Thermal interface material having different thicknesses in packages

1. A method comprising:

bonding a first package component and a second package component to a third package component;

encapsulating the first package component and the second package component in an encapsulant;

applying a thermal interface material, wherein a bottom surface of the thermal interface material is in contact with top surfaces of the encapsulant, the first package component, and the second package component; and

placing a metal cap onto the thermal interface material, wherein a top surface of the thermal interface material is in contact with an additional bottom surface of the metal cap, and wherein one of the bottom surface and the top surface of the thermal interface material comprises a lower portion and a higher portion higher than the lower portion.

2. The method of claim 1 , wherein the bottom surface of the thermal interface material comprises the lower portion and the higher portion.

3. The method of claim 2 , wherein the encapsulating comprises:

applying the encapsulant;

planarizing the encapsulant to be coplanar with top surfaces of the first package component and the second package component; and

recessing a part of the encapsulant to form a recess, wherein the thermal interface material fills the recess.

4. The method of claim 3 , wherein recessing the part of the encapsulant is performed through cutting using a blade, milling, or grinding.

5. The method of claim 3 , wherein the recessed part of the encapsulant is between the first package component and the second package component.

6. The method of claim 1 , wherein the top surface of the thermal interface material comprises the lower portion and the higher portion, and wherein the method further comprises:

pre-forming the metal cap; and

pressing the metal cap to shape the thermal interface material and to make the top surface of the thermal interface material to have the lower portion and the higher portion.

7. The method of claim 1 , wherein the first package component comprises a first edge and a second edge joining with each other to form a corner, and wherein the lower portion of the top surface overlaps:

the corner;

a portion of the first package component comprising the corner; and

a portion of the encapsulant, with the portion of the encapsulant joining the corner.

8. The method of claim 7 , wherein the encapsulant comprises a side portion joining the first edge, and the higher portion of the top surface of the thermal interface material overlaps a portion of the first edge and the side portion of the encapsulant.

9. The method of claim 1 , wherein the bottom surface of the thermal interface material is in direct contact with a top surface of each of the encapsulant, the first package component, and the second package component.

10. A method comprising:

encapsulating a first package component and a second package component in an encapsulant;

performing a planarization process to level a first top surface of the first package component, a second top surface of the second package component, and a third top surface of the encapsulant;

recessing the third top surface of the encapsulant to form a recess;

applying a thermal interface material to contact the first package component, the second package component, and the encapsulant, wherein the thermal interface material further extends into the recess; and

attaching a cap overlying and contacting the thermal interface material.

11. The method of claim 10 , wherein in the recessing, an intermediate portion of the encapsulant between the first package component and the second package component is recessed.

12. The method of claim 11 , wherein in the recessing, a portion of the first package component joining the intermediate portion of the encapsulant is also recessed.

13. The method of claim 11 , wherein after the cap is attached to the thermal interface material, an entirety of a top surface of the thermal interface material is coplanar.

14. The method of claim 10 , wherein in the recessing, a corner portion of the encapsulant adjoining a corner of the first package component is recessed.

15. The method of claim 14 , wherein a first edge of the first package component joins a second edge of the first package component to form the corner of the first package component, and wherein an edge portion of the encapsulant contacting the first edge is not recessed.

16. A method comprising:

bonding a device die to a package component;

molding the device die in a molding compound;

removing a first top surface portion of the device die and a second top surface portion of the molding compound to form a recess;

applying a thermal interface material extending into the recess; and

placing a metal cap over the thermal interface material.

17. The method of claim 16 further comprising, before the removing, planarizing top surfaces of the device die and the molding compound.

18. The method of claim 16 , wherein the removing is selectively preformed on first portions of the device die and the molding compound without being performed on second portions of the device die and the molding compound.

19. The method of claim 16 , wherein the removing is performed through a method selected from cutting using a blade, milling, and grinding.

20. The method of claim 16 , wherein the first top surface portion of the device die comprises a corner portion of the device die.