Donald L. Schmidt

Adhesion of Cyclotene™ (BCB) Coatings on Silicon Substrates

This work examines the adhesion of coatings derived from divinylsiloxane bisbenzocyclobutene, mixed stereo and positional isomers of 1,3-bis(2-bicyclo[4.2.0]octa-1,3,5-trien-3-ylethenyl)-1,1,3,3-tetramethyl disiloxane (CAS 117732–87–3), on oxidized silicon substrates treated with silane coupling agents.This material, commercially available as Cyclotene™ 3022, can be used in the construction of high performance electronic circuits, such as multichip modules. Silane coupling agents examined in this study were 3-aminopropyltriethoxysilane (CAS 01760-24-3)(APTES)(, vinyltriethoxysilane (CAS 00078–08–0)(VTES), and 3-methacryloxypropyl trimethoxysilane (CAS 02530–85–0) (MOP-TMS). Measurement of the interfacial adhesion was performed using microindentation. Bond strengths obtained by this method exceed 200 MPa for the most effective coupling agents. However, these high bond strengths were not found to correlate with acceptable adhesive performance in all cases. In addition to the choice and preparation of the coupling agent, process related chemical exposure has been found to be a key element in the observed adhesive performance. The effect of the cure schedule for the thermoset coating has also been found to be a controlling factor. A short cycle test vehicle was developed consisting of a single 20 gIm polymer layer etched with anisotropic sidewalls. This test vehicle was used to evaluate the efficacy of the coupling agents during process exposures and subsequent thermal shock testing. A solution of MOP-TMS pre-hydrolyzed in methanol was found to produce the most reliable interface with high bond strength.

Some fluoroalanes and related intermediates

Abstract Fluoroalanes, AlFnX3−n·m(THF), and related intermediates, AlYn[OCH(CH3)2]3−n·m(THF), [XCl, Br, I, OCH(CH3)2; YH, Cl; n = 1,2; m = 0–2], were prepared and studied. Monofluoroalanes were isolated as bis(tetrahydrofuran)dihalofluoroalanes, AlFX2·2 THF); the notable exception was nonsolvated AlF[OCH(CH3)3]2. The corresponding difluoroalanes were less solvated but still tractable. Molecular weight determinations in THF indicated that difluoroalanes were more polymeric (D.P. 4–14) than the corresponding monofluoroalanes. Infrared and NMR data were consistent with fluorine bridged bonding especially for the difluoroalanes.

Photoinitiated Polymerization of Aryl Cyclic Sulfonium Salts

Polymers are produced by direct photolysis of substituted aryl cyclic sulfonium Zwitterionic salts in solution or film. Analysis of zwitterionic monomers via 13C NMR, UV, and IR spectroscopy as well as X-ray diffraction clearly identifies the structures taking part in the photoinduced polymerization in the solid crystalline films. The protonated form of the zwitterionic monomers, however, fails to produce detectable amounts of polymer upon photolysis under any conditions.

Rapid-set, waterborne coatings from polyzwitterionic polymers formulated with a critical solvent combination

Waterborne coatings that rapidly set and become tack-free can be prepared from polymers containing both pendant anionic (acidic, carboxylate, or strong-acid groups such as sulfonate) and cationic functionality (quaternary ammonium groups). This phenomenon is related to anion-cation interactions that function as ionic crosslinks and dramatically enhance the physical properties and water resistance of the coatings. We define this process as “controlled ionic-coacervation.” The best coating properties can only be obtained by using a “critical solvent combination.” The critical solvent combination requires water plus at least two organic solvents: (1) a lower boiling (70 to 134°C) water-soluble organic solvent having at least one hydroxyl group and (2) a higher boiling (135 to about 250°C) organic solvent. Loss of only a small amount of solvent causes a coating to rapidly become tack-free. Ionization of acid functionalities on the polymers by an increase in pH (e.g., through the loss of CO2) can initiate controlled ionic interactions. The influence of polymer and solvent compositions on coating properties is discussed.

Zwitterionic polymerization of 1‐[4‐[(4‐hydroxy‐1‐naphthyl)thio]butyl]quinuclidinium hydroxide inner salt

The zwitterion, 1-[4-[(4-hydroxy-1-naphthyl)thio]butyl]quinuclidinium hydroxide inner salt, was synthesized from tetrahydro-1-(4-hydroxy-1-naphthyl)thiophenium hydrochloride and quinuclidine and characterized by NMR and IR spectroscopy. Polymerization of the zwitterion was studied over the temperature range 175–225°C. The polymer was identified as poly(1,4-piperidinediylethyleneoxy-1,4-naphthylenethiotetramethylene) based on NMR and IR spectroscopy. The polymer was found to contain 3-butenylthio and 4-hydroxy-1-naphthyl end groups. Based on the signal area of the olefinic end group, the polymer M⌅n varied between 8500 and 13,000. The highest molecular weight was achieved at the lowest temperature, indicating that termination became more favored at higher temperature. A mechanism is proposed to describe the polymerization.

The effect of surfactant properties on a rigid foam system

Surfactants required for rigid, isocyanate-based foam formulations appear to fill at least two roles. The first role is the stabilization of the rising foam. Thus, when gas is generated via vaporization of the blowing agent, the liquid formulation will boil rather than foam unless the proper surfactant is present. As the foam rises the surfactant must stabilize the foam until enough polymerization takes place that it becomes self supporting and the cell walls are resistant to opening. A second role of the surfactant is the dispersion and emulsification of the reactants. If the reactants form multiple phases, then the reaction rate and final foam chemistry are dependent upon ease of emulsification during mixing. Generally a silicone surfactant is selected for a particular foam formulation by trial and error. The manufacturers of surfactants often classify them only in terms of their use in flexible, or rigid foams, etc. but methods that systematically compare surfactants have not generally been used. Kanner, et al. [1], has reported that both simple foaming tests in liquid polyols and water and the spread of monolayers of surfactant on water have a correlation with the initial stages of urethane foaming. These tests however were not able to predict whether the surfactant could prevent premature collapse of the flexible foams.