Polyimide electrical properties

Relatively few processible polyimides, particularly at a reasonable cost and iu rehable supply, are available commercially. Users of polyimides may have to produce iutractable polyimides by themselves in situ according to methods discussed earlier, or synthesize polyimides of unique compositions iu order to meet property requirements such as thermal and thermoxidative stabilities, mechanical and electrical properties, physical properties such as glass-transition temperature, crystalline melting temperature, density, solubility, optical properties, etc. It is, therefore, essential to thoroughly understand the stmcture—property relationships of polyimide systems, and excellent review articles are available (1—5,92). 

Benzenetetracarboxylic dianhydride (pyromellitic dianhydride) is a typical bifunctional acid anhydride, and it is a useful raw material for preparing many useful chemicals. Polyimides and polyimidazopyrrolons prepared from this dianhydride have excellent heat and chemical resistance, as well as excellent mechanical and electrical properties. Pyromellitic dianhydride is produced by the oxidation of 1,2,4,5-tetraalkylbenzenes such as 1,2,4,5-tetramethylbenzene (commonly known as durene) and 4,6-diisopro-pyl-l,3-dimethylbenzene. Durene, in particular, is a fundamental raw material for the production of the dianhydride 1-8). 

Table II. Electrical Properties of Dry Air Cured Cobalt Chloride Modified Condensation Polyimide Filins...

OPTICAL, PHYSICAL, AND ELECTRICAL PROPERTIES OF PERFLUORINATED POLYIMIDES... 

Aromatic polyimides have excellent thermal stability in addition to their good electrical properties, light weight, flexibility, and easy processability. The first aromatic polyimide film (Kapton, produced by DuPont) was commercialized in the 1960s and has been developed for various aerospace applications. The structure of a typical polyimide PMDA/ODA prepared from pyromellitic dianhydride (PMDA) and 4,4 -oxydianiline (ODA), which has the same structure as Kapton, is shown in (1). Aromatic polyimides have excellent thermal stability because they consist of aromatic and imide rings. 

High water absorption is die other problem with insulation materials, because it causes corrosion of metal wiring and instability of electrical properties such as the dielectric constant. Conventional polyimides have relatively high water absorption because of tiie presence of polar imide rings. However, the water absorption decreases when fluorine is introduced into polyimide molecules because of the former s hydrophobic nature. ... 

This book reviews some of the results of investigations of chemical conversions of chloral and TNT to new aromatic di(poly)amines and aromatic tetracarboxylic acid dianhydrides useful for the preparation of new polyimides combining good thermal, mechanical and electrical properties with improved processability. 

Z. Ounaies, C. Park, K.E. Wise, E.J. Siochi, and J.S. Harrison, Electrical properties of single wall carbon nanotube reinforced polyimide composites, Compos. Sci Technol., 63(11) 1637-1646, August 2003. 

Polyimide films have excellent electrical properties and a tensile modulus of over 400,000 psi at 25°C. Over 60 percent of this modulis is retained at 200°C. Polyimide wire enamels are stable for up to 100 Oiousand hours at 200°C. Polyimide fibers have a tenacity of 7 g/denier at 25°C and over 1000 hrs at 2833C is required to reduce the value to 1 g/denier. 

A recent review [1] on polyimide adhesion to metal and ceramic surfaces shows the relevance of this topic to many different technological areas. Of all the polyimides studied thus far, it is evident that the most popular one is PMDA-ODA. It has very good mechanical, thermal, and electrical properties, but it suffers from poor adhesion characteristics. This problem is often overcome by the application of an adhesion promoter to the surface of interest. The most popular adhesion promoter appears to be APS. An excellent review concerning APS has been written by Ishida [2]. A wealth of information concerning silane coupling agents can also be found in the book by Plueddemann [3],... 

Polyimide (PI) caps all other polymers in its temperature range of use (-200 to 260 °C in air short-time even up to 500 °C). Because of its high price, it is used in special cases only, such as space vehicles, nuclear reactors and some electronic parts. Newer developments, related to polyimide, are the polyether imides (e.g. Ultem ), polyester imides and polyamide imides (e.g. Torlon ), all with very good mechanical, thermal and electrical properties and self-extinguishing. 

These PEI plastics show good physical and electrical properties at high temperatures and a 20,000 h service life at 230C (446F). Their thermal-oxidative stabilities are described as being less than the best polyimides, but better than the aromatic polyesters. 

Polyimide films are extensively used in the microelectronic industry as insulators for multilevel interconnect systems because of their excellent thermal and electrical properties. In some cases,... 

Because of their extremely good thermal and electrical properties, thin polyimide films are widely used in the electronics industry. 

Along with their excellent high temperature stability, polyimides also possess remarkable electrical properties. A detailed review of the electrical and optical properties of polyimides can be found in Ref. 62. Electrical properties of polyimides were primarily investigated in view of their low dielectric constants and insulating properties. Figure 14 shows the dependence of electrical conductivity of vapor deposited and... 

Polyimides Excellent electrical properties. Excellent barrier properties, eg., H2O High thermal Stability Two step deposition process CVD films not completely characterized... 

Excellent, isotropic electrical properties. Dielectric constants of 2.4 to 2.6 have been demonstrated. Low dielectric constant is crucial as interconnect density increases. As space between conducting lines shrinks, inductance and cross-talk become problematic, but can be mitigated with lower dielectric constant materials. Polyimides, which are used extensively in the industry, exhibit anisotropic electrical properties in-plane dielectric constant can be as high as 4 while out of plane dielectric constant is generally above 3. 

In the stand-alone application (Figure la) the SOG film must have good dielectric characteristics and a thickness range of 1-2 microns. No such SOG materials are currently commercially available. Polyimides have adequate electrical characteristics and can be spin-applied into films up to several microns thick. However, they have not been widely adopted because of difficult processing required in their use and certain Inherent limitation in material characteristics. The smoothing layers schemes ( ), (c), and (d) of Figure 1 require a thickness of only 1000-3000A for the SOG film. The electrical properties of the SOG film in these structures are relatively less critical since the bulk of the dielectric function is... 

Aromatic polyimides have gained wide popularity as dielectric materials in a variety of applications in the manufacturing of electronic circuits due to their thermal, mechanical and electrical properties. Most notable among these applications are as interlayer dielectrics in multilevel VLSI circuits and in multilevel interconnects, as well as in the packaging of integrated circuits. 

---