Co-reporter:Hongbin Wang, Ning Wang, Tao Hang, Ming Li
Applied Surface Science 2016 Volume 372() pp:7-12
Publication Date(Web):30 May 2016
DOI:10.1016/j.apsusc.2016.02.146
Highlights
- •
A 3D porous micro-nano hierarchical structure Cu films were prepared.
- •
The evolution of morphology and wettability with deposition time was reported.
- •
The effects of EDA on the microscopic morphology were revealed.
- •
A high contact angle of 162.1° was measured when deposition time is 5 s.
- •
The mechanism of super-hydrophobicity was illustrated by two classical models.
Co-reporter:Junhong Zhang, Junyan Cai, Ming Li
Applied Surface Science 2016 Volume 386() pp:309-318
Publication Date(Web):15 November 2016
DOI:10.1016/j.apsusc.2016.06.008
Highlights
- •
PMMA brushes were covalently bonded to Cu surface by a simple polymerization method.
- •
The one-step method was carried out in aqueous solvent at room temperature and open air condition.
- •
The PMMA brushes/micro-cone structured Cu surface exhibited superhydrophobicity after treated with acetone.
- •
The superhydrophobic surface had good stability in acidic environment and in six months storage.
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:Junhong Zhang, Ming Li, Wenqi Zhang, and Liqiang Cao
Langmuir 2016 Volume 32(Issue 34) pp:8709-8716
Publication Date(Web):July 21, 2016
DOI:10.1021/acs.langmuir.6b01931
A facile and one-pot dipping method was proposed in this article for the first time to prepare vinylic polymer films on a silicon (Si) surface. This novel process was conducted in acidic aqueous media containing 4-nitrobenzene diazonium (NBD) tetrafluoroborate, hydrofluoric acid (HF), and vinylic monomers at room temperature in the open air and without any apparatus requirement. The formation of the polyvinyl film was confirmed by corroborating evidence from ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscope (AFM) analysis. The results revealed that both polymers of poorly water soluble methyl methacrylate (MMA) and water-soluble acrylic acid (AA) monomers were covalently grafted onto the Si surface via this simple process. The polyvinyl film was composed of polynitrophenyl (PNP) and polyvinyl, where PNP was doped into polyvinyl chains throughout the entire film. From a mechanistic point of view, the simple dipping method took advantage of the ability of the NBD cation to be spontaneously reduced at the Si surface at open circuit potential, providing aryl radicals. These radicals can be covalently bonded to the Si surface to form the PNP primer layer. Although the PNP sublayer was thinner and difficult to detect, it was necessary to graft polyvinyl chains. Furthermore, the aryl radicals were used to initiate the polymerization of vinylic monomers. The radical-terminated polyvinyl chains formed in the solution were then added to the aromatic rings of the primer layer to form the expected polyvinyl film.
Co-reporter:Junhong Zhang and Ming Li
Langmuir 2016 Volume 32(Issue 15) pp:3746-3753
Publication Date(Web):March 29, 2016
DOI:10.1021/acs.langmuir.6b00343
Covalent grafting of a homopolymer film onto a p-Si(100) surface was performed by use of surface electroinitiated emulsion polymerization. This polymerization method was one-step and cost-effective, and worked in the aqueous dispersed media containing both nitrobenzenediazonium (NBD) tetrafluoroborate and methyl methacrylate (MMA) monomer. NBD was reduced in the vicinity of substrate at the cut-on voltage of the pulsed voltage and was successively grafted on a Si surface, leading to a polynitrophenyl (PNP) layer. The reduction of NBD simultaneously initiated the polymerization of MMA. The resulting PMMA macroradicals in the solution can react with the previously grafted PNP at the cutoff voltage of the pulsed voltage for thickening the polymer film. The prepared polymer layer completely covered the Si surface, as investigated by the scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. Importantly, chemical components and the thickness of the grafted polymer film were well controlled by the applied voltage and the charge flow passing through the Si electrode. X-ray photoelectron spectroscopy (XPS) measurement further confirmed the Si–C bond between the polymer layer and the Si substrate. The homopolymer film was extremely effective in protecting the underlying Si from atmospheric oxidation.
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:Junhong Zhang, Wei Luo, Yi Li, Liming Gao, Ming Li
Applied Surface Science 2015 Volume 359() pp:736-741
Publication Date(Web):30 December 2015
DOI:10.1016/j.apsusc.2015.10.214
Highlights
- •
Vacuum pretreatment was used to enable the electrolyte permeating the via.
- •
The via was properly wetted by deionized water with lower temperature.
- •
A model was proposed to describe the wetting process.
- •
Void-free copper filling in TSVs was achieved by vacuum pretreatment.
Co-reporter:Xiu Mo, Yunwen Wu, Junhong Zhang, Tao Hang, and Ming Li
Langmuir 2015 Volume 31(Issue 39) pp:10850-10858
Publication Date(Web):September 21, 2015
DOI:10.1021/acs.langmuir.5b02472
Inspired by the self-cleaning of cicada wings, well-aligned Au-coated Ni nanocone arrays (Au@Ni NAs) have been fabricated by a simple and cheap electrodeposition method. After surface modification of n-hexadecanethiol, self-cleaning can be realized on this long-lived superhydrophobic surface with extremely low adhesive force. Switchable adhesion is obtained on its complementary porous surface. The porous Au structure is fabricated by a geometric replica of the nanocone arrays. After the same surface modification, it shows superhydrophobicity with high adhesion. The different adhesive behaviors on the two lock-and-key Au structures are ascribed to their different contact modes with a water droplet. Combining the superhydrophobic properties of the two complementary structures, they can be used to transport precious microdroplets without any loss. The bioinspired periodic Au@Ni NAs can also be potentially employed as surface-enhanced Raman scattering (SERS) substrates due to its electromagnetic enhancement effect, especially at the tips of the nanocones. Thus, superhydrophobic, SERS, long-lived, self-cleaning, microtransportation functions are realized on the basis of the two surfaces.
Co-reporter:Yunwen Wu, Tao Hang, Zheyin Yu, Lan Xu and Ming Li
Chemical Communications 2014 vol. 50(Issue 61) pp:8405-8407
Publication Date(Web):12 Jun 2014
DOI:10.1039/C4CC03878A
Lotus leaf-like and petal-like substrates were fabricated by chemical deposition, which have quite different superhydrophobic properties. Excellent, non-sticky, self-cleaning and durable properties were obtained based on the lotus leaf-like substrate.
Co-reporter:Haiyong Cao, Tao Hang, Huiqin Ling, Wei Luo, Xue Feng, Ming Li
Microelectronic Engineering 2014 Volume 116() pp:1-5
Publication Date(Web):25 March 2014
DOI:10.1016/j.mee.2013.11.011
•A new kind of chip with a special TSV structure was used in this paper.•ANSYS® was used to simulate the overall electric field distribution.•Simulation and electroplating shows bottom-up filling of conventional TSV.•Deposition of special TSV is mainly controlled by the electric field distribution.The filling mechanism of a special through silicon vias (TSV) structure is investigated by electrochemical test and simulation technique compared with the conventional TSV structure in this paper. The effects of additives in methanesulfonic solution are briefly studied by cyclic voltammetry to obtain the suitable copper plating condition for conventional TSV. The electric field distribution in the special TSV during the electrodeposition has been simulated by the software ANSYS. Different from the conventional TSV, the electric field gathered at the bottom of the via in the initial stage of special TSV, which benefit the bottom up filling in the via. And after the deposited copper spread to the whole surface of the chip, the electric field distribution becomes similar to the conventional TSV. With the help of the additives, the void free copper electrodeposition in special TSV was finally achieved.
Co-reporter:Rui Guo, Liming Gao, Dali Mao, Ming Li, Xu Wang, Zhong Lv, Hope Chiu
Microelectronics Reliability 2014 Volume 54(Issue 11) pp:2550-2554
Publication Date(Web):November 2014
DOI:10.1016/j.microrel.2014.04.005
•The EFO current was the key factor to influence the Ag–8Au–3Pd alloy FAB size and morphology.•Mechanisms of FAB defects including off-center and ripple formation were discussed by solidification process.•A medium flow rate was suitable for Ag–8Au–3Pd alloy FAB formation.•Under the protection of shielding gas, oxidation and sulfuration of the Ag–8Au–3Pd alloy FAB were effectively prevented.An innovative Ag–8Au–3Pd alloy wire has been developed as an alternative to the traditional gold wire bonding. This paper focused on the free air ball (FAB) formation of 0.7 mil Ag–8Au–3Pd alloy wire, which was vital for the yield of the subsequent bonding process. During electric flame-off (EFO) process, the wire tail was melted by a high voltage spark, and then the FAB was shaped by the effects of surface tension and gravity. The EFO current was the key factor to influence the Ag–8Au–3Pd alloy FAB size and morphology due to the energy input via arc discharging. The defects including off-center and ripple appeared on the Ag–8Au–3Pd alloy FABs were discussed by cooling and solidification. It is suggested that low EFO current will effectively avoid FAB defects. The contaminants on the Ag–8Au–3Pd alloy FAB surface were analyzed by Auger electron spectroscopy (AES). Under the protection of the shielding gas, oxidation and sulfuration have been effectively prevented.
Co-reporter:Yunwen Wu, Tao Hang, Ning Wang, Zheyin Yu and Ming Li
Chemical Communications 2013 vol. 49(Issue 88) pp:10391-10393
Publication Date(Web):11 Sep 2013
DOI:10.1039/C3CC45592K
Non-sticky and highly adhesive superhydrophobic microball-nanosheet hierarchically structured silver films were obtained after surface modification and storage respectively.
Co-reporter:Qinghua Zhao, Anmin Hu, Ming Li, Jiangyan Sun
Microelectronics Reliability 2013 Volume 53(Issue 2) pp:321-326
Publication Date(Web):February 2013
DOI:10.1016/j.microrel.2012.08.010
In this paper, Sn–3.5Ag solder bumps were prepared using multilayer electroplating method. The effect of electroplating layer structure (Sn/Ag, Ag/Sn, Ag/Sn/Ag) on shear property and microstructure of solder bumps was investigated.Shear test revealed that Sn/Ag bumps displayed the highest shear strength among different electroplating layer structures, which was 89.3% higher than that of pure Sn bumps, and 43.5% higher than that of Ag/Sn bumps. The interfacial microstructure evolution during reflowing process was also observed. It was found that Cu6Sn5 intermetallic compound formed at the interface between solder and Cu and its grain size increased as reflow time increased for all three electroplating structures. When there was Ag electroplated between Sn and Cu (Ag/Sn/Ag and Ag/Sn structures), the morphology of Cu6Sn5 was thin, hexagonal and scattered, which could be attributed to the adsorption of Ag3Sn on the surface of Cu6Sn5. In contrast, when Sn was electroplated on Cu directly (Sn/Ag structure), the morphology of Cu6Sn5 was thick, rod-like and continuous, which displayed high shear strength.Highlights► Multilayer electroplating, as a novel method, is proposed to form alloy bumps. ► The comparison between different electroplating layer structures is discussed. ► Sn/Ag structure shows the highest shear strength with smooth Cu6Sn5 IMC layer. ► The morphology of IMC layer at the interface is influenced by electroplating orders.
Co-reporter:Qinghua Zhao, Zhuo Chen, Anmin Hu, Ming Li
Microelectronic Engineering 2013 Volume 106() pp:33-37
Publication Date(Web):June 2013
DOI:10.1016/j.mee.2013.01.055
A novel method, multilayer electroplating, was proposed to prepare alloy bumps. It consists to electroplating different structural elements of alloys sequentially and then forming uniform alloy through reflowing. The formation of eutectic SnAg alloy bumps was taken as an example to verify the applicability of the method in this study.Near-eutectic SnAg solder bumps were formed successfully through multilayer electroplating. After reflowing for 1 min at 250 °C, SnAg alloy with homogeneous structure and composition was obtained from multilayer structure. Fine Ag3Sn particles with uniform distribution were precipitated inside the solder and Cu6Sn5 intermetallic compounds (IMCs) in scallop-like shape formed at the SnAg solder/Cu interface. As reflow time increasing, the morphology of Ag3Sn remained unchanged but the thickness of Cu6Sn5 layer increased. The characteristic of multilayer electroplated SnAg solder bumps was similar to that of traditional alloy, which indicated that it was a suitable method to form SnAg alloy solder bumps.Graphical abstractHighlights► A novel method, multilayer electroplating, was proposed to form alloy bumps. ► The method had precise control of composition ratio and simple processing technique. ► After reflowing, SnAg bumps with homogeneous structure and composition were obtained.
Co-reporter:Wenjing Zhang, Xue Feng, Haiyong Cao, Anmin Hu, Ming Li
Applied Surface Science 2012 Volume 258(Issue 22) pp:8814-8818
Publication Date(Web):1 September 2012
DOI:10.1016/j.apsusc.2012.05.096
Abstract
Cu–Ni–P films with different morphologies were fabricated via electroless deposition route, due to the crystalline modification of polyethylene glycol (PEG). Effect of PEG molecular weight on morphology and structure of Cu–Ni–P films were investigated by field emission scanning electron microscopy and X-ray diffractometer. SEM observation reveals that electrolytes containing PEG 2000, 10000 and 20000, respectively can result in the formation of three kinds of unique architectures: pyramid with star-shaped cross section, cone and column. As PEG molecular weight increases, volume of the as-prepared microstructures increases but density decreases. The XRD pattern indicates the Cu–Ni–P coating is well-crystallized and preferred orientation formed in electrolyte without PEG, with PEG 2000, PEG 10000 and PEG 20000 are (1 1 1), (2 2 0), (1 1 1) and (1 1 1), respectively. Based on the proposition that properties of materials were affected by their size and morphology, wettability of the as-prepared Cu–Ni–P films were investigated. The hydrophobicity of coating deposited with PEG 2000 reached a climax exhibiting a contact angle of 123.8°.
Co-reporter:Wenjing Zhang, Zheyin Yu, Zhuo Chen, Ming Li
Materials Letters 2012 Volume 67(Issue 1) pp:327-330
Publication Date(Web):15 January 2012
DOI:10.1016/j.matlet.2011.09.114
Micro-nano hierarchical structured Cu/Ni multilayer coating was prepared by a simple two-step method combined with electroless and electro deposition. Structure and morphology of the as-prepared Cu/Ni multilayer coating were analyzed by X-ray diffractometer and field emission scanning electron microscopy. Results show that micro-nano Cu/Ni coating is well-crystallized and exhibits sea cucumber-like microstructure with Ni nanocone arrays uniformly dispersed perpendicular to the circular conical surface of Cu cone. Static contact angles were measured to investigate the surfaces' wettability. The result reveals that the Cu/Ni multilayer coating is super-hydrophobic, of which the static contact angle with test liquid (water) was 156°(> 150°).Due to its super-hydrophobic property and unique shape, Cu/Ni multilayer coating is expected to have extensive practical applications.Highlights► We created a two-step method to fabricate hierarchical Cu/Ni coating. ► Novel Cu/Ni coating consists of Cu cones ~5 μm high and Ni nano-cone array ~500 nm high. ► Cu/Ni coating exhibits super-hydrophobic property. ► It is expected to have extensive applications.
Co-reporter:Mingzhi Ni, Ming Li, Dali Mao
Microelectronics Reliability 2012 Volume 52(Issue 1) pp:206-211
Publication Date(Web):January 2012
DOI:10.1016/j.microrel.2011.07.095
The weak adhesion between the Epoxy Molding Compound (EMC) and Pd Preplated leadframes (Pd PPF’s) often causes delaminations and reduces the reliability of integrated circuit. This paper reports on a practical method of dramatically improving the adhesion between EMC and Pd PPF’s using electroplating of shaped nickel layers. Button shear tests indicate that the adhesions between the EMC and three different shaped PPF’s are 100%, 160%, 169% higher than that of conventional PPF’s. The mechanical interlocking effect caused by increased surface roughness is the major reason for the improved adhesion as well as for the failure mode transition from adhesive failure to cohesive failure.Highlights► 3 shaped PPF electroplated. ► EMC–PPF adhesion improved by 169%. ► Interlocking caused the improvement. ► Adhesive failure changed to cohesive.
Co-reporter:Wenjing Zhang, Wei Luo, Anmin Hu, Ming Li
Microelectronics Reliability 2012 Volume 52(Issue 6) pp:1157-1164
Publication Date(Web):June 2012
DOI:10.1016/j.microrel.2011.12.024
For microelectronic industry, Cu-based substrate and epoxy molding compound (EMC) interface is inherently weak and most likely to delaminate, well-known as a major threat for integrated circuits (ICs) reliability. In this paper, hierarchical whisker-like oxide/Cu cone structure was for the first time to be fabricated by combining electroless plating with heat treatment methods to enhance the interface adhesion between Cu-based substrate and EMC. The surface morphology was characterized by scanning electron microscope (SEM). Result shows that the hierarchical whisker-like oxide/Cu cone film is fine, dense and uniform; Single Cu cone structure is about 3–5 μm in height and 1 μm in root diameter; a layer of whisker-like oxide grows perpendicularly to circular surface of Cu cone, with length ranging from tens to hundreds of nanometers. Adhesion strength between the as-prepared substrates and EMC were measured by button shear test. With consideration of oxidation caused by practical processes (e.g. wire bonding), the interface of EMC and porous oxide formed at 260 °C for 5 min was taken as standard sample, representative of practical interface. To further study the effect of whisker-like oxide and Cu cone solely on adhesion performance, whisker-like oxide, porous oxide/Cu cone were investigated as well. Button shear test results reveal that interfacial adhesion strength of EMC and whisker-like oxide, porous oxide/Cu cone, hierarchical whisker-like oxide/Cu cone are 85%, 110% and 162% higher than that of standard interface. Moreover, the mechanism for adhesion improvement was discussed by facture surface observation, failure path assumption and force–displacement curve analysis. Results show that interface of EMC and hierarchical whisker-like oxide/Cu cone exhibits brittle/ductile property with about 3–5 μm thick EMC left on the fracture surface, indicating cohesive failure caused by remarkable mechanical interlocking effect.Highlights► Whisker/Cu cone was fabricated by electroless plating and heat treatment. ► EMC and whisker/Cu cone exhibits the best state of adhesion performance. ► It is attributed to mechanical interlocking effect caused by whisker and Cu cone.
Co-reporter:Yunwen Wu, Tao Hang, Ning Wang, Zheyin Yu and Ming Li
Chemical Communications 2013 - vol. 49(Issue 88) pp:NaN10393-10393
Publication Date(Web):2013/09/11
DOI:10.1039/C3CC45592K
Non-sticky and highly adhesive superhydrophobic microball-nanosheet hierarchically structured silver films were obtained after surface modification and storage respectively.
Co-reporter:Yunwen Wu, Tao Hang, Zheyin Yu, Lan Xu and Ming Li
Chemical Communications 2014 - vol. 50(Issue 61) pp:NaN8407-8407
Publication Date(Web):2014/06/12
DOI:10.1039/C4CC03878A
Lotus leaf-like and petal-like substrates were fabricated by chemical deposition, which have quite different superhydrophobic properties. Excellent, non-sticky, self-cleaning and durable properties were obtained based on the lotus leaf-like substrate.
![4-Benzoxazolecarboxylicacid,5-(methylamino)-2-[[(2R,3R,6S,8S,9R,11R)-3,9,11-trimethyl-8-[(1S)-1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-](http://img.cochemist.com/ccimg/52700/52665-69-7.png)
![4-Benzoxazolecarboxylicacid,5-(methylamino)-2-[[(2R,3R,6S,8S,9R,11R)-3,9,11-trimethyl-8-[(1S)-1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl]-1,7-dioxaspiro[5.5]undec-2-yl]methyl]-](http://img.cochemist.com/ccimg/52700/52665-69-7_b.png)
