Packages with molding structures and methods of forming the same

1. A method comprising:

molding a device die in a molding material, wherein a metal pillar of the device die is exposed through a surface of the molding material;

adhering a substrate to the molding material, wherein the substrate comprises a redistribution layer, and the redistribution layer comprises redistribution lines;

plating into a first through-opening in the substrate to form a first through-via, wherein the first through-via is plated on the metal pillar of the device die, wherein before the first through-via is formed, a redistribution line in the redistribution layer is exposed to the first through-opening, and after the first through-via is formed, the redistribution line is joined to the first through-via; and

forming an electrical connector to electrically couple to the first through-via.

2. The method of claim 1 , wherein the adhering the substrate to the molding material comprises:

applying an adhesive on a dielectric layer of the substrate, wherein the adhesive joins the dielectric layer to a surface of the molding material.

3. The method of claim 1 further comprising, after the adhering, forming the first through-opening in the substrate, wherein the metal pillar is exposed through the first through-opening.

4. The method of claim 1 , wherein the forming the electrical connector comprises forming a solder region.

5. The method of claim 1 further comprising, when the plating into the first through-opening is performed, plating into a second through-opening in the substrate to form a second through-via, wherein when the forming the electrical connector is performed, a dielectric layer is in contact with a top surface of the second through-via.

6. The method of claim 5 , wherein the second through-via is electrically floating.

7. The method of claim 1 , wherein the substrate comprises a plurality of redistribution layers, and wherein the first through-via has a height equal to or greater than a total thickness of the plurality of redistribution layers.

8. The method of claim 1 , wherein after the adhering the substrate to the molding material, a via in the substrate is in contact with an additional metal pillar in the device die, and the via is pre-formed in the substrate before the adhering.

9. The method of claim 1 further comprising:

molding a second through-via in the molding material, wherein the second through-via has a top surface coplanar with a top surface of the metal pillar, and a bottom surface lower than a bottom surface of the device die;

forming a second through-opening in the substrate, wherein the second through-via is exposed through the second through-opening; and

plating a third through-via in the second through-opening.

10. A method comprising:

providing a substrate comprising:

a plurality of redistribution layers; and

a plurality of dielectric layers, with the plurality of redistribution layers in the plurality of dielectric layers, wherein the plurality of dielectric layers forms an integrated unit with the plurality of redistribution layers;

molding a device die in a molding material using expose molding, wherein a metal pillar of the device die is exposed after the expose molding;

attaching the substrate as the integrated unit to the molding material;

forming a first through-opening in the substrate to expose the metal pillar; and

plating into the first through-opening to form a first through-via, wherein the first through-via is plated on the metal pillar of the device die.

11. The method of claim 10 further comprising forming a solder region over and in contact with the first through-via.

12. The method of claim 11 further comprising:

forming a second through-opening in the substrate, with an additional metal pillar of the device die exposed to the second through-opening;

plating into the second through-opening in the substrate to form a second through-via, wherein the second through-via is plated on the additional metal pillar of the device die; and

forming a dielectric layer over and in contact with a top surface of the second through-via, wherein when the solder region is formed, no solder region is formed to contact the second through-via.

13. The method of claim 10 , wherein after the forming the first through-opening in the substrate, a sidewall of a redistribution line in the plurality of redistribution layers is exposed to the first through-opening, and wherein the first through-via is in contact with the sidewall of the redistribution line.

14. A method comprising:

forming a plurality of through-vias;

encapsulating a device die and the plurality of through-vias in an encapsulating material;

performing a planarization to remove excess portions of the encapsulating material, wherein the plurality of through-vias and conductive features in the device die are revealed;

pre-forming a substrate comprising:

a plurality of dielectric layers; and

redistribution lines in the plurality of dielectric layers;

adhering the pre-formed substrate to the encapsulating material and the device die, wherein portions of the redistribution lines are in contact with first portions of the plurality of through-vias and the conductive features;

patterning the substrate to form a plurality of through-openings penetrating through the pre-formed substrate, with second portions of the plurality of through-vias and the conductive features being revealed through the plurality of through-openings; and

filling the plurality of through-openings with a conductive material to form a plurality of conductive vias.

15. The method of claim 14 further comprising:

forming a dielectric layer to cover the substrate and the second portions of the plurality of through-vias and the conductive features;

patterning the dielectric layer to expose a first one of the plurality of conductive vias; and

forming a solder region electrically coupled to the first one of the plurality of conductive vias.

16. The method of claim 15 , wherein during the patterning the dielectric layer, a second one of the plurality of conductive vias remains to be covered by the dielectric layer.

17. The method of claim 14 , wherein the pre-formed substrate is adhered to the encapsulating material and the device die through an adhesive.

18. The method of claim 14 , wherein in the patterning the substrate to form the plurality of through-openings, an edge of one of the redistribution lines is exposed to one of the plurality of through-openings.

19. The method of claim 14 , wherein the filling the plurality of through-openings comprises plating the conductive material.