Adhesion testing of glass-ceramic thick films on metal substrates

The adhesion of thick glass-ceramic films bonded to metal substrates was measured using five different tests: tensile delamination using a bonded stud, scratch testing, an interfacial shear test, indentation and a bend test. All the tests proved to have limitations, and no test gave a fully quantitative measure of adhesion. However, the different tests did rank the samples in the same order of adhesion strength. This indicates that although a fully quantitative method of testing the adhesion of thick films has not yet been developed, many of the published tests can be used to obtain qualitative data.     

Adhesion strength of silver thick-film conductors by solder-free test

Adhesion of silver thick-film conductors to alumina substrates was studied by a solderless testing method, in which alumina substrates were bonded with a silver thick-film and pulled vertically under a constant strain rate to fracture. The fracture behaviour was studied on thick films prepared under different conditions, and the effect of microstructure on the adhesion strength was studied. A new parameter has been introduced for evaluating the resistance to crack propagation. Hence, microstructural requirements for high adhesion strength thick films have been proposed. The adhesion strength data of silver thick films have been best described by a log-normal distribution function. This revised version was published online in November 2006 with corrections to the Cover Date.     

Effect of inorganic binders on the properties of silver thick films

The technology for realizing conductive thick films from metal powders is of considerable importance in the manufacture of various electronic devices, such as hybrid integrated circuits, multilayer ceramic capacitors, three-dimensional circuits for mobile communication, etc. Silver thick films have been extensively used to provide electrical contacts in silicon solar cells, hybrid circuits, and other devices, as they have the lowest resistivity as well as the lowest cost among the noble metals. Metal powders for thick-film pastes are normally obtained through chemical precipitation from an aqueous or organic solution of their corresponding salts. This method is able to provide the desired particle shape and size and also offers a low preparation cost. In this paper, we have reported the effect of inorganic binders on the properties of silver thick films. The thick-film pastes were formulated from specially treated silver powders and using the three different types of inorganic binders such as glass frit, metal oxides, and a mixture of both. The effect of these inorganic binders on the surface structure, adhesion with alumina, solderability, and electrical properties was determined by analyzing the physical and chemical behavior of the inorganic binders in the silver thick films during firing. The films with an addition of glass frit and mixtures of glass frit and metal oxide did not provide good adhesion and solderability simultaneously. However, the silver thick films containing 10 wt % bismuth oxides exhibited excellent characteristics, i.e. high adhesion strength, good solderability, and low sheet resistivity. As expected, the adhesion strength decreased with decrease in the binder content.     

Solid–liquid interdiffusion bonding between In-coated silver thick films

Solid–liquid interdiffusion (SLID) bonding between two pieces of In-coated silver thick films was investigated. The silver thick film was prepared by screen-printing of silver paste on an aluminum oxide substrate. Indium was coated in thickness ranging from 3 to 12 μm onto the silver thick films using thermal deposition (in vacuum). Two pieces of the In-coated thick films were placed in intimate contact (with a compressive stress of 0.04 MPa) and heated (at 180–250 °C) for various durations (600–3600 s) to undergo SLID bonding. Measurement of the bonding strength indicated that the SLID bond in 3-μm-In-coated thick-film couples is stronger than that in 8-μm-In-coated couples. X-Ray diffraction, scanning electron microscopy and electron probe microanalysis were used to analyze the bond. The stronger bond comprises a central zone of γ-Ag₂In sandwiched by two Ag films; the weaker bond comprises a central zone of AgIn₂ sandwiched by two layers of γ-Ag₂In. In the latter case, diffusion of excess indium from the coat into the interface between the silver film and alumina substrates is responsible for bond weakening. The development of microstructures in the SLID process for both strong and weak bonds is proposed.     

影响SiO2薄膜中银粒子发光强度的因素分析

用sol-gel法在玻璃表面制备了含银纳米粒子的二氧化硅薄膜。拍摄了银粒子的TEM照片。在室温下有拉曼光谱仪测定了样品的光致发光谱。研究了样品的光致光强度与纳米银的掺杂量、镀膜时的提拉速度和热处理之间的关系。     

影响SiO_2薄膜中银粒子发光强度的因素分析

用ｓｏｌ－ｇｅｌ法在玻璃表面制备了含银纳米粒子的二氧化硅薄膜．拍摄了银粒子的ＴＥＭ照片．在室温下用拉曼光谱仪测定了样品的光致发光谱．研究了样品的光致发光强度与纳米银的掺杂量、镀膜时的提拉速度和热处理温度之间的关系．     

Applying Anand model to low-temperature sintered nanoscale silver paste chip attachment

Tensile behaviors of low-temperature sintered films of a nanoscale silver paste used for chip-attachment are studied. Stress–strain curves of partially sintered films were measured at different temperatures and strain rates on a dynamic mechanical analyzer (DMA). The tensile strength of the sintered silver films decreased with increasing temperature or with decreasing strain rate. Then the uniaxial tensile inelastic deformation behaviors of the material were simulated by a unified visco-plastic constitutive model, Anand model. Finally, finite element simulation of chip-attachment using this interface material under thermal cycling was done with Anand model via ANSYS software. The simulation results showed that accumulation of plastic strain took place in the silver-bonding layer during thermal cycling, which might lead to the final failure of the chip-attachment.     

Evolution of surface plasmon resonance for silver particle film on mesoporous Si02 and soda-lime glass during heating in air and H2

Thin and thick Ag films on SiO2 substrates (mesoporous SiO2 and Soda-lime glass) were respectively prepared by thermal evaporation and spin-coating. The evolution of surface plasmon resonance absorption of the as-prepared samples was investigated when alternately heated in air and H2. It has been shown that the evolution behaviours were very different with Ag film thickness and substrates. The results were explained in terms of subtle difference of the two SiO2-based substrates in micro-structure or chemical composition, the redox of silver and relative Ag content.     

Preparation of micron size flake silver powders for conductive thick films

The preparation of micron size flake silver powders with chemical-mechanic method was investigated. Reaction of silver nitrate with ascorbic acid gives fine spherical silver powders. The spherical silver powders were processed by globe mill to make micron size flake silver powders having excellent dispersability and uniform shape. The XRD and thermal analyzer were employed to analyze as—prepared flake silver powders. The flake silver powders were employed to make polymer silver thick film and fire-type thick film. The application of small molecule surfactant in the stage of synthesizing precursor and large specific area of flake particles give a low resistivity of polymer thick film. The fire-type silver thick film was studied by SEM and EDX. SEM photograph shows that the grain boundaries of silver are prominently visible, and the densification of the fired thick film is high. The fire-type thick film has a low bulk resistivity and high adhesion strength.     

Electrical properties of silver paste prepared from nanoparticles and lead-free frit

Recently, PbO containing glass systems in commercial silver paste have been used due to their low glass transition temperature, good thermal and electrical properties. However, PbO is a hazardous material to both health and the environment. In this study, Pb-free silver paste was prepared by mixing commercial silver powder and silver nanoparticles. The commercial powder has an average particle size of 1.6 microm. The silver nanoparticles with particles size of 20-50 nm were synthesized by a chemical reduction method using surfactant. Pb-free frit was added into the mixed silver powder as the amounts of 3, 6 and 9 wt%. Using the obtained paste, thick films were fabricated by a screen printing on alumina substrate and the films were fired at temperature from 400 to 550 degrees C. The films had thickness of 6-11 microm and sheet resistivity of about 4-11 microomega cm.     

Tensile strain engineering of Si thin films using porous Si substrates

Highly tensile strained (up to 2.2%) thin monocrystalline silicon (mc-Si) films were fabricated by a simple and low-cost method based on the in-plane expansion of meso-porous silicon (PS) substrates upon low temperature oxidation. To control the film thickness below 100 nm, an original “two wafer” technique was employed during the porosification process. This method enables the fabrication of a 60 nm thick mc-Si films on 250 μm thick meso-porous silicon substrates over areas as large as 2 in. with a surface roughness and cleanliness comparable to that of standard Si wafers. Crack-free 60 nm thick Si films can be strained up to 1.2% by controlled low temperature oxidation of the PS substrate. Structural and strain analysis of the PS/mc-Si structures performed by transmission electron microscopy and micro-Raman scattering spectroscopy are reported.     

基于表面改性的国产T800碳纤维/高韧性环氧树脂复合材料胶接性能

本文通过打磨、喷砂、等离子处理方法对国产T800碳纤维/高韧性环氧树脂复合材料的待胶接面进行改性,分别制备了J-116B胶膜和J-375胶膜的浮辊剥离性能及拉伸剪切性能试验件。测试了不同处理条件下J-116B胶膜和J-375胶膜的剥离和剪切性能。采用SEM对老化前后、未经刻蚀和刻蚀后的剥离试样形貌进行观察。采用接触角测试仪测试了不同表面处理方法对国产T800碳纤维/高韧性环氧树脂复合材料胶接面润湿性的影响,并采用XPS光电子能谱分析仪对等离子处理前后的国产T800碳纤维/高韧性环氧树脂复合材料胶接面表面理化性能进行研究。结果表明:尽管J-375胶膜的室温剥离性能不如J-116B胶膜,但J-375胶膜具有更好的湿热老化性能。等离子处理后的国产T800碳纤维/高韧性环氧树脂复合材料的破坏模式由黏附破坏为主转变为内聚破坏为主,因此使两种胶膜的拉剪和剥离性能均有明显提高。这是由于等离子体处理能够重组复合材料表面的分子链,在胶接表面形成新的活性基团。      

Adhesion and vacuum forming properties of tin-zinc thin films deposited on polyester film substrate

Sn-Zn alloy thin films were deposited on a polyester (PET) film substrate by co-evaporation and evaluated their surface, tensile and adhesion properties with a vacuum forming test and pull test.Relationship between the surface roughness and elemental composition of these thin films was evaluated. The surface roughness decreased with increase of the Sn content.The tensile property was estimated by observations of micro-cracks of the thin films due to a vacuum forming test. Sn-Zn alloy thin film, whose elemental composition is 85:15 (wt%), had high vacuum forming durability.The adhesion strength between the Sn-Zn alloy thin films and PET substrate was measured with a pull test apparatus. The pull strength decreased with increase of the Sn content.     

纳米银晶粒镶嵌氧化硅薄膜的光致发光

用SOL GEL法在浮法玻璃表面制备了掺杂纳米银晶粒的二氧化硅薄膜。在室温下测定了其可见光透过率和光致发光谱。研究了样品的光致发光强度与纳米银的掺杂量、镀膜时的提拉速度和热处理温度之间的关系     

Tungsten film as a hard and compatible carrier for antibacterial agent of silver

Silver-containing tungsten (W–Ag) films for antibacterial applications were deposited on glass, silicon, and 316L stainless-steel substrates by magnetron sputtering with the silver target current of 0–2.0 A. The addition of silver improves adhesion of the films on glass substrate due to the reduced residual stress in the films. SEM and EDX analyses reveal Ag-rich tiny dots (~?20 nm) at the surface of W–Ag films with high silver contents. In XRD patterns, silver peaks are present for the samples deposited at 1.5 and 2.0 A, and tungsten grain size is decreased from?~?23 to 10 nm by silver addition. XPS analysis shows that tungsten is slightly oxidized (WO₃) at the top surface of the film, and silver presents mainly in metallic state. The low Ag/W ratios and the small surface roughness (<?8 nm) indicate that silver segregation at the film surface is not obvious. Microhardness of the samples with ≤?6.7 at.% silver is nearly seven times that of the stainless steel (~?250 HV). The coated samples are hydrophobic tested by contact angle measurement. The potentiodynamic polarization and the soaking test simulating the inflammatory state show that even corrosion occurs and silver addition decreases corrosion resistance of the films. The antibacterial ratio of the coated samples increases with silver content, being 91% at 4.2 at.% silver content tested by agar plate counting method. In agar disk diffusion assay, no inhibition zone is observed for all samples. The antibacterial property of the W–Ag films is localized, long-lasting, and reusable, which would be beneficial for their potential biomedical and environmental applications.     

Camphor‐Enabled Transfer and Mechanical Testing of Centimeter‐Scale Ultrathin Films

Camphor is used to transfer centimeter‐scale ultrathin films onto custom‐designed substrates for mechanical (tensile) testing. Compared to traditional transfer methods using dissolving/peeling to remove the support‐layers, camphor is sublimed away in air at low temperature, thereby avoiding additional stress on the as‐transferred films. Large‐area ultrathin films can be transferred onto hollow substrates without damage by this method. Tensile measurements are made on centimeter‐scale 300 nm‐thick graphene oxide film specimens, much thinner than the ≈2 μm minimum thickness of macroscale graphene‐oxide films previously reported. Tensile tests were also done on two different types of large‐area samples of adlayer free CVD‐grown single‐layer graphene supported by a ≈100 nm thick polycarbonate film; graphene stiffens this sample significantly, thus the intrinsic mechanical response of the graphene can be extracted. This is the first tensile measurement of centimeter‐scale monolayer graphene films. The Young's modulus of polycrystalline graphene ranges from 637 to 793 GPa, while for near single‐crystal graphene, it ranges from 728 to 908 GPa (folds parallel to the tensile loading direction) and from 683 to 775 GPa (folds orthogonal to the tensile loading direction), demonstrating the mechanical performance of large‐area graphene in a size scale relevant to many applications.     

Long-range surface plasmon polariton waveguides containing very thin spin-coated silver films

We fabricated very thin solid silver films with thicknesses below 50 nm using a spin coating method. An aqueous silver ionic complex solution was spin-coated and then thermally cured for a few minutes at a low temperature. The properties of the spin-coated silver films were compared to the properties of silver films deposited by thermal evaporation. The spin-coated thin silver films possessed silver crystallinity and a surface roughness of ~ 2.83 nm, while the thermally evaporated thin silver films also possessed silver crystallinity with a surface roughness of ~ 2.44 nm. Long-range surface plasmon polariton (LR-SPP) waveguides fabricated by both spin coating and thermal evaporation were also characterized and compared. The propagation losses of the 23 nm thick spin-coated and the 19 nm thick evaporated LR-SPP waveguides with strip widths of 7 μm were 3.6 and 4.2 dB/cm, respectively, and their coupling losses were 1.4 and 1.0 dB/2facets, respectively. The use of the spin coating method is a very cost effective solution because the films can be formed at low temperature in a short period of time without requiring a vacuum system. In addition, there are many potential applications of using spin-coated very thin solid silver films in LR-SPP waveguides and nano electrical circuit patterns.     

Experimental analysis of the strength of silver–alumina junction elaborated at solid state bonding

The mechanisms of ceramics–metal assemblies, particularly silver and alumina, can be better understood by studying the strength of their adhesion. These two materials are a priori non-reactive, their thermodynamic work of adhesion is low and the difference between their thermal coefficients of expansion in very considerable. In this study, the strength of silver–alumina junctions elaborated at solid state by thermo-compression is tested by an indirect tensile test and shearing one. The effects of several parameters such as: the pressure of bonding, the time of bonding, the temperature, and the oxygen dissolve in metal solid solution on the strength of the junction are analyzed. The obtained results show that the resistance of the junction is affected by all this parameters and it is essential to optimize these different parameters in order to increase the durability of the junction. It was also shown that the diffusion of the silver in alumina could be the cause of the damage of alumina near the interface.     

Al／PET和Cu／PET蒸镀膜包装材料附着力及微观结构的研究

利用真空镀方法在聚酯(PET)薄膜上沉积Al(Cu),制得Al/PET(Cu/PET)复合薄膜包装材料。用直接牵引拉伸法和划痕法测定这两种薄膜的附着力,获得其附着力与蒸镀条件(真空度、温度、蒸发时间)的规律;用扫描电镜(SEM)观察镀层微观结构,得到镀层晶粒度与蒸镀条件的对应关系;用金相显微镜测量镀层厚度,获得镀层厚度与时间的对应关系。     

Characterization of single crystal silicon and electroplated nickel films by uniaxial tensile test with in situ X-ray diffraction measurement

In this study, mechanical properties of micron‐thick single crystalline silicon (Si) and electroplated nickel (Ni) films at intermediate temperatures are investigated by means of X‐ray diffraction (XRD) tensile testing. The developed tensile test technique enables us to directly measure lateral (out‐of‐plane) elastic strain of microscale crystalline specimen using XRD during tensile loading, and determines Young's modulus, Poisson's ratio and tensile strength of the Si and Ni specimens. The specimens, measuring 10 μm thick, 300 μm wide and 3 mm long, are prepared through a conventional micro‐machining process, and the ultraviolet lithographie galvanoformung abformung (UV‐LIGA) process including a molding and an electroplating. The Si specimens, showing brittle fracture at room temperature (R.T.), have average Young's modulus and Poisson's ratio of 169 GPa and 0.35, respectively, in very good agreement with analytical values. The Ni specimens, showing ductile fracture, have those of 190 GPa and 0.24, lower than bulk coarse grained Ni. Young's moduli of both the Si and Ni specimens decrease with increasing temperature, but Poisson's ratios are independent of temperature. The influence of specimen size on elastic‐plastic properties of the specimens is discussed.