Decrease In Adhesion Strength Research Articles

The Aspects of Thermal Anneal to Intrinsic Stress and Hicrostructure of Multilayer Thin Films

AbstractAdhesion degradation mechanism at the interface of a multilayer thin film was studied as a function of annealing temperature. The multilayer thin films employed for current investigation of the temperature effect were constructed by sputtering 500 Å Cr and 10K Å Cu on both sides of kapton. A steady decrease of adhesion strength was found as a result of increasing the annealing temperature from 150°C to 350°C. Thin film and interfacial properties in association with degradation of adhesion were characterized by several techniques, including intrinsic stress measurement, Auger, TEN and SIMS. Several changes were observed by elevating the annealing temperature. It was found that the intrinsic stress in each layer changed. Both Cu and Cr grain size increased with the annealing temperature. The interface at kapton and metal became more defined. The Cu atoms were found to become mobile and diffused into Cr and kapton layer after a 350 degree annealing. In addition, a change of molecular orientation and chemistry in kapton near the interface was observed by SIMS and XPS studies. A combination of these factors resulted in a decline of adhesion strength.

The Aspects of Thermal Anneal to Intrinsic Stress and Microstructiire of Multilayer Thin Films

AbstractAdhesion degradation mechanism at the interface of a multilayer thin film was studied as a function of annealing temperature. The multilayer thin films employed for current investigation of the temperature effect were constructed by sputtering 500 Å Cr and 10K Å Cu on both sides of kapton. A steady decrease of adhesion strength was found as a result of increasing the annealing temperature from 150°C to 350°C. Thin film and interfacial properties in association with degradation of adhesion were characterized by several techniques, including intrinsic stress measurement, Auger, TEM and SIMS. Siveral changes were observed by elevating the annealing temperature. It was found that the intrinsic stress in each layer changed. Both Cu and Cr grain size increased with the annealing temperature. The interface at kapton and metal became more defined. The Cu atoms were found to become mobile and diffused into Cr and kapton layer after a 350 degree annealing. In addition, a change of molecular orientation and chemistry in kapton near the interface was observed by SIMS and XPS studies. A combination of these factors resulted in a decline of adhesion strength.

Photolithography of Polytetrafluoroethylene for Tailored Adhesion

AbstractIrradiation of polytetrafluoroethylene (PTFE) with Mg(Ka) X-rays is shown to protect the surface against the chemical etching steps used to prepare PTFE for adhesion. Pre-irradiated etched samples of PTFE have adhesion strengths of less than 3% of that for non-irradiated etched samples. The major portion of this decrease in adhesion strength occurs for X-ray exposures of less than 10 min (∼4.8×103 mrads) and failure in every case occurs in PTFE and not in the bonded transition region. XPS measurements (20 Å sampling depth) show little difference in F content between irradiated and non-irradiated samples, but thermal desorption shows increasing fluorocarbon desorption with irradiation time. These results are consistent with the known radiation chemistry of PTFE. Irradiation produced free radicals lead to branching and/or cross-linking, and a surface rich in low molecular weight fluorocarbons. The more rigid cross-linked surface is resistant to deep (10,000 Å) chemical attack and the bond formed is with a surface rich in short chain fluorocarbons. Both a thin boundary region and bonding to short chain species is expected to lead to weak adhesive bonding. Electron irradiation is shown to lead to protection against chemical etching comparable to that obtained with X-rays. With electrons one has the capability of rastering the electron beam and drawing low adhesion strength patterns with resolution limited by the beam diameter.

The Effect of Contamination on Adhesive Strength: Wettability Characterization by the CSC Method

Abstract The correlation between the adhesive strength of joints of aluminum alloys and the wettability of their surfaces was studied. Two alloys, Al-1100 and Al-2024, were used, with two commercial epoxy adhesives, FM-73 and FM-300K, and the BR-127 primer. The wettability of the surfaces was modified by applying coatings of silicone oil and stearic acid at various concentrations. Wettability was characterized by the “complete spreading concentration” (CSC) method and by advancing contact angles. The CSC method was proven to be more reliable than contact angle measurements in detecting variations in the surface energy of the aluminum alloys studied. The adhesive strength was measured by the lap shear strength (LSS) and by the T-peel strength. The adhesive strength is only mildly sensitive to the concentration of silicone oil for the two adhesive systems. For FM-300K, the LSS decreases when the concentration of stearic acid in the coating increases. For FM-73, the LSS is only mildly sensitive to the concentration of stearic acid, but the T-peel strength shows appreciable sensitivity. The failure mode becomes more adhesive as the concentration of stearic acid and thereby the CSC increase. It is only mildly dependent on the concentration of silicone oil. The results indicate that silicone oil probably interacts with either the primer or an adhesive component in a way which counteracts the expected decrease in adhesive strength due to the reduction in surface energy and wettability of the adherends. However, the effect of stearic acid on the adhesive strength is associated with decreased wettability. All cases for which a pronounced decrease in the adhesive strength was measured are associated with contact angles larger than 90° and with either high CSC values or nonspreading situations.

The adhesive behaviour of poly(p-phenylene benzobisthiazole) (PBT)/epoxy composites

A modified scarf joint specimen was developed for characterizing the adhesive behaviour of poly (p-phenylene benzobisthiazole) (PBT) film/epoxy composites. This method subjected samples to varying amounts of normal stress (tensile or compressive) and shear stress. This resulted in the determination of two adhesive strengths; one in the absence of shear stress and one in the absence of normal stress. As a result, the dependence of the adhesive strength on the degree of normal stress was determined. The adhesive behaviour of PBT/epoxy composites was investigated at cure temperatures of 55, 85, 115 and 215°C. Adhesive strengths of 3.5 and 8.2 MPa were measured in the absence of shear and normal stress, respectively, for samples cured at 55° C. A decrease in adhesive strength with increasing cure temperature was attributed to residual cure and thermal stresses. The fracture of these composites was predominantly adhesive, resulting in a clean delamination of the PBT film from the epoxy surface. A modified Tsai-Wu failure criterion is suggested for these composites.

Practical Adhesion of an Ag - Pd Thick-Film Conductor: An Acoustic Emission Study of Pull Tests-Part II, Aged Adhesion

The practical adhesion strength of an aged (150°C for 48 h) Ag-Pd thick-film conductor on 96-percent alumina was investigated using an acoustic emission monitoring system and a 90° bent wire pulltest configuration. The presence of solder-metal-binder glass reactions and reaction products resulted in a decrease in adhesion strength by about 50 percent from the initial test values. The acoustic emissions recorded for the aged samples showed a large amount of low-level continuous emissions during pull testing. These emissions were distinguishable from those found on unaged parts.

A sub-half-micron gate-length GaAs MESFET with new gate structure

New gate structure and fabrication technique for GaAs MESFET's have been developed. Utilizing the gate structure, sub-half-micron gate length can easily be obtained by conventional projection photolithography without any gate resistance increase and mechanical adhesion strength decrease.

Evaluation of the service life of galvanized steel sheet coated with polyvinyl chloride resin.

This paper report about the evaluation of the service life of a galvanized steel sheet coated with thermoplastic polyvinyl chloride resin and intended for an exterior building material. It can be summarized as follows:(1) A dew cycle weathering test is the best method as an accelerated weathering test because it gives a high acceleration to deterioration and reveals the similar deteriorated condition to outdoor weathering testing.(2) It can be safely said that the polyvinyl chloride resin is oxidized and the double bond is formed because of the dechloridization of the polyvinyl chloride resin in the film surface layer.(3) Of all the deterioration factors, ultraviolet rays and heat are most significant.(4) Appearance change, physical change, and decrease in adhesion strength between film and steel sheet are caused by the chemical change of the resin.(5) Although the film surface of polyvinyl chloride resin on a galvanized steel sheet deteriorates, the bulk material does not deteriorate. Accordingly, the evidence accounts for the high corrosion resistance of the film.

Evaluation of the service life of galvanized steel sheet coated with silicone polyester resin.

This paper reports about the evaluation of the service life of a galvanized steel sheet coated with thermosetting silicone polyester resin and intended for an exterior building material. The contents are as follows:(1)A composite cycle test is the best method as an accelerated weathering test because it gives a largest acceleration rate to deterioration and reveals the similar deteriorated condition to the outdoor weathering test.(2) A complex deterioration of the resin proceeds in the film surface layer, with the thickening of remaining silicon dioxide being observed in particular.(3) Complex deterioration factors affect the properties of the material.(4) Appearance change, physical change and decrease in adhesion strength between film and steel sheet are caused by the chemical change of the film.(5) The silicone polyester resin coated galvanized steel sheet has a high abrasion and corrosion resistance.

The photo-ageing of polyethylene and its effect on polyethylene adhesion to steel

The structural changes in macromolecules which take place during photo-ageing consist of structural orientation and are accompanied by chemical changes associated with an increase of the oxygen-containing groups, especially of carbonyl. The extremal nature of the adhesive strength of the polyethylen (PE)-steel binding compounds as a function of the extent of oxidation of the polymer, found in this work, is due to macromolecular crosslinking at the surface and the surface and the restriction of mobility. The increase in the concentration of oxygen-containing groups at the PE surface causes inter-crystal plasticization and reduces the micro-hardness at the surface, but also intensifies the reactions between macro-radicals which contain the groups capable of adsorption on the surface of the substrate. A decrease in adhesive strength at greater oxidations of the polymer is explained by the cohesive strength deterioration of the PE subjected to irradiation with UV-light.