal cycling.
The advantages of the x-ray approach over the cross-sectional electron microscopy generally used to study solder joints were immediately apparent. "In a two-dimensional cross section, one does not necessarily know what has been removed or what is underneath the surface. With three-dimensional full illumination of the joint, we were able to prove that we did indeed primarily have single crystals in some joints and tricrystals in others," said Bieler.
"To clearly predict the lifetime of a certain joint,” said Lee, “we need to understand the failure mechanism. This study allowed us to see inside the joint while imposing thermal cycles in situ. Most of the earlier studies use destructive analysis to see the microstructure development after things happened. But the APS synchrotron lets us see the microstructure evolution during the event."
The x-ray diffraction measurements also provide a more dynamic picture of what happens inside the solder joint as it passes through different phases over time. For example, although there are only a few different tin crystal orientations in a given SAC lead-free solder joint, different orientations are always observed after melting and resolidification. Recrystallization behavior under thermal cycling also results in evolution of the tin crystal orientation.
Lee was surprised by "the overall tin material response to the external factors. I considered tin as a 'dead' material with a certain crystal structure, but the more you look into this material, it seems to react like a living thing."
“What the APS data has especially enabled us to do is get a comprehensive picture of the very beginning of the thermal fatigue process [on beamline 6-ID-D] and connect it with what happens toward the end [on beamline 34-ID-E]," Bieler said.
Observing how the x-ray diffraction peaks changed from initial solidification and proceeded to spread out over repeated thermal cycles, Bieler said, "really helped us get to the point where we could describe the sequential mechanism from the moment of solidification up to the first crack that forms. We are able to explain everything that happened and why it happened in these solder joints as a result of what we've been able to do at the APS. The APS has been very helpful for understanding the early stage as well as the stage just before cracks form."
These fresh insights into the failure mechanism of lead-free solder joints guide scientists in their development of models for making reliability predictions. Although it is too early to proclaim any definite remedy for improving reliability in lead-free solder joints, the work provides some important clues.
"To find the right mitigation, you need to find the right failure mechanism," Lee said. "Based on the study so far, we identified that the grain refinement in tin interconnects is bad for thermal cycling performance. But at the same time it is beneficial for resistance to mechanical shock. So there are no golden rules, but at least we are beginning to understand why."
As for next steps, Bieler said that "finding a reliable, automated way to index diffraction patterns from multi-crystal joints would greatly speed up our ability to mine the data we have more effectively. Analysis strategies to obtain stress and strain would naturally follow using established methods. Continuing in situ measurements in thermomechanical cycling specimens, and looking toward comparing the microstructure before and after shock conditions (or possibly in situ), could also be effective. Microbeam diffraction in solder bumps is also a desirable thing to do, as the volumes are small, and this method is well suited for exploring tiny places." — Mark Wolverton
http://www.aps.anl.gov/Science/Highlights/Content/APS_SCIENCE_20121008.php
'via Blog this'
Friday, June 22, 2012
Acceleration of the growth of Cu 3Sn voids in solder joints
Scopus: Soldering to Cu surface finishes usually leads to the formation of a bi-layer intermetallic structure, Cu 3Sn/Cu 6Sn 5, that provides a more robust bond than common alternatives. Occasionally, and so far unpredictably, voids may however grow within the Cu 3Sn over time and allow for premature failure of microelectronics products in service. A quantitative assessment of the reliability risk of voids observed after accelerated aging requires the knowledge of the variation of void growth with temperature and time. It is argued that in the case of realistic solder joints diffusion controlled void growth kinetics are unlikely to follow simple Arrhenius and parabolic dependencies, respectively. Nevertheless, three very different sets of samples were all shown to exhibit void growth that could be well approximated by a parabolic time dependence and an effective activation energy of 0.65-0.80 eV.
Microelectronics Reliability
Volume 52, Issue 6, June 2012, Pages 1121-1127
Acceleration of the growth of Cu 3Sn voids in solder joints
Borgesen, P.a, Yin, L.b , Kondos, P.b
a Department of Systems Science and Industrial Engineering, Binghamton University, Binghamton, NY 13902, United States
b Universal Instruments Corporation, Conklin, NY 13748, United States
Microelectronics Reliability
Volume 52, Issue 6, June 2012, Pages 1121-1127
Acceleration of the growth of Cu 3Sn voids in solder joints
Borgesen, P.a, Yin, L.b , Kondos, P.b
a Department of Systems Science and Industrial Engineering, Binghamton University, Binghamton, NY 13902, United States
b Universal Instruments Corporation, Conklin, NY 13748, United States
Development of thermodynamic and kinetic databases in micro-soldering alloy systems and their applications
Scopus: Recent progress in the development of thermodynamic and kinetic databases of micro-soldering alloys, which were constructed within the framework of the Thermo-Calc and DICTRA software, was presented.
Especially, a thermodynamic tool, ADAMIS (alloy database for micro-solders) was developed by combining the thermodynamic databases of micro-solders with Pandat, a multi-component phase diagram calculation software program. ADAMIS contains 11 elements, namely, Ag, Al, Au, Bi, Cu, In, Ni, Sb, Sn, Zn and Pb, and can handle all combinations of these elements in the whole composition range. The obtained thermodynamic and kinetic databases can not only provide much valuable thermodynamic information such as phase equilibria and phase fraction, but also shows the kinetics and the evolution of microstructures when they are combined with some appropriate software programs and models, such as the phase field method and ADSTEFAN software. From the viewpoints of computational thermodynamics and kinetics, some technical examples were given to demonstrate the great utility of these databases for the applications in the development of micro-soldering materials. These databases are expected to be powerful tools for the development of micro-solders and Cu substrate materials, as well as for promoting the understanding of interfacial phenomena and microstructure evolution between solders and substrates in electronic packaging technology.
Progress in Natural Science: Materials International
Volume 21, Issue 2, April 2011, Pages 97-110
Development of thermodynamic and kinetic databases in micro-soldering alloy systems and their applications
Liu, X.-J.a , Wang, C.-P.a, Ohnuma, I.b, Kainuma, R.b, Ishida, K.b
a Department of Materials Science and Engineering, College of Materials, Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005, China
b Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
Especially, a thermodynamic tool, ADAMIS (alloy database for micro-solders) was developed by combining the thermodynamic databases of micro-solders with Pandat, a multi-component phase diagram calculation software program. ADAMIS contains 11 elements, namely, Ag, Al, Au, Bi, Cu, In, Ni, Sb, Sn, Zn and Pb, and can handle all combinations of these elements in the whole composition range. The obtained thermodynamic and kinetic databases can not only provide much valuable thermodynamic information such as phase equilibria and phase fraction, but also shows the kinetics and the evolution of microstructures when they are combined with some appropriate software programs and models, such as the phase field method and ADSTEFAN software. From the viewpoints of computational thermodynamics and kinetics, some technical examples were given to demonstrate the great utility of these databases for the applications in the development of micro-soldering materials. These databases are expected to be powerful tools for the development of micro-solders and Cu substrate materials, as well as for promoting the understanding of interfacial phenomena and microstructure evolution between solders and substrates in electronic packaging technology.
Progress in Natural Science: Materials International
Volume 21, Issue 2, April 2011, Pages 97-110
Development of thermodynamic and kinetic databases in micro-soldering alloy systems and their applications
Liu, X.-J.a , Wang, C.-P.a, Ohnuma, I.b, Kainuma, R.b, Ishida, K.b
a Department of Materials Science and Engineering, College of Materials, Research Center of Materials Design and Applications, Xiamen University, Xiamen 361005, China
b Department of Materials Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
Effect of Sn Grain Orientation on the Cu 6Sn 5 Formation in a Sn-Based Solder Under Current Stressing
Scopus: A SnAgCu-based solder stripe between two Cu electrodes is current stressed with a density of 5 10 4 A/cm 2 at 393 K (120 C). After current stressing for 24 hours, electromigration induces the Cu dissolution from the cathode-side Cu electrode, leading to the Cu 6Sn 5 formation in the solder stripe. Very interestingly, the Cu 6Sn 5 phase is selectively formed within a specific Sn grain. Electron backscattering diffraction analysis indicates the crystallographic orientations of Sn grains play an important role in the selective Cu 6Sn 5 formation
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
2012, Pages 1-3
Effect of Sn Grain Orientation on the Cu 6Sn 5 Formation in a Sn-Based Solder Under Current Stressing ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Lin, C.-F., Lee, S.-H., Chen, C.-M.
Department of Chemical Engineering, National Chung Hsing University, Taichung, 402, Taiwan
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
2012, Pages 1-3
Effect of Sn Grain Orientation on the Cu 6Sn 5 Formation in a Sn-Based Solder Under Current Stressing ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Lin, C.-F., Lee, S.-H., Chen, C.-M.
Department of Chemical Engineering, National Chung Hsing University, Taichung, 402, Taiwan
Effects of Sn grain structure on the electromigration of Sn-Ag solder joints
Scopus: In this article, we investigated the effect of Sn grain structure on the electromigration (EM) reliability of Sn-2.5Ag (wt%) solder joints used in flip-chip packages. The electron backscattering diffraction technique was applied to characterize the Sn grain size and orientation of the solder joints. Failure analyses on Sn-2.5Ag solder joints after EM tests showed that the Sn grain structure was important in controlling the kinetics of the intermetallic compound growth and void formation under EM. Further microstructural analysis revealed that the grain sizes and orientations of the solder joints after multiple solder reflows were statistically different from those with a single solder reflow and resulted in an improved EM reliability. Thermal annealing effect was also investigated to separate the thermal effect from the EM-induced effect. Results obtained in this study demonstrated that EM reliability of Pb-free solder joints could be improved by optimization of the Sn grain structure.
Journal of Materials Research
Volume 27, Issue 8, 28 April 2012, Pages 1131-1141
Effects of Sn grain structure on the electromigration of Sn-Ag solder joints
Wang, Y.a, Lu, K.H.b, Gupta, V.c, Stiborek, L.c, Shirley, D.c, Chae, S.-H.c, Im, J.a, Ho, P.S.a
a Microelectronics Research Center, University of Texas at Austin, Austin, TX 78758, United States
b Intel Corp., Chandler, AZ 85226, United States
c Texas Instruments Inc., Dallas, TX 75243, United States
Journal of Materials Research
Volume 27, Issue 8, 28 April 2012, Pages 1131-1141
Effects of Sn grain structure on the electromigration of Sn-Ag solder joints
Wang, Y.a, Lu, K.H.b, Gupta, V.c, Stiborek, L.c, Shirley, D.c, Chae, S.-H.c, Im, J.a, Ho, P.S.a
a Microelectronics Research Center, University of Texas at Austin, Austin, TX 78758, United States
b Intel Corp., Chandler, AZ 85226, United States
c Texas Instruments Inc., Dallas, TX 75243, United States
Thermodynamic calculations and kinetic simulations of soldering/brazing systems and processes
Scopus: A new thermodynamic database for solder systems, TCSLD1, has been developed using the CALPHAD methodology, based on experimental and theoretical data. This new database contains all the important Au-/Ag-/Cu-/Sn-based solder alloy phases within a 16-element framework [Ag-Al-Au-Bi-Co-Cu-Ge-In-Ni-Pb-Pd-Pt-Sb-Si- Sn-Zn] and in total 150 phases (most of them as multicomponent alloy solutions and/or intermediate compound solutions, with the rest as intermediate stoichiometric compounds) are included. The database can be used with the Thermo-Calc software package and application programming interfaces for predicting various thermodynamic properties, stable/metastable phase equilibria and phase transformations of Au-/Ag-/Cu-/Sn-based solder systems (Pb-containing/ Pbfree), and for simulating the effects of non-equilibrium solidification and micro-segregation of various soldering/brazing processes. The results from these predictions can be applied to eliminate candidate solder alloys for which the calculations reveal unsuitable freezing temperature range from further testing, and thus to accelerate design of new solder alloys as well as to improve understanding of existing solder alloys in terms of their processing and in-service behavior. Future work is also planned to develop a mobility database to consider kinetic effects including diffusion and precipitation, coarsening kinetics.
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 315-318
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Thermodynamic calculations and kinetic simulations of soldering/brazing systems and processes ( Conference Paper )
Mason, P.a, Chen, Q.b, Engström, A.b, Shi, P.b, Bratberg, J.b, Markström, A.b, Liu, H.c, Jin, Z.c
a Thermo-Calc Software Inc, 4160 Washington Road, McMurray, PA 15317, United States
b Thermo-Calc Software AB, Norra Stationsgatan 93, SE-113 64 Stockholm, Sweden
c Central-South University, Changsha, Hunan, China
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 315-318
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Thermodynamic calculations and kinetic simulations of soldering/brazing systems and processes ( Conference Paper )
Mason, P.a, Chen, Q.b, Engström, A.b, Shi, P.b, Bratberg, J.b, Markström, A.b, Liu, H.c, Jin, Z.c
a Thermo-Calc Software Inc, 4160 Washington Road, McMurray, PA 15317, United States
b Thermo-Calc Software AB, Norra Stationsgatan 93, SE-113 64 Stockholm, Sweden
c Central-South University, Changsha, Hunan, China
The effect of Cu content on performance of SnAgCuBiNi /Cu soldering
Scopus: In recent years, SnAgCu (SAC) lead-free solder is widely used to substitute for SnPb solder. However, there are still two issues to be solved urgently. One is that the price of mainstream SAC solder is much higher because of higher Ag content in the solder.
The other is that high-Ag lead-free solder appears more brittle and is susceptible to impact and vibration. This is difficult to meet the requirement of electronic product, especially in the field of mobile devices. Accordingly, it is necessary to develop a low-Ag lead-free solder with low cost, excellent solderability and improved strength. In this paper, a new low-Ag lead-free SAC solder is shown. The effect of Cu content on the solderability and joint performance are investigated. The high-temperature storage (HTS) aging is conducted for accelerating failure. Shear strength test and shock test are used to evaluate the shear strength and shock resistance of solder joint. Interfacial IMC layer morphology and microstructure of joint are analyzed by SEM, Deep-etched. It is revealed that varying Cu content from 0 to 1.5%, do not nearly influence on the melting range and wettability of solder alloy. A little bit higher shear strength of joint appears only Cu content in bulk solder alloy is 0.5%. Polyhedron IMC grains appear in the interface after aging and fracture occurs in the IMC layer. As Cu content increases in solder alloys, the interface IMC layer is thinner and IMC grain size is bigger. On the other hand, the morphology of IMC in bulk solder varies from flaky to bar, the size and number of IMC increase with increasing Cu content. It is approved that Low-Ag SACBiNi/Cu shows better shock resistance than the SAC305/Cu soldering by shock test.
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 228-232
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
The effect of Cu content on performance of SnAgCuBiNi /Cu soldering ( Conference Paper )
Sun, F. , Liu, Y., Wang, Y., Zou, P.
School of Materials Sci. and Eng., Harbin Uni. of Sci. and Tech., Harbin, China
The other is that high-Ag lead-free solder appears more brittle and is susceptible to impact and vibration. This is difficult to meet the requirement of electronic product, especially in the field of mobile devices. Accordingly, it is necessary to develop a low-Ag lead-free solder with low cost, excellent solderability and improved strength. In this paper, a new low-Ag lead-free SAC solder is shown. The effect of Cu content on the solderability and joint performance are investigated. The high-temperature storage (HTS) aging is conducted for accelerating failure. Shear strength test and shock test are used to evaluate the shear strength and shock resistance of solder joint. Interfacial IMC layer morphology and microstructure of joint are analyzed by SEM, Deep-etched. It is revealed that varying Cu content from 0 to 1.5%, do not nearly influence on the melting range and wettability of solder alloy. A little bit higher shear strength of joint appears only Cu content in bulk solder alloy is 0.5%. Polyhedron IMC grains appear in the interface after aging and fracture occurs in the IMC layer. As Cu content increases in solder alloys, the interface IMC layer is thinner and IMC grain size is bigger. On the other hand, the morphology of IMC in bulk solder varies from flaky to bar, the size and number of IMC increase with increasing Cu content. It is approved that Low-Ag SACBiNi/Cu shows better shock resistance than the SAC305/Cu soldering by shock test.
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 228-232
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
The effect of Cu content on performance of SnAgCuBiNi /Cu soldering ( Conference Paper )
Sun, F. , Liu, Y., Wang, Y., Zou, P.
School of Materials Sci. and Eng., Harbin Uni. of Sci. and Tech., Harbin, China
Morphologies and grain orientations of Cu-Sn intermetallic compounds in Sn3.0Ag0.5Cu/Cu solder joints
Scopus: Electron Backscatter Diffraction (EBSD) technology combined with Scanning Electron Microscope (SEM) was employed to investigate morphologies and orientations of Cu-Sn intermetallic compounds formed between Sn3.5Ag0.5Cu lead-free solder alloy and copper substrate. After long-time soldering, two small planes with a break angle appear on top and side of Cu 6Sn 5 scallop, and the angle between the adjacent planes was approximately 120�. Round plate-type defects were found on the top side of Cu substrate. Preferable IMCs grain orientation was Cu 6Sn 5 (0001) //substrate surface, Cu 3Sn (1̄00) & (100) //substrate surface. Single crystal Cu-Sn IMCs preferable grain orientation was Cu 3Sn (100)// Cu 6Sn 5 (0001).
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 217-220
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Morphologies and grain orientations of Cu-Sn intermetallic compounds in Sn3.0Ag0.5Cu/Cu solder joints ( Conference Paper )
Tian, Y. , Liu, W., Hang, C., Wang, X., Liu, R., Wang, C.
State Key Lab. of Advanced Joining and Welding, Harbin Institute of Technology, Harbin, 150001, China
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 217-220
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Morphologies and grain orientations of Cu-Sn intermetallic compounds in Sn3.0Ag0.5Cu/Cu solder joints ( Conference Paper )
Tian, Y. , Liu, W., Hang, C., Wang, X., Liu, R., Wang, C.
State Key Lab. of Advanced Joining and Welding, Harbin Institute of Technology, Harbin, 150001, China
Interfacial reactions between lead free solder alloys and metallic substrates: Thermodynamics and kinetics
Scopus: Ternary alloys based on Sn-rich, Sn-Cu and Sn-Ag binary eutectics have attracted considerable attention as potential Pb-free solders. However, intermetallic layers formed at the interface between the solder and pads of a printed circuit board may adversely affect the reliability of solder joints due to excessive growth during storage and service. The inherent complexity of the substrate-solder systems and a large variety of possible reactions in these materials (their sequential and concurrent occurrence) makes it extremely difficult to develop a predictive model that describes quantitatively morphological evolution within the solder joints. This problem becomes more complex with the continuing trend towards increasing miniaturization of microchips.
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 213-216
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Interfacial reactions between lead free solder alloys and metallic substrates: Thermodynamics and kinetics ( Conference Paper )
Hodaj, F.
SIMAP, CNRS UMR-5622, Grenoble Institute of Technology, Domaine Universitaire, 1130 rue de la piscine, 38402 Saint Martin d'Hères, France
IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 213-216
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Interfacial reactions between lead free solder alloys and metallic substrates: Thermodynamics and kinetics ( Conference Paper )
Hodaj, F.
SIMAP, CNRS UMR-5622, Grenoble Institute of Technology, Domaine Universitaire, 1130 rue de la piscine, 38402 Saint Martin d'Hères, France
Wednesday, May 16, 2012
Effect of Ni on phase stability and thermal expansion of Cu 6-xNi xSn 5 (X = 0, 0.5, 1, 1.5 and 2)
Scopus: The crystallography of the Cu 6Sn 5 intermetallic that forms at the solder-substrate interface in many soldering operations can be influenced by Ni additions. It has been established that when Ni is present at 5-9 at%, the high-temperature hexagonal Cu 6Sn 5 (η) does not transition to the low-temperature monoclinic Cu 6Sn 5 (η') at the equilibrium temperature of 186 'C. In fact, the hexagonal phase remains stable from room temperature to 250 'C. This paper shows the stabilising effect of Ni exists in the range of 4.6-17.2 at% Ni in stoichiometric samples, over the larger temperature range of -100 to 250 'C using synchrotron X-ray diffraction. The results are also used in combination with dilatometry experiments and show that Ni decreases the magnitude of thermal expansion, and prevents the discontinuity in expansion that occurs with the polymorphic transformation
Intermetallics
Volume 26, 2012, Pages 78-85
Effect of Ni on phase stability and thermal expansion of Cu 6-xNi xSn 5 (X = 0, 0.5, 1, 1.5 and 2) ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Nogita, K. , Mu, D., McDonald, S.D., Read, J., Wu, Y.Q.
School of Mechanical and Mining Engineering, The University of Queensland, 43 Cooper Rd., St. Lucia, Brisbane, Queensland 4072, Australia
Intermetallics
Volume 26, 2012, Pages 78-85
Effect of Ni on phase stability and thermal expansion of Cu 6-xNi xSn 5 (X = 0, 0.5, 1, 1.5 and 2) ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Nogita, K. , Mu, D., McDonald, S.D., Read, J., Wu, Y.Q.
School of Mechanical and Mining Engineering, The University of Queensland, 43 Cooper Rd., St. Lucia, Brisbane, Queensland 4072, Australia
Tuesday, May 15, 2012
Crystal grain size and orientation important in solder fatigue for BGAs
Scopus: This paper presents the influence of the micro structure on the crack propagation in lead free solder joint. The author's group have studied the Manson-Coffin's law for lead free solder joint by using the isothermal fatigue test and FEM analytical approaches to establish the practicable evaluation of thermal fatigue life of solder joints, for example, for the Sn-Cu-Ni solder, because this solder is attracted from the aspect of the decrease of solder leach in the flow process and material cost. However, even if the same loading is given to the solder joints of BGA test piece, there was a large dispersion in the fatigue life.
Even though the effect of the shape difference has been considered, the range of the dispersion could not been explained sufficiently.
In the study, the fatigue crack propagation modes in the solder joints were investigated, and an internal fatigue crack mode and an interfacial fatigue crack mode were confirmed. And the tendency of a shorter on fatigue life in the interfacial fatigue mode was confirmed. To clarify the mechanism of these fatigue crack modes, the crystal grain size in the solder joints was investigated before the fatigue test and also after the test. Furthermore, the verification of the mechanism using FEM models considering the crystal grain size was carried out. First of all, each element in FEM models matching to the average crystal grain size was made. Second, the inelastic strain ranges in each FEM models were studied.
As a result, it was shown that the influence of the crude density of the crystal grain to the fatigue crack progress can be evaluated. In addition, the micro structure of the solder joint of large-scale electronic devices is observed, and FEM model was made based on the observation result. As a result, it was shown that the influence of the directionality with the crystal grain to the fatigue crack progress can be evaluated.
ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, InterPACK 2011
Volume 2, 2011, Pages 691-700
ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, InterPACK 2011;Portland, OR;6 July 2011through8 July 2011;Code89456
Effect of micro structure on fatigue characteristics of lead free solder joints ( Conference Paper )
Akutsu, T., Yu, Q.
Yokohama National University, Yokohama, Kanagawa, Japan
Even though the effect of the shape difference has been considered, the range of the dispersion could not been explained sufficiently.
In the study, the fatigue crack propagation modes in the solder joints were investigated, and an internal fatigue crack mode and an interfacial fatigue crack mode were confirmed. And the tendency of a shorter on fatigue life in the interfacial fatigue mode was confirmed. To clarify the mechanism of these fatigue crack modes, the crystal grain size in the solder joints was investigated before the fatigue test and also after the test. Furthermore, the verification of the mechanism using FEM models considering the crystal grain size was carried out. First of all, each element in FEM models matching to the average crystal grain size was made. Second, the inelastic strain ranges in each FEM models were studied.
As a result, it was shown that the influence of the crude density of the crystal grain to the fatigue crack progress can be evaluated. In addition, the micro structure of the solder joint of large-scale electronic devices is observed, and FEM model was made based on the observation result. As a result, it was shown that the influence of the directionality with the crystal grain to the fatigue crack progress can be evaluated.
ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, InterPACK 2011
Volume 2, 2011, Pages 691-700
ASME 2011 Pacific Rim Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Systems, InterPACK 2011;Portland, OR;6 July 2011through8 July 2011;Code89456
Effect of micro structure on fatigue characteristics of lead free solder joints ( Conference Paper )
Akutsu, T., Yu, Q.
Yokohama National University, Yokohama, Kanagawa, Japan
Corrosion Behavior of Sn-3.0Ag-0.5Cu Lead-Free Solder in Potassium Hydroxide Electrolyte
Scopus : The corrosion behavior of Sn-3.0Ag-0.5Cu (SAC305) solder alloy in 6 M potassium hydroxide electrolyte was investigated using polarization analysis. The results revealed that SAC305 is susceptible to corrosion because of the dissolution of the Sn phase. The corrosion potential (E corr) and corrosion current density (i corr) obtained from the sample was -1.108 V vs Hg/HgO and 1.795 � 10 -4 A cm -2, respectively. In addition, microstructural and elemental characterization revealed the presence of tin oxide, Cu, and/or Ag-containing corrosion product on the surface of the corroded sample. The morphology of the samples was also observed to contain several pits, cracks, and pore-like structures
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
2012, Pages 1-6
Corrosion Behavior of Sn-3.0Ag-0.5Cu Lead-Free Solder in Potassium Hydroxide Electrolyte ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Liew, M.C., Ahmad, I., Lee, L.M., Nazeri, M.F.M., Haliman, H., Mohamad, A.A.
School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
2012, Pages 1-6
Corrosion Behavior of Sn-3.0Ag-0.5Cu Lead-Free Solder in Potassium Hydroxide Electrolyte ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Liew, M.C., Ahmad, I., Lee, L.M., Nazeri, M.F.M., Haliman, H., Mohamad, A.A.
School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia
Tuesday, April 10, 2012
Effect of Cooling Rate on the Intermetallic Layer in Solder Joints
IPC Outlook While it has long been known that the Cu6Sn5 intermetallic that plays a critical role in the reliability of solder joints made with tin-containing alloys on copper substrates exists in two different crystal forms over the temperature range to which electronics circuitry is exposed during assembly and service, it has only recently been recognized that the change from one form to the other has implications for solder joint reliability. Under equilibrium conditions the change from the hexagonal to monoclinic form occurs in the cooling solder joint at 186°C. However, cooling rates after common commercial soldering processes are typically faster than the rate that would permit complete transformation under such equilibrium conditions. In this paper the authors report a study of the effect of cooling rates on Cu6Sn5 crystals. Cooling rates from 200°C ranged from 10°C/minute to 100°C/minute and the effect of isothermal ageing at intermediate temperatures was also studied. The extent of the phase transformation after each regime was determined using synchrotron X-ray diffraction. The findings have important implications for the manufacture of solder joints and their in-service performance.
Presented at APEX 2012, Feb 29th 2012
Authored By:
Keith Sweatman, Tetsuro Nishimura
Nihon Superior Co. Ltd.
Osaka, Japan
Stuart D. McDonald, Kazuhiro Nogita
University of Queensland
Brisbane, Australia
This program first published April 2012
Presented at APEX 2012, Feb 29th 2012
Authored By:
Keith Sweatman, Tetsuro Nishimura
Nihon Superior Co. Ltd.
Osaka, Japan
Stuart D. McDonald, Kazuhiro Nogita
University of Queensland
Brisbane, Australia
This program first published April 2012
Friday, March 23, 2012
On the relationship between solder-controlled and intermetallic compound (IMC)-controlled fracture in Sn-based solder joints
Scopus: The strain-rate-dependent mechanical behavior of Sn-rich solder is of fundamental importance. Dynamic solder joint strength is hypothesized to be controlled by two factors. At low strain rates it is believed to be controlled by the bulk solder and at high strain rates by the brittle intermetallic layer. In this paper, the dynamic solder joint strength of Sn-3.9Ag-0.7Cu solder joints was experimentally quantified to verify the solder and intermetallic compound-controlled behavior hypothesis.
Scripta Materialia
Volume 66, Issue 8, April 2012, Pages 586-589
On the relationship between solder-controlled and intermetallic compound (IMC)-controlled fracture in Sn-based solder joints
Yazzie, K.E.,Xie, H.X.,Williams, J.J.,Chawla, N.
Materials Science and Engineering, School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287-6106, United States
Scripta Materialia
Volume 66, Issue 8, April 2012, Pages 586-589
On the relationship between solder-controlled and intermetallic compound (IMC)-controlled fracture in Sn-based solder joints
Yazzie, K.E.,Xie, H.X.,Williams, J.J.,Chawla, N.
Materials Science and Engineering, School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287-6106, United States
Thermochemical and phase diagram studies of the Bi-Ni-Sn system
Scopus: The phase diagram Bi-Ni-Sn was studied by means of SEM (scanning electron microscopy)/EDS (energy-dispersive solid state spectrometry), by DSC (differential scanning calorimetry) and RT-XRD (room temperature X-Ray diffraction) in order to attain more information about this ternary phase diagram. The samples were positioned in three isopleths with nickel contents of: 0.05 (section 1), 0.10 (section 2) and 0.15 (section 3) mole fractions, respectively. The mole fractions of Sn corresponding to the particular sections were as follows: from 0.19 to 0.76 (section 1), from 0.18 to 0.72 (section 2); from 0.17 to 0.68 (section 3). Mixtures of pure metals were sealed under vacuum in amorphous silica ampoules and annealed at 350 C. A binary Bi-Sn eutectic sample was synthesized and used as internal standard. The existence of a previously reported ternary eutectic reaction was confirmed. Liquidus temperatures were identified and the results were compared to CALPHAD-type calculations. It was found that ternary samples' liquidus temperatures were higher than the calculated ones. Six more groups of thermal arrests were registered except the eutectic and liquidus related peaks.
Thermochimica Acta
Thermochemical and phase diagram studies of the Bi-Ni-Sn system ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Milcheva, N.a,Broz, P.bc,Buršík, J.d,Vassilev, G.P.a
a Faculty of Chemistry, University of Plovdiv, 24 Tsar Asen str., 4000 Plovdiv, Bulgaria
b Masaryk University, Faculty of Science, Kotlářská 2, 61137 Brno, Czech Republic
c Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 625 00, Brno, Czech Republic
d Institute of Physics of Materials, Academy of Sciences, Žižkova 22, 61662 Brno, Czech Republic
Thermochimica Acta
Thermochemical and phase diagram studies of the Bi-Ni-Sn system ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )
Milcheva, N.a,Broz, P.bc,Buršík, J.d,Vassilev, G.P.a
a Faculty of Chemistry, University of Plovdiv, 24 Tsar Asen str., 4000 Plovdiv, Bulgaria
b Masaryk University, Faculty of Science, Kotlářská 2, 61137 Brno, Czech Republic
c Masaryk University, Central European Institute of Technology, CEITEC, Kamenice 753/5, 625 00, Brno, Czech Republic
d Institute of Physics of Materials, Academy of Sciences, Žižkova 22, 61662 Brno, Czech Republic
Monday, January 9, 2012
Effect of reflow soldering process on metallurgical bonding between Sn3.5Ag solder and ENIG substrates
Scopus: Reflow soldering process is one of the important steps in the manufacturing process for ball grid arrays. The purpose of this study is to observe the metallurgical bonding between Sn3.5Ag solder ball and electroless nickel immersion gold (ENIG) substrates after reflow soldering process.
The reflow soldering process was performed at peak temperatures Tpeak of 246 and 251'C for 50 s by the rapid thermal processing system. Visual micrographs of these solder joints were performed in order to support the metallurgical bonding of Sn3.5Ag solder ball and ENIG substrate after the reflow soldering process.
The formation of Ni3Sn4 intermetallic compounds (IMCs) at the Sn3.5Ag solder/Ni interface was dependent and continuous with one another compared to the initial IMC formation at Tpeak of ̃246�C. It was also found that the initial IMCs thickness of Sn3.5Ag solder/Ni interface was lower and thinner at Tpeak of y251uC during the reflow soldering process.
As a conclusion, the metallurgical bonding between Sn3?5Ag solder/ENIG substrate was formed better at Tpeak of ̃251�C during the reflow soldering process using the rapid thermal processing system.
Muhammad, N.A.a , Bais, B.H.a , Ahmad, I.b , Isnin, A.c
a Department of Electrical, Electronic and System Engineering, Faculty of Engineering and Built, Environment, Universiti Kebangsaan Malaysia (UKM), Bangi 43600, Malaysia
b Department of Electronics and Communication, College of Engineering UNITEN, km 7, Jln Kajang-Puchong, Kajang 43009, Malaysia
c AMREC, SIRIM Berhad, Lot 34, Jln Hi-Tech 2/3, Kulim Hi-Tech Park, Kulim 09000, Malaysia
Friday, January 6, 2012
Long-term behavior of IMCs in lead-free solder joints
Scopus: This article deals with the creation and growth of intermetallic compounds (IMCs) in solder joints. The test specimens of copper substrate were made for this experiment. The soldered joints were created on the test specimens by hand soldering process at the temperature of 250'C.
Four lead-free solder alloys and one tin-lead solder alloy were chosen for research of IMCs. The test specimens were divided into several groups. These groups differ in two parameters. The first parameter is soldering process, concretely soldering time. Half of the specimens were soldered for a period of 10 seconds and the second half of specimens were soldered for a period of 60 seconds. The second parameter is a thermal stress. The test specimens were exposed to elevated aging for research of long-term behavior of IMCs in solder joint. The specimens were thermal stressed in hot air oven at the temperature of 150'C for a periods of 4, 8, 12, 16 and 20 weeks. The results of analysis of IMCs in solder joints using confocal and metallographic microscopes are presented in this article
Novak, T., Hujer, T., Steiner, F.
Department of Technologies and Measurement, Faculty of Electrical Engineering, University of West Bohemia in Pilsen, Pilsen, Czech Republic
34th International Spring Seminar on Electronics Technology: "New Trends in Micro/Nanotechnology", ISSE 2011; Tratanska Lomnica; 11 May 2011 through 15 May 2011; Category number CFP11509-ART; Code 87529
Monday, October 31, 2011
Coarsening mechanisms, texture evolution and size distribution of Cu6Sn5 between Cu and Sn-based solders
Scopus: During the reflowing procedure, the Cu concentration in the solder affects the coarsening mechanisms of intermetallic compound (IMC) grains. For the Sn3Cu solder, the mean radius of the IMC grains was proportional to the cube root of the reflowing time; while it follows the square root relation with the reflowing time for the SnAgCu and Sn solders.
It is proposed that the flux from the substrate was only consumed to coarsen the IMC grains for Sn3Cu solder, while it was separated into two fluxes for the SnAgCu and Sn solders at the reflowing initial procedure. For the Sn3.8Ag0.7Cu/Cu and Sn/Cu couples, the size distribution of the IMC grains well agrees with the modified flux driven ripening (FDR) model when the value of r/〈r〉 is above 1; while it would closely match with Marqusee and Ross analysis when the value of r/〈r〉 is below 1.
For Sn3Cu/Cu couple, the size distribution of IMC grains shows good agreement with the FDR model. However, for SnPb/poly-Cu, during the solid-state aging procedure, the mean radius of the IMC grains was proportional to the cube root of the aging time. And the size distribution of IMC grains is well consistent with the FDR model
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