Flexible broadband microshield for electromagnetic interference and electrostatic discharge
A multilayer shield is used as an absorber for attenuating electromagnetic radiation (e.g., EMI) includes both metal and ferrite powder layers. Radiation transmitted through one of the metal layers be transmitted to an additional metal layer, and the radiation can be reflected between the metal layers. While reflected by the metal layers, the radiation is absorbed by one of the ferrite powder layers positioned between the metal layers, causing the ferrite powder layer to convert the radiation to thermal energy. Based on energy losses of the radiation due to reflection and thermal energy conversion, the radiation is sufficiently attenuated to limit disruption of nearby transmission signals, including high frequency transmission signals.
1 . An assembly, comprising:
a first shield, comprising:
a first metal layer;
a second metal layer coupled to the first metal layer, the second metal layer comprising ferrite powder; and
a third metal layer coupled to the second metal layer, wherein in response to receiving electromagnetic radiation (EMR) energy:
the first metal and the second metal are configured to reflect a first amount of the EMR energy transmitted through the first metal layer, and
the ferrite powder is configured to absorb at least some of the first amount of EMR energy and convert the absorbed EMR energy into thermal energy;
a flexible circuit comprising:
a dielectric material, and
transmission lines positioned in the dielectric material; and
a first ground plane positioned between the first shield and the flexible circuit; and
a second shield, wherein the flexible circuit is positioned between the first shield and the second shield.
2 . The assembly of claim 1 , wherein:
the first metal layer overlays the second metal layer, and
the second metal layer overlays the third metal layer.
3 . The assembly of claim 1 , further comprising:
a fourth metal layer coupled to the third metal layer, the fourth metal layer comprising ferrite powder; and
a fifth metal layer coupled to the fourth metal layer.
4 . The assembly of claim 3 , wherein:
the third metal layer and the fifth metal layer are configured to reflect a second amount of the EMR energy that is transmitted by the second metal, and
the ferrite powder in the fourth metal layer is configured to absorb at least some of the second amount of EMR energy that is reflected by the second metal and the third metal and convert the absorbed EMR energy into additional thermal energy.
5 . The assembly of claim 3 , wherein each of the first metal layer and the third metal layer comprises indium tin oxide.
6 . The assembly of claim 3 , wherein:
the third metal layer overlays the fourth metal layer, and
the fourth metal layer overlays the fifth metal layer.
7 . The assembly of claim 3 , wherein each of the ferrite powder of the second metal layer and the ferrite powder of the fourth metal layer comprises spinel nano ferrite powder.
8 . The assembly of claim 3 , wherein:
the ferrite powder of the second metal layer comprises a first molecular composition, and
the ferrite powder of the fourth metal layer comprises a second molecular composition different from the first molecular composition.
9 . The assembly of claim 1 , wherein:
the first metal layer comprises a first thickness, and
the second metal layer comprises a second thickness greater than the first thickness.
10 . The assembly of claim 9 , further comprising a fourth metal layer, wherein the fourth metal layer comprises a third thickness less than the second thickness.
11 . The assembly of claim 1 , further comprising a second ground plane, wherein the flexible circuit is positioned between the first ground plane and the second ground plane.
12 . The assembly of claim 11 , wherein:
the first ground plane comprises a first hatched ground plane, and
the second ground plane comprises a second hatched ground plane.
13 . The assembly of claim 11 , wherein:
wherein the first metal layer is configured to transmit at least some of the EMR energy, and
the first shield is configured to attenuate the EMR energy prior to exposure of the EMR energy to the transmission lines.
14 . The assembly of claim 11 , wherein:
the transmission lines emit the EMR energy in response to carrying a signal, and
the first shield is configured to attenuate the EMR energy from the transmission lines.
15 . The assembly of claim 11 , wherein the first shield further comprises:
a fourth metal layer coupled to the third metal layer, the fourth metal layer comprising ferrite particles; and
a fifth metal layer coupled to the fourth metal layer.
16 . An electronic device, comprising:
a circuit board;
an image sensor;
a flexible circuit electrically coupled to the circuit board and the image sensor; and
a shield first positioned on a surface of the flexible circuit, the first shield comprising:
a first metal layer comprising a first metal;
a second metal layer coupled to the first layer, the second layer comprising a first plurality of ferrite powder; and
a third metal layer coupled to the second layer, the third layer comprising a second metal, wherein in response to receiving electromagnetic radiation (EMR) energy:
the first metal and the second metal are configured to reflect a first amount of the EMR energy transmitted through the first metal layer, and
the ferrite powder is configured to absorb at least some of the first amount of EMR energy and convert the absorbed EMR energy into thermal energy;
a flexible circuit comprising:
a dielectric material, and
transmission lines positioned in the dielectric material; and
a first ground plane positioned between the first shield and the flexible circuit; and
a second shield, wherein the flexible circuit is positioned between the first shield and the second shield.
17 . The electronic device of claim 16 , wherein:
the flexible circuit comprises a connector electrically coupled to the flexible circuit, and
the shield covers the connector.
18 . The electronic device of claim 16 , wherein the first shield further comprises:
a fourth metal layer coupled to the third layer, the fourth metal layer comprising a second plurality of ferrite powder; and
a fifth layer coupled to the second layer, the fifth layer comprising a third metal.
19 . The electronic device of claim 18 , wherein:
the first plurality of ferrite powder comprises a first impedance value based on a first molecular composition,
the second plurality of ferrite powder comprises a second impedance value based on a second molecular composition different from the first molecular composition, and
the second impedance value is different from the first impedance value.
20 . The electronic device of claim 16 , further comprising a hatched ground plane positioned between the first shield and the flexible circuit.