Electrically isolated via in a multilayer ceramic package

#The present invention relates to multilayer ceramic devices, and more particularly to a method for forming a multilayer ceramic package having an electrically isolated via and an isolated electrical connection.

#Certain multilayer ceramic packages are formed by layering a ceramic layer such as green tape (e.g., alumina tape, zirconia tape or the like) with one or more additional layers, such as conducting layers provided in a paste or other form. Thereafter, the conductive layers and the green tape layers are densified, such as by sintering. Some of these ceramic layers could be conductive (ionic or electronic) at high temperatures (e.g., zirconia) and a multilayer ceramic package designer may desire to form one or more electrically isolated vias in one or more of the conductive layers of a multilayer ceramic package. There is therefore a need for a method of efficiently and effectively forming electrically isolated vias in multilayer ceramic packages and for electrical connections formed with such vias.

#FIG. 1 illustrates a sequence for processing a layer for a multilayer ceramic package so that the layer includes a via and an electrical connection according to one aspect of the present invention;

#FIG. 2 illustrates a cross-sectional view of a layer having multiple electrical connections formed according to an aspect of the present invention;

#FIG. 3 illustrates a cross-sectional view of multiple layers, each having an electrical connection formed according to an aspect of the present invention;

#In accordance with one aspect of the present invention, a method is employed for forming an electrically isolated via in a layer of a ceramic device. In general, the method includes the steps of providing a ceramic green tape and forming a first via in the green tape. A hardenable non-conductive paste is placed in the first via and is hardened. A second via is formed in the hardened non-conductive paste and within the first via. Thereafter, a conductive paste is placed in the second via for forming an electrical connection.

#More specifically, according to one step of the method, and referring to FIG. 1, a first ceramic layer 10 is provided. The first ceramic layer 10 has a first surface 12 and an opposing second surface 14 separated by a thickness “t”. The first layer 10 is preferably an unsintered ceramic material, e.g., a ceramic material in its green state. By way of example, the ceramic material is provided as a green tape which optionally is layered adjacent a metal pad or a ground-plane structure. In one preferred embodiment, the first layer 10 is formed from a suitable ceramic material such as a metallic oxide, nitride, boride or the like. Specific preferred examples include, but are not limited to, zirconia, yttria stabilized zirconia or the like.

#A first via 30 is formed in the first layer 10 wherein the first via 30 is at least partially defined by a wall surface 32 of the first layer 10. The first via 30 may be formed using any suitable method of material removal, including punching, drilling, ablating, laser cutting, chemical removal techniques or another suitable technique.