Packages with multi-thermal interface materials and methods of fabricating the same

1. A package, comprising:

a die on a surface of a package component;

a first die stack on the surface of the package component;

a first thermal interface material (TIM) having a first thermal conductivity and disposed on the first die stack; and

a second thermal interface material having a second thermal conductivity and disposed on the die, wherein the first thermal conductivity of the first TIM is different from the second thermal conductivity of the second TIM, and the first TIM is in direct contact with the second TIM.

2. The package as claimed in claim 1 , wherein the die consumes a higher amount of power than the first die stack, and the second thermal conductivity of the second TIM is higher than the first thermal conductivity of the first TIM.

3. The package as claimed in claim 2 , further comprising:

a substrate, wherein the package component is bonded on a surface of the substrate; and

an adhesive on the surface of the substrate and around the package component, wherein the first TIM and the adhesive are made of the same material.

4. The package as claimed in claim 1 , wherein the first TIM comprises a first base material and a plurality of first fillers in the first base material, the second TIM comprises a second base material and a plurality of second fillers in the second base material, and the first fillers have a particle size that is larger than the particle size of the second fillers.

5. The package as claimed in claim 1 , further comprising:

a second die stack on the surface of the package component, wherein the first TIM is also on the second die stack.

6. The package as claimed in claim 1 , further comprising:

a substrate, wherein the package component is bonded on a surface of the substrate;

a passive device on the surface of the substrate; and

an adhesive on the surface of the substrate and around the package component, wherein the passive device is disposed between the adhesive and the package component.

7. The package as claimed in claim 6 , further comprising:

a lid attached on the substrate using the adhesive, and attached on the die and the first die stack using the first TIM and the second TIM, wherein the passive device is between the lid and the substrate.

8. The package as claimed in claim 7 , further comprising:

a ring between the lid and the adhesive, wherein the ring is attached to the lid using an additional adhesive.

9. The package as claimed in claim 1 , wherein the package component comprises an interposer, a package substrate or a printed circuit board (PCB).

10. The package as claimed in claim 1 , further comprising a molding compound encircling and contacting the die and the first die stack, wherein the molding compound is disposed on the package component and top surfaces of the die and the first die stack are exposed through the molding compound.

11. The package as claimed in claim 1 , wherein an interface between the first TIM and the second TIM is on a top surface of the first die stack.

12. A package, comprising:

a first die stack disposed over and bonded to a surface of a substrate;

a second die stack disposed over and bonded to the surface of the substrate, wherein the first die stack consumes a relatively low amount of power than the second die stack;

a first thermal interface material (TIM) having a first thermal conductivity and dispensed on the first die stack; and

a second thermal interface material having a second thermal conductivity and dispensed on the second die stack, wherein the first thermal conductivity of the first TIM is lower than the second thermal conductivity of the second TIM, and the second TIM covers the first die stack and the second die stack.

13. The package as claimed in claim 12 , further comprising:

an adhesive on the surface of the substrate and around the first die stack and the second die stack; and

a lid attached on the substrate using the adhesive, and attached on the first die stack and the second die stack using the first TIM and the second TIM.

14. The package as claimed in claim 12 , wherein the first TIM comprises a plurality of first fillers dispersed in a first polymer material, the second TIM comprises a plurality of second fillers dispersed in a second polymer material, and the first fillers have a particle size that is larger than the particle size of the second fillers.

15. The package as claimed in claim 12 , further comprising:

a molding compound encircling and contacting the first die stack and the second die stack;

an adhesive on the surface of the substrate and around the molding compound; and

a plurality of passive devices on the surface of the substrate and disposed between the molding compound and the adhesive.

16. A package, comprising:

a die over a substrate;

a first die stack over the substrate and adjacent to the die;

a first thermal interface material (TIM) disposed on the first die stack;

a second thermal interface material disposed on the die, wherein the second TIM is in direct contact with the die and the first die stack; and

an adhesive on the substrate and surrounding the die, the first die stack, the first TIM and the second TIM.

17. The package as claimed in claim 16 , further comprising a second die stack over the substrate and adjacent to the first die stack.

18. The package as claimed in claim 17 , wherein the first TIM extends across the first die stack and the second die stack.

19. The package as claimed in claim 16 , wherein the adhesive layer comprises a plurality of discrete pieces, and the first TIM and the adhesive are made of the same material.

20. The package as claimed in claim 17 , further comprising a third die stack over the substrate and adjacent to the die, wherein the second TIM is in direct contact with the third die stack.