Adhesion of polyimides

An additional advantage inherent to polyfamic alkyl esters) relates to their behavior at metal interfaces. When investigating the interface and adhesion of polyimide to several different metals, i.e. Au, Cr, Ni, and Cu, it was found that... 

The above results are certainly unexpected in light of an earlier report on adhesion of polyimide films [47]. Here it was shown that adhesion between two polyimide films could only be achieved when polyimide chains from the one surface extended approximately 300 A into the other surface. Because of the extended nature of the polyimide chains the potential for significant entanglements near the respective interfaces is low, thus requiring much deeper penetration by the PI to provide the necessary frictional forces for good adhesion. In the... 

Adhesion of polyimide to fluorine-contaminated SiOz surface. Effect of aminopropyltriethoxysilane on the adhesion... 

Adhesion of polyimides to ceramics Effects of aminopropyltriethoxysilane and temperature and humidity exposure on adhesion... 

Adhesion of polyimides to inorganic substrates is of great importance to the microelectronics industry [1, 2]. The polyimide films are deposited most often by spin coating the polyamic acid (PAA) usually from a TV-methylpyrrolidone (NMP) solution onto the substrate surface followed by thermal imidization at temperatures up to 400<>C. The most studied polyimide is the pyromellitic dianhydride-oxydianiline (PMDA-ODA), which exhibits excellent mechanical and dielectric properties, but not so good adhesion characteristics. The latter has been generally overcome by application of an adhesion promoter, such as y-aminopropyltriethoxysilane [3-7]. The reactions of APS (coated from water solution) with the silicon dioxide surface as well as with polyamic acid have been well characterized by Linde and Gleason [4] however, we do not have such detailed information available on APS interaction with other ceramic surfaces. 

After deposition, the films are cured by heating at a controlled rate in a convection oven, hot plate, or tube furnace to evaporate solvents and reaction products (primarily H20) and to convert the polyamic acid to the polyimide. The final properties and adhesion of polyimide films depend on the curing rate and final curing temperature, which can range from 300 to 450 °C. 

Figure 9. Schematic test site for measurement of residual stress, modulus, tensile stress, and adhesion of polyimide.

Some general conclusion from these studies are (1) Cu/PI TFML structures have excellent thermal and mechanical stability under extremes of temperature, humidity, and radiation (2) the adhesion of polyimide is highly dependent on interface chemistry and surface preparation (3) PI rapidly absorbs and desorbs water, which has an appreciable effect on its dielectric properties and thus the electrical charactersitics of TFML interconnections the electrical design tolerances must accommodate these variations or the package must be hermetically sealed (4) properly baked and sealed TFML packages can maintain MIL-STD internal moisture levels of less than 5000 ppm at 100°C. 

The accelerated tests have shown dramatic improvements in the adhesion of polyimide coatings, even to noble metal substrates, when... 

Buchwaiter LP. Adhesion of Polyimides to Metals and Metal Oxides. J Adhesion Sci... 

A more sophisticated peel tester has been implemented to evaluate the adhesion of polyimide films at elevated temperature and in high-humidity environment [70]. The peel strength values measured in dry atmosphere rapidly degrades when the devices are exposed to humidity, temperature-humidity, or thermal cycle tests. 

A more sophisticated peel tester has been implemented to evaluate the adhesion of polyimide films at... 

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