Thermal flow sensor having recesses in a substrate

1. A thermal flow sensor comprising:

a first substrate having a first side and a second opposite side;

a second substrate having a first side and a second opposite side, said first substrate being connected to said second substrate such that said second side of said first substrate abuts said first side of said second substrate;

a third substrate having a first side and a second opposite side, said third substrate being connected to said second substrate such that said second side of said second substrate abuts said first side of said third substrate;

wherein said second substrate having a groove formed therein so as to form a conduit bounded by said second substrate and said second side of said first substrate and said first side of said third substrate,

a heater disposed on said first side of said first substrate opposed to said conduit;

a first temperature sensor disposed on said first side of said first substrate opposed to said conduit; and

a second temperature sensor disposed on said first side of said first substrate opposed to said conduit;

wherein a first recess being formed in at least one of said first side and said second side of said first substrate between said heater and one of said first temperature sensor and said second temperature sensor.

2. The thermal flow sensor of claim 1 ,

wherein a second recess being formed in said first side of said first substrate between said heater and the other one of said first temperature sensor and said second temperature sensor.

3. The thermal flow sensor of claim 2 ,

wherein a second recess being formed in said first side of said first substrate between said heater and the other one of said first temperature sensor and said second temperature sensor, said second recess extends into said first substrate for about half of the thickness of said first substrate.

4. The thermal flow sensor of claim 1 ,

wherein said first recess extends into said first substrate for about half of the thickness of said first substrate.

5. The thermal flow sensor of claim 1 ,

wherein said first recess is disposed immediately adjacent to said heater.

6. The thermal flow sensor of claim 1 ,

wherein said first recess is disposed immediately adjacent to said heater, a second recess being formed in said first side of said first substrate between said heater and the other one of said first temperature sensor and said second temperature sensor, said second recess is disposed immediately adjacent to said heater on an opposite side of said heater from said first recess.

7. The thermal flow sensor of claim 1 , wherein said first recess is disposed in said first side of said first substrate.

8. The thermal flow sensor of claim 1 , wherein said first recess is disposed in said second side of said first substrate.

9. The thermal flow sensor of claim 1 , wherein said first recess is comprised of a first recess and a second recess, said first recess is disposed in said first side of said first substrate and said second recess is disposed in said second side of said first recess.

10. A thermal flow sensor comprising:

a first substrate having a first side and a second opposite side;

a second substrate having a first side and a second opposite side, said first substrate being connected to said second substrate such that said second side of said first substrate abuts said first side of said second substrate;

wherein at least one of said first substrate and said second substrate having a groove formed therein so as to form a conduit bounded by said first and second substrates;

a heater disposed on said first side of said first substrate opposed to said conduit;

a first temperature sensor disposed on said first side of said first substrate opposed to said conduit; and

wherein a first recess being formed in at least one of said first side and said second side of said first substrate between said heater and said first temperature sensor.

11. The thermal flow sensor of claim 10 , further comprising a second temperature sensor disposed on said first side of said first substrate opposed to said conduit.

12. The thermal flow sensor of claim 11 , further comprising a second recess formed in said first side of said first substrate between said heater and said second temperature sensor.

13. The thermal flow sensor of claim 12 , wherein said second recess extends into said first substrate for about half of the thickness of said first substrate.

14. The thermal flow sensor of claim 12 , wherein said first recess is disposed immediately adjacent to said heater, said second recess is disposed immediately adjacent to said heater on an opposite side of said heater from said first recess.

15. The thermal flow sensor of claim 10 , wherein said first recess extends into said first substrate for about half of the thickness of said first substrate.

16. The thermal flow sensor of claim 10 , wherein said first recess is disposed immediately adjacent to said heater.

17. The thermal flow sensor of claim 10 , wherein said first recess is disposed in said first side of said first substrate.

18. The thermal flow sensor of claim 10 , wherein said first recess is disposed in said second side of said first substrate.

19. The thermal flow sensor of claim 10 , wherein said first recess is comprised of a first recess and a second recess, said first recess is disposed in said first side of said first substrate and said second recess is disposed in said second side of said first recess.

20. A thermal flow sensor comprising:

a first substrate having a first upper side and a second opposite lower side, and at least one side edge extending between said first upper side and said second lower side, a conduit formed therein having an inlet opening and an outlet opening, each of said openings being formed in said at least one edge

a heater disposed on said first side of said first substrate opposed to said conduit;

a first temperature sensor disposed on said first side of said first substrate opposed to said conduit; and

wherein a first recess being formed in at least one of said first side and said second side of said first substrate between said heater and said first temperature sensor.

21. The thermal flow sensor of claim 20 , further comprising a second temperature sensor disposed on said first side of said first substrate opposed to said conduit.

22. The thermal flow sensor of claim 21 , further comprising a second recess formed in said first side of said first substrate between said heater and said second temperature sensor.

23. The thermal flow sensor of claim 22 , wherein said second recess extends into said first substrate for about half of the thickness of said first substrate.

24. The thermal flow sensor of claim 22 , wherein said first recess is disposed immediately adjacent to said heater, said second recess is disposed immediately adjacent to said heater on an opposite side of said heater from said first recess.

25. The thermal flow sensor of claim 20 , wherein said first recess extends into said first substrate for about half of the thickness of said first substrate.

26. The thermal flow sensor of claim 20 , wherein said first recess is disposed immediately adjacent to said heater.

27. A method of determining the flow rate of a fluid within a conduit within a body, said body having a first upper side and a second opposite lower side, and at least one side edge extending between said first upper side and said second lower side, a conduit formed within the body having an inlet opening and an outlet opening, each of said openings being formed in said at least one side edge, said method comprising the steps of:

permitting a fluid to enter into the inlet opening of the conduit;

heating the fluid with a heater disposed on the first side of the body opposed to and remote from the conduit;

detecting a temperature of the fluid with a first temperature sensor disposed on the first side of the body opposed to and remote from the conduit;

creating a first recess in at least one of the first side and second side of the body between the heater and the first temperature sensor; and

determining the flow rate of the fluid based on the detected temperature.

28. The method according to claim 27 , wherein the body comprises a first substrate having a first side and a second opposite side, and at least a second substrate having a first side and a second opposite side, said first substrate being connected to said second substrate such that said second side of said first substrate abuts said first side of said second substrate, said second substrate having a groove formed therein so as to form the conduit bounded by said second substrate and said second side of said first substrate,

wherein in said creating step, said first recess is formed in said first side of said first substrate.

29. The method according to claim 27 further comprising the steps of:

detecting a temperature of the fluid with a second temperature sensor disposed on the first side of the body opposed to and remote from the conduit;

creating a second recess in at least one of the first side and the second side of the body between the heater and the second temperature sensor.

30. The method according to claim 29 , wherein in said creating step, said first recess and said second recess are formed about half of the thickness of the first substrate.