Wetting Force Measurements Research Articles

Industrial Soldering Process Simulator

Determination of the physico-chemical interactions between liquid and solid substances is a key technological factor in many industrial processes in metallurgy, electronics or the aviation industry, where technological processes are based on soldering/brazing technologies. Understanding of the bonding process, reactions between materials and their dynamics enables to make research on new materials and joining technologies, as well as to optimise and compare the existing ones. The paper focuses on a wetting force measurement method and its practical implementation in industrial applications. Soldering simulation is a process in which simulation tools are used to model and simulate soldering processes. With simulation, different soldering methods and parameters can be tested to identify the best approach and minimize the risk of errors and failures in the real process. Soldering simulation can be used to optimize the soldering process and increase productivity, as well as to train personnel.

Comment on: “Reactive wetting of solders on Cu and Cu6Sn5/Cu3Sn/Cu substrates using wetting balance”

In this contribution, as comments to the paper in Scripta Materialia, Volume 55, Issue 9, Pages 823-826, November 2006, will be shown that the residual force marked as Fd is not correctly described. This residual force is recorded during wetting force measurement by wetting balance method, and it was wrongly used as a part of withdrawal force Fwd. The correct relation between residual force Fd and withdrawal force Fwd will be explained more deeply in this comment.

Changes in the wettability of polymer electrolyte fuel cells components during cationic contamination and mitigation

Foreign cations are shown to cause mass transport losses, in particular due to wettability changes in the micro-porous layers (MPL) and the carbon paper substrate, and have a major impact on the durability and the performance of polymer electrolyte fuel cells. We studied the effects of cationic impurities on fuel cell system performance, especially on the water management by employing in-situ and ex-situ contamination methods. Changes in the wettability of the carbon paper surface following the in-situ contamination injection were quantified using the Wilhelmy plate method. The CaSO4 precipitation on the macro-pores of the carbon paper substrate after the contamination injection causes a higher wettability leading to increased flooding of the carbon paper substrate and consequent mass transport losses. An ex-situ cleaning with an acid solution is shown to be very effective in removing the salt deposits of the carbon paper substrate. During the mitigation, the highly hydrophobic MPL acts as a barrier to the transport of the recovery solution into the membrane-electrode assembly (MEA), therefore isopropanol (IPA) was added to both the contaminant solution and the recovery solution to increase the wettability of the MPL. Wetting force measurements confirm that the added IPA can alter the wettability of the MPL and can render it fully hydrophilic, enabling the transport of the recovery solution into the MEA.

Semi-Automatic Apparatus for Measuring Wetting Properties at High Temperatures

Abstract Determination of the physico-chemical interactions between liquid and solid substances is a key technological factor in many industrial processes in metallurgy, electronics or the aviation industry, where technological processes are based on soldering/brazing technologies. Understanding of the bonding process, reactions between materials and their dynamics enables to make research on new materials and joining technologies, as well as to optimise and compare the existing ones. The paper focuses on a wetting force measurement method and its practical implementation in a laboratory stand – an integrated platform for automatic wetting force measurement at high temperatures. As an example of using the laboratory stand, an analysis of Ag addition to Cu-based brazes, including measurement of the wetting force and the wetting angle, is presented.

Surface modification of PET films by atmospheric pressure plasma exposure with three reactive gas sources

The surface modification of poly (ethylene terephthalate) (PET) film was carried out using an atmospheric pressure plasma (APP) jet device with three reactive gases: air, N2, and Ar. The water contact angles on the PET film were found to decrease considerably after the APP exposure. The changes in the advancing and receding contact angles of water on the APP-exposed PET film with aging time were examined by the wetting force measurements employing the Wilhelmy method. The hydrophobic recovery due to the rinsing with water as well as the aging in air was observed only for the advancing angle, which was probably caused by the dissolution of low molecular weight oxidized materials into water, the loss of volatile oxidized species to the atmosphere and the reorientation and the migration of polymer chains. The wettability and the surface free energy of the APP-exposed PET film after diminishing hydrophobic recovery was sufficiently large compared with the untreated film. X-ray photoelectron spectroscopy confirmed that the PET film surface was oxidized due to the APP exposure. When N2 gas was used for the APP exposure, the surface nitrogen concentration was found to increase with decreasing D. The surface oxygen concentration on the APP-exposed PET film was reduced by rinsing with water, in accordance with the hydrophobic recovery behavior. From atomic force microscopy, surface topographical change due to the APP exposure was observed. The changes in the PET surface properties due to the APP exposure as mentioned above were remarkable for using N2 gas.

Single Fiber Wettability in PET Fibrous Assembly Exposed to Atmospheric Pressure Plasma

Poly (ethylene terephthalate), PET, fibrous assembly was treated by atmospheric pressure plasma (APP) jet with three different reactive gas sources, air, nitrogen and argon. The change in the wettability of single fiber surface due to the treatment was determined by the wetting force measurement with moving the fiber/water/air three-phase boundary. Both advancing and receding contact angles of water on the PET fiber decreased considerably by the APP treatment, even if the hydrophobic recovery of the treated fiber surface after the aging in air and rinsing with water was taken into consideration. The contact angles on a treated single fiber surface showed periodic variation along the fiber axis, indicating that the fiber surfaces were not treated uniformly because of fiber crimps due to the structure of the fibrous assembly. The water wicking into the capillaries of the fibrous assembly was promoted after the APP treatment, in good agreement with single fiber wettability. From X-ray photoelectron spectroscopy and atomic force microscopy, the oxygen concentration and the roughness on the PET fiber surface were found to enhance after the APP treatment. The above changes in the surface properties of a single fiber were remarkable for using nitrogen as a reactive gas.

Wettability characteristics of poly(ethylene terephthalate) films treated by atmospheric pressure plasma and ultraviolet excimer light

Two dry processes, atmospheric pressure plasma (APP) exposure and 172 nm ultraviolet (UV) excimer light irradiation, were carried out to enhance the hydrophilic nature of poly(ethylene terephthalate) (PET) film. The wettability change in the PET film surface after the processes were carried out was recorded by the wetting force measurements employing the Wilhelmy method. After the dry processes, drastic decreases in the advancing and receding contact angles of water were observed, especially for the APP exposure. The advancing angle on the treated PET surface was found to increase by rinsing with water or aging in air, whereas the receding one remained almost the same. The hydrophobic recovery diminished more rapidly for the UV-treated film. Surface characterizations of the PET film were performed. We discuss the influence of the dry processes on the physicochemical properties of the PET surface.

Determination of reactive wetting properties of Sn, Sn–Cu, Sn–Ag, and Sn–Pb alloys using a wetting balance technique

Wetting properties of lead-free solders, Sn–0.7 wt.% Cu and Sn–3.5 wt.% Ag, pure Sn, and conventional Sn–40 w.t% Pb on Ni, Cu, and Ag substrates at 250 and 240 °C were determined by using a wetting balance technique. Wetting times and wetting forces were determined directly from the wetting curves, and surface tensions of molten solders were calculated from the wetting force measurements. A statistic tool, analysis of variance (ANOVA), was used to analyze the experimental results. By using the wetting time as an indication, it was found that Sn–Pb exhibited the best wetting followed by Sn–Ag, Sn–Cu, and Sn, in that order. A very significant but frequently ignored issue is that most solders react with substrates, and the molten solders are not in contact with the original substrates but rather with intermetallic compounds. On the basis of theoretical analysis and experimental observations, it was concluded that the withdrawing forces and the surface tensions of the molten solders determined by the present technique are not significantly affected by the interfacial reactions if the interfacial reactions are not too excessive. However, wetting times are strong functions of both solders and substrates and the interfacial reactions between them.

Chemical Modifications on Human Hair Studied by Means of Contact Angle Determination

Wetting properties of a solid surface can change as a consequence of chemical treatment. There is a relationship between the molecular structure of a surface and the macroscopic properties of this surface such as wetting and adhesion. Information on the surface energy of a solid was obtained by calculating polar and dispersion force contributions by means of contact angle determination. The superficial modification undergone by human hair treatments with or without hydrogen peroxide at alkaline pH was studied by means of wetting force measurements. The wetting increase in treated human hair fibers was analyzed following the Hüttinger method using contact angle data, taking into account the acid–base and dispersion components of the total wetting adhesion work. The hydrogen peroxide treatment at alkaline pH leads to a partial removal of hydrocarbon chains and to the formation of ionic groups (cysteic acid residues) on the outer scale cell surface. The latter phenomenon was observed by means of an increase in the acid–base adhesion work versus water wetting liquid at alkaline pH.

Surface properties and solderability behaviour of nickel–phosphorus and nickel–boron deposited by electroless plating

AbstractX‐ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM), atomic force microscopy (AFM) and wetting force measurements have been applied to various nickel deposits prepared by standard electroless plating for probing the origins of solderability behaviour of ‘electroless nickel’. By controlling the plating chemicals and plating conditions, three kinds of electroless nickel deposits have been prepared, namely electroless nickel–high phosphorus (EN‐HP), electroless nickel–low phosphorus (EN‐LP) and electroless nickel–boron (EN‐B). Wetting balance measurements confirmed the solderability strength decreased in the order of EN−B>EN−LP>EN−HP. Unexpectedly, among the three EN deposits, EN‐B was found by XPS to have the thickest surface oxide, which opposes the traditional correlation of good solderability with thin surface oxide. On the other hand, SAM and AFM studies showed that the average nodule size increased in the order of EN−B<EN−LP<EN−HP. Accordingly, there appeared to be a correlation of small nodule size with good solderability. Solderability of ‘electroless nickel’ thus depended more on surface morphology than on surface oxidation. Nevertheless, further studies of the wetting kinetics of the EN deposits revealed that among the three EN deposits EN‐HP had the oxide structure that was most difficult to penetrate and thus the slowest to ‘wet’. The structure of the surface oxide therefore was found to affect the wetting kinetics of ‘electroless nickel’. Copyright © 2001 John Wiley & Sons, Ltd.

Liquid/Fiber and Solidified-Liquid/Fiber Contact Angles Compared

Data are presented showing that the contact angle formed by a liquid resin droplet placed on a single fiber is comparable with a receding contact angle. This was ascertained by comparing Wilhelmy wetting force measurements with liquid droplet profile analysis. Subsequently, the latter analysis was carried out on cured (solidified) epoxy droplets placed on Kevlar fibers. Dimensional changes observed after curing showed that the contact angles of the solid droplets were smaller than that for liquid resin: however, the presence of residual stresses because of adhesion to the fiber may make droplet profile analysis inaccurate for obtaining an equilibrium receding contact angle for the solid droplets.

Effects of oven aging on plasma treated ultra high strength polyethylene

The effects of radio-frequency plasma treatment on ultra high strength polyethylene (UHSPE) fibers using ammonia, oxygen, and argon plasmas were evaluated. The effects of oven aging on adhesion of UHSPE fibers were determined; two methods of oven aging, in air and in water, were used in this study. The effects of aging on the bond between the plasma treated UHSPE and epoxy resin were mechanically evaluated using single fiber pull-out tests. Electron spectroscopy for chemical analysis (ESCA) and wetting force measurements were used to evaluate chemical changes. ESCA results indicate that O-C=0 groups are important for improving IFSS between epoxy and UHSPE.

Local deviation in contact angles on heterogeneous fibrous solids

Wetting force measurements in solid/water/n-alkane systems were carried out using carbon fibers, boron fiber, fibrous quartz, and polymeric fibers by the Wilhelmy technique. Contact angles of water were independent of the velocity of the moving three-phase boundary on repyrolyzed PAN-based carbon fibers which did not show any contact angle hysteresis. Hysteresis in contact angles due to surface heterogeneity began to appear after irradiation with atomic oxygen which oxidized the carbon fibers. On atomic oxygen exposed carbon fibers, advancing contact angles increased and receding ones decreased with increasing velocity, and there was a region where both angles were constant. The range of deviations in contact angles due to surface heterogeneity was determined from local deviations in weight traces at the velocity of three-phase boundary of 0.3 mm min-1 where both angles were independent of the velocity. Deviations in contact angles, Δ, were larger in advancing than in receding for hydrophilic solids (e.g....

Surface Characterization of Carbon Fibers Exposed to 5 eV Energetic Atomic Oxygen Beam Studied by Wetting Force Measurements

Changes in contact angle hysteresis and surface free energy of carbon fibers due to the irradiation of 5 eV energetic atomic oxygen beam were investigated. Atomic oxygen with kinetic energy of 5 eV was used in order to simulate the low earth orbit. Contact angle hysteresis in carbon fibers became larger with respect to the fluence of atomic oxygen. Auger electron spectroscopic analysis shows that the hysteresis of the contact angle is proportional to surface oxygen concentration as well as the polar component of surface free energy. Since adsorbed oxygen or the surface functional group plays an important role in the hysteresis, it is clear that the carbon fiber surface was destroyed due to the attack of atomic oxygen.

Wetting characteristics of poly( p-phenylene terephthalamide) single fibers and their adhesion to epoxy

the circumferential dimension of poly( p-phenylene terephthalamide) (PPTA), or Kevlar 49, single fibers and their wetting behavior and adhesion properties with an epoxy resin were evaluated. A tensiometer employing the Wilhelmy principle was described for fiber size and wetting force measurements. For the fine PPTA fibers, the fiber size could be most consistently measured by the wetting force profiling along the fiber axis in a total wetting liquid. The wetting characteristics of Kevlar 49 fibers in stepwise steady-state wetting, dynamic wetting, and multiple immersions in water and in an epoxy resin were detailed. Argon glow discharge significantly improved water wettability of the Kevlar 49 fibers but lowered their wettability in the epoxy resin. The observation on wettability in water and resin and the effects of glow discharge on wettability suggested that the polar nature of the Kevlar fiber surface may be a dominant factor in determining its wettability in these liquids. Upon argon glow discharge, the resin wettability of the Kevlar 49 fiber and the interfacial shear strength between the fiber and the epoxy were both lowered.

Fundamental interfacial properties of alkyl-branched sulfate and ethoxy sulfate surfactants derived from Guerbet alcohols. 3. Dynamic contact angle and adhesion tension

The influence of hydrocarbon chain branching (Guerbet branching) on the interfacial properties at the solid-water interface was studied by using the Wilhelmy type wetting force measurement technique (dynamic contact angle analyzer). Dynamic contact angles were determined at the Teflon-water interface for a series of well-characterized Guerbet sulfate and monodisperse ethoxy sulfate surfactants. Comparison of C 16 linear with C 16 Guerbet surfactants revealed that hydrocarbon chain branching decreases the advancing and receding angles by about 30°, representing increased wetting effectiveness

Estimation of surface free energies and hamaker constants for fibrous solids by wetting force measurements

Wetting force at three-phase line was measured by the Wilhelmy technique using fibrous solids/liquid/liquid systems. Advancing and receding contact angles were calculated from the wetting forces during fiber immersion and emersion. The obtained results showed that contact angle hysteresis was due to the heterogeneity of the fiber surfaces. The dispersive and polar components of surface free energies of the fibers were determined from the advancing and receding contact angles, respectively. The Hamaker constants of the fibers were estimated from the dispersive components of their surface free energies.

Contact angle hysteresis in carbon fibers studied by wetting force measurements

The surface free energy of polyacrylonitrile carbon fibers was investigated by using the Wilhelmy technique. The difference in surface free energy between immersion and emersion was observed for the carbon fiber pyrolyzed at 2500 °C.

Preparation of brittle thermoset specimens for surface characterization by contact angles

AbstractA convenient and accurate method for surface analysis by contact angle studies is described. The specimen developed is particularly useful for brittle thermoset materials which must be prepared in a simple regular geometry for wetting force measurement by the Wilhelmy method. The procedure involves dip‐coating wires to make smooth cylindrical specimens of cured thermoset resin for wettability (contact angle) analysis. The results from this type specimen were cross‐checked with cast film specimen results to ensure that measured contact angles were material properties and were not influenced by geometry or presence of wire substrate. Results are presented for some modified and unmodified brittle thermoset resins showing changes in surface energetics.

Wetting force measurements on single fibers

Wilhelmy-type wetting force measurements utilizing sensitive instrumentation are being used more and more to quantify the surface energetics of solids generally, and of filaments in particular. This report describes a recommended methodology for such measurements. It is shown that, under certain conditions, advancing and receding contact angles can be obtained from wetting force measurements alone without the need for independent determinations of specimen perimeter or liquid surface tension. Factors that may complicate or interfere with such contact angle determinations are discussed, including corrections for buoyancy, limitations on the magnitude of the contact angle, and specimen geometry requirements. Experiments demonstrating the use, reproducibility, and sensitivity of the methodology are summarized.