Stock material or miscellaneous articles – Composite – Including interfacial reaction product of adjacent layers
Reexamination Certificate
1999-06-04
2003-04-15
Gallagher, John J. (Department: 1733)
Stock material or miscellaneous articles
Composite
Including interfacial reaction product of adjacent layers
C106S286700, C156S246000, C156S001000, C156S325000, C206S568000, C264S001210, C359S793000
Reexamination Certificate
active
06548176
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a bonding process involving hydroxide-catalyzed hydration/dehydration of substrate surfaces. This invention further relates to a highly reproducible, precision bonding method involving an alkaline hydroxide-ions-based bonding material. This invention still further relates to a bonding material composition; to a method of applying a bonding material to a surface; to a novel composite material; to a method of coating a substrate with a bonding material; and to a method of forming objects of a particular geometry from a bonding material.
2. Background of the Related Art
The bonding of materials is critical in making high performance instruments or devices. Depending on the particular application, the quality of a bonding method is judged on criteria such as bonding precision, mechanical strength, optical properties, thermal properties, chemical properties, and the simplicity of the bonding process. Three popular bonding methods of the prior art are optical contacting, epoxy bonding, and high temperature frit bonding. The salient features of each of these three prior art methods are summarized below.
Optical contacting is a room temperature process which employs no bonding material, and is thus suitable only for certain precision applications involving surfaces having reasonably good surface figure match. Ideally, if the bonding surfaces are thoroughly cleaned prior to bonding, the resulting interface will have low thermal noise and contain almost nothing susceptible to oxidation, photolysis, and/or pyrolysis. However, due to its sensitivity to surface particulate and chemical contamination (such as by air-borne contaminants) and other environmental factors (such as humidity), optical contacting produces bonds which are generally unreliable in strength. In addition, surface figure mismatch almost always exists to some extent. Consequently, strong chemical bonds rarely occur extensively across the interface, and voids are sometimes seen in the interface. Bonds produced by optical contacting do not consistently survive thermal shocks. Typically, optical contacting has a low first-try success rate. In case of failure, de-bonding usually degrades surface quality, and thus lowers success rate in re-bonding.
Epoxy bonding is usually a room temperature process and has a good success rate for regular room temperature applications. However, because epoxy bonding is typically organic based, the bonding is susceptible to pyrolysis (such as by high intensity lasers) and/or photolysis (such as by ultra-violet light) in high power density applications. The strength of the epoxy bond varies with temperature and chemical environment. Because the resulting wedge and thickness cannot always be precisely controlled, epoxy bonding is unsuitable for certain precision structural work. Epoxy bonding creates a relatively thick interface which makes optical index matching more of a concern in optical applications.
Frit bonding is a high-temperature process which creates a high-temperature rated interface. The interface is mechanically strong and chemically resistant in most applications. Because the frit material is physically thick and thus thermally noisy, it is unsuitable for precision structural work. For example, when optimized for bonding fused silica, frit bonding usually creates good coefficient of thermal expansion (CTE) matching with the bonded substrates at room temperature. The matching usually does not hold to a wider temperature range, however, resulting in strain and stress at or near the interface. Furthermore, a frit bond is opaque and inapplicable in transmission optics. Due to its high temperature requirement, frit bonding requires high temperature rated fixturing for alignment, and is thus expensive. Frit bonding is unsuitable if high temperature side effects, such as changes in the physical or chemical properties of the substrates, are of concern. Thus, each of the above prior art bonding methods has limitations and disadvantages.
U.S. Pat. No. 5,669,997 to Robbert et al. discloses a method of bonding optical or semiconductor members, in which grooves are formed in one of the surfaces to be bonded using high precision laser ablation. A low viscosity adhesive is provided in the grooves to allow chemical bonding of the members, essentially without the formation of an adhesive layer interface between the members.
U.S. Pat. No. 5,053,251 to Hara et al. discloses a method of repairing glass-lined equipment by a sol-gel process, the method including the repeated steps of applying a repair agent to a damaged area of the glass layer, and heating the repair agent for solidification and adherence to the glass. The '251 also discloses an apparatus for heating the repair agent at the damaged area.
U.S. Pat. No. 5,143,275 also to Hara et al. discloses an improved method for repairing a glass layer of glass-lined equipment, in which a metallic fiber-containing sheet is disposed on the metal substrate of the damaged area, and welded to the metal substrate. A repairing agent may be supplied to the metallic sheet, and the damaged area heated to about 300° F. to 350° F.
U.S. Pat. No 3,007,832 to Milne discloses the sealing of joints between flexible sheets of alkali-soluble cellulosic material by applying a solution of alkali to the cellulosic material, and pressing the surfaces of the cellulosic material together. The incorporation of urea as a plasticizer in the sheet to be sealed allows superior sealing using lower concentrations (3-4%) of alkali.
U.S. Pat. No. 3,409,198 to Peterman discloses a bonding apparatus, including scanning means for detecting the presence on mating surfaces of surface roughness or contaminants which impede the bonding of the mating surfaces.
Japanese patent no. 3255-603-A to SONY Corp. discloses the junction of single-crystal ferrite and polycrystalline ferrite in which at least one hydroxide of K, Rb and Cs is formed at the junction interface of at least the polycrystalline ferrite.
Soviet Union/Russian reference SU 703-514 to RSFSR discloses a binder composition for building applications, comprising a mixture of 0.1 to 1.0% by weight of a metal sulphate (e.g., sodium sulphate), 1.0 to 10% by weight of alkali hydroxide (e.g., sodium hydroxide), and ground glass (the balance).
The present invention provides bonding methods and compositions which have numerous advantages over prior art methods and materials.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for producing bonds which are as precise and transparent as optical contact bonds and which also have the strength and reliability of frit bonds. It is a further object of the invention to provide such a bonding method which may be performed simply and inexpensively either at room temperature or over a broad temperature range.
One feature of the invention is that it provides an effective but simple and inexpensive precision bonding method. Another feature of the invention is that it provides a bonding method for substrate surfaces having surface figure mismatch. Another feature of the invention is that it provides a bonding method for substrate surfaces having good surface figure match. Another feature of the invention is that it provides a composite material including a bonding material. Another feature of the invention is that it provides a method of forming a composite material including a bonding material. Another feature of the invention is that it provides a method of coating a substrate surface with a bonding material.
One advantage of the invention is that it provides a reliable method for assembling Precision optical, optomechanical, and mechanical components. Another advantage of the invention is that it provides precision and non-precision bonding methods which can be performed under ambient conditions in air. Another advantage of the invention is that it provides a bonding interface which is thermally, optically, and electrically thin. Another advantage of the invention is that
Gallagher John J.
Lumen Intellectual Property Services Inc.
The Board of Trustees of the Leland Stanford Junior University
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