Co-reporter:Menglong Sun, Xiaoping Long, Mengya Dong, Yuanyuan Xia, Fengtian Hu, An-min Hu, Ming Li
Materials Characterization 2017 Volume 134(Volume 134) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.matchar.2017.11.002
•Tin whisker growth is mitigated effectively by inserting Ni nanocones.•Ni nanocones impede Sn dynamic recrystallization by blocking dislocation motions.•The inhibition method and mechanism are important to the study of tin whisker.An innovative controllable way has been proposed to mitigate tin whisker growth by inserting Ni nanocones prepared by electrodeposition. The results reveal that, after inserting Ni nanocones, tin whisker formation is mitigated effectively for 1.6 μm Sn coating but there is no inhibition effect for 4.5 μm Sn coating. The coatings are characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectrometer and electron backscatter diffraction (EBSD). The EBSD results show that Sn grain size without Ni nanocones increases significantly after indentation test compared with Sn grains with Ni nanocones. The inhibition effect of Ni nanocones on whisker growth can be ascribed to its specific structure which prevents dynamic recrystallization and produces horizontal grain boundaries of Sn grains. The structural inhibition method and mechanism proposed are of great importance to the research of tin whisker.Download high-res image (101KB)Download full-size image
Co-reporter:Longlong Ju;Menglong Sun;Lei Ye
Journal of Materials Science: Materials in Electronics 2017 Volume 28( Issue 22) pp:17370-17377
Publication Date(Web):18 August 2017
DOI:10.1007/s10854-017-7670-3
Reduced graphene oxide (RGO) thin film was used to improve the performance of a low-temperature bonding process based on Cu microcones and Sn/Cu bumps (diameter: 25 μm), which has potential applications in high-density packaging. Under bonding conditions of a weight of 1500 g applied to each wafer for 10 min at a temperature of 120 °C, and incorporating a thin RGO layer, a compact bonding structure was obtained without interface voids. The RGO interlayer served as a barrier against interatomic diffusion of metals under zero applied pressure, and the formation of intermetallic compounds at the interface was thereby effectively reduced after bonding. Probable mechanisms for this bonding process are discussed. The investigation used standard 25 μm-diameter Sn/Cu bumps to simulate realistic industrial production.
Co-reporter:Penghui Xu, Fengtian Hu, Jing Shang, Anmin Hu, Ming Li
Materials Letters 2016 Volume 176() pp:155-158
Publication Date(Web):1 August 2016
DOI:10.1016/j.matlet.2016.04.109
•An ambient temperature ultrasonic bonding technology is introduced.•Successful bonding joints can be achieved under 8 Mpa and 1 s.•Possible mechanisms of the bonding method have been proposed.An ambient temperature ultrasonic bonding based on Cu micro-cone arrays (MCAs) plated with thin Sn for potential application in 3D packaging is introduced. The interfacial morphology is investigated in joints bonded by this method. As the thickness of Sn layer in bonding interface was about 300 nm, the best bonding quality was obtained under the condition of low pressure of 8 Mpa and short time of 1 s, meanwhile, the voids of interfaces vanished. Under the effect of ultrasound, the Cu MCAs embedded into each other effectively and a stable physical occlusion was formed. The thin Sn transformed into Cu3Sn in the bonding interface due to quick atom diffusion. The bonding materials of two sides are the same, which makes the preparation of bonding process easier. Without solder balls, ultrasonic bonding joints with smaller size can be directly achieved using Cu MCAs plated with a thin Sn layer.
Co-reporter:Zhangjian Zhao, Jing Shang, Anmin Hu, Ming Li
Materials Letters 2016 Volume 185() pp:92-95
Publication Date(Web):15 December 2016
DOI:10.1016/j.matlet.2016.08.115
•The effects of Sn solder grain size on the morphology of Cu6Sn5 were investigated.•Sn of different grain size was electroplated by adding additives into the solution.•The morphology of Cu6Sn5 was observed from the top-view and cross-section.Three Sn layers of different grain size were electroplated on Cu foils to investigate the effects of Sn solder grain size on the morphology and evolution of Cu6Sn5 during aging. In the early stage, scallop Cu6Sn5 formed in three joints. For the joint with Sn layer of 2 µm grain size, the Cu6Sn5 grain size was uniform and small, and the scallops had many facets. For the joints with Sn layers of 8 µm and 16 µm grain sizes, the Cu6Sn5 forming along the Sn grain boundary was of larger grain size than that forming inside the Sn grain, so it displayed network shape. And the scallop had fewer facets. As the aging time prolonged, the facets of Cu6Sn5 in the joint with Sn layer of 2 µm grain size became less and the scallop-type gradually transformed into rod-like. For the joints with Sn layers of 8 µm and 16 µm grain sizes, the Cu6Sn5 transformed from scallop-type to granular-like in a ripening growth, leading to the disappearing of Cu6Sn5 crystal network. Moreover, the interfacial intermetallic compound layer tended to be thicker in the joint with Sn layer of smaller grain size.
Co-reporter:Fengtian Hu, Penghui Xu, Wenqi Zhang, Anmin Hu, Ming Li
Materials Letters 2016 Volume 181() pp:165-168
Publication Date(Web):15 October 2016
DOI:10.1016/j.matlet.2016.06.030
•No high temperature and flat surface because of nano dimension of Ni microcone arrays.•Ductile Ag can manage CTE mismatch between chips and packages.•No molten phase involved, joint shape and geometry can be maintained.•No intermetallic compound formed, reliability issues do not exist.A low temperature solid state bonding between Cu bump coated with Nickel microcone arrays (Ni MCAs) and Ag layer is put forward. Ag, as an excellent electrical and thermal conductivity material, is used as a bonding medium between Cu substrate and Cu bumps. The bonding process is conducted under low temperature and flat surface because of the presence of nano dimension of Ni MCAs and deformation of Ag. The best bonding quality is obtained under the bonding pressure of 180 MPa, time of 20 min and temperature of 250 °C in ambient air. No molten phase is involved in the bonding process. Scanning Electron Microscopy showed that the Ni MCAs have been effectively embedded into Ag layer without voids and intermetallic compounds (IMC). Thus, reliability is enhanced. Transmission Electron Microscopy results demonstrated a sufficient insertion and atomic scale bonding between Ni MCAs and Ag. This work is expected for extensive practical application.
Co-reporter:Han Xiao, Anmin Hu, Tao Hang, Ming Li
Applied Surface Science 2015 Volume 324() pp:319-323
Publication Date(Web):1 January 2015
DOI:10.1016/j.apsusc.2014.10.156
Highlights
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We synthesized different structured cobalt films by adjusting electrodeposition conditions.
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The fluffy shells structured Co films exhibit excellent non-sticky superhydrophobic behaviors.
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A contact model between Cassie and Wenzel state is introduced to discuss the morphology induced hydrophobicity.
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By tuning of deposition parameters along with heating or dipping into stearic acid, the Co film can achieve a switch between sticky and non-sticky as well as quick transfer between superhydrophobic and superhydrophilic.
Co-reporter:Fengtian Hu, Penghui Xu, Haozhe Wang, Un byoung Kang, Anmin Hu and Ming Li
RSC Advances 2015 vol. 5(Issue 126) pp:103863-103868
Publication Date(Web):17 Nov 2015
DOI:10.1039/C5RA20638C
In this work, we present a simple method for fabricating a microstructured Cu/Ni–W alloy coating by combining electroless and electro deposition. Field emission scanning electron microscopy (FESEM) results show that a layer of Ni–W alloy has covered uniformly the conical surface of Cu microcone arrays, forming a multilayer coating. The Tafel curve shows the prominent anti-corrosion property of the as-deposited Ni–W film. Wettability results reveal that the water contact angles can be increased from 106° to 153.2° by adjusting the electrodeposition time of the Ni–W layer. The liquid–solid–air contact mode between the superhydrophobic Ni–W hemisphere decorated Cu microcone array and the water drop is briefly discussed. This work also showed potential for use in a wide range of applications, such as the commercial production of anti-wetting and anti-corrosion devices.
Co-reporter:Haozhe Wang, Anmin Hu and Ming Li
CrystEngComm 2014 vol. 16(Issue 34) pp:8015-8019
Publication Date(Web):04 Jul 2014
DOI:10.1039/C4CE00967C
Hierarchical mushroom-like cobalt materials were synthesized by galvanostatic electroplating. The morphology of the product, which can evolve from cone-like to mushroom-like nanostructures, is controllable by changing the deposition parameters. The nanostructure is a single hexagonal close-packed crystal with a <100> preferential growth direction. The proposed growth mechanism is based on the metal ion deficient layer (MIDL) theory which explains both the time-dependent morphology evolution and the effects of the crystalline modifier C2H4(NH2)2. Depositions using several organic crystalline modifiers were compared; only C2H4(NH2)2 yielded the mushroom-like structure.
Co-reporter:Shixin Gao, Zhuo Chen, Anmin Hu, Ming Li, Kaiyou Qian
Journal of Materials Processing Technology 2014 Volume 214(Issue 2) pp:326-333
Publication Date(Web):February 2014
DOI:10.1016/j.jmatprotec.2013.09.017
•This paper has developed a low-cost thin-gold-film substrate for Au wire bonding.•The substrate bonding performance is improved with Ni/Au microcones on the top.•Insertion weld between the Ni/Au microcones and Au wire is formed.•The bondability of Ni/Au Microcones with varying sizes is studied.•The mechanism explains advantages of Ni/Au microcones for Au wire bonding.In wire bonding, the bonding quality between the substrate Au film and metal wire has an effect on productivity and reliability. Au film thickness is important for substrate bondability. It is required to reduce the Au film thickness as thin as possible without deteriorating the level of bondability to cut down extremely high cost of Au consumption. In this study, electrodeposited Ni/Au microcones were fabricated and thermosonic bonded with Au wire. The thickness of Au film was only 0.05 μm. Bonded with Au wire 17.5 μm in diameter, the 0.4 μm-height microcones showed excellent and stable bondability with average pull strength 6.29 gf and small standard deviation. Microscopic observation showed that Ni/Au microcones inserted into Au wire effectively, thus insertion weld between microcones and Au wire was formed. Pull fracture scanning electron microscopy (SEM) images showed an improvement of stitch bonding quality when using Ni/Au microcones. Mechanism of bonding process between the Ni/Au microcones and Au wire was put forward by three stages.
Co-reporter:Jiaxing Liang, Tingbi Luo, Anmin Hu, Ming Li
Microelectronics Reliability 2014 Volume 54(Issue 1) pp:245-251
Publication Date(Web):January 2014
DOI:10.1016/j.microrel.2013.08.008
•Interfacial reactions between Sn -8Zn -3Bi -0.3Cr solder and Cu, Ni, Ni -W substrates were studied.•The main IMC and its thickness between solder and substrates were different.•Ni -W barrier film was easy to cracked and Zn atoms diffused to the substrate as ageing.In this paper, the formation and growth of intermetallic compounds (IMCs) of Sn–8Zn–3Bi–0.3Cr solder on Cu, Ni and Ni–W substrates have been investigated. For the Cu substrate, only Cu5Zn8 intermetallic compound was observed. For the Ni substrate, a Ni5Zn21 film formed at the interface due to the fast reaction between Ni and Zn. For the Ni–W substrate, a thin Ni5Zn21 film appeared between the solder and Ni–W layer, whose thickness decreases with the increase of W content. A bright layer was also found to form below the Ni5Zn21 layer as aging time extended, which is caused by the diffusion of Zn into Ni–W layer.
Co-reporter:Zhuo Chen, Tingbi Luo, Tao Hang, Ming Li and Anmin Hu
CrystEngComm 2013 vol. 15(Issue 48) pp:10490-10494
Publication Date(Web):02 Oct 2013
DOI:10.1039/C3CE41713A
Interfacial reactions of Ni micro cones with Sn at solid state temperatures from 373 K to 473 K were studied and compared with Sn/flat Ni diffusion couples. Due to its morphological characteristics, cone-structured Ni enhanced the nucleation of Ni3Sn4, resulting in thicker Ni3Sn4, which is also smaller in grain size and different in texture. At lower annealing temperatures (<423 K), cone-Ni also strongly suppresses the nucleation of metastable NiSn3. The stripe-like micromorphology and special texture of Ni cones are believed to be the reasons for enhanced Ni3Sn4 nucleation.
Co-reporter:Yishi Tao, Anmin Hu, Tao Hang, Li Peng, Ming Li
Applied Surface Science 2013 Volume 282() pp:632-637
Publication Date(Web):1 October 2013
DOI:10.1016/j.apsusc.2013.06.023
Highlights
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Electroless deposition of NiP, NiWP thin film on p-type Si as the barrier layer was investigated.
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Cu atom could diffuse through NiP barrier layer at 450 °C, while Cu could hardly diffuse through NiWP layer at 550 °C.
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With W added, the barrier performance is improved meanwhile the resistances of the three stacked layers of are close.
Co-reporter:Qin Lu, Zhuo Chen, Wenjing Zhang, Anmin Hu, Ming Li
Applied Surface Science 2013 Volume 268() pp:368-372
Publication Date(Web):1 March 2013
DOI:10.1016/j.apsusc.2012.12.102
Abstract
A low-temperature solid state bonding method based on surface Cu–Ni alloying microcones for potential application in 3D integration is introduced. Surface Cu–Ni alloying microcones were fabricated by electroless deposition and bonded with Sn–3.0Ag–0.5Cu (wt.%) solder at 190 °C (solid state) in ambient air. Microscopic observation showed that Cu–Ni microcones inserted into the soft solder effectively and a thin intermetallic compound layer formed along the bonding interface. The bonding joint strength was measured and the result showed that it was higher than that of reflow soldering.
Co-reporter:Na Huang, Anmin Hu, Ming Li
Materials Letters 2013 Volume 109() pp:8-11
Publication Date(Web):15 October 2013
DOI:10.1016/j.matlet.2013.07.047
•The Cu substrates used were not single Cu.•The different morphologies of IMCs formed on the Cu with different texture orientation were investigated.•Cu substrate (200)/Sn/electroplated Cu (200) sandwich structures were prepared by electroplating.•Cross-sectional microstructure evolution revealed that texture of Cu has significant influence on the growth of Cu–Sn IMCs.Influence of Cu texture orientation on the growths of IMCs in the joints with small volume of solder (10 μm electroplated Sn layer) was investigated. IMCs (Cu6Sn5 and Cu3Sn) formed on the Cu with different texture orientation displayed different morphologies. The average grain size of IMCs on the electroplated Cu with text orientation (220) is larger than that of Cu substrate with the text orientation (200), and the thickness of the IMCs at the electroplated Cu (220) is larger than those formed at the Cu substrate (200). After aging at 150 °C for 96 h, the IMCs almost penetrated the entire Sn layer at some points.
Co-reporter:Tingbi Luo, Zhuo Chen, Anmin Hu, Ming Li, Peng Li
Microelectronics Reliability 2013 Volume 53(Issue 12) pp:2018-2029
Publication Date(Web):December 2013
DOI:10.1016/j.microrel.2013.06.010
•When Zn content in Sn–2Ag–xZn/Cu joint is more than 2 wt%, the IMC of Sn–Ag–Zn/Cu altered from Cu6Sn5 to Cu5Zn8.•When Zn content increased to 2 wt%, the interfacial layer is enhanced with higher shearing strength.•A strong Cu–Sn intermetallic reaction takes place in Sn–Ag–Zn/Cu solder joints and forms Ag3Sn particles when aged at 150 °C.The eutectic Sn–Ag–Cu solder is the most popular lead free solder. But reliability and cost issues limit its application. On the other hand, Sn–Ag–Zn system has many advantages comparing with Sn–Ag–Cu. In this paper, interfaces of Sn–xAg–1Zn/Cu and Sn–2Ag–xZn/Cu (x = 1, 2, 3), Sn–2Ag–2.5Zn/Cu and Sn–1.5Ag–2Zn/Cu solders joints were studied to understand effects of Ag and Zn contents. Results show that shearing strength of as-reflowed Sn–2Ag–2Zn/Cu and Sn–1.5Ag–2Zn/Cu joints is higher than other joints. Because of the strong Cu–Sn reaction and the formation of Ag3Sn, the Sn–Ag–Zn series solder joints are not suitable for use above 150 °C temperature. After 250 °C soldering for 4 h, while the Zn content increased from 1 wt% to 2 wt%, the interfacial IMC of Sn–Ag–Zn/Cu altered from Cu6Sn5 to Cu5Zn8. The Cu5Zn8 interface has higher shearing strength than Cu6Sn5 interface. Relationships among microstructure, strength and aging condition are discussed.
Co-reporter:Zhuo Chen, Feifei Tian, Anmin Hu, Ming Li
Surface and Coatings Technology 2013 Volume 231() pp:88-92
Publication Date(Web):25 September 2013
DOI:10.1016/j.surfcoat.2012.01.053
Nickel surface with nanocone array structure was fabricated by electrodeposition. By controlling electrodeposition condition, various nickel films with different cone sizes were also fabricated. Wettability results revealed that with the increase of cone height, water contact angles increased from 148°to 154°while sliding contact angles dramatically decreased from 90° (sticky condition) to nearly 0°. Three-phase contact model and a simple calculation were given to demonstrate the relations between sliding angles and surface structures.Highlights► Nanocone arrays with different height were fabricated by electrodeposition. ► The relationship of sliding angle, contact angle and cone height were investigated. ► Three-phase contact mode and a simple calculation were proposed to explain the wetting behavior.
Co-reporter:Feifei Tian, Anmin Hu, Ming Li, Dali Mao
Applied Surface Science 2012 Volume 258(Issue 8) pp:3643-3646
Publication Date(Web):1 February 2012
DOI:10.1016/j.apsusc.2011.11.130
Abstract
In this work, a superhydrophobic nickel surface is fabricated by coupling electro and electroless deposition without chemical modification. SEM study reveals that electrodeposited nickel surface is characterized by nanocone arrays and has a contact angle of about 135°. After adding electroless deposition, as the second step, hemispherically topped nickel nanocone arrays are formed which leads to a high contact angle of 153.6°. That is, nickel surface has successfully transformed from hydrophobic to superhydrophobic. This transition is investigated both from the aspects of chemical composition and surface structure and proves the latter is the dominant factor. The present study inspires us to do more research about the creation of rough surfaces and enriches our comprehension about superhydrophobicity.
Co-reporter:Wenyan Geng, Zhuo Chen, Anmin Hu, Ming Li
Materials Letters 2012 Volume 78() pp:72-74
Publication Date(Web):1 July 2012
DOI:10.1016/j.matlet.2012.03.027
A novel low temperature insertion bonding technology based on micro-nano cones array (MCA) for 3D package is introduced. Hot-pressure insertion bonding was performed below the melting point of the soft solder (160 °C to 200 °C), the MCA was embedded into the solder and a thin diffusion layer occurred along the interface. The bonding strength can meet the industrial criterion. We predicted a reasonable initial void shape of the bond interface, which was in good accordance with both experimental and numerical simulation results. In addition, it was found that mechanical interlocking and fast diffusion between the MCA and the solder were the main mechanisms of this bonding process.Highlights► A low temperature insertion bonding technology based on micro-nano cones array (MCA) is introduced. ► At below the melting point of the solder, the MCA was inserted into the solder. ► The bonding strength can meet the industrial criterion.
Co-reporter:Tingbi Luo, Anmin Hu, Jing Hu, Ming Li, Dali Mao
Microelectronics Reliability 2012 Volume 52(Issue 3) pp:585-588
Publication Date(Web):March 2012
DOI:10.1016/j.microrel.2011.10.005
In this paper, the effect of trace addition of Cr on the mechanical properties and reliability on Sn–8Zn–3Bi solder alloys was investigated. It has been demonstrated that the microstructure of solder alloys was refined after doping traces of Cr. The elongation reaches up to 40.63% after doping 0.1% Cr; and the fracture mechanism converts from quasi-cleavage fracture into ductile fracture. With aging time of 0, 4, 9 and 16 days, mechanical property of Sn–8Zn–3Bi–0.3Cr alloy was improved slightly. It was found that the Sn–Zn–Cr phase was increased and Zn in alloy was consumed after aging, so that the amount of primary Zn phase was reduced and microstructure was improved.
Co-reporter:Jinglin Bi, Huiqin Ling, Anmin Hu, Tao Hang, Ming Li
Applied Surface Science 2011 Volume 257(Issue 8) pp:3723-3727
Publication Date(Web):1 February 2011
DOI:10.1016/j.apsusc.2010.11.121
Abstract
Wetting process of electrolyte in high density Cu/Sn micro-bumps electrodepositing is reported in this paper. Three methods were adopted to enable electrolyte to permeate photo-etching micro-holes with high aspect ratio, including plasma treatment, adding wetting additive in electrolyte and mechanical action. Wettability of the samples with electrolyte was improved by the first two methods, according to contact angle and surface tension measurement. However, electrolyte still cannot reach up to the bottom of micro-hole. And then, electrolyte was subjected to mechanical action, including agitation and ultrasonic vibration. Under mechanical action, void free Cu/Sn micro-bumps fabrication was achieved in photo-etching micro-holes with depth of 60 μm and radius of 30 μm. At last, we proposed a model to show wetting process of electrolyte in photo-etching micro-holes.
Co-reporter:Jinglin Bi, Anmin Hu, Jing Hu, Tingbi Luo, Ming Li, Dali Mao
Microelectronics Reliability 2011 Volume 51(Issue 3) pp:636-641
Publication Date(Web):March 2011
DOI:10.1016/j.microrel.2010.09.028
Intermetallic compounds (IMCs) growth on the Sn–8Zn–3Bi (–Cr) solder joints with Cu and electroplated Ni substrates was investigated after aging at 150 °C. It was found that the IMCs were the Cu5Zn8 and Ni5Zn21 at the solder/Cu and solder/Ni interface, respectively. The IMCs growth rate at the Sn–8Zn–3Bi–Cr/Cu and Ni interface was slower than that at Sn–8Zn–3Bi/Cu interface (about 1/2 times) and Sn–8Zn–3Bi/Ni interface (about 1/4 times) during aging. The reason may be that Cr reacts with Zn and forms the Sn–Zn–Cr phase which block the diffusion of Zn atom to the interface and slow down the IMCs growth rate.
Co-reporter:Wenyan Gen, Xi Chen, Anmin Hu, Ming Li
Microelectronics Reliability 2011 Volume 51(Issue 4) pp:866-870
Publication Date(Web):April 2011
DOI:10.1016/j.microrel.2010.10.010
It was found that trace Ag on surface has great effect on the oxidation failure of Cu-base lead frame. Trace Ag on the surface increases its peeling resistance in dry condition, while decreases that under hygrothermal aging treatment. The oxide thickness, morphology and compositions were examined to understand the key factor of peeling of oxide film. It becomes evident that Ag has ability to block the diffusion of copper atoms, and so hold back the oxidation of copper. But adhesive strength between copper and oxide layer has little relation with oxide thickness but more important influence comes from internal compressive stress which has great relations with initial structure of the copper lead frame.
Co-reporter:Jing Hu;Tingbi Luo;Ming Li;Dali Mao
Journal of Electronic Materials 2011 Volume 40( Issue 7) pp:1556-1562
Publication Date(Web):2011 July
DOI:10.1007/s11664-011-1650-9
Electrochemical corrosion behaviors of Sn-9Zn-3Bi-xCr solder in 3.5 wt.% NaCl solution were investigated in this work through potentiodynamic polarization measurements. After electrochemical testing, fracture surfaces were investigated by scanning electron microscopy, energy-dispersive x-ray spectroscopy, and x-ray diffractometry. The results show that adding a small amount of Cr can improve the corrosion resistance of Sn-9Zn-3Bi-xCr solder. The corrosion potential of Sn-9Zn-3Bi solder is −1.251 V. For Sn-9Zn-3Bi-0.5Cr solder, it is −1.200 V. The corrosion potential increased when raising the Cr content, and the Sn-9Zn-3Bi-0.5Cr solder showed the best corrosion resistance. After polarization, a passivation film covered the surface of the Cr-bearing solders. The higher the Cr content, the more compact the passivation film. Long-term aging worsened the corrosion resistance. After 4 days of aging, the corrosion potential of Sn-9Zn-3Bi solder was −1.254 V. After 9 days, it was −1.268 V.
Co-reporter:Jin Hu, Anmin Hu, Ming Li, Dali Mao
Materials Characterization 2010 Volume 61(Issue 3) pp:355-361
Publication Date(Web):March 2010
DOI:10.1016/j.matchar.2009.12.019
In this paper, the effect of 0.1 wt.% Cr addition into Sn–9Zn lead-free solder alloys on the growth of intermetallic compound (IMC) with Cu substrate during soldering and subsequent isothermal aging was investigated. During soldering, it was found that 0.1 wt.% Cr addition did not contribute to forming the IMC, which was verified as the same phase structure as the IMC for Sn–9Zn/Cu. However, during solid-state isothermal aging, the IMC growth was remarkably depressed by 0.1 wt.% Cr addition in the Sn–9Zn solder, and this effect tended to be more prominent at higher aging temperature. The activation energy for IMC growth was determined as 21.2 kJ mol− 1 and 42.9 kJ mol− 1 for Sn–9Zn/Cu and Sn–9Zn–Cr/Cu, respectively. The reduced diffusion coefficient was confirmed for the 0.1Cr-containing solder/Cu. Energy-dispersive X-ray mapping and point analysis also showed ZnCr phase existing in solder matrix, which can reduce diffusion rate of Zn atoms.
Co-reporter:Anmin Hu, Ming Li, Dali Mao
Materials Characterization 2009 60(12) pp: 1529-1533
Publication Date(Web):
DOI:10.1016/j.matchar.2009.09.001
