Patent ID: 7036369

Claim:
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.