Fluorocarbon polymers, adhesion metals

In this paper, we report the studies on the adhesion between metals and fluorocarbon polymer films. Fluorocarbon polymer has a dielectric constant of 2.1, lower than that of polyimide, 3.2-3.5, and is attractive to packaging. We have studied the adhesion of Cu to bulk Teflon, a polytetrafluoroethylene (PTFE) polymer, and found enhanced adhesion using a presputtering treatment of the Teflon prior to the deposition of Cu (4). Further analysis shows that the morphological changes of the Teflon due to the sputtering treatment could be a major contributor to the enhanced adhesion observed (5). 

In summary, several fluorocarbon polymer films are compared for their adhesion to metals. A strong adhesion, as measured by the peel strength, is obtained for Ti and Cr bonding to the polymers with a high concentration of carbon atoms with three fluorine neighbors. 

Adhesion of metals to polymers has been an intensively studied subject over the past decades This is due to the wide application of polymers to electronic packaging and, to a lesser extent, to device inter-connect The increasing demand in density for devices and speed for packaging, in turn, prompts searches for polymers with reduced dielectric constants than that of the widely used polyimide. Some fluorocarbon polymers, notably Teflon, have lower dielectric constants, 2.1, vis-i-vi the values of 3.0-3.5 for polyimides. The fluorocarbon polymers, however, have very weak adhesion to metals. An enhancement in adhesion is thus a primary requirement for the application of such polymers to technologies. A wide range of studies have been made in the past to understand and enhance the adhesion between metals and fluorocarbon polymers In this paper we review some of our earlier work, and present new observations related to the enhanced adhesion between metals and fluorocaiton polymers. We present results address three contributions to enhanced adhesion between metals and fluorocarbon polymers chemical, mechanical, and thermal. 

The thermal treatments of the metal/fluorocarbon polymer systems show both stable structures and enhanced peel strengths. Such information is important to the application of fluorocarbon polymers to the packaging uses. Differently enhanced adhesion is noted for samples using mixed polymers, which may serve further purposes to technologies depending on the specific uses. 

Polyolefins and fluorocarbon polymers have low values of 7 and are said to have low energy surfaces these materials are difficult to wet and bond. Metals, ceramics and polar polymers have high value of 7 (high energy surfaces), can be readily wet by many organic adhesives, and exhibit good bondability. 

Liquid or solid films which reduce or prevent adhesion between surfaces solid-solid, solid-paste, solid-liquid. Waxes, metallic soaps, glycerides (particularly stearates), polyvinyl alcohol, polyethene, silicones, and fluorocarbons are all used as abherents in metal, rubber, food, polymer, paper and glass processing. 

C. P. J. van der Aar, et al., Adhesion of EPDMs and Fluorocarbons to Metals by Using Water-Soluble Polymers, Rubber World, November 1998. 

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