Electric heating – Metal heating – By arc
Reexamination Certificate
2000-04-17
2002-04-09
Heinrich, Samuel M. (Department: 1725)
Electric heating
Metal heating
By arc
C219S121640, C219S121720
Reexamination Certificate
active
06369351
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for machining a component or a component array by means of electromagnetic radiation, in which the component or the component array comprises at least two materials disposed in succession in the incident direction of the electromagnetic radiation.
BACKGROUND OF THE INVENTION
It is well known to use electromagnetic radiation, in particular laser radiation, for joining components. From German Patent Disclosure DE 195 20 336 A1, a method for soldering electronic components onto a circuit substrate is known, in which laser radiation is employed to heat and melt the solder.
Similar methods are also known from German Patent Disclosures DE 40 17 286 A1, DE 40 38 765 A1, and DE 195 29 388 A1.
It is also known to use laser radiation for soldering components of ceramic material to components of metal. The metal is disposed downstream of the ceramic material in the incident direction, and there is a glass solder between the two materials. The laser radiation is aimed at the ceramic material and is partly absorbed by it and partly passed through to the glass solder, disposed downstream of the ceramic material in the incident direction, and to the metal disposed downstream of the glass solder in the incident direction. The absorption of the laser radiation in the ceramic material and in the metal leads to heating of these materials, and as a result the glass solder is also heated and melts. Once the glass solder has melted in the desired way, the laser radiation can be turned off. In the ensuing solidification of the glass solder, this solder bonds the ceramic material to the metal.
One disadvantage of this known method is that a high intensity of the laser radiation is required in order to assure that a sufficient proportion of the laser radiation will be passed through to the metal so that it can be absorbed by it. This entails a high temperature gradient, which leads to thermal stresses and often to cracking in the ceramic body, which destroys the component. For this reason, the known method has proved to be of only limited utility.
SUMMARY OF THE INVENTION
One object of the invention is to provide an improved technique for machining a component or a component array.
Another object of the invention is to provide a technique for machining a component or a component array with electromagnetic radiation, which technique is also suitable for joining components.
A further object of the invention is to provide a technique for machining a component or a component array with electromagnetic radiation in which damage to the components is reliably avoided.
The fundamental concept of the teaching according to the invention is to employ electromagnetic radiation of different wavelengths for machining components or component arrays that comprise different materials; at least some of the different materials of the component or the component array are assigned electromagnetic radiation of a wavelength that is absorbed more strongly by the affected material than by the other materials. In this way, selective machining of the various materials is made possible, since the electromagnetic radiation assigned to one material acts predominantly or exclusively on that material.
When components of ceramic material are soldered to components of metal, laser radiation of a first wavelength and second wavelength can for instance be used; the first wavelength is absorbed more weakly by the ceramic material than by the metal. In this way, the absorption of the laser radiation of the first wavelength in the ceramic material is reduced, so that on the one hand adequate absorption by the metal and thus adequate heating of the metal is attained. On the other hand, an undesired absorption of laser radiation of this wavelength by the ceramic material is averted. In this way, the risk of cracking from thermal stresses because of an overly high temperature gradient in the ceramic material, and thus the risk of damage to the component, are reliably avoided.
The method of the invention can be performed simply and quickly and in manifold ways. It is especially well-suited to joining components or component arrays of different materials, for instance for soldering, welding or adhesive bonding of them.
The wavelengths of the electromagnetic radiation can be selected within wide limits to suit the particular materials to be machined. The radiation sources for generating the electromagnetic radiation can likewise be selected within wide limits to suit the applicable requirements and the materials to be machined. Both radiation sources whose electromagnetic radiation has a single wavelength and radiation sources whose electromagnetic radiation has multiple wavelengths can be used. The wavelengths can also be selected such that a material absorbs electromagnetic radiation of a plurality of wavelengths.
An especially advantageous feature of the teaching of the invention provides that the first and the second wavelength are selected such that the electromagnetic radiation of the second wavelength is absorbed by the first material, while the electromagnetic radiation of the first wavelength is passed substantially completely through from the first material to the second material disposed downstream of the first material in the incident direction. In this embodiment, the electromagnetic radiation of the first wavelength is substantially not absorbed by the first material but instead is substantially passed completely through to the second material. In this way, an undesired absorption of the electromagnetic radiation of the first wavelength in the first material is substantially avoided. The electromagnetic radiation of the first wavelength is instead passed through to the second material, in which it is absorbed and acts in the desired way on that material.
In principle, it is possible for the electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength to be generated by the same radiation source, such as a radiation source that generates electromagnetic radiation in a wavelength band that includes the first wavelength and the second wavelength. An advantageous embodiment, however, provides that the electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength are generated by different radiation sources. In this embodiment, an adaptation of the various radiation sources to the various materials is made possible; for instance, the intensity of the electromagnetic radiation can be selected for the various materials separately from one another. Furthermore, the action time of the electromagnetic radiation or the type of action, such as continuous or pulsed operation, can be selected for the various materials separately from one another.
Another refinement provides that the electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength are generated by radiation sources of different types of radiation. The electromagnetic radiation of the first wavelength and the electromagnetic radiation of the second wavelength can, however, also be generated by radiation sources of the same type of radiation, as another refinement provides. In the aforementioned embodiments, laser radiation and/or infrared radiation can for instance be employed as the types of radiation. In the embodiment having the radiation sources of different types of radiation, at least one of the radiation sources can for instance be formed a laser and at least one another radiation source can be formed an infrared radiator. In the embodiment with the radiation sources of the same type of radiation, lasers can for instance be used exclusively as the radiation sources.
The shape, size and geometry of the component or the component array to be machined can be selected within wide limits. One embodiment provides that the second material immediately follows the first material in the incident direction of the electromagnetic radiation. In this embodiment, the two materials are placed adj
Frishauf, Holtz Goodman, Langer & Chick, P.C.
Heinrich Samuel M.
Patent - Treuhand Gesellschaft fur Elektrische - Gluhlampen mbH
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