Importance

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Abstract

Via holes in a thin planar layer of unfired ceramic which consists essentially of a mixture of an inorganic nonmetallic powder having a high melting temperature and a binder having a lower vaporizing temperature, are formed by the steps of: directing a laser beam, in a sequence, at certain locations on the layer where the via holes are to be formed; controlling the power density in the directed laser beam to a low level at which the binder vaporizes at each of the locations while the powder stays unsintered and unmelted; and removing from the directed laser beam during the above steps, both the vaporized binder and the unbound powder which remains where the binder vaporizes. Preferably, the vaporizing temperature of the binder and the melting temperature of the binder and the melting temperature of the powder are selected such that they differ by at least 200.degree. C.; the power density of the laser is controlled to be between 5 kW/cm.sup.2 and 75 kW/cm.sup.2 ; and the removing step is performed by impinging a gas jet at each location where the laser beam is directed and simultaneously vacuuming the location.

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First Claim