Electric heating – Metal heating – By arc
Patent
1994-03-21
1996-07-23
Evans, Geoffrey S.
Electric heating
Metal heating
By arc
21912171, 21912173, B23K 2606
Patent
active
055391753
ABSTRACT:
A method and apparatus is disclosed for laser ablation of openings with a specified wall profile in materials such as polyimide. The method includes identifying the opening profile of choice. This profile of choice is then divided into convex portions which can be "stably" formed and concave portions which are "unstably" formed. With respect to convex portions of apertures, after ablation to their desired depth, these convex portions remain substantially unchanged with additional exposure to otherwise ablating radiation. With respect to concave portions of apertures, these concave portions change with additional exposure to ablating radiation. Accordingly, techniques are disclosed for controlling exposure to ablating radiation, controlling the profile of the ablating radiation, or both. In either case, the intensity profile of the working image containing the ablating light is shaped in accordance with the depth and slope of the sidewalls of the opening desired. Intensity of the working image is tailored across the opening to levels above the ablation threshold in accordance with the desired wall shape. Exposure to ablating radiation occurs with this exposure closely monitored only in the case of unstable concave profiles. The technique can be practiced with imaging systems or, preferably, practiced with masks containing computer generated holograms where light efficiencies are improved, sometimes by factors >1000. There results the ability to mass produce matrices of precisely shaped images by laser ablation.
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Hunter, Jr. Robert O.
McArthur Bruce B.
Smith Adlai H.
Evans Geoffrey S.
Litel Instruments
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