Fluid level sensor

• US 6,539,286 B1
• Filed: 01/26/1998
• Issued: 03/25/2003
• Est. Priority Date: 01/26/1998
• Status: Expired due to Fees

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Jiang, Tongbi
• Primary Examiner(s): Gordon, Paul P.
• Application Number:
  US09/013,418
• Time in Patent Office: 1,884 Days
• Field of Search: 700/282, 700/283, 700/240, 700/281, 156/51, 156/47, 239/63, 239/65, 239/68, 239/69, 239/99, 733/04.R
• US Class Current: 700/282
• CPC Class Codes: A61M 2205/3389 Continuous level detection A61M2205/3393 takes precedence
• CPC Class Codes: A61M 5/1684 by detecting the amount of infusate remaining, e.g. signalling end of infusion
• CPC Class Codes: G01F 23/24 by measuring variations of resistance of resistors due to contact with conductor fluid
• CPC Class Codes: H01L 2224/32245 the item being metallic
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01079 Gold [Au]
• CPC Class Codes: H01L 2924/181 Encapsulation

Abstract

A fluid level sensor is used in a container in a system for dispensing adhesive used in the formation of electronic devices. The sensor includes a pair of electrical conductors positioned inside the container. A voltage is applied across the conductors to cause a current flow through the fluid in the container. The magnitude of the current flow represents the amount of fluid remaining in the container. If an empty container is detected, the system is shut off.

Claims

1. A method of applying an adhesive onto an electronic device, the method comprising:

storing the adhesive in a container having electrical conductors positioned inside the container;

applying a voltage across the conductors;

measuring current flow through the adhesive to determine the adhesive level in the container; and

supplying the adhesive to the electronic device until the adhesive level drops below a predetermined amount.

2. The method of claim 1, wherein storing the adhesive comprises storing an electrically conductive adhesive in the container.

3. The method of claim 1, wherein storing the adhesive in the container having electrical conductors positioned inside the container comprises storing the adhesive in the container having electrical conductors, wherein each of the conductors contains a material selected from the group consisting of copper, gold, silver, and tungsten.

4. The method of claim 1, wherein storing the adhesive comprises storing the adhesive comprising electronically conductive fillers.

5. The method of claim 4, wherein storing the adhesive comprises storing the adhesive comprising filler material containing nickel.

6. The method of claim 4, wherein storing the adhesive comprises storing the adhesive comprising filler material containing gold.

7. The method of claim 4, wherein storing the adhesive comprises storing the adhesive comprising filler material containing silver.

8. The method of claim 1, wherein applying a voltage across the conductors comprises applying a varying voltage across the conductors.

9. The method of claim 1, further comprising:

determining a resistance value based on the applied voltage and measured current.

10. The method of claim 9, further comprising:

comparing the determined resistance to a threshold resistance to determine if the container is empty.

11. The method of claim 1, wherein applying the voltage comprises applying a voltage based on a conductivity of the adhesive.

12. The method of claim 1, wherein storing comprises storing the adhesive in the container having the electrical conductors coated on an inside wall of the container.

13. The method of claim 1, comprising supplying the adhesive until the adhesive level drops below the predetermined amount, wherein the predetermined amount is based on the measured current.

14. A system for dispensing an adhesive onto an electronic device, comprising:

a container adapted to store the adhesive and a port through which the adhesive can flow;

electrical conductors positioned inside the container; and

a controller adapted to apply a voltage across the electrical conductors, wherein a current is induced through the adhesive, the current being measured to determine a level of the adhesive in the container and to supply the adhesive to the electronic device based on the measured current.

15. The system of claim 14, wherein the current decreases with the amount of adhesive adapted to be stored in the container.

16. The system of claim 14, wherein a voltage is applied across the electrical conductors.

17. The system of claim 14, wherein each of the conductors contains a material selected from the group consisting of copper, gold, silver, and tungsten.

18. The system of claim 14, wherein the electrical conductors comprise a first conductor and a second conductor, and wherein the first and second conductors are of substantially same length.

19. The system of claim 14, wherein the adhesive is dispensed onto a leadframe in the electronic device.

20. The system of claim 14, wherein the adhesive flow is stopped when the detected adhesive level drops below a predetermined level.

21. The apparatus of claim 14, wherein the controller compares a determined resistance to a threshold resistance to determine if more adhesive is desired.

22. Apparatus for detecting a level of an adhesive inside a container, comprising:

electrical conductors positioned inside the container;

a controller electrically coupled to the electrical conductors to apply a voltage to the conductors;

a measurement device configured to measure current flow through the adhesive capable of being stored inside the container to determine the adhesive level and a port to provide the adhesive to a device until the measured current is a preselected value.

23. The apparatus of claim 22, wherein each of the electrical conductors is coated to a corresponding inner wall of the container.

24. The apparatus of claim 22, wherein the electrical conductors include probes placed inside the container.

25. The apparatus of claim 22, wherein the adhesive is electrically conductive.

26. The apparatus of claim 25, wherein the adhesive contains an electronically conductive filler.

27. The apparatus of claim 22, wherein the adhesive includes a material selected from a group consisting of a thermoset compound, a thermoplastic compound, and a mixture of thermoset and thermoplastic compounds.

28. The apparatus of claim 22, wherein the controller applies the voltage based on a conductivity of the adhesive.

29. The apparatus of claim 22, wherein the controller determines a resistance value based on the applied voltage and measured current.

30. A method, comprising:

allowing application of a voltage across electrical conductors positioned inside a container capable of storing an adhesive;

enabling measuring current flow through the adhesive to determine a adhesive level in the container; and

enabling supplying the adhesive to an electronic device in response to measuring the current flow through the adhesive.

31. The method of claim 30, wherein enabling supplying the adhesive to the electronic device in response to measuring the current flow comprises enabling supplying the adhesive to the electronic device until the adhesive level drops below a predetermined amount.

32. The method of claim 30, further comprising enabling determining a resistance value based on the applied voltage and measured current.

33. The method of claim 32, further comprising enabling comparison of the determined resistance to a threshold resistance to determine if the container is empty.

34. An apparatus comprising:

conductors positioned inside a container;

a controller communicatively coupled to the conductors to apply a voltage to the conductor; and

a device to detect presence of current through an adhesive inside the container to determine a level of the adhesive and to supply the adhesive to a device based on the determined adhesive level.