100°C drop in melting point could help make Nano-Solders a reality

Reduction synthesis of tin nanoparticles using various precursors and melting behavior - Springer: "To achieve a more significant melting point drop through finer particles, chemical reduction synthesis of tin nanoparticles were conducted using four tin precursor agents: tin(II) acetate, tin(II) chloride, tin(II) sulfate, and tin(II) 2-ethylhexanoate. Depending on the precursor type, the sizes and size distributions of the synthesized Sn nanoparticles were highly diverse. Tin nanoparticles synthesized with tin(II) sulfate or tin(II) 2-ethylhexanoate displayed characteristics of monodispersity at reduced size. The nanoparticles had average diameters of just ∼3 nm and ∼6 nm, respectively, and exhibited melting points of 102.2°C and 131.1°C, which represented extreme drops by 130.4°C and 101.5°C in comparison with the melting point of bulk tin."

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New nanoalloys for high temperature soldering

New nanoalloys for high temperature soldering:


Nanowerk News) Removing lead from manufacturing processes and products is high priority for the EU. A European research programme has tackled the problem of high-temperature solders used in the electronics industry.
On soldering components on a printed circuit board, it is crucial that the joints do not remelt in subsequent soldering operations. The electronics industry is therefore inclined to use solder material containing a high percentage of lead with a higher melting point (300 °C and above).
One solution is to use so-called nanosolders based on tin-antimony (Sn-Sb) alloys. Nanoparticles have a lower melting point than the bulk substance. Funded by the EU, the project 'A chemical approach to lead-free nanosolders' (Nanosold) aimed to develop new lead-free high-temperature solders with Sn-Sb-M alloys. M is silver (Ag), copper (Cu) and nickel (Ni).
Concentrating on the two ternary alloy systems Sn-Sb-Ag and Sn-Sb-Cu, the Nanosold project investigated the thermodynamic properties, the sum of the features of the individual phases. The team used the so-called 'Computer coupling of phase diagrams and thermochemistry' (Calphad) method enabling the scientists to reliably predict the thermodynamic properties without experimental information.
To refine the phase relations in the Sn-Sb-Ni system, Nanosold used other complementary methods. These included powder X-ray diffraction, electron probe micro-analysis, scanning electron microscopy and differential thermal analysis.
A reduction in melting point of up to 11 °C was achieved using nanoalloys rich in Sn prepared by a chemical reduction method. Particle size was modified to be in the range of 50 to 150 nm which would translate into a size-dependent lowering of soldering temperature in any practical application.
Although there are further problems to be worked on, solder pastes based on nanoalloys would achieve a decrease in melting point. From an environmental point of view, the new nanoalloys remove a very toxic element from electronic appliances' manufacturing.
Source: Cordis



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Solder foams, nano-porous solders, foamed-solder balls

A foamed solder or a nano-porous solder is formed on a substrate of an integrated circuit package. The foamed solder exhibits a low modulus that resists cracking during shock and dynamic loading. The foamed solder is used as a solder bump for communication between an integrated circuit device and external structures.



Page bookmark TWI358340  (B)  -  Solder foams, nano-porous solders, foamed-solder b
Inventor(s): CHOE HEEMAN [KR]; SUH DAEWOONG [KR] +
Applicant(s): INTEL CORP [US] +
Classification:
- international: B23K35/02; B23K35/14; H01L21/66
- European: B23K35/02D5P; B23K35/22; H05K3/34C4B; H05K3/34F1
Application number: TW20060146439 20061212 
Priority number(s): US20050323218 20051230
Also published as:
US2007152016  (A1)   US7745013  (B2)   WO2007078717  (A2)   WO2007078717  (A3)   KR20080083127  (A)   more 

Wettability of a Cu-nanoparticle-reinforced solder matrix paste composite

Scopus: This paper summarizes a phenomenological preliminary study of nano-particle reinforced composite solder pastes' spreading over Cu substrates. The nano reinforcements included Cu and non-Cu particles. Solder matrix were lead and lead-free systems (including binder and flux). This report focuses in particular on Cu reinforced Sn-Pb materials and indicates some differences vs. lead-free systems. Wettability of the composite over Cu substrates was investigated using a realtime in-situ visualization of the triple line movement as well as the equilibrium contact angle measurements. It was established that the addition of Cu nanoparticles hampers spreading of the eutectic Sn-Pb solder paste and lowers the melting temperature of a nano- composite, but does not significantly change the spreading time, the final spread domain and the equilibrium contact angle, if the content of nano particles is less than 2.5 %. Further increase of nano - particles' content up to 5% indicates a decrease in the final spreading domain and increase in the equilibrium contact angle.


IBSC 2012 - Proceedings of the 5th International Brazing and Soldering Conference
2012, Pages 475-479
5th International Brazing and Soldering Conference, IBSC 2012;Las Vegas, NV;22 April 2012through25 April 2012;Code90195
Wettability of a Cu-nanoparticle-reinforced solder matrix paste composite  ( Conference Paper )

Chen, M.a, Zhao, H.b, Liu, W.c, Sekulic, D.P.c 

a  Key Laboratory for Liquid-solid Structural Evolution and Processing of Materials, Shandong University, Jinan 250061, China
b  Creative Thermal Solutions, Inc., Urbana-Champagne, IL 61802, United States
c  Mechanical Engineering Department, College of Engineering, University of Kentucky, Lexington, KY 40506, United States

Nanoindentation Creep Behavior of Nanocomposite Sn-Ag-Cu Solders

Scopus: High-density, ultrasmall-pitch electronic applications require miniaturized solder bumps with improved thermomechanical performance. In addition, novel techniques which are able to precisely characterize these solder bumps are needed. One approach to meeting both of these requirements is to make use of recently developed nanocomposite solders with enhanced creep resistance, and to characterize these solders using a nanoindentation technique. In the present study, the creep behavior of ceria-reinforced nanocomposite solder foils fabricated by the accumulative roll-bonding process was characterized using a depth-sensing nanoindentation technique. It was found that the creep resistance of the composites increased with increasing volume fraction of CeO 2 reinforcement, and it was deduced that the creep deformation of this nanocomposite proceeded by deformation of the matrix, with the role of the reinforcement being to increase the creep resistance by reducing the effective stress acting on the matrix. The values of the creep exponent suggested that the dominant creep deformation mechanisms involved were diffusion creep and grain boundary sliding.

Journal of Electronic Materials
2012, Pages 1-8
Nanoindentation Creep Behavior of Nanocomposite Sn-Ag-Cu Solders  ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )

Roshanghias, A.a , Kokabi, A.H.a, Miyashita, Y.b, Mutoh, Y.c, Ihara, I.b, Guan Fatt, R.G.b, Madaah-Hosseini, H.R.a 

a  Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11369466, Tehran, Iran
b  Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka, Japan
c  Department of System Safety, Nagaoka University of Technology, Nagaoka, Japan

Influence of TiO 2 nanoparticles addition on the microstructural and mechanical properties of Sn0.7Cu nano-composite solder

Scopus: Composites of SC solder reinforced with 0, 0.25, 0.5 and 1wt.% of TiO 2 nanoparticles were fabricated using a mechanical technique. With increased addition of TiO 2 nanoparticles, the SC nano-composite solder was found to have a slightly lower melting temperature. The addition of TiO 2 nanoparticles can also effectively refine the microstructure as so β-Sn and Cu 6Sn 5, and increase the percentage of eutectic area. The mechanical properties (microhardness, 0.2% YS and UTS) increase with the increasing presence of reinforcement, far exceeding the strength of the eutectic SC solder. The yield strength improvement was attributed to (i) the Hall-Petch effect due to β-Sn grain size refinement. (ii) Orowan strengthening, (iii) generation of geometrically necessary dislocations to accommodate CTE mismatch between the matrix and the second phase (Cu 6Sn 5 and TiO 2), and (iv) the load-bearing effects due to the presence of nano-sized reinforcements.

Materials Science and Engineering A
Volume 545, 30 May 2012, Pages 194-200
Influence of TiO 2 nanoparticles addition on the microstructural and mechanical properties of Sn0.7Cu nano-composite solder

Tsao, L.C.a , Huang, C.H.b, Chung, C.H.a, Chen, R.S.b 

a  Graduate Institute of Materials Engineering, National Pingtung University of Science and Technology, 1, Hseuhfu Road, Neipu, Pingtung 91201, Taiwan
b  Department of Engineering Science, National Cheng-Kung University, 1, University Road, Tainan City 701, Taiwan

Co-electrodeposited graphite and diamond-loaded solder nanocomposites as thermal interface materials

Scopus: This paper describes a novel co-electrodeposition process to form thin bonding structures based on solder-graphite and solder-diamond nanocomposites for thermal interface materials (TIM). Using this novel processing route, inorganic nanoparticles can be co-plated along with a solder matrix to form unique nanocomposite structures with much enhanced thermal conductivity, engineered thermomechanical properties such as coefficient of thermal expansion (CTE), strength and fatigue resistance, while enabling the benefits of electroplating such as thin film and fine-pitch processing, low-temperature deposition and compatibility with semiconductor and packaging infrastructure. Si-Si and Cu-Cu bonding were demonstrated with these solder nanocomposites having high graphite loading. Pressure-assisted bonding enhanced solder wetting on nanoparticles and improved the bonding characteristics


Proceedings - Electronic Components and Technology Conference
2010, Article number 5490744, Pages 1708-1712
60th Electronic Components and Technology Conference, ECTC 2010;Las Vegas, NV;1 June 2010through4 June 2010;Category number10CH38220;Code81304
Co-electrodeposited graphite and diamond-loaded solder nanocomposites as thermal interface materials  ( Conference Paper )
Reddy, G.P.a, Raj, P.M.a , Nataraj, N.a, Rajesh, P.M.a, Jha, G.a, Choudhury, A.a, Kumbhat, N.a, Tummala, R.a, Brese, N.b, Toben, M.b, Szöcs, E.b  
a  3D Systems Packaging Research Center, Georgia Institute of Technology, Atlanta, GA 30332-0560, United States
b  Dow Chemical Company, 455 Forest St., Marlborough, MA 01752, United States

LinkedIn:

Any break through in high temp resistant Pb free solder for power electronics ????
March 27, 2011


Nikhil Kolhatkar • Mixing C-Nanotubes or Nano-Diamonds with solder has been researched to provide good thermal characteristics. It is a costly affair though but with a remarkable results.

Nano-Ag would be the best choice considering better thermal , electrical and manufacturing cost for power electronics.

Disabling of Nanoparticle Effects at Increased Temperature in Nanocomposite Solders

Scopus : The use of nanoparticles to control grain size and mechanical properties of solder alloys at high homologous temperature is explored. It is found that silica nanoparticles in the 100 nm range coated with 2 nm to 3 nm of gold can be dispersed within solders during the normal reflow soldering process, and that these particles are effective in hardening the solder and restricting dynamic grain growth during compression testing at low homologous temperature. As the homologous temperature increases towards 0.75, the effects of the nanoparticles on both mechanical properties and dynamical grain growth reduce, and by homologous temperatures of 0.86 the effects have completely disappeared. This behavior is explained by introducing the concept of an effective volume fraction of pinning nanoparticles, and the practical implications for using nanoparticles to control solder properties via Zener pinning at high homologous temperatures are discussed.

Journal of Electronic Materials
2012, Pages 1-8
Disabling of Nanoparticle Effects at Increased Temperature in Nanocomposite Solders  ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )

Mokhtari, O.a ,Roshanghias, A.b,Ashayer, R.a,Kotadia, H.R.c,Khomamizadeh, F.b,Kokabi, A.H.b,Clode, M.P.a,Miodownik, M.c,Mannan, S.H.c 

a  Materials Research Group, Division of Engineering, King's College London, London, WC2R 2LS, United Kingdom
b  Department of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran
c  Department of Physics, King's College London, Strand, London, WC2R 2LS, United Kingdom

Influence of 0.03 wt.% Carbon Black Addition on the Performance of Sn-3.5Ag Lead-Free Solder

Scopus: In an effort to improve the performance of lead-free solder, Sn-3.5 wt.%Ag (Sn-3.5Ag) solder alloy with 0.03 wt.% carbon black was prepared under high pressure (5.5 GPa) and high temperature (1200'C). We have investigated the microstructure, melting behavior, and mechanical properties of the alloy using x-ray diffraction, differential scanning calorimetry (DSC), Vickers hardness testing, tensile testing, and scanning electron microscopy (SEM). The melting point was found to be unchanged, while the hardness and the tensile strength increased with the addition of carbon black. SEM images showed that the average thickness of the intermetallic compound (IMC) layer decreased with the addition of carbon black, indicating improvement in solder joint reliability

 Journal of Electronic Materials
2012, Pages 1-5
Influence of 0.03 wt.% Carbon Black Addition on the Performance of Sn-3.5Ag Lead-Free Solder  ( Articles not published yet, but available online Article in press About articles in press (opens in a new window) )

Van Son, P.ab,Fujitsuka, A.a,Ohshima, K.-I.a 

a  Institute of Materials Science, University of Tsukuba, Tsukuba, 305-8573, Japan
b  Department of Physics, Danang University of Education, 459 Ton Duc Thang, Danang, Viet Nam

Effect of Ni-coated carbon nanotubes on the corrosion behavior of Sn-Ag-Cu solders

Scopus: In this paper, varying weight percentages of Ni-coated carbon nanotubes (Ni-CNTs) was incorporated into Sn-Ag-Cu (SAC) solder matrix, to form composite solder. Up to 0.05% of Ni-CNTs were successfully incorporated. After that, the electrochemical behavior of Sn-Ag-Cu with varying weight percentages of Ni-coated carbon nanotubes (Ni-CNTs) composite solder were investigated in 0.3% Na 2SO 4 solution by using potentiodynamic polarization method. Scanning microscopy was used to characterize the samples after the electrochemical tests. It was observed that the corrosion resistance decreased when the content of Ni-CNTs reached a certain level.

Advanced Materials Research
Volume 418-420, 2012, Pages 1171-1174
2nd International Conference on Advances in Materials and Manufacturing, ICAMMP 2011;Guilin;16 December 2011through18 December 2011;Code87920
Effect of Ni-coated carbon nanotubes on the corrosion behavior of Sn-Ag-Cu solders  ( Conference Paper )

Tang, S.a ,Jing, H.a ,Xu, L.a ,Han, Y.a ,Lu, G.ab  

a  School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China
b  Dept Mat Sci and Engn, Virginia Polytech Inst and State Univ, Blacksburg, VA 24061, United States

Development of SnAg-based lead free solders in electronics packaging

ScienceDirect.com: Lead free solder alloys for electronic assembly is being driven by environmental and health concerns regarding toxicity of lead and, more importantly, by the perceived economic advantage of marketing “green” products

Of the currently available lead free solders, SnAg has the greatest potential. In this solder, the Ag3Sn compound is distributed in a eutectic network throughout the β-Sn matrix and these results represent mechanical strength. In order to further improve the microstructures and properties of SnAg-based alloys, alloying elements such as rare earth, Zn, In, P, Cu, Ni and particles such as ZrO2, POSS are selected to meet the requirement of high reliability of high-density electronics devices. For SnAg solder bearing rare earth (Ce and La), the creep-rupture life of solder joints can be remarkably increased up to four times more than that of the original SnAg solder joints at room temperature, meanwhile, rare earths can dramatically reduce the thickness of IMCs layer at solder/pad interfaces and also refine the microstructure of the alloy which results in the enhancement of mechanical properties of the SnAg solder. Moreover, the addition of ZrO2 nanoparticles significantly refined the size of Ag3Sn due to the adsorption effect of the ZrO2 nanoparticles. This paper summarizes the effects of alloying elements and particles on the wettability, mechanical properties, creep behavior, microstructures, etc. of SnAg-based lead free solder alloys.


Microelectronics Reliability
Volume 52, Issue 3, March 2012, Pages 559–578
Special section on International Seminar on Power Semiconductors 2010

Liang Zhanga, , , Cheng-wen Hea, Yong-huan Guoa, Ji-guang Hana, Yong-wei Zhanga, Xu-yan Wangb
a School of Mechanical and Electrical Engineering, Xuzhou Normal University, Xuzhou 221116, China
b The 14th Research Institute, China Electronics Technology Group Corporation, Nanjing 210013, China

Received 27 July 2011. Revised 5 October 2011. Accepted 5 October 2011. Available online 9 November 2011.

Carbon nanotubes solder composite for high performance interconnect (US8100314)

US8100314: Composite paste, used in any interconnect applications such as die attachment to a package substrate, comprises a solder paste comprising solder powder and a paste ingredient, and carbon nanotubes

A bump comprising:

a solder paste comprising solder powder and a paste ingredient mixed with the solder powder; and

carbon nanotubes (CNTs) dispersed within the solder paste with a pre-defined volume fraction, wherein the pre-defined volume fraction ranges from approximately 30% to 40%, to provide high electrical conductivity; wherein the solder paste is attached to at least one of a die or a package substrate.

Intel Corporation, Santa Clara, CA, United States of America

Published / Filed: 2012-01-24 / 2010-01-19

Properties of the SAC solder paste with different nanoparticles

Scopus Our research objective is trying to mofy the SAC solder paste properties by addition a different nanoparticles. It is continuation of our previous work on including to the SAC solder paste the silver nanoparticles with different grain sizes. Improvement of the wetting results of investigated "nano solder pastes" on copper substrate depends especially for the 4% silver nanopowders. It forced us to enlarge our work on nickel and copper nanoparticles. The SAC "nanopastes" were obtained by adding from 0.05 to 4% of Ni, Cu and Ag nanoparticles. The results were compared with previously obtained for SAC with silver nanoparticles. We measured spreading, wettability, solder ball and slump of the "nanopastes". We obtained contrary results of wettability for nNi and nCu addition than for the silver nanoparticles addition. Wetting of the SAC solder paste with nNi and nCu decreases with increasing of the nanoparticles addition. Using SEM and EDS spectroscopy we measure the "nanosolder" pastes microstructure for establishing the differences between type of nanoparticles and their amount added to SAC solder paste. The microstructure of the cross-sectional solder joints as well as creates the IMC scallop or rod layers with different thickness after reflow process will be presented.


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


Bukat, K.a b , Kościelski, M.a b , Sitek, J.a b , Jakubowska, M.a b c , Młozniak, A.c  
a  Tele and Radio Research Institute, Warsaw, Poland
b  Warsaw University of Technology, Warsaw, Poland
c  Institute of Electronic Materials Technology, Warsaw, Poland

Investigation preparation method and soldering behaviors of Sn-58Bi lead-free solder with carbon nanotubes

Scopus: Varying weight fraction of multi-walled carbon nanotubes were incorporated into Sn-58Bi soler alloy by ball-milling and low temperature melting methods, the morphologies of carbon nanotubes in solder alloy and the influences of carbon nanotubes on the pull-off strength were investigated by SEM, EDS, and DSC.

The experimental results indicate that part of carbon nanotubes are incorporated into Sn-58Bi soler alloy after ball-milling and low temperature melting; 0.03% CNTs can improve the wettability; the melting point of Sn-58Bi-CNTs solder does not change much; the dispersive distribution of carbon nanotubes could refine the microstructure of Sn-58Bi-CNTs joints and the reliability of solder joints also is improved by the influences of CNTs on the fracture mechanism of solder joints


He, P.a , An, J.b , Ma, X.c , Chen, S.c , Qian, Y.b , Lin, T.a  
a  State Key Lab of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001, China
b  Shenzhen Graduate School, Harbin Institute of Technology, Shenzhen 518055, China
c  Yik Shing Tat Industrial Co., Ltd, Shenzhen 518101, China

An investigation of microstructure and mechanical properties of novel Sn3.5Ag0.5Cu-XTiO2 composite solders as functions of alloy composition and cooli

Scopus: In the present study, the influence of both TiO2 nanoparticle addition and cooling rate on the melting temperature, microstructure, and mechanical behaviour of Sn3.5Ag0.5Cu (SAC) solder alloys was studied. The composite solders were prepared by mechanical mixing of TiO2 nanoparticles with SAC solder. With the addition of TiO2 nanoparticles into the eutectic SAC alloy, a novel SAC composite solder was successfully prepared. The melting temperature for the SAC composite solders was found to be only 1.56 �C higher than that of the SAC solder, indicating that the novel SAC composite solder is fit for existing soldering process. The cooling rate and TiO2 nanoparticle addition affected the solidification of the microstructure dramatically. Notably, SEM observation of the microstructure of the SAC composite solders under the rapid-cooled condition revealed fine dot-like nano-Ag3Sn IMC in the solder matrix. The ultimate tensile strength (UTS), 0.2% yield strength (0.2YS), and microhardness of the SAC composite solder increased with the increase of TiO2 nanoparticle content by 0.25-1.0 wt.% and the cooling rate, which could be attributed to the dispersion strengthening mechanisms. However, the ductility of the composite solders was found to decrease because of microporosity at the Ag3Sn network grain boundary

Tsao, L.C.

Department of Materials Engineering, National Pingtung University of Science and Technology, 1, Hseuhfu Road, Neipu, Pingtung 91201, Taiwan

Influence of temperature and strain rate on tensile properties of single walled carbon nanotubes reinforced Sn-Ag-Cu lead free solder alloy composites

Scopus: The effect of temperature and strain rate on the tensile properties of Sn-3.8Ag-0.7Cu (SAC387) alloy as well as SAC387 alloy reinforced with two different weight percentages (wt.%) of SWCNT was investigated. It was found that addition of 0.05 wt.% SWCNT to SAC387 alloy results in an increase in yield and ultimate tensile strengths without affecting the total elongation at all temperatures and strain rates studied, although the increase in strength values at 75 °C was marginal. Further increasing the SWCNT to 0.1 wt.% did not result in any significant improvements in the strengths as compared to the composite containing 0.05 wt.% SWCNT. Temperature and strain rate were observed to have a significant effect on the strengths in both SAC387 alloy as well as the composites. Both the yield and ultimate tensile strengths were observed to decrease with increase in temperature and increase with increase in strain rates in SAC387 alloy as well as the composites. This behaviour was attributed to the competing effects of work hardening and dynamic recovery processes and the effect of temperature and strain rates on these processes.

Niranjani, V.L.a , Rao, B.S.S.C.b , Singh, V.a , Kamat, S.V.a

a Defence Metallurgical Research Laboratory, Hyderabad, India

b Department of Mechanical Engineering, National University of Singapore, Singapore

Material and method of manufacturing of a solder joint with high thermal conductivity and high electrical conductivity (US8034195)

US8034195: A solder composition for forming a solder joint. The composition includes a powder material including a solid metal matrix material and a filler material.

The solid metal matrix material includes one or more of tin-silver-copper (Sn—Ag—Cu), tin-copper (Sn—Cu), tin-copper-nickel (Sn—Cu—Ni), tin-silver (Sn—Ag), tin-silver-bismuth (Sn—Ag—Bi), tin-bismuth-indium (Sn—Bi—In), tin-gold (Au—Sn), tin-zinc (Sn—Zn), tin-zinc-bismuth (Sn—Zn—Bi), tin-bismuth-silver (Sn—Bi—Ag), tin (Sn), tin-indium (Sn—In), indium (In), indium-silver (In—Ag), and tin-lead (Sn—Pb). The filler material includes one or more of copper (Cu), gold (Au), nickel (Ni), nickel-gold (Ni—Au), carbon, silver (Ag), aluminum (Al), molybdenum (Mo), nickel (Ni) or nickel-gold (Ni—Au) coated carbon, the platinum group metals (PGM's), and their alloys.

Schmid, Richard K.; Gerlikon, Switzerland

Doesburg, Jacobus C.; Westbury, NY, United States of America

Assignee: Sulzer Metco (US), Inc.

Effect of addition of TiO2 nanoparticles on the microstructure, microhardness and interfacial reactions of Sn3.5AgXCu solder

Scopus: "In this work, TiO2 nanoparticles were successfully incorporated into Sn3.5Ag and Sn3.5Ag0.7Cu solder, to synthesize novel lead-free composite solders.

Effects of the TiO2 nanoparticle addition on the microstructure, melting property, microhardness, and the interfacial reactions between Sn3.5AgXCu and Cu have been investigated. Experimental results revealed that the addition of 0.5 wt.% TiO2 nanoparticles in Sn3.5AgXCu composite solders resulted in a finely dispersed submicro Ag3Sn phase.

This apparently provides classical dispersion strengthening and thereby enhances the shear strength of composite solder joints. After soldering, the interfacial overall intermetallic compounds (IMC) layer of the Sn3.5AgXCu lead-free solder joint was observed to have grown more significantly than that of the Sn3.5AgXCu composite solder joints, indicating that the Sn3.5AgXCu composite solder joints had a lower diffusion coefficient. This signified that the presence of TiO2 nanoparticles was effective in retarding the growth of the overall IMC layer"

SAC TiO2 nanocomposites

Factiva: "Sn-Ag-Cu composite solders reinforced with nano-sized, nonreacting, noncoarsening 1 wt% TiO2 particles were prepared by mechanically dispersing TiO2 nano-particles into Sn-Ag-Cu solder powder and the interfacial morphology of the solder and flexible BGA substrates were characterized metallographically. At their interfaces, different types of scallop-shaped intermetallic compound layers such as Cu6Sn5 for a Ag metallized Cu pad and Sn-Cu-Ni for a Au/Ni and Ni metallized Cu pad, were found in plain Sn-Ag-Cu solder joints and solder joints containing 1 wt% TiO2 nano-particles"

In addition, the intermetallic compound layer thicknesses increased substantially with the number of reflow cycles. In the solder ball region, Ag3Sn, Cu6Sn5 and AuSn4 IMC particles were found to be uniformly distributed in the beta-Sn matrix. However, after the addition of TiO2 nano-particles, Ag3Sn, AuSn4 and Cu6Sn5 IMC particles appeared with a fine microstructure and retarded the growth rate of IMC layers at their interfaces,"

The researchers concluded: "The Sn-Ag-Cu solder joints containing 1 wt% TiO2 nano-particles consistently displayed a higher hardness than that of the plain Sn-Ag-Cu solder joints as a function of the number of reflow cycles due to the well-controlled fine microstructure and homogeneous distribution of TiO2 nano-particles which gave a second phase dispersion strengthening mechanism

wrote A.K. Gain and colleagues, City University of Hong Kong.

Heraeus Materials Technology - Innolot

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InnoRel Paste
InnoRel Rework Flux
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innolot@heraeus.com
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