Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-10-19
2002-06-18
Mayes, Curtis (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S089110, C156S306600, C065S036000, C065S043000
Reexamination Certificate
active
06406578
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to hard vacuum seals. More particularly, this invention is related to a method of providing a gas laser with a hard vacuum frit seal for laser components attached to a gas discharge cavity body.
BACKGROUND OF THE INVENTION
In many laser devices, a gas discharge cavity is provided by a tube or block, herein referred to as the laser block, consisting of glass, ceramic, glass ceramic, metal, or the like. Generally, attached to the laser block is a plurality of electrodes typically consisting of a metal such as aluminum, nickel-iron alloys, and the like. Further, attached to the laser block is at least two mirrors for establishing an optical path. For ring lasers, at least three mirrors are attached to the laser block for establishing a closed-loop optical path.
In order to provide low cost manufacturing of laser devices, the electrodes and mirrors may be attached to the laser block by a frit seal, sometimes referred to as a solder glass seal. Of course, for lasers, the frit seal must provide a hermetic seal between the components and the laser block, as particularly taught in U.S. Pat. No. 4,817,112, entitled “Low Cost Ring Laser Angular Rate Sensor”, issued to Weber et al.
Another patent which shows the use of a frit seal is U.S. Pat. No. 4,233,568, entitled “Laser Tube Mirror Assembly”, issued to Hamerdinger et al. As particularly described therein, a selected glass frit is chosen on the basis of its coefficient of thermal expansion. More particularly, the coefficient of thermal expansion of the frit material is generally selected to closely match the components which are being affixed to each other.
In order to apply the frit material to either a junction of two articles or sandwiched between mounting surfaces of the two articles, the frit material is typically mixed with a low viscosity vehicle to form a resultant slurry, with the frit material suspended therein. U.S. Pat. No. Re. 25,791 is exemplary in describing the characteristics of a solder glass or frit sealing process.
In manufacturing of lasers using the above glass frit/slurry, the components to be attached to the laser block, for example the electrodes and mirrors, are placed in position, and held in place with a light force, e.g. a spring loaded force. In turn, the frit/slurry, or simply “the slurry”, is applied to the peripheral junction of the component to be attached and the laser block by a variety of techniques, including, among others, dipping, pressure flow, brushing, use of a syringe, or other “toothpaste-like” dispensing techniques.
After the slurry has been applied to the peripheral junction of the component and the laser block, the temperature of the components, laser block, and slurry are raised to a fritting temperature sufficient to allow the frit material to change to its liquid or fluid state which results in a liquid glass surrounding the aforementioned junction. This step is followed by a cooling period during which time the frit material returns to its “glass” state thereby forming a hermetic seal at the junction of the component to the laser block.
The aforementioned process is described in further detail in the aforementioned U.S. Pat. No. 4,233,568. However, with respect to laser devices, it should be noted that the aforementioned process is preferably one of placing the frit material around the junction of the components and the laser block, as opposed to being sandwiched between the mounting surface of the component and a mounting surface of the laser block.
Although the “slurry” process as just described provides an adequate hermetic seal, it has a number of disadvantages. For example, the frit/slurry combination is sensitive to the “mix ratio” of the frit material and the vehicle. This may lead to inconsistencies in the completeness, strength, coefficient of thermal expansion induced stress, and the hermeticity of the seal. Secondly, the slurry process does not lend itself to consistent application of the slurry material from one component to the next, thereby decreasing the reliability of the seal in high volume production. Lastly, the frit/slurry process does not lend itself to “automated” production techniques because of the difficulties encountered in the application of the slurry surrounding the junction of the component and the laser block.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a frit seal without the disadvantages of a frit/slurry seal method.
Another object of the invention is to provide a consistent frit seal between two articles intended to be affixed to each other.
The present invention pertains to both a method and apparatus of a novel seal particularly useful in the manufacture of lasers, and other kinds of gas discharge devices. More particularly, this invention pertains to the attachment of electrodes and/or mirrors to a body which provides a gas discharge cavity.
In the present invention, two articles are provided with mounting surfaces which are to be joined together. The first article is held against second article forming a peripheral junction. A ring shaped preform is placed on the mounting surface of the second article in proximity of the first and second articles. The preform material consists substantially of a frit material for forming a seal between the two articles which are intended to be attached to each other. The combination of the two articles and preform is heated to a sufficient temperature to cause the frit material to change to a liquid state to thereby form a hermetic seal after cooling.
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Beckwith Timothy A.
Jossi Shari L.
Olson Stuart D.
Ostertag Thomas G.
Schober Christina M.
Bremer Dennis C.
Honeywell Inc.
Mayes Curtis
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