Electric heating – Metal heating – By arc
Reexamination Certificate
1999-07-14
2001-09-11
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
By arc
C156S292000
Reexamination Certificate
active
06288360
ABSTRACT:
TECHNICAL FIELD
The instant invention relates to ablation patterning, particularly to ablation patterning of multilaminate materials.
BACKGROUND OF THE INVENTION
The use of ablation patterning of various polymeric materials, e.g., polyimides, is known. U.S. Pat. No. 4,508,749, for example, disclosed the use of ultraviolet (U.V.) radiation for etching through a polyimide layer. This patent is primarily directed to producing tapered openings through a polyimide layer for exposing surface areas of an underlying layer of metal. Electrical connections are then made through the openings to the metal layer. U.S. Pat. No. 5,236,551 likewise disclosed ablation etching for patterning a polymeric material layer which is then used as an etch mask for etch patterning, using wet or chemical etchants, an underlying layer of metal.
In a typical ablation process, a beam of laser energy is directed against an exposed surface of a body to be ablated. The laser energy is absorbed by the material and, as a result of photochemical, thermal and other effects, localized explosions of the material occur, driving away, for each explosion, tiny fragments of the material. The process requires that significant amounts of energy be both absorbed and retained within small volumes of the material until sufficient energy is accumulated in each small volume to exceed a threshold energy density al which explosions occur.
Polymeric materials, such as polyimides, are well suited for use in the process because such materials have a high absorptivity for U.V. light while having a relatively low thermal diffusivity for limiting the spread of the absorbed energy away from the volume where the energy was absorbed. Thus, the energy level quickly builds above the required energy density threshold.
When an excimer laser is used, because of the unique optical focusing requirements; of the excimer laser it is important to the manufacturing process that the material to be ablated flat, with a typical peak-to peak roughness of less than about 20 microns, i.e., ±10 microns for a given ablation operation. This need and others are addressed by the instant invention.
SUMMARY OF THE INVENTION
One aspect of the invention is a method of ablating holes in a material, the method comprising providing a laminated material comprising first and second layers, said first and second layers having different coefficients of thermal expansion, said first layer having within it a hole, wherein a target region of said second layer in said laminated material is not laminated to said first layer but is surrounded entirely by laminated regions wherein the first layer is laminated to the second layer; providing a laser source producing energy of a wavelength and a power level that can ablate material from said first layer, changing the temperature of the laminated material so as to place said target region under tension; and directing said laser source onto said target region and ablating a portion thereof. The coefficient of thermal expansion of the first laminates layer may be greater than or less than that of the second laminate layer.
A further aspect of the invention is a method of preparing a laminated material for laser ablation, comprising laminating a first layer to a second layer, wherein said first and second layers have different coefficients of thermal expansion, and wherein said second layer has an interior hole such that when the laminated substrate is formed, a region of the first layer aligned with said hole is not laminated to the second layer and is surrounded by laminated regions.
A further aspect of the invention is a laminated material comprising first and second layers, wherein said first and second layers have different coefficients of thermal expansion, and wherein said second layer has an interior hole such that a region of the first layer aligned with said hole is not laminated to the second layer and is surrounded by laminated regions.
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Aradigm Corporation
Borden Paula A.
Bozicevic, Field & Francis
Evans Geoffrey S.
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