Method of forming a seal between a housing and a diaphragm of a capacitance sensor
The axial distance between opposing conductors of a capacitance pressure transducer can depend, in part, upon the thickness of a seal that is disposed between a housing and a diaphragm of the capacitance pressure transducer. The present invention utilizes spacer elements and sealing beads to form a seal that is disposed between the housing and the diaphragm of a capacitance pressure transducer. The sealing beads have a melting temperature that is lower than the melting temperature of the spacer elements. The sealing beads are melted so that they flow around and surround the unmelted spacer elements. Upon solidifying, the sealing beads and the spacer elements thus form the seal. The thickness of the seal can be established accurately and uniformly by controlling the height of the spacer elements. By utilizing a seal that has an accurate and uniform thickness, the opposing conductors of the capacitance pressure transducer can be accurately positioned and oriented in relationship to each other during the manufacturing process.
1. A method of forming a seal between a housing and a diaphragm of a capacitance pressure transducer, the method comprising:
depositing a first set of beads onto a sealing area, the sealing area being either a portion of the housing or a portion of the diaphragm, the beads in the first set being characterized a first melting temperature;
depositing a second set of beads onto the sealing area, the beads in the second set being characterized by a second melting temperature, the second melting temperature being lower than the first melting temperature;
biasing the housing and the diaphragm towards one another such that at least a portion of the second set of beads contact the housing and the diaphragm;
heating the diaphragm and housing to a temperature between the first and second melting temperatures and thereby melting at least some of the beads in the second set; and
cooling the diaphragm and housing to a temperature below the second melting temperature.
2. The method of claim 1 , wherein the diaphragm is comprised of a ceramic material.
3. The method of claim 2 , wherein the ceramic material is comprised of aluminum oxide.
4. The method of claim 1 , wherein the housing is comprised of a ceramic material.
5. The method of claim 1 , wherein the beads of the first and second sets are comprised of a glass material.
6. The method of claim 1 , wherein the diaphragm and the housing consist of a ceramic material comprising aluminum oxide and wherein the beads of the first and second sets are comprised of a glass material.
7. The method of claim 1 , further comprising:
establishing that each bead of the first set has substantially the same bead height.
8. The method of claim 6 , wherein establishing that each bead of the first set has substantially the same bead height comprises:
measuring a bead height of each bead of the first set;
comparing the measured bead heights to a targeted bead height; and
polishing a bead to achieve the targeted bead height if the measured bead height of the bead exceeds the targeted bead height.
9. The method of claim 1 , wherein the biasing is caused by placing an additional weight on the capacitance pressure transducer.
10. The method of claim 1 , wherein the biasing is caused by an external force that is applied between the housing and the diaphragm.
11. The method of claim 1 , further comprising:
continuing to apply the force and heating the diaphragm and housing until at least a portion of the first set of beads contact the housing and the diaphragm.
12. The method of claim 1 , wherein the first and second sets of beads are deposited via a printing process.
13. The method of claim 1 , wherein each bead of the first set of beads is comprised of glass particles.
14. The method of claim 13 , further comprising:
drying the deposited first set of beads;
degassing at least a portion of any organic solvents and binding agents which may be present in the deposited first set of beads;
fusing together within each bead of the first set of beads at least a portion of the glass particles that are contained within each bead;
cooling the first set of beads so that the first set of beads solidify;
measuring the bead height of each bead of the first set of beads;
comparing the measured bead heights of each bead of the first set of beads to a targeted bead height; and
polishing a bead of the first set of beads to the targeted bead height if the measured bead height of the bead exceeds the targeted bead height.
15. The method of claim 14 , wherein each bead of the second set of beads is comprised of glass particles.
16. The method of claim 15 , further comprising:
drying the deposited second set of beads;
degassing at least a portion of any organic solvents and binding agents which may present in the deposited second set of beads;
fusing together within each bead of the second set of beads at least a portion of the glass particles that are contained within each bead;
cooling the second set of beads so that the second set of beads solidify;
measuring the bead height of each bead of the second set of beads;
comparing the measured bead heights of each bead of the second set of beads to a second targeted bead height; and
polishing a bead of the second set of beads to the second targeted bead height if the measured bead height of the bead exceeds the second targeted bead height.
17. The method of claim 1 , wherein the first and second sets of beads are deposited on the sealing surface so that channels are present between adjacent beads.