Magnetic Field Sensor Integrated Circuit with Integral Ferromagnetic Material

Abstract

A magnetic field sensor includes a lead frame, a passive component, semiconductor die supporting a magnetic field sensing element and attached to the lead frame, a non-conductive mold material enclosing the die and at least a portion of the lead frame, and a ferromagnetic mold material secured to a portion of the non-conductive mold material. The lead frame has a recessed region and the passive component is positioned in the recessed region. The ferromagnetic mold material may comprise a soft ferromagnetic material to form a concentrator or a hard ferromagnetic material to form a bias magnet.

What is claimed is: 
     
         1 . A magnetic field sensor, comprising:
 a lead frame having a first surface, a second opposing surface, a recessed region, and a plurality of leads;   a passive component coupled to at least one of said plurality of leads and positioned in the recessed region of the lead frame;   a semiconductor die having a first surface in which a magnetic field sensing element is disposed and a second opposing surface, wherein the first surface of the semiconductor die is attached to the first surface of the lead frame;   a non-conductive mold material enclosing the die, at least a portion of the lead frame, and said at least one capacitor; and   a ferromagnetic mold material secured to a portion of the non-conductive mold material.   
     
     
         2 . The magnetic field sensor of  claim 1  wherein the ferromagnetic mold material comprises a hard ferromagnetic material to form a bias magnet. 
     
     
         3 . The magnetic field sensor of  claim 2  wherein the hard ferromagnetic material comprises 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. 
     
     
         4 . The magnetic field sensor of  claim 1  wherein the ferromagnetic mold material comprises a soft ferromagnetic material to form a concentrator. 
     
     
         5 . The magnetic field sensor of  claim 4  wherein the soft ferromagnetic material comprises at least one of NiFe, Ni, a Ni alloy, steel, or ferrite. 
     
     
         6 . The magnetic field sensor of  claim 1  wherein the ferromagnetic mold material has a non-contiguous central region extending from adjacent to the first end of the ferromagnetic mold material to the second end of the ferromagnetic mold material. 
     
     
         7 . The magnetic field sensor of  claim 6  wherein the ferromagnetic mold material forms a substantially D-shaped, O-shaped, U-shaped, or C-shaped structure. 
     
     
         8 . The magnetic field sensor of  claim 6  wherein the non-conductive mold material comprises a protrusion extending into the central region of the ferromagnetic mold material. 
     
     
         9 . The magnetic field sensor of  claim 8  wherein the protrusion extends from adjacent to the first end of the ferromagnetic mold material to the second end of the ferromagnetic mold material. 
     
     
         10 . The magnetic field sensor of  claim 9  wherein the protrusion extends from adjacent to the first end of the ferromagnetic mold material to terminate before the second end of the ferromagnetic mold material, and wherein the ferromagnetic mold material covers the protrusion. 
     
     
         11 . The magnetic field sensor of  claim 6  further comprising a third mold material disposed in and secured to the central region of the ferromagnetic mold material, wherein the third mold material is comprised of a soft ferromagnetic material. 
     
     
         12 . The magnetic field sensor of  claim 1  wherein the passive component comprises a capacitor. 
     
     
         13 . The magnetic field sensor of  claim 1  further comprising a securing mechanism between the non-conductive mold material and the ferromagnetic mold material.