Polymer metallization, metal diffusion

Wool [32] has considered the fractal nature of polymer-metal and of polymer-polymer surfaces. He argues that diffusion processes often lead to fractal interfaces. Although the concentration profile varies smoothly with the dimension of depth, the interface, considered in two or three dimensions is extremely rough [72]. Theoretical predictions, supported by practical measurements, suggest that the two-dimensional profile through such a surface is a self-similar fractal, that is one which appears similar at all scales of magnification. Interfaces of this kind can occur in polymer-polymer and in polymer-metal systems. 

Polymer-metal fractal interfaces may result from processes such as vacuum deposition and chemical vapour deposition where metal atoms can diffuse con-... 

After polarization to more anodic potentials than E the subsequent polymeric oxidation is not yet controlled by the conformational relaxa-tion-nucleation, and a uniform and flat oxidation front, under diffusion control, advances from the polymer/solution interface to the polymer/metal interface by polarization at potentials more anodic than o-A polarization to any more cathodic potential than Es promotes a closing and compaction of the polymeric structure in such a magnitude that extra energy is now required to open the structure (AHe is the energy needed to relax 1 mol of segments), before the oxidation can be completed by penetration of counter-ions from the solution the electrochemical reaction starts under conformational relaxation control. So AHC is the energy required to compact 1 mol of the polymeric structure by cathodic polarization. Taking... 

Polyimide was used as a model material in studies of polymer metal interfaces where metal layers were formed by metallization, plasma deposition, chemical vapor deposition, electrochemical deposition, etc In most of the cases studied, the interpenetration of metal was so good that the metal layer could not be removed by any other means but abrasion. An investigation of interface, determined that the metal particles were found in the surface layers in diminishing quantities perpendicular to the surface and not, as expected, in the form of a sharp borderline between the metal and polymer. Some difficulties exist when metallized polyimides are used for chip production. These diffuse layers of metals complicate design and performance due to the gradients of conductivity which they produce. 

First, noble metal diffusion in DIP and Pc were carried out. As Ag diffusion in polymers is well studied and understood [12, 13, 15-17, 32, 33], depth profiles for Ag diffusion in Pc and DIP were obtained. Comparison with the depth profiles of polymers will help to further the understanding of the nature of noble metals in these organic semiconductors. 

Alternatively, delamlnatlon may not be related directly to permeation, but may be due Instead to thermal and/or UV effects that are followed by the corrosive failure. Some studies and models Indicate that the polymer/metal Interface morphology, and the changes In the morphology with exposure to the environment, play a key role In corrosion rates. These characteristics may be even more Important In corrosion control than either the diffusion of vapors through the pol5mier or the Inherent corrosion resistance of the metal. 

In the case of a three-boundary layer between an electrolyte, the polymer, and the metal, water molecules, water clusters and hydrated ions can diffuse into the polymer/metal interface. 

As a scanning electrochemical technique, the SKP is able to detect an electrolytic conductance along the polymer/metal interface between the defect border (negative potential) and the polymer-coated area. When the ions diffuse into the polymer/metal interface, the interfacial resistance is lowered in the respective area and the corresponding potential is shifted to more negative values - ideally to the electrode potential of the defect. Based on this shift of the interfacial electrode potential, the transport of ions along the interface can be studied to a very high accuracy. 

While the adsorption theory is the most accepted one, mechanical interlocking comes into play in case of substrates with a special kind of roughness such as galvannealed steel where the liquid can spread into cavities and thereby interlock with the substrate. The diffusion theory does not play an important role for polymer-metal interfaces. The contribution of the electrostatic theory is not easy to estimate. However, the electrical component of the adhesive force between the planar surfaces of solids becomes important if the charge exchange density corresponds to 10 electronic charges, meaning about 1% of the surface atoms [71]. 

Metal Diffusion During Metallization of High-Temperature Polymers... 

This paper aims to give a brief review of our present understanding of metal diffusion during polymer metallization and of the implications for the formation and structure of metal-polymer interfaces. For recent more extended reviews the reader is also referred to references 2-4. 

In view of the marked tendency of metals to aggregate we do not expect metal diffusion into polymers to occur from continuous films. Diffusion rather... 

The volume is divided into three parts Part I. Metallization Techniques and Properties of Metal Deposits, Part II, Investigation of Interfacial Interactions," and Part III, "Plastic Surface Modification and Adhesion Aspects of Metallized Plastics. The topics covered include various metallization techniques for a variety of plastic substrates various properties of metal deposits metal diffusion during metallization of high-temperature polymers investigation of metal/polymer inlerfacial interactions using a variety of techniques, viz., ESCA, SIMS, HREELS, UV photoemission theoretical studies of metal/polymer interfaces computer simulation of dielectric relaxation at metal/insulalor interfaces surface modification of plastics by a host of techniques including wet chemical, plasma, ion bombardment and its influence on adhesion adhesion aspects of metallized plastics including the use of blister test to study dynamic fracture mechanism of thin metallized plastics. 

Let us consider a particular example of the effect of RS substances on the water resistance of adhesive-bonded joints. Adhesives based on imsaturated polyester resins, such as PN-1, are distinguished by low water resistance. The influence of water on a steel joint cemented by such an adhesive actually results in some initial increase of the specific electrical resistance along the adhesive-steel interface and then in an abrupt drop (Fig. 5.5). The increase is explained by more complete consumption of the monomer in the system. When ATG is added to the adhesive (which decreases the interphase tension) the specific electrical resistance stabilizes after a drop. The decrease seems to be related to the processes of relaxation of the internal stresses in the adhesive interlayer. The stresses facilitate the diffusion of liquids in polymeric materials, in particular the stress concentration at the polymer-metal interface. 

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