Method of manufacturing a microbalance

• US 6,784,381 B2
• Filed: 07/05/2002
• Issued: 08/31/2004
• Est. Priority Date: 08/13/2001
• Status: Active Grant

• Current Assignee: Sierra Instruments, Inc.
• Original Assignee: David Michael Korpi
• Inventors: Korpi, David Michael
• Primary Examiner(s): Gibson, Randy W.
• Application Number:
  US10/188,823
• Publication Number:
  US 20030066689A1
• Time in Patent Office: 788 Days
• Field of Search: 312/236, 177/210.FP, 73/190.3, 735/80, 73/240.1, 295/921
• US Class Current: 177/210.0FP
• CPC Class Codes: G01G 23/48 Temperature-compensating arrangements G01G1/14, G01G1/42, G01G3/18 take precedence
• CPC Class Codes: G01G 3/16 measuring variations of frequency of oscillations of the body
• CPC Class Codes: G01G 3/165 Constructional details
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

22A temperature and/or pressure compensated microbalance is disclosed. Temperature compensation is achieved by applying heat to at least a part of the microbalance, measuring a temperature-dependent variable, and controlling the amount of heat applied to the microbalance to keep the temperature-dependent variable substantially constant. In one embodiment, the heat is applied to the microbalance by passing electrical current through a resistive element provided on or embedded in the oscillating element of the microbalance. Pressure compensation is achieved by taking into account the variation in the mass or density of fluid passing through the microbalance. Various materials and methods of construction are also disclosed, including micro-machining and electroforming.

Claims

1. A method of manufacturing a microbalance, comprising the steps of:

providing a form onto which an oscillating element of a microbalance can be electroformed;

electroforming the oscillating element of a microbalance onto the form; and

removing the oscillating element of a microbalance from the form.

2. The method of claim 1 further comprising the step of:

forming an insulating layer on the oscillating element.

3. The method of claim 2 further comprising the step of:

providing a resistive element on the insulating layer.

4. A method of manufacturing a microbalance, comprising the steps of:

depositing a spacer layer on a piece of silicon;

layering a microstucture layer on top of the spacer

etching the microstucture layer to define a resonant microstructure of a microbalance; and

etching the spacer layer thereby to make the resonant microstructure of a microbalance

freestanding.

5. The method of claim 4 further comprising the step of:

forming a motion sensing layer that uses proximity detection by capacitance or reluctance.

6. The method of claim 5 further comprising the step of:

providing an excitation structure comprising an electrostatic comb drive to drive the resonant microstructure.

7. The method of claim 5 wherein the resonant microstructure includes an impaction plate or a filter holder.