Multi-TIM packages and method forming same

1 . A method comprising:

placing a package comprising:

a first package component;

a second package component;

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

an underfill between the first package component and the second package component, wherein a first top surface of the underfill is coplanar with second top surfaces of the first package component and the second package component;

attaching a first thermal interface material over the first package component, wherein the attaching the first thermal interface material comprises attaching the first thermal interface material having a plurality of elements;

attaching a second thermal interface material over the second package component;

after the first thermal interface material and the second thermal interface material are attached, dispensing a filling material into an air space between the first thermal interface material and the second thermal interface material, wherein the filling material is different from the first thermal interface material, and wherein the filling material contacts the first top surface;

after the filling material is dispensed, dispensing an adhesive on an additional package component that is underlying the first package component and the second package component; and

attaching a heat sink over both of the first thermal interface material and the second thermal interface material, wherein the heat sink is attached to the additional package component through the adhesive.

2 . The method of claim 1 , wherein the attaching the first thermal interface material and the attaching the second thermal interface material are performed by separate processes.

3 . The method of claim 1 , wherein the filling material has a first Young's modulus value lower than second Young's modulus values of the first thermal interface material and the second thermal interface material, and wherein the filling material has a first elongation value greater than second elongation values of the first thermal interface material and the second thermal interface material.

4 . The method of claim 1 , wherein the first package component is harder than the second thermal interface material.

5 . The method of claim 1 , wherein the heat sink physically contacts the filling material.

6 . The method of claim 1 , wherein the first thermal interface material and the second thermal interface material are pre-formed films that are formed as solids before being attached to the first package component and the second package component.

7 . The method of claim 1 , wherein the dispensing the filling material into the air space comprises dispensing a gel.

8 . The method of claim 7 , wherein the dispensing the filling material into the air space comprises dispensing silicone.

9 . The method of claim 1 further comprising molding the first package component and the second package component in a molding compound, wherein the second thermal interface material comprises:

a first portion over and contacting the second package component to form a first interface, wherein the first portion comprises a first sidewall vertically aligned to a second sidewall of the second package component; and

a second portion over and contacting the molding compound, wherein the second portion comprises a third sidewall vertically aligned to a fourth sidewall of the molding compound.

10 . A method comprising:

dispensing an underfill, wherein a portion of the underfill is between and contacting a first package component and a second package component, and the underfill comprises a first top surface;

applying a molding compound encapsulating the first package component and the second package component, wherein the first top surface is coplanar with a second top surface of the molding compound;

attaching a first thermal interface material over and contacting the first package component, wherein the first thermal interface material comprises a part extending laterally beyond a first edge of the first package component to contact a top surface of the molding compound;

attaching a second thermal interface material over and contacting the second package component, wherein the second thermal interface material is a soft film that is rolled onto the second package component;

after the first thermal interface material and the second thermal interface material are attached, dispensing a filling material different from the first interface material separating, and in contact with both of, the first thermal interface material and the second thermal interface material, wherein the filling material is over and contacts the first top surface; and

attaching a heat sink over both of the first thermal interface material and the second thermal interface material.

11 . The method of claim 10 , wherein the first thermal interface material and the second thermal interface material comprise different materials.

12 . The method of claim 10 , wherein the first thermal interface material and the second thermal interface material comprise a same material.

13 . The method of claim 10 , wherein the first thermal interface material and the second thermal interface material are physically spaced apart from each other by an air gap, and the filling material fully fills the air gap.

14 . The method of claim 13 further comprising:

after the filling material is dispensed, dispensing an adhesive on an additional package component that is under the first package component and the second package component, wherein the heat sink is further attached to the additional package component through the adhesive.

15 . The method of claim 14 , wherein the filling material is dispensed after both of the first thermal interface material and the second thermal interface material are attached.

16 . The method of claim 14 , wherein the filling material is different from both of the first thermal interface material and the second thermal interface material.

17 . The method of claim 10 , wherein the first thermal interface material comprises:

a first sidewall vertically aligned to a second sidewall of the first package component; and

a third sidewall vertically aligned to a fourth sidewall of the molding compound.

18 . A method comprising:

bonding a first device die to a package component;

bonding a second device die to the package component, wherein an underfill is located between the first device die and the second device die;

dispensing a first thermal interface material over the first device die, wherein the first thermal interface material has a first thermal conductivity value;

dispensing a second thermal interface material over the second device die, wherein the second thermal interface material has a second thermal conductivity value greater than the first thermal conductivity value; and

after the first thermal interface material and the second thermal interface material are dispensed, dispensing a filling material filling a space between the first thermal interface material and the second thermal interface material, wherein the filling material and the underfill form an interface level with a top surface of the first device die, wherein the filling material has a first Young's modulus lower than second Young's modulus values of the first thermal interface material and the second thermal interface material.

19 . The method of claim 18 , wherein the first device die is encircled by a first molding compound, and the second device die is encircled by a second molding compound, and wherein the first thermal interface material and the second thermal interface material are in contact with the first molding compound and the second molding compound, respectively.

20 . The method of claim 18 , wherein the filling material has a first elongation value greater than second elongation values of the first thermal interface material and the second thermal interface material.