Polyimide adhesion

Taylor, L. T. St. Clair, A. K. NASA Langley Research Center, "Aluminum Ion Containing Polyimide Adhesives , U. S. Patent 284,461 (1981). 

Keywords Polyimide adhesion fluorine contamination aminosilane moisture effects. 

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],... 

Keywords Polyimide adhesion ceramics aminosilane humidity. 

Polyimide adhesion to the substrate surface is not only important initially after the interface preparation, but also after exposure for extended times to elevated temperature and humidity (T H) conditions. As Plueddemann [7] states Water molecules diffuse through any plastic and thus will reach the interface in composites exposed to humid environment. Individual water molecules, however, are relatively harmless at the interface unless they are capable of clustering into a liquid phase. The concentration of water at the interface is not determined by the rate of permeation of the water through the polymer matrix (silicones and... 

Edelman R (1985) A new high temperature polyimide adhesive use with kapton film. Natl SAMPE Symp Exhib (Proc) 30 (Adv Technol Mater Processes) 230... 

Morishige S, Kaneda K, Terajima K, Takeda T, Sakamoto Y, Suzuki T. Polyimide adhesive compositions for ceramics and semiconductor devices. Eur Pat Appl EP 531867 A1 930317 10 pp... 

Although the mechanisms of polyimide/metal adhesion remain to be fundamentally elucidated, it is generally accepted that the interfacial diffusion of metallic entities into the polyamic acid plays a key role at the interface [156-158]. Two main theories have been reported explaining the adhesion of the Pl/metal bond chemical and mechanical bonding [159]. Initial work emphasized mechanical bonding and most efforts were dedicated to the physical roughening of the substrate by different abrasive methods as well as chemical treatments in order to improve metal to polyimide adhesion by increasing the metal surface area [156,160-164]. 

Arsenic-based antioxidants, such as arsenic pentoxide and arsenic thioarsenate, had been used extensively in the past to retard oxidation. In a polyimide adhesive formulation, for example, arsenic compounds were found to improve thermal resistance. At 315°C no loss in strength was exhibited after 1000 h and substantial strength (1300 psi) was retained after 2000-h exposure. Without the arsenic additive there was marked reduction after only 200 h at 315°C. 

Alternative etch for alloys to be bonded with polyimide adhesives is nitric hydrofluoric water in a ratio of 5 1 27 by wetght. Etch 30 s at 20°C. 

Polyimide surface modification by a wet chemical process is described. Poly(pyromellitic dianhydride-oxydianiline) (PMDA-ODA) and poly(bisphenyl dianhydride-para-phenylenediamine) (BPDA-PDA) polyimide film surfaces are initially modified with KOH aqueous solution. These modified surfaces are further treated with aqueous HC1 solution to protonate the ionic molecules. Modified surfaces are identified with X-ray photoelectron spectroscopy (XPS), external reflectance infrared (ER IR) spectroscopy, gravimetric analysis, contact angle and thickness measurement. Initial reaction with KOH transforms the polyimide surface to a potassium polyamate surface. The reaction of the polyamate surface with HC1 yields a polyamic acid surface. Upon curing the modified surface, the starting polyimide surface is produced. The depth of modification, which is measured by a method using an absorbance-thickness relationship established with ellipsometry and ER IR, is controlled by the KOH reaction temperature and the reaction time. Surface topography and film thickness can be maintained while a strong polyimide-polyimide adhesion is achieved. Relationship between surface structure and adhesion is discussed. 

Polyimide-Polyimide Adhesion. To study polyimide-polyimide adhesion (10). a thin layer (200 A) of gold was sputter-coated onto one side (20% of the total area) of the polyimide sample to initiate peel (polyimide has a poor adhesion to gold). The surface of the polyimide in the exposed area was modified to the polyamic acid surface. PMDA-ODA polyamic acid in NMP solvent was spin-coated to the surface-modified (to polyamic acid) polyimide film, and subsequently cured at 400 °C under nitrogen. Thickness of the adherate layer (peel layer) after curing is approximately 20 um and the width of the peel layers is 5 mm. The peel strengths were measured by 90° peel of the top polyimide layer. The failure occurs at the interface between... 

Heat resistant Intractable thermoset polylmides (Vespel, Kinel, Kapton) have been supplemented by injection moldable polyamlde-lmides (Torlon) and modified polylmides (Kanox, Toramid).( Thermoplastic polyimide adhesives were cited as one of the top 100 Inventions in 1981. Polyimide foam does not Ignite at temperatures below 4300C and is being considered as a cushioning material in public conveyances. 

Polyimide adhesives are commercially available as electrically conductive or insulative pastes used for die attachment. They are also available as thermoplastic preforms for chip-on-lead and lead-on-chip attachments. 

Chem. Descrip. Decabromobiphenyl oxide CAS 1163-19-5 EINECS/ELINCS 214-604-9 Uses Flame relardant for thermoplastic, elastomeric, and Ihemioset polymer systems incl. HIPS, PBT, ABS, njrfons, PP, PC, PET, polybulylene, PVC, LDPE, EPDM, unsat. polyesters, epoxies, flexible PL) foam, wire insulation (polyolefin, TPE, PU elastomer, polyamide/polyimide), adhesives, coatings, textiles... 

In view of the above efforts, it is surprising that the majority of recent patents on adhesives are for solvent-based systems.The new inventions include a universal primer, an adhesive composition in which solvents have been selected based on Snyder s polarity (only solvents which belong to group III are useful in adhesive for automotive applications to avoid a deleterious effect on paint), a low VOC adhesive for pipes and fittings, a solvent-containing heat-resistant adhesive based on siloxane polyimide, a water-based polyimide adhesive,and two-component solvent-free polyurethane adhesive system for use in automotive door paneling. ... 

Electrically conductive, polyimide adhesive for high bond strength at elevated temperatiues Ablebond 71-1 Ablestik Laboratories 240 41 -... 

Polyimide Adhesives Modified with ATBN and Silicone Elastomers... 

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