Adhesion, siloxane polyimide

The aminosilane coupling agent 3-aminopropyltriethoxysilane or y-amino-propyltriethoxy silane—also abbreviated as 3-APS, y-APS, APS or A1100 (Union Carbide)—is widely used to promote adhesion between polyimide thin films and mineral surfaces such as native-oxide silica, alumina and various glass ceramics [1, 2]. The structure of APS and the hydrolysis reaction sire shown in Fig. 1. Typically, dilute aqueous solutions of 0.1 vol% or approximately 0.080 wt % are employed to prime the mineral surface. The mechanism for the interaction of the bifunctional aminosilane with the mineral surface is the subject of much speculation, although it is conjectured by Linde and Gleason [3] that the amine end initially forms an electrostatic bond with surface hydroxyls. Subsequently, possibly as the result of elevated temperatures, the silanol end of the molecule proceeds to form a siloxane-like bond with the surface and the amine... 

JP 05125345 (Japanese) 1993 Poly(vinyl butyral) blend adhesive composition for flexible printed circuit boards Ube Industries, Japan H Inoe, S Takabayashi, T Muramatsu, T Funakoshi Formulated resins having good flexibility and heat resistance are useful adhesives for polyimide/Cu foil laminated circuit boards Maleimide-terminated siloxane-imide block copolymers were formulated with poly(vinyl butyral) and melamine resins to give adhesive compositions. 

Current interest in siloxane polyimides is triggered by opportunities for such materials in military, aerospace and electronic applications as coatings, films, adhesives, molding compounds and composite matrix materials which are subject to demanding operating conditions. These polymers offer advantages such as excellent interlevel adhesion, plasma resistance, low water absorption, and stability at high temperatures. 

Because of the improved thermal stability for PADS containing polyimides vis a vis other available siloxane polyimides, a screening program to correlate properties such as Tg, solubility, thermal stability, adhesion properties, and water absorption characteristics to structure was undertaken. Several copolymers were prepared from diamines and co-dianhydrides. An ODAN/ ODA copolymer in which 30 mole % PADS was substituted for ODAN, was prepared and TGA analysis at 450°C indicated that the material was the first siloxane containing polyimide identified that exceeded the established thermal stability criteria for interlevel dielectric applications. Stability and solubility of these materials as a function of PADS concentration is illustrated in Table VI. 

PADS containing siloxane polyimide compositions were evaluated for adhesion to silicon wafers according to the identical test protocol employed by Davis (7). As shown in Table VIII, these polymers had adhesive properties similar to the GAP derived siloxane polyimides however, the PADS containing materials are of higher thermostability than the GAP derived materials. Thus, the PADS class of materials offers a balance of adhesive and thermal qualities not hitherto attainable. 

Adhesion for PADS-based siloxane polyimides was obtained over a range of comonomer compositions. The spun-on "PADS coatings generally had to be annealed at 300°C to impart adhesion to silicon. In at least one series of copolymer compositions, the PADS content could be decreased to 10 mole % while maintaining adhesion to silicon as determined by the Tape Peel Test. 

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. ... 

St. Clair et. al. investigated a series of maleimide and nadimide terminated polyimides and developed LARC-13 [8,9]. Changing the terminal group from maleimide to nadimide, the value of the lap shear strength of a titanium lap shear joint increased from 7 to 19 MPa [9]. They also added an elastomeric component to the adhesive formulation. The introduction of 15 wt% of a rubbery component, ATBN (amine terminated butadiene nitrile polymer) and ADMS (aniline terminated polydimethyl siloxane) enhanced the adhesive properties as follows 19 MPa to 25 MPa (ATBN) titanium T-peel strength 0.2 kN/m to 1.4... 

More recently, St. Clair and co-workers176) reported the use of aromatic amine terminated polydimethylsiloxane oligomers of varying molecular weights in an effort to optimize the properties of LARC-13 polyimides. They observed the formation of two phase morphologies with low (—119 to —113 °C) and high (293 to 318 °C) temperature Tg s due to siloxane and polyimide phases respectively. The copolymers were reported to have improved adhesive strengths and better thermal stabilities due to the incorporation of siloxanes. 

JP 05306386 (Japanese) 1993 Heat-resistant adhesive composition Ube Industries, Japan H Inoe, S Takabayashi, T Muramatsu, T Hirano Resin formulation useful for bonding Cu foils to polyimide films for electronic applications Heat-resistant adhesives were formulated to include imide-siloxanes with softening points <300° C. Diaminopolysiloxanes and aromatic amines were used maleimide termination also utilized. 

JP 05311144 (Japanese) 1993 Heat-resistant adhesive compositions containing polyimide-siloxane block copolymers Ube Industries, Japan H Inoe, S Takabayashi, T Funakoshi, K Sonoyana Useful for Cu-clad laminates of printed circuit boards and tape-automated bonding with good flexibility and heat resistance Formulated compositions containing siloxane-imide block copolymers made from aromatic tetracarboxylic acids and aromatic diamines and aminosiloxanes... 

EP 0518060 (European) 1992 Polyimide-si-loxane extended block copolymers Occidental Chemical S Rojstaczer Useful as coatings and adhesives in microelectronic have higher Tg than the corresponding non-ext ended block copolymers while retaining solubility Siloxane-imide block copolymers were prepared using amino-terminated siloxanes and organic diamines along with pref. aromatic dianhydrides... 

US 5,204,399 (American) 1991 Thermally conductive thermoplastic polyimide film die attach adhesives and their preparation National Starch and Chemical Investment Holding Corp. R Edelman Adhesive formulations having excellent die shear strength A polyimide-siloxane was prepared from aromatic amines, bis aminophe-noxybutylsiloxane and aromatic dianhydrides... 

JP 62246978 (Japanese) 1987 Heat-resistant adhesives containing siloxanes and imide-containing resins Shin-Etsu Chemical Industry Co. Ltd., Japan S Ueno, N Nakanishi, S Hoshida Adhesives showed good adhesion and flexibility useful in the preparation of flexible laminates Resin was prepared from the reaction product of bismaleimides, diamines, amino-terminated siloxanes and a bisphenol A cyanate adduct. The adhesive formulation was used on polyimide films... 

Some new electronic applications of polyimide-siloxane adhesives have been already partially reviewed. In addition, the development of photo-crosslinkable copolymers has been of great interest for the development of components of electronic devices [126]. The general field of photosensitive polymers was reviewed by Horie and Hamishita in 1995 [127]. A number of papers have investi-... 

Segmented polyimide-polydimethylsiloxane copolymers have been successfully synthesized both in laboratory and industrial quantities to produce multiphase siloxane-modified polyimides. The siloxane detracts somewhat from the otherwise excellent thermo oxidative stability of the polyimide, but it does produce a number of important properties. These include multiphase behavior, improved adhesion to many substrates, improvements in fire resistance and enhanced gas and liquid separation membranes, where one wishes not only to maximize the contribution of the siloxane to permeability, but also to utilize the imide to re-... 

Yoon TH, Arnold-McKenna CA, McGrath JE (1992) Adhesion behavior of thermoplastic polyimides and poly(imide siloxane) segmented copolymers influence of test temperatures J Adhes 39(100) 15... 

Yoon TH, Arnold CA, McGrath JE (1989) Titanium 6/4 single lap shear adhesive performance of polyimide homopolymers and poly(siloxane imide) segmented copolymers. Mater Res Soc Symp Proc 153 (Interfaces Polym Met Ceram) 211... 

Furukawa N,Yuasa M.Omoro F,YamadaY (1996) Adhesive properties of siloxane-mod-ified polyimides and application for multi-layer printed circuit boards. J Adhes 59 1,281... 

Rosenfeld JC, Rojstaczer SR, Tyrell JA. Three-layer polyimide-siloxane adhesive tapes PCT Int Appl WO 9421744 A1 940929 24 pp... 

Inoue H Takabayash S Muramatsu T, Funagoshi T, Hirano T. Polyimide-siloxane block copolymer-based heat-resistant adhesive compositions. US Patent 5180627 A 930119 11 pp... 

Lastly, resins are commercially available where siloxane structures have been incorporated into the polyimide chains. These polysiloxaneimides are noted for their flexibility and low moisture absorption. They are thermoplastics that are processed as hot-melt adhesives. ... 

Polyimides are of particular interest for many engineering applications due to their excellent thermal and mechanical properties in the aerospace and microelectronics industries. Many important applications have been developed (1,2 The poiyimide siloxane segmented copolymers have been of particular interest since incorporation of amine functionalized polysiioxanes into polyimides have resulted in improved solubility and processability, decreased water absorption, atomic oxygen resistance (3), lower dielectric constants (4) and enhanced adhesion (5). The copolymers are generally synthesized as shown in Scheme 1 from a combination of a dianhydride and... 

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