Magnetic field sensor integrated circuit with integral ferromagnetic material

• US 9,812,588 B2
• Filed: 01/24/2013
• Issued: 11/07/2017
• 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.
• Primary Examiner(s): Schindler, David M.
• Application Number:
  US13/748,999
• Publication Number:
  US 20130249029A1
• Time in Patent Office: 1,748 Days
• 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 central aperture having a surface extending from the non-conductive mold material to an outer peripheral surface of the ferromagnetic mold material, wherein the surface of the central aperture comprises a bend at an intermediate location such that the surface of the central aperture has a first slope from the non-conductive mold material to the bend and a second slope different than the first slope from the bend to the outer peripheral surface of the ferromagnetic mold material.

2. The magnetic field sensor of claim 1 wherein the ferromagnetic mold material is further secured to and in direct contact with a second portion of the lead frame that extends beyond the non-conductive mold material and terminates in the ferromagnetic 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 is selected from the group consisting of a ferrite, a SmCo alloy, a NdFeB alloy, a thermoplastic polymer with hard magnetic particles, and a thermoset polymer with hard magnetic particles.

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

6. The magnetic field sensor of claim 1 wherein the non-conductive mold material consists of a thermoset or thermoplastic mold compound.

7. The magnetic field sensor of claim 1 further comprising a non-conductive adhesive coupled between the first surface of the lead frame and the second surface of the semiconductor die.

8. The magnetic field sensor of claim 7 wherein the non-conductive adhesive consists of a non-conductive epoxy or a die attach tape.

9. A magnetic field sensor comprising:

a lead frame having a first surface, a second opposing surface, and having 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, wherein the ferromagnetic mold material comprises an aperture having a surface extending from the non-conductive mold material to an outer peripheral surface of the ferromagnetic mold material, wherein the surface of the aperture comprises a bend such that the surface of the aperture has a first slope from the non-conductive mold material to the bend and a second slope different than the first slope from the bend to the outer peripheral surface of the ferromagnetic mold material.

10. The magnetic field sensor of claim 9 wherein the ferromagnetic mold material is further secured to and in direct contact with a second portion of the lead frame that extends beyond the non-conductive mold material and terminates in the ferromagnetic mold material.

11. The magnetic field sensor of claim 9 wherein the non-conductive mold material consists of a thermoset or thermoplastic mold compound.

12. The magnetic field sensor of claim 9 further comprising a non-conductive adhesive coupled between the first surface of the lead frame and the second surface of the semiconductor die.

13. The magnetic field sensor of claim 12 wherein the non-conductive adhesive consists of a non-conductive epoxy or a die attach tape.

14. The magnetic field sensor of claim 9 wherein the ferromagnetic mold material comprises a hard ferromagnetic material to form a bias magnet.

15. The magnetic field sensor of claim 14 wherein the hard ferromagnetic material is selected from the group consisting of a ferrite, a SmCo alloy, a NdFeB alloy, a thermoplastic polymer with hard magnetic particles, and a thermoset polymer with hard magnetic particles.