Electric heating – Microwave heating – With heat exchange
Reexamination Certificate
2002-10-31
2004-05-11
Hoang, Tu Ba (Department: 3742)
Electric heating
Microwave heating
With heat exchange
C219S678000, C219S680000
Reexamination Certificate
active
06734409
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to the bonding together of components and, more particularly, relates to a microwave assisted joining technique for bonding together components, such as electronic and fiber optic components.
2. Technical Background
The packaging of many electronic and fiber optic (e.g., photonic) devices generally requires the joining together of components by employing adhesive bonding, soldering, or diffusion bonding/welding techniques. Many conventional bonding techniques employed for such packaging generally experience drawbacks. For example, in-situ precision alignment and adhesive bonding of photonic components may exhibit thermally induced repositioning due to ultraviolet (UV) light or heat-assisted curing. Some electronic and photonic components employ brittle glass that can be easily damaged due to thermal generally require an adhesive layer be directly and completely exposed to the ultraviolet light. Due to various shapes of components and the metal units that typically hold these components, problems of shadowing can prevent the ultraviolet light from reaching some portions of the adhesive layer, thereby increasing unwanted repositioning as well as the time required to cure the adhesive.
Bonding techniques utilizing induction-heating have been employed in which heat is produced via eddy currents generated by magnetically induced currents. The application of induction-heating to the adhesive can reduce the cure time required. However, in conventional induction-heat assisted bonding techniques, heat is typically generated by heating elements in ovens and delivered through radiation, convection, or conduction to the adhesive or solder interface. Thus, the delivery of thermal energy (heat) is an outside-to-inside heat transfer process that generally experiences high thermal energy losses.
It is also known to utilize microwave energy to weld thermoplastic substrates together or to cure a thermal setting adhesive to accelerate the rate of cure. Examples of known microwave assisted bonding techniques are disclosed in U.S. Pat. Nos. 5,338,611, 4,626,642, 5,879,756, and 6,312,548, the entire disclosures of which are hereby incorporated herein by reference. Although some polymer adhesives well absorb the microwave radiation and, therefore, can be heated in microwave assisted bonding, the bonding of components is often facilitated by a conductive pattern, which generates heat upon being irradiated with microwave energy. The electrically conductive pattern generally is positioned on a joining surface of two components and a heat curable adhesive is typically applied thereto, so the components are bonded together along the conductive pattern.
While the above-described conventional microwave assisted bonding techniques are capable of generating heat in a region near the adhesives, the conventional approaches generally cannot be applied to thin bond layers (e.g., layers less than ten microns) commonly used in micro-optic packaging. Additionally, conventional prefabricated conductive patterns, which may include perforated metal or carbon film, are generally thick, and therefore may reflect a large portion of the microwave energy. In such situations, the absorption of the microwave energy for heat generation may be inefficient. The prefabricated conductive pattern conducts heat to the adherent components and also magnifies the thermal excursion of the assembly, thereby lowering the precision optical alignment. The prefabrication of some conductive patterns generally increases the process complexity and the assembly cost. Further, conventional conductive patterns may not be effectively used to bond sub-microcomponents having thermal masses similar to that of the conductive pattern.
The relatively thick prefabricated conductive patterns generally are not optically transparent. As a consequence, the conventional conductive patterns block light and, thus, cannot be utilized for joining optical components which require light transmission therethrough. This becomes a problem when the prefabricated pattern is required to cover the joining interface almost completely to equalize the thermal field.
Accordingly, it is therefore desirable to provide for a method of bonding together first and second components that is optically precise and heat efficient and can be used in electronic, fiber optic, and photonic packaging. It is further desirable to provide for such a cost-effective method of bonding together components to perform adhesive bonding, soldering, and/or diffusion bonding, by efficiently depositing the microwave energy so as to effectively generate heat at the bonding interface.
SUMMARY OF THE INVENTION
In accordance with the teachings of the present invention, a method of bonding together first and second components and a resultant joint are provided. The method includes the steps of applying a film coating of electrically conductive material to an adjoining interface of a first component surface of the first component and a second component surface of the second component. The film coating has a thickness of less than 200 nanometers. The method also includes the step of positioning the first and second components such that the film coating is disposed between the first and second component surfaces. The method further includes the step of irradiating a microwave energy field to the film coating to generate thermal energy on the film coating to bond together the first and second components.
According to another aspect of the present invention, a joint interconnecting first and second components is provided. The joint includes a first component having a first component surface and a second component having a second component surface. The joint further includes a film coating of electrically conductive material disposed at an adjoining interface between the first and second component surfaces of the first and second components. The film coating has a thickness of less than 200 nanometers. The joint is formed by irradiating a microwave energy field to the film coating such that the film coating generates thermal energy to bond together the first and second component surfaces to form the joint.
Accordingly, the joint and method of bonding first and second components according to the present invention advantageously provides for precise and thermally efficient bonding together of components. The bonding method is cost-effective and may be used to provide adhesive bonding, soldering, or diffusion bonding, all of which are particularly useful for bonding small (e.g., micro) components together in electronic, fiber optic, and photonic packaging.
Additional features and advantages of the invention will be set forth in the detailed description which follows and will be apparent to those skilled in the art from the description or recognized by practicing the invention as described in the description which follows together with the claims and appended drawings.
It is to be understood that the foregoing description is exemplary of the invention only and is intended to provide an overview for the understanding of the nature and character of the invention as it is defined by the claims. The accompanying drawings are included to provide a further understanding of the invention and are incorporated and constitute part of this specification. The drawings illustrate various features and embodiments of the invention which, together with their description serve to explain the principals and operation of the invention.
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Hellman Scott
Townley-Smith Paul
Ushinsky Michael
Wang Liusheng
Corning Incorporated
Hoang Tu Ba
Redman Mary Y.
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