Magnetic Field Sensor Integrated Circuit with Integral Ferromagnetic Material

• US 20130249029A1
• Filed: 01/24/2013
• Published: 09/26/2013
• Est. Priority Date: 03/20/2012
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Vig, Ravi, Taylor, William P., David, Paul, Scheller, P. Karl, Friedrich, Andreas P.
• Granted Patent: US 9,812,588 B2
• Time in Patent Office: Days
• US Class Current: 257/427
• CPC Class Codes: G01D 2205/40 Position sensors comprising arrangements for concentrating or redirecting magnetic flux
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01R 15/207 Constructional details independent of the type of device used
• CPC Class Codes: G01R 33/0047 Housings or packaging of magnetic sensors packaging of semiconductor devices H01L23/00; Holders
• CPC Class Codes: G01R 33/0052 Manufacturing aspects; Manufacturing of single devices, i.e. of semiconductor magnetic sensor chips devices based on galvano-magnetic effect or the like H10N50/85
• CPC Class Codes: G01R 33/06 using galvano-magnetic devices
• CPC Class Codes: H01L 2224/45147 Copper (Cu) as principal constituent
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/73215 Layer and wire connectors
• CPC Class Codes: H01L 24/45 of an individual wire connector
• CPC Class Codes: H01L 29/82 controllable by variation of the magnetic field applied to the device
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00011 Not relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01033 Arsenic [As]

Abstract

A magnetic field sensor includes a lead frame, a semiconductor die having a first surface in which a magnetic field sensing element is disposed and a second surface attached to the lead frame, and a non-conductive mold material enclosing the die and at least a portion of the lead frame. The sensor may include a ferromagnetic mold material secured to a portion of the non-conductive mold material. Features include a multi-sloped taper to an inner surface of a non-contiguous central region of the ferromagnetic mold material, a separately formed element disposed in the non-contiguous central region, one or more slots in the lead frame, a molded ferromagnetic suppression device spaced from the non-conductive mold material and enclosing a portion of a lead, a passive device spaced from the non-conductive mold material and coupled to a plurality of leads, and a ferromagnetic bead coupled to a lead. Also described is a coil secured to the non-conductive mold material and a lead having at least two separated portions with a passive component coupled across the two portions.

Claims

1. A magnetic field sensor comprising:

a lead frame having a first surface and a second opposing surface;

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 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, wherein the ferromagnetic mold material comprises a non-contiguous central region extending from a first end proximate to the lead frame to a second end distal from the lead frame, wherein the central region has an inner surface with a taper established by at least two differently sloped portions.

2. The magnetic field sensor of claim 1 wherein the ferromagnetic mold material is secured to a portion of the non-conductive mold material and a second portion of the lead frame that extends beyond the non-conductive mold material.

3. The magnetic field sensor of claim 1 wherein the ferromagnetic mold material is a hard ferromagnetic material.

4. The magnetic field sensor of claim 3 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.

5. The magnetic field sensor of claim 1 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.

6. The magnetic field sensor of claim 1 further comprising a separately formed element disposed in and secured to the central region of the ferromagnetic mold material.

7. The magnetic field sensor of claim 6 wherein the separately formed element is comprised of a hard ferromagnetic material, a soft ferromagnetic material, or a non-ferromagnetic material.

8. The magnetic field sensor of claim 1 wherein the lead frame comprises at least one slot.

9. A magnetic field sensor comprising:

a lead frame having a first surface and a second opposing surface;

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 non-conductive mold material enclosing the die and at least a portion of the lead frame;

a ferromagnetic mold material secured to a portion of the non-conductive mold material, wherein the ferromagnetic mold material comprises a non-contiguous central region extending from a first end proximate to the lead frame to a second end distal from the lead frame; and

a separately formed element disposed in and secured to the central region of the ferromagnetic mold material.

10. The magnetic field sensor of claim 9 wherein the separately formed element is comprised of a hard ferromagnetic material, a soft ferromagnetic material, or a non-ferromagnetic material.

11. The magnetic field sensor of claim 9 wherein the ferromagnetic mold material is secured to a portion of the non-conductive mold material and a second portion of the lead frame that extends beyond the non-conductive mold material.

12. The magnetic field sensor of claim 9 wherein at least one of the separately formed element and the ferromagnetic mold material is a hard ferromagnetic material.

13. The magnetic field sensor of claim 12 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.

14. The magnetic field sensor of claim 9 wherein the lead frame comprises at least one slot.

15. A magnetic field sensor comprising:

a lead frame having a first surface, a second opposing surface, and at least one slot;

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 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.

16. The magnetic field sensor of claim 15 wherein the ferromagnetic mold material comprises a hard ferromagnetic material to form a bias magnet.

17. A magnetic field sensor comprising:

a lead frame having a first surface, a second opposing surface, 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 non-conductive mold material enclosing the die and at least a portion of the lead frame; and

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.

18. The magnetic field sensor of claim 17 further comprising a ferromagnetic mold material secured to a portion of the non-conductive mold material.

19. The magnetic field sensor of claim 18 wherein at least one of the molded ferromagnetic suppression device and the ferromagnetic mold material comprises a hard ferromagnetic material.

20. The magnetic field sensor of claim 19 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.

21. The magnetic field sensor of claim 18 wherein at least one of the molded ferromagnetic suppression device and the ferromagnetic mold material comprises a soft ferromagnetic material.

22. The magnetic field sensor of claim 21 wherein the soft ferromagnetic material comprises at least one of NiFe, Ni, a Ni alloy, steel or ferrite.

23. The magnetic field sensor of claim 17 wherein the molded ferromagnetic suppression device comprises a first molded element enclosing the portion of the at least one lead and a second molded element enclosing at least a portion of the first molded element.

24. The magnetic field sensor of claim 23 wherein the first molded element comprises a non-conductive mold material and the second molded element comprises a ferromagnetic material.

25. The magnetic field sensor of claim 17 further comprising at least one of a passive component or a ferromagnetic bead coupled to the at least one lead and enclosed by the molded ferromagnetic suppression device.

26. A magnetic field sensor, comprising:

a lead frame having a first surface, a second opposing surface, 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;

a non-conductive mold material enclosing the die and at least a portion of the lead frame;

a ferromagnetic mold material secured to a portion of the non-conductive mold material; and

at least one capacitor coupled to at least two of the plurality of leads and spaced from the non-conductive mold material.

27. The magnetic field sensor of claim 26 further comprising a molded ferromagnetic suppression device enclosing the at least one capacitor.

28. The magnetic field sensor of claim 27 wherein at least one of the molded ferromagnetic suppression device and the ferromagnetic mold material comprises a hard ferromagnetic material.

29. The magnetic field sensor of claim 27 wherein at least one of the molded ferromagnetic suppression device and the ferromagnetic mold material comprises a soft ferromagnetic material.

30. The magnetic field sensor of claim 26 wherein the lead frame comprises at least one slot.

31. The magnetic field sensor of claim 26 further comprising at least one ferromagnetic bead coupled to at least one of the plurality of leads.

32. A magnetic field sensor, comprising:

a lead frame having a first surface, a second opposing surface, 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;

a non-conductive mold material enclosing the die and at least a portion of the lead frame;

a ferromagnetic mold material secured to a portion of the non-conductive mold material; and

at least one ferromagnetic bead coupled to at least one of the plurality of leads.

33. The magnetic field sensor of claim 32 wherein the at least one ferromagnetic bead is enclosed by the non-conductive mold material.

34. The magnetic field sensor of claim 32 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.

35. The magnetic field sensor of claim 34 wherein the at least one ferromagnetic bead is enclosed by the molded ferromagnetic suppression device.

36. A magnetic field sensor comprising:

a lead frame having a first surface and a second opposing surface;

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 non-conductive mold material enclosing the die and at least a portion of the lead frame; and

a conductive coil secured to the non-conductive mold material.

37. The magnetic field sensor of claim 36 wherein the non-conductive mold material encloses the coil.

38. The magnetic field sensor of claim 37 further comprising at least one ferromagnetic bead enclosed by the non-conductive mold material.

39. The magnetic field sensor of claim 37 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.

40. The magnetic field sensor of claim 37 wherein the lead frame comprises at least one slot.

41. The magnetic field sensor of claim 37 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.

42. The magnetic field sensor of claim 36 further comprising a second mold material secured to a portion of the non-conductive mold material, wherein the second mold material encloses the coil.

43. The magnetic field sensor of claim 36 wherein the non-conductive mold material comprises a protrusion and wherein the coil is positioned concentrically with respect to the protrusion.

44. A magnetic field sensor comprising:

a lead frame having a first surface, a second opposing surface, and at least one lead comprising 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;

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 non-conductive mold material enclosing the die and at least a portion of the lead frame; and

a passive component coupled between the end of the first lead portion and the end of the second lead portion.

45. The magnetic field sensor of claim 44 further comprising a ferromagnetic mold material secured to a portion of the non-conductive mold material.

46. The magnetic field sensor of claim 45 wherein the passive component is a resistor.