Coplanar control for film-type thermal interface

1. A method comprising:

bonding a first package and a second package over a package component;

adhering a first Thermal Interface Material (TIM) and a second TIM over the first package and the second package, respectively;

dispensing a first adhesive feature on the package component;

placing a heat sink over and contacting the first adhesive feature, wherein the heat sink comprises a portion over the first TIM and the second TIM, wherein at a first time after the first adhesive feature is dispensed and before the first adhesive feature is cured, the first adhesive feature has a first top surface higher than a second top surface of the first TIM, and wherein at a second time after the heat sink is placed, the first adhesive feature has a third top surface coplanar with the second top surface of the first TIM; and

curing the first adhesive feature.

2. The method of claim 1 , wherein the first adhesive feature is spaced apart from the first package and the second package.

3. The method of claim 1 further comprising dispensing an underfill between the first package and the package component, wherein the first adhesive feature has a lower modulus value than the underfill.

4. The method of claim 1 , wherein the first adhesive feature is dispensed to a first side of the first package, and the second package is on a second side of the first package opposite to the first side.

5. The method of claim 1 further comprising dispensing a second adhesive feature over the package component, wherein the second adhesive feature has a fourth top surface lower than the second top surface of the first TIM.

6. The method of claim 5 , wherein the heat sink comprises:

an upper portion higher than the first TIM and the second TIM; and

a heat sink bar extending from a bottom surface of the upper portion into a space between the first package and the second package, wherein the heat sink bar is inserted into the second adhesive feature.

7. The method of claim 1 further comprising dispensing an adhesive ring surrounding the first package and the second package, wherein the heat sink comprises a lower portion contacting the adhesive ring.

8. The method of claim 1 , wherein the first adhesive feature comprises a base material and filler particles mixed in the base material.

9. The method of claim 1 , wherein the first TIM and the second TIM are pre-formed solid TIMs when adhered over the first package and the second package, respectively.

10. A method comprising:

bonding a first package and a second package over a package component;

disposing a first Thermal Interface Material (TIM) and a second TIM over the first package and the second package, respectively;

dispensing a first adhesive feature on the package component; and

placing a heat sink over and contacting the first adhesive feature, wherein the heat sink is further over the first TIM and the second TIM, and a portion of the heat sink is inserted into the first adhesive feature.

11. The method of claim 10 , wherein the heat sink is placed in physical contact with the first TIM and the second TIM, and wherein the first adhesive feature is pressed by the heat sink, so that a first top surface of the first adhesive feature is pressed to be coplanar with a second top surface of the first TIM.

12. The method of claim 10 , wherein the first adhesive feature comprises non-straight sidewalls when disposed, and wherein after the portion of the heat sink is inserted, a straight sidewall of the first adhesive feature is generated.

13. The method of claim 10 further comprising dispensing an underfill between the first package and the package component, wherein a first portion of the first adhesive feature is over and contacting a second portion of the underfill.

14. The method of claim 10 , wherein the first adhesive feature is between the first package and the second package, and is separated from the heat sink by an air gap.

15. The method of claim 10 , wherein the heat sink comprises:

an upper portion higher than the first TIM and the second TIM; and

a heat sink bar extending from a bottom surface of the upper portion, wherein the heat sink bar is inserted into the first adhesive feature.

16. A method comprising:

bonding a package component over a package substrate, the package component comprising:

an interposer;

a device die over and bonding to the interposer; and

a molding compound molding the device die;

dispensing an underfill between the package component and the package substrate;

dispensing a first adhesive feature to the package substrate, wherein a first top surface of the first adhesive feature is higher than a second top surface of the package component, and wherein the first adhesive feature is softer than both of the molding compound and the underfill; and

placing a lid comprising an upper portion over the package component, wherein the lid contacts the first adhesive feature, and is attached to the package component through a thermal interface material.

17. The method of claim 16 further comprising dispensing a second adhesive feature on the package substrate, wherein the lid comprises a portion inserted into the second adhesive feature.

18. The method of claim 1 , wherein the first adhesive feature is dispensed as a flowable adhesive, and wherein the flowable adhesive is in physical contact with the package component.

19. The method of claim 10 , wherein the first adhesive feature is in physical contact with a top surface of the package component.

20. The method of claim 16 , wherein the first adhesive feature is softer than both of the molding compound and the underfill.