Magnetic Field Sensors and Methods for Fabricating the Magnetic Field Sensors

Abstract

Magnetic field sensors and associated methods of manufacturing the magnetic field sensors include molded structures to encapsulate a magnetic field sensing element and an associated die attach pad of a lead frame and to also encapsulate or form a magnet or a flux concentrator.

What is claimed is: 
     
         1 - 22 . (canceled) 
     
     
         23 . A magnetic field sensor, comprising:
 a lead frame comprising a die attach pad, wherein the die attach pad comprises first and second opposing surfaces;   a magnetic field sensor circuit die coupled proximate to the first surface of the die attach pad;   a molded capsule comprised of a mold compound, the molded capsule enclosing the magnetic field sensor circuit die, wherein the molded capsule covers the second surface of the die attach pad with the mold compound, and wherein the mold compound of the molded capsule forms an insulating layer over the second surface of the die attach pad, wherein a thickness of the insulating layer is less than a combined thickness of the die attach pad and the magnetic field sensor circuit die;   a magnet coupled proximate to the second surface of the die attach pad so that the insulating layer is between the magnet and the second surface of the die attach pad; and   a molded enclosure surrounding the magnet.   
     
     
         24 . The magnetic field sensor of  claim 23 , further comprising an adhesive material disposed between the magnet and the insulating layer. 
     
     
         25 . The magnetic field sensor of  claim 23 , wherein the molded enclosure also surrounds the molded capsule. 
     
     
         26 . The magnetic field sensor of  claim 23 , wherein the molded capsule consists of one uniform material 
     
     
         27 . The magnetic field sensor of  claim 23 , further comprising a glass filled epoxy disposed on the second surface of the die attach pad. 
     
     
         28 . The magnetic field sensor of  claim 23 , further comprising a capacitor coupled across at least two leads of the lead frame at a position that results in the capacitor being encased within the molded capsule. 
     
     
         29 . The magnetic field sensor of  claim 23 , wherein the magnet has a magnetic field oriented approximately perpendicular to the first and second surfaces of the die attach pad, and wherein the magnetic field sensor circuit die comprises a magnetic field sensing element having a maximum response axis approximately perpendicular to the first and second surfaces of the die attach pad. 
     
     
         30 . The magnetic field sensor of  claim 23 , wherein the magnet has a magnetic field oriented approximately parallel to the first and second surfaces of the die attach pad, and wherein the magnetic field sensor circuit die comprises a magnetic field sensing element having a maximum response axis approximately parallel to the first and second surfaces of the die attach pad. 
     
     
         31 - 33 . (canceled) 
     
     
         34 . A magnetic field sensor, comprising:
 a lead frame comprising a die attach pad, wherein the die attach pad comprises first and second opposing surfaces;   a magnetic field sensor circuit die coupled proximate to the first surface of the die attach pad;   a molded capsule enclosing the magnetic field sensor circuit die, wherein the molded capsule covers the second surface of the die attach pad forming an insulating layer over the second surface of the die attach pad; and   a first molded structure disposed proximate to the second surface of the die attach pad, wherein the first molded structure is filled with ferromagnetic particles to either generate a magnetic field or to concentrate a magnetic field, wherein the insulating layer formed from the mold compound is disposed between the first molded structure filled with ferromagnetic particles and the die attach pad; and   a second molded structure enclosing the first molded structure, wherein the second molded structure is configured to retain the first molded structure proximate to the die attach pad.   
     
     
         35 . The magnetic field sensor of  claim 23 , wherein the magnet comprises a solid magnet. 
     
     
         36 . The magnetic field sensor of  claim 23 , wherein the magnet comprises a mold compound filled with ferromagnetic particles. 
     
     
         37 . The magnetic field sensor of  claim 23 , wherein the insulating layer comprises a substantially flat outer surface, forming a substantially flat surface upon which the magnet is disposed, and wherein a surface of the magnet proximate to the insulating layer is substantially flat. 
     
     
         38 . The magnetic field sensor of  claim 34 , wherein the second molded structure further encloses at least a portion of the molded capsule. 
     
     
         39 . The magnetic field sensor of  claim 34 , wherein a surface between the molded capsule and the first molded structure is substantially flat throughout the surface. 
     
     
         40 . The magnetic field sensor of  claim 34 , wherein a thickness of the insulating layer is less than a combined thickness of the die attach pad and the magnetic field sensor circuit die.