Magnetic shielding material with insulator-coated ferromagnetic particles
View Patent ↗A non-conductive magnetic shield material is provided for use in magnetic shields of semiconductor packaging. The material is made magnetic by the incorporation of ferromagnetic particles into a polymer matrix, and is made non-conductive by the provision of an insulating coating on the ferromagnetic particles.
1. A device, comprising:
a semiconductor die;
a mixture covering a first portion of the semiconductor die and having:
a plurality of first ferromagnetic particles;
an insulating coating encapsulating each of the plurality of ferromagnetic particles; and
a matrix containing the first ferromagnetic particles; and
a matrix of epoxy material covering a second portion of the semiconductor die and having a plurality of second ferromagnetic particles in electrical contact with each other, wherein the mixture is non-conductive at a higher particle volume to mixture volume ratio (PMR) than the matrix of epoxy material having a plurality of second ferromagnetic particles in electrical contact with each other.
2. The device of claim 1 , wherein the plurality of ferromagnetic particles are of a material having a high magnetic permeability.
3. The device of claim 1 wherein the matrix comprises a polymeric material.
4. The device of claim 1 wherein the matrix comprises a glob-top fill.
5. The device of claim 1 wherein the matrix comprises a die underfill.
6. The device of claim 1 wherein the matrix comprises a semiconductor package molding compound.
7. The device of claim 1 wherein the insulating coating comprises a polymer.
8. The device of claim 1 wherein the insulating coating comprises a dielectric oxide.
9. The device of claim 1 , wherein the matrix of epoxy material is a magnetic epoxy and the device further comprises a first shield plate coupled to the magnetic epoxy.
10. The device of claim 9 , further comprising a second shield plate coupled to the magnetic epoxy, wherein the first shield plate is above the semiconductor die and the second shield plate is below the semiconductor die.
11. The device of claim 10 , wherein the second shield plate is in contact with the magnetic epoxy.
12. A device, comprising:
a semiconductor die having a plurality of die terminals;
a package input/output interface having a plurality of package input terminals and a plurality of package output terminals;
a mixture covering a first portion of the semiconductor die including a non-conductive magnetic shield element shielding a first portion of the semiconductor die;
a conductive magnetic shield element shielding a second portion of the semiconductor die; and
a plurality of electrical connectors electrically coupling respective die terminals to corresponding package input terminals, each of the electrical connectors extending through and in physical contact with the non-conductive magnetic shield element.
13. The device of claim 12 wherein the non-conductive magnetic shield element includes a mixture comprising:
a plurality of ferromagnetic particles;
an insulating coating encapsulating each of the plurality of ferromagnetic particles; and
a matrix containing the encapsulated ferromagnetic particles.
14. The device of claim 13 wherein the insulating coating is a ceramic material.
15. The device of claim 13 wherein the matrix is a polymer.
16. The device of claim 14 , wherein the plurality of ferromagnetic particles are of a material having a high magnetic permeability.
17. The device of claim 12 , wherein the conductive magnetic shield element includes a magnetic epoxy.
18. A method, comprising:
forming a mixture of first ferromagnetic particles, each having an insulating coating, and matrix material at a volume ratio of first ferromagnetic particles to mixture that imparts a selected magnetic permeability to the mixture; and
positioning the mixture around and between a plurality of electrical connectors that electrically couple contact terminals of a semiconductor die with contact terminals of an input/output interface; and
positioning, on the semiconductor die, a magnetic epoxy including a plurality of second ferromagnetic particles on the semiconductor die, wherein the magnetic epoxy has a higher conductivity than the mixture based on conduction between the second ferromagnetic particles.
19. The method of claim 18 , further comprising positioning a first shield plate coupled to the magnetic epoxy.
20. The method of claim 19 , further comprising positioning a second shield plate coupled to the magnetic epoxy.