Capacitive pressure transducer and method of making same

An economical, high production method for making precision capacitive pressure transducers comprising the steps of:

• preparing two members of substantially zero hysteresis nonconducting material with flat matching opposed surfaces, and the opposing surfaces of each member lying substantially in a single plane, and at least one of said members being thin enough to be flexible;
• screening an electrically conductive layer onto said flat surface of each of said two nonconductive members in a predetermined pattern for each member, with a main central area and outwardly extending conductive pathways for external electrical connections;
• firing the two nonconductive members to bond the conductive layers to the nonconductive members;
• applying a thin layer of glass frit around the main central conductive area onto said flat surface of at least one of said nonconducting members with said outwardly extending conductive pathways extending beyond said frit;
• disposing one member onto the other with the fired conductive layers facing each other, and with the glass frit forming the only spacing between the planar opposing surfaces of said members;
• firing the members, thereby bonding the two members together such that said conductive layers are opposite each other, and separated by a gap less than 0.010 inch in thickness produced only by said glass frit engaging both of said planar opposed surfaces over an outwardly extending distance substantially greater than the thickness of said gap, insulated one from the other, and substantially sealed around the main conductive areas on said members by said glass frit with said outwardly extending conductive pathways extending through the seal provided by the fired glass frit;
• and
• making electrical connections to said outwardly extending pathways, outside of said glass frit to permit detection of changes in the capacitance between said conductive layers as the pressure applied to said transducer varies.

An economical, high production method for making precision capacitive pressure transducers comprising the steps of:

• preparing two plates of substantially zero hysteresis nonconducting material with flat matching opposed surfaces, and the opposing surfaces of each member lying substantially in a single plane, at least one of said plates being thin enough to be flexible;
• screening an electrically conductive layer onto each of said two plates in a predetermined pattern for each member, with a main central area and outwardly extending conductive pathways for external electrical connections;
• firing the two plates to bond the conductive layers to the plates;
• applying a thin layer of glass frit around the main central conductive area on at least one of said nonconducting plates with said outwardly extending conductive pathways extending beyond said frit;
• disposing one member onto the other spaced apart by a distance of about one-half to several thousandths of an inch, with the fired conductive layers facing each other, and with the glass frit extending between the planar opposing surfaces of said members;
• firing the members, thereby bonding the two members together such that said conductive layers are opposite each other, and separated by a gap less than 0.010 inch in thickness;
• insulated one from the other, and substantially sealed around the main conductive areas on said members by said glass frit engaging both of said planar opposed surfaces over an outwardly extending distance substantially greater than the thickness of said gap, with said outwardly extending conductive pathways extending through the seal provided by the fired glass frit;
• and
• making electrical connections to said outwardly extending pathways, outside of said glass frit, to permit detection of changes in the capacitance between said conductive layers, as the pressure applied to said transduer varies.

An economical, high production method for making precision capacitive pressure transducers comprising the steps of:

• preparing two members of substantially zero hysteresis nonconducting material with flat matching opposed surfaces, and the opposing surfaces of each member lying substantially in a single plane, at least one of said members being thin enough to be flexible;
• applying electrically conductive layer onto each of said two nonconductive members in a predetermined pattern for each member, with a main central area and outwardly extending conductive pathways for external electrical connections;
• applying a thin layer of ceramic sealing material around the main central conductive area on at least one of said nonconducting members with said outwardly extending conductive pathways extending beyond said ceramic sealing material, said ceramic sealing material having a coefficient of thermal expansion substantially equal to that of said nonconductive members,
• disposing one member onto the other with the conductive layers facing each other, and with the ceramic sealing material extending between the planar opposing surfaces of said members;
• firing the members, thereby bonding the two members together such that said conductive layers are opposite each other, separated by a gap less than 0.010 in thickness produced only by said ceramic sealing material, insulated one from the other, and sealed around the main conductive areas on said members by said ceramic sealing material engaging both of said planar opposed surfaces over an outwardly extending distance substantially greater than the thickness of said gap, with said outwardly extending conductive pathways extending through the seal provided by the fired ceramic sealing material;
• and
• making electrical connections to said outwardly extending pathways, outside of said ceramic sealing material to permit detection of changes in the capacitance between said conductive layers, as the pressure applied to said transducer varies.

An economical, high production method for making precision capacitive pressure transducers comprising the steps of:

• preparing two members of substantially zero hysteresis nonconducting material with flat matching opposed surfaces, and the opposing surfaces of each member lying substantially in a single plane, and at least one of said members being thin enough to be flexible;
• screening an electrically conductive layer onto said flat surface of each of said two nonconductive members in a predetermined pattern for each member, with a main central area for forming a capacitor plate;
• firing the two nonconductive members to bond the conductive layers to the nonconductive members;
• applying a thin layer of glass frit around the main central conductive area onto said flat surface of at least one of said nonconducting members;
• disposing one member onto the other with the fired conductive layers facing each other, and with the glass frit extending between the planar opposing surfaces of said members;
• firing the members, thereby bonding the two members together, such that said conductive layers are opposite each other, separated by a gap less than 0.010 inch in thickness, insulated one from the other, and sealed around the main conductive areas on said members by said glass frit engaging both of said planar opposed surfaces over an outwardly extending distance substantially greater than the thickness of said gap;
• and
• making electrical connections to each of said conductive layers, to permit detection of changes in the capacitance between said conductive layers as the pressure applied to said transducer varies.

A method for making a capacitive pressure transducer comprising:

• preparing two members of substantially zero hysteresis nonconducting material with planar matching opposed surfaces, at least one of said members being thin enough to be flexible;
• applying an electrically conductive layer onto each of the two nonconductive members in a predetermined pattern to form the plates of the capacitive transducer;
• applying glass frit about the marginal perimeter of at least one of said members;
• disposing one member onto the other with the conductive layers facing each other with the glass frit between the flat matching surfaces of said members and the members and their respective associated conductive layers spaced a predetermined distance apart;
• and
• firing the members thereby bonding the two members together such that said conductive layers are opposite each other, and separated by a gap having said predetermined distance less than 0.010 inch, insulated by a gap having said predetermined distance, insulated one from the other, and sealed around the periphery of said members by said glass frit engaging both of said planar opposed surfaces over an outwardly extending distance substantially greater than the thickness of said gap.

A method for making a capacitive pressure transducer comprising:

• preparing two members of substantially zero hysteresis nonconducting material with flat matching opposed surfaces, at least one of said members being thin enough to be flexible;
• screening an electrically conductive layer onto each of two nonconductive members in a predetermined pattern, comprising a central portion defining a nonconductive cut-out portion and an outer portion substantially surrounding said central portion and spaced away from said central portion;
• applying glass frit having a coefficient of expansion substantially the same as the two members about the marginal perimeter of at least one of at least one of said members;
• disposing one member onto the other with the conductive layers facing each other, with the glass frit forming the only spacing between the flat matching surfaces of said members to form a predetermined spacing;
• and
• firing the members thereby bonding the two members together such that said conductive layers are opposite each other, and separated by a gap produced only by said glass frit, insulated one from the other, and sealed around the periphery of said members by said glass frit.

A method for fabricating a capacitive pressure sensor comprising the steps of:

• providing two glass plates, at least one of said glass plates being flexible enough to be capable of responding to a change in pressure, and each having a substantially plane surface;
• providing conductive electrodes on said substantially plane surfaces;
• applying a sealing glass material to at least one of said two glass plates;
• positioning said two glass plates to place said conductive electrodes in a substantially parallel relationship having a space therebetween;
• evacuating the space between said spaced apart electrodes;
• heating said glass plates to cause said sealing glass material to flow and to seal said glass plates together, said glass plates and said sealing glass material bounding an evacuated volume.