Polyimide insulation

Additional drawbacks to the use of polyimide insulators for the fabrication of multilevel structures include self- or auto-adhesion. It has been demonstrated that the interfacial strength of polyimide layers sequentially cast and cured depends on the interdiffusion between layers, which in turn depends on the cure time and temperature for both the first layer (Tj) and the combined first and second layers (T2) [3]. In this work, it was shown that unusually high diffusion distances ( 200 nm) were required to achieve bulk strength [3]. For T2 > Tj, the adhesion decreased with increasing T. However, for T2 < Tj and Tj 400 °C, the adhesion between the layers was poor irrespective of T2. Consequently, it is of interest to combine the desirable characteristics of polyimide with other materials in such a way as to produce a low stress, low dielectric constant, self-adhering material with the desirable processabiHty and mechanical properties of polyimide. 

Wilson, A. M., "Polyimide Insulators for Multilevel Interconnections", Thin Solid Films, SI, 145-163 (1981). 

Amoco A-I Polyimide insulative and conductive coatings Amoco Chem. Corp. 

Du Pont Bulletin H65-4, Experimental Polyimide Insulating Varnishes, RC-B-24951 and RC-5060, January 1965. 

During the processing of semiconductor silicon by deposition of polyimide insulating layers on silicon wafers, it was noted that small solid particles were present in the polyimide, which caused serious problems during further processing. The composition of these particles was identified by infrared microspectroscopy as dicyclohexylurea. This material is formed by reaction of dicyclocarbodiimide, a reagent used in preparation of polyimide, with water. Apparently excess dicyclocarbodiimide was used in preparation of certain batches of polyimide. This excess material reacted with moisture from the air over a period of time to form an impurity if an impurty exists, the spectrum obtained for each isolated unit often provides positive identification. 

Figure 33 Hybrid multichip module stmcture with five copper conductor levels and six polyimide insulating films deposited by spin coating onto a doped silicon wafer. In this process, the integrated circuits are inserted in cavities that are created by laser drilling or anisotropic chemical etching of the silicon substrate. IC chips are bonded to the substrate by means of a heat-resistant insulating adhesive.

Figure 39 Cross-section of the silicon-on-silicon AT T s advanced VLSI packaging process comprising four copper layers for ground, power, and routing signal planes with polyimide insulating films, (reprinted from Ref. [98], Copyright 1987 IEEE.)...

Nanometer-sized disk-shaped SECM tips were prepared from etched Pt wires insulated with a polyimide layer [69]. Polymerization of the polyimide insulating flhn was thermally triggered the etched Pt wire was immersed into a A,A-dimethylacetamide solution containing 1,2,4,5-benzenetetracarboxylic anhydride and 4,4 -diaminodiphenyl ether and the electrode body was heated np nntil an insnlating film formed. The apex of the electrode was exposed by dipping the coated wire in 0.01 M NaOH for a few minntes. 

Polyimide. Polyimide is a biaxiaHy oriented high performance film that is tough, flexible, and temperature- and combustion-resistant. Its room temperature properties compare to poly(ethylene terephthalate), but it retains these good characteristics at temperatures above 400°C. Its electrical resistance is good and it is dimensionally stable. The principal detriment is fairly high moisture absorbance. The main uses are for electrical insulation, particularly where high temperatures are prevalent or ionizing radiation is a problem. The films may be coated to reduce water absorption and enhance... 

Polyimide and Melamine. These are both low density, essentially open-ceU foams used as pipe insulations, particularly those involved with fluids operating at temperatures up to 530 K. Because these foams operate at higher temperatures and have improved flammabiHty characteristics compared to other foams, they are also used for some aircraft and marine appHcations. 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Polyimide is extensively used in electrical industry for insulation coating of electromagnetic wirings. Actually the wire is coated with polyamic acid and baked at 300°C under an inert atmospheres when the polyimide gets deposit on the surface of the wire. 

Heat shields, insulation shields for sparkplug heads in polyimide sheet. 

The polyimide foams are flexible and have a very low density (7 kg/m ), associated with good fire behaviour, a broad service temperature range and good soundproofing and thermal insulation qualities. These materials are sensitive to diluted strong bases, concentrated salts and acids. Other foams have densities varying from 15-250 kg/m. ... 

As insulation between the coil and the magnetic core, a hard-cured (to 200°C) photoresist insulator is patterned. It is a novolak polymer or polyimide about 5 fim thick, which is popular for its high insulator and photolithographic properties. This provides electrical insulation as well as a planar surface for subsequent deposition of copper cods. 

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