Tall and fine pitch interconnects

1. A method, comprising:

applying a conductive layer to a temporary carrier;

patterning the conductive layer to form a patterned conductive structure;

applying a nonwettable layer to the patterned conductive structure;

patterning the nonwettable layer to form nonwettable barriers on the patterned conductive structure;

depositing a reflowable conductive material on the patterned conductive structure, between the nonwettable barriers, to form interconnect structures;

mounting a first microelectronic element to the interconnect structures;

removing the temporary carrier;

mounting a second microelectronic element with interconnect structures onto the patterned conductive structure, on a side previously occupied by the temporary carrier; and

coupling the IC die to the patterned conductive structure via heated reflow.

2. The method of claim 1 , further comprising patterning the nonwettable layer by removing the nonwettable layer from the patterned conductive structure, except at one or more edges of the patterned conductive structure.

3. The method of claim 1 , further comprising forming nonwettable barriers having closed geometric shapes with open interiors on the patterned conductive structure.

4. The method of claim 1 , further comprising forming nonwettable barriers having partly-closed predefined shapes with open interiors on the patterned conductive structure.

5. The method of claim 1 , wherein the nonwettable layer comprises a polymer or poly imide material.

6. A method, comprising:

applying a nonwettable layer to a first side and a second side of a conductive layer;

patterning the nonwettable layer to form nonwettable barriers with open interiors on the first side and the second side of the conductive layer;

depositing a reflowable conductive material within the open interiors of the nonwettable barriers of the first side of the conductive layer to form interconnect structures;

mounting a first microelectronic element to the interconnect structures;

applying a patterned resist mask to the second side of the conductive layer, including over the nonwettable barriers of the second side of the conductive layer;

patterning the conductive layer to form a patterned conductive structure, based on the patterned resist mask;

removing the patterned resist mask; and

mounting a second microelectronic element with interconnect structures onto the patterned conductive structure, such that the interconnect structures of the second microelectronic element are located within the open interiors of the nonwettable barriers of the second side of the conductive layer.

7. The method of claim 6 , further comprising underfilling between the second microelectronic element and the first microelectronic element.

8. The method of claim 6 , further comprising depositing a diffusion barrier layer to at least the first side of the conductive layer.

9. The method of claim 6 , further comprising depositing a precious metal layer to at least the first side of the conductive layer.

10. The method of claim 6 , further comprising supporting the conductive layer with a support layer while depositing the reflowable conductive material within the nonwettable barriers on the conductive layer.

11. The method of claim 6 , further comprising underfilling around the patterned conductive structure, the interconnect structures, and/or the nonwettable barriers.

12. The method of claim 6 , wherein the nonwettable barriers on the first side and/or the second side of the conductive layer are substantially elliptically shaped with open interiors.

13. The method of claim 6 , further comprising patterning the conductive layer to form conductive pads covering the open interiors of the nonwettable barriers; and patterning the conductive layer to form conductive traces electrically coupling two or more of the conductive pads.

14. The method of claim 13 , further comprising depositing one or more interconnect components onto the patterned conductive structure, such that the one or more interconnect components are located within one or more respective open interiors of the nonwettable barriers of the second side of the conductive layer, the one or more interconnect components arranged to couple at least a third microelectronic element to the first microelectronic element.

15. The method of claim 14 , wherein at least one of the one or more interconnect components includes an additional conductive pad having at least one additional nonwettable barrier with an open interior thereon, and an additional reflowable conductive material bump deposited within the open interior of the additional nonwettable barrier.

16. The method of claim 6 , further comprising depositing one or more additional reflowable conductive material bumps onto the first microelectronic element outside the perimeter of the second microelectronic element, the one or more additional reflowable conductive material bumps including a conductive pad stacked thereon, thereby increasing a height of the one or more additional reflowable conductive material bumps, to couple at least a third microelectronic element to the first microelectronic element.

17. A method, comprising:

applying an nonwettable layer to at least a first side of a conductive layer;

patterning the nonwettable layer to form openings in the nonwettable layer;

patterning the conductive layer to form conductive pads covering the openings in the nonwettable layer;

depositing a reflowable conductive material onto the conductive pads and within the openings in the nonwettable layer to form first interconnect structures;

mounting a first microelectronic element to the first interconnect structures;

mounting a second microelectronic element with second interconnect structures onto the conductive pads, such that the second interconnect structures of the second microelectronic element are located on the conductive pads on a side opposite of the first interconnect structures; and

underfilling between the second microelectronic element and the first microelectronic element.

18. The method of claim 17 , further comprising removing additional portions of the nonwettable layer to provide additional electrical interconnections.

19. The method of claim 17 , wherein the nonwettable layer holds the conductive pads in a desired physical arrangement during processing, including during depositing the reflowable conductive material, mounting the first microelectronic element, and/or mounting the second microelectronic element.