Magnetic field sensor integrated circuit with an integrated coil enclosed with a semiconductor die by a mold material
A magnetic field sensor includes a lead frame, a semiconductor die, a conductive coil, a mandrel, and a non-conductive mold material. The lead frame has a first surface, a second opposing surface, at least one slot, and a plurality of leads. The semiconductor die has a first surface in which a magnetic field sensing element is disposed and a second opposing surface attached to the first surface of the lead frame. The conductive coil is secured to the second surface of the lead frame and configured to operate as a back bias magnet to provide a magnetic field used to detect movement of a target. The coil is would around the mandrel and the mandrel is comprised of a ferromagnetic material. The non-conductive mold material encloses the die, the conductive coil, the mandrel, and at least a portion of the lead frame.
1. A magnetic field sensor comprising:
a lead frame having a first surface, a second opposing surface, at least one slot, and a plurality of leads;
a semiconductor die having a first surface in which a magnetic field sensing element is disposed and a second opposing surface attached to the first surface of the lead frame;
a conductive coil directly attached to the second surface of the lead frame with adhesive and configured to operate as a back bias magnet to provide a magnetic field used to detect movement of a target;
a mandrel around which the coil is disposed, wherein the mandrel is comprised of a ferromagnetic material, wherein the mandrel is directly attached to the second surface of the lead frame with adhesive; and
a non-conductive mold material enclosing the die, the conductive coil, the mandrel, and at least a portion of the lead frame.
2. The magnetic field sensor of claim 1 further comprising a ferromagnetic mold material secured to a portion of the non-conductive mold material.
3. The magnetic field sensor of claim 2 wherein the ferromagnetic mold material is a soft ferromagnetic mold material.
4. The magnetic field sensor of claim 2 wherein the ferromagnetic mold material is a hard ferromagnetic mold material.
5. The magnetic field sensor of claim 4 wherein the hard ferromagnetic material comprise at least one of a ferrite, a SmCo alloy, a NdFeB alloy, a thermoplastic polymer with hard magnetic particles, or a thermoset polymer with hard magnetic particles.
6. The magnetic field sensor of claim 1 wherein the at least one slot in the lead frame is substantially vertically aligned with respect to the magnetic field sensing element.
7. The magnetic field sensor of claim 1 wherein the lead frame comprises a securing mechanism to enhance attachment of the non-conductive mold material to the lead frame.
8. The magnetic field sensor of claim 7 wherein the securing mechanism comprises a portion of the lead frame that extends beyond the non-conductive mold material.
9. The magnetic field sensor of claim 1 wherein the magnetic field sensing element comprises a Hall effect element.
10. The magnetic field sensor of claim 1 wherein the magnetic field sensing element comprises a magnetoresistive element.
11. The magnetic field sensor of claim 10 wherein the magnetoresistive element comprises one or more of a GMR element, a AMR element, a TMR element, and a MTJ element.
12. The magnetic field sensor of claim 1 further comprising at least one passive component coupled to at least two of the plurality of leads and spaced from the non-conductive mold material.
13. The magnetic field sensor of claim 12 wherein the at least one passive component comprises a capacitor.
14. The magnetic field sensor of claim 1 wherein at least one lead comprises a first lead portion having an end and a second lead portion having an end spaced from and proximate to the end of the first lead portion, wherein the magnetic field sensor further comprises a passive component coupled between the end of the first lead portion and the end of the second lead portion such that the passive component is electrically connected in series with the at least one lead, wherein the passive component is enclosed by the non-conductive material.
15. The magnetic field sensor of claim 14 wherein passive component comprises a resistor.
16. The magnetic field sensor of claim 1 further comprising a molded ferromagnetic suppression device spaced from the non-conductive mold material and enclosing a portion of at least one of the plurality of leads.