Magnetic field sensor integrated circuit with an integrated coil

• US 10,916,665 B2
• Filed: 01/21/2019
• Issued: 02/09/2021
• 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 A., Scheller, P. Karl, Friedrich, Andreas P.
• Primary Examiner(s): Patidar, Jay
• Application Number:
  US16/252,789
• Publication Number:
  US 20190157465A1
• Time in Patent Office: 750 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, a second opposing surface, at least one slot extending from the first surface to the second surface in a vertical direction, 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, wherein the at least one slot is aligned with the semiconductor die in the vertical direction;

a non-conductive mold material enclosing the die and at least a portion of the lead frame, the non-conductive mold material having a first surface adjacent to the first surface of the semiconductor die and a second opposing surface adjacent to the second surface of the lead frame, wherein the non-conductive mold material comprises a protrusion having tapered side walls extending from the second surface of the non-conductive mold material; and

a conductive coil secured to the second surface of the non-conductive mold material and positioned concentrically with respect to the protrusion of the non-conductive mold material, wherein the conductive coil is configured to operate as a back bias magnet to provide a magnetic field used to detect movement of a target.

2. 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.

3. The magnetic field sensor of claim 1 wherein the conductive coil is disposed outside of the non-conductive mold material.

4. The magnetic field sensor of claim 3 further comprising a second mold material secured to a portion of the non-conductive mold material, wherein the second mold material encloses the coil.

5. The magnetic field sensor of claim 4 wherein the second mold material comprises a ferromagnetic mold material.

6. The magnetic field sensor of claim 5 wherein the ferromagnetic mold material is a soft ferromagnetic mold material.

7. The magnetic field sensor of claim 5 wherein the ferromagnetic mold material is a hard ferromagnetic mold material.

8. The magnetic field sensor of claim 7 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.

9. The magnetic field sensor of claim 5 wherein the lead frame comprises a securing mechanism to enhance attachment of the non-conductive mold material to the ferromagnetic mold material.

10. The magnetic field sensor of claim 9 wherein the securing mechanism comprises a portion of the lead frame that extends beyond the non-conductive mold material.

11. The magnetic field sensor of claim 5 further comprising a separately formed element disposed in and secured to a central region of the ferromagnetic mold material.

12. The magnetic field sensor of claim 11 wherein the separately formed element is comprised of a hard ferromagnetic material, a soft ferromagnetic material, or a non-ferromagnetic material.

13. 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.

14. The magnetic field sensor of claim 13 wherein the at least one passive component comprises a capacitor.

15. 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.

16. The magnetic field sensor of claim 15 wherein passive component comprises a capacitor.

17. 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.

18. The magnetic field sensor of claim 1 wherein the magnetic field sensing element comprises a Hall effect element.

19. The magnetic field sensor of claim 1 wherein the magnetic field sensing element comprises a magnetoresistive element.

20. The magnetic field sensor of claim 19 wherein the magnetoresistive element comprises one or more of a GMR element, a AMR element, a TMR element, and a MTJ element.