Impedance controlled packages with metal sheet or 2-layer rdl

1. A microelectronic assembly comprising:

an interconnection element having a face;

a microelectronic device overlying the face of the interconnection element, the microelectronic device having a surface, a plurality of first device contacts disposed at the surface, at least one second device contact disposed at the surface, and at least one trace deposited on the surface and electrically connected to the interconnection element, the at least one trace electrically connecting at least one of the first device contacts with the at least one second device contact;

at least one first bond element electrically connecting the at least one second device contact with at least one of the element contacts; and

at least one metal plane electrically connected to the interconnection element and attached to the microelectronic device at a height from the surface greater than a height of the at least one trace from the surface, the at least one metal plane being connectable to a source of reference potential, such that a desired impedance is achieved for the at least one trace, the at least one trace having at least a substantial portion extending in a direction substantially parallel to a direction in which the metal plane extends; and

at least one second bond element electrically connecting the metal plane with a reference element of the interconnection element, the reference element being electrically connectable with a source of reference potential.

2. The microelectronic assembly of claim 1 , wherein the substantial portion of the at least one trace is a length that is at least 25% of the total length of the at least one trace.

3. The microelectronic assembly of claim 1 , wherein the substantial portion of the at least one trace is a length of at least 1 millimeter.

4. The microelectronic assembly of claim 1 , wherein the second bond element extends beyond a first edge of the microelectronic device, and the second bond element extends beyond a second edge of the microelectronic device.

5. The microelectronic assembly of claim 4 , wherein the first and second edges meet at a corner of the microelectronic device.

6. The microelectronic assembly of claim 1 , wherein the metal plane reduces an inductance in the electrical connection between the device contact and a source of fixed voltage.

7. The microelectronic assembly of claim 4 wherein the first bond element is a plurality of first bond elements and the at least one second bond is positioned between at least two of the plurality of first bond elements.

8. The microelectronic assembly of claim 1 , wherein the at least one second bond element extends in a direction transverse to the direction in which the at least one first bond element extends.

9. The microelectronic assembly of claim 1 , wherein the metal plane is comprised of multiple sections, wherein at least a first section is a power plane and a second section is a ground plane.

10. The microelectronic element of claim 9 , wherein the first section is adjacent one edge of the device contacts and the second section is adjacent the opposed edge of the device contacts.

11. The microelectronic element of claim 9 , wherein the first and second sections are adjacent the same edge of the device contacts.

12. The microelectronic assembly of claim 9 , wherein the first section is comprised of a first portion and a second portion, and the device contacts extend between the first and second portions.

13. The microelectronic assembly of claim 9 , wherein the second section is comprised of a first portion and a second portion, and the device contacts extend between the first and second portions.

14. The microelectronic assembly of claim 12 , wherein at least one third bond element electrically connects device contacts with the first portion or second portion of at least one of the first section and second section.

15. The microelectronic assembly of claim 1 , wherein at least one third bond element electrically connects at least one device contact with at least one surface conductive element.

16. The microelectronic assembly as claimed in claim 1 , further comprising at least one third bond element electrically connecting the metal plane with a reference contact of the interconnection element.

17. The microelectronic assembly of claim 1 , wherein the microelectronic device is a first microelectronic device, and the reference conductor is a first reference conductor, the assembly further comprising a second microelectronic device having a plurality of third device contacts disposed at a surface remote from the first microelectronic device, at least one fourth device contact disposed at the surface, and at least one trace extending along the surface and electrically connecting at least one of the third device contacts with the at least one fourth device contact, and

the at least one second reference conductor overlying the surface of the second microelectronic device at a height from the surface greater than a height of the at least one trace from the surface of the second microelectronic device, the at least one second reference conductor being connectable to a source of reference potential, such that a desired impedance is achieved for the at least one trace of the second microelectronic device, the second reference conductor having at least a substantial portion extending in a direction substantially parallel to a direction in which the at least one trace of the second microelectronic device extends.

18. A system comprising an assembly according to claim 1 and one or more other electronic components electrically connected to the assembly.

19. The system of claim 18 , further comprising a housing, the assembly and the other electronic components being mounted to the housing.