Package structure and method for fabricating the same

1 . A method for fabricating a package structure, comprising:

premixing cellulose nanofibrils (CNFs) as a first one-dimensional (1D) nanomaterial and a first two-dimensional (2D) material in a solvent to form a first solution, wherein a weight of the CNFs to a weight of the first 2D material define a first premixing weight ratio;

removing the solvent from the first solution to form a first composite filler;

mixing a first prepolymeric material with the first composite filler to form a first composite material;

dispensing the first composite material between a package substrate and a semiconductor package device disposed over the package substrate;

premixing a second 1D nanomaterial and a second 2D material in a second solution, such that a second premixing weight ratio of a weight of the second 1D nanomaterial to a weight of the second 2D material is different than the first premixing weight ratio of the weight of the CNFs to the weight of the first 2D material;

drying the second solution to form a second composite filler;

melt-mixing a second prepolymeric material with the second composite filler to form a second composite material; and

dispensing the second composite material over the semiconductor package device and the package substrate, wherein the second 2D material comprises hexagonal boron nitride.

2 . The method of claim 1 , wherein mixing the first prepolymeric material with the first composite filler further comprises:

melting the first prepolymeric material to mix the melted first prepolymeric material and the first composite filler.

3 . The method of claim 1 , wherein removing the solvent from the first solution comprises:

evaporating the solvent.

4 . The method of claim 1 , wherein removing the solvent from the first solution is performed such that the first composite filler is in solid form.

5 . The method of claim 1 , further comprising: before dispensing the first composite material between the package substrate and the semiconductor package device, encapsulating a die in the semiconductor package device using a third composite material, the third composite material comprising a third prepolymeric material and a third composite filler, the third composite filler being prepared from a third solution comprising a third 1D nanomaterial and a third 2D material.

6 . The method of claim 1 , wherein dispensing the first composite material between the package substrate and the semiconductor package device is performed such that the CNFs and the first 2D material form a network in the first composite material.

7 . The method of claim 1 , wherein dispensing the first composite material between the package substrate and the semiconductor package device is performed such that the first prepolymeric material is cured to be a polymeric material, and the first 2D material has an in-plane thermal conductivity greater than a thermal conductivity of the polymeric material.

8 . The method of claim 1 , wherein dispensing the first composite material between the package substrate and the semiconductor package device is performed such that the first prepolymeric material is cured to be a polymeric material, and the first 2D material has an out-of-plane thermal conductivity greater than a thermal conductivity of the polymeric material.

9 . The method of claim 1 , wherein the first 2D material comprises graphene.

10 . A method for fabricating a package structure, comprising:

premixing a first one-dimensional (1D) nanomaterial and a first 2D material in a first solution, wherein the first 1D nanomaterial has a higher length-to-width ratio than the first 2D material, such that a first premixing weight ratio of a weight of the first 1D nanomaterial to a weight of the first 2D material is in a range from about 10% to about 90%;

drying the first solution to form a first composite filler;

melt-mixing a first prepolymeric material with the first composite filler to form a first composite material;

encapsulating a die using the first composite material;

attaching the die to a package substrate;

premixing a second 1D nanomaterial and a second 2D material in a second solution, such that a second premixing weight ratio of a weight of the second 1D nanomaterial to a weight of the second 2D material is different than the first premixing weight ratio of the weight of the first 1D nanomaterial to the weight of the first 2D material;

drying the second solution to form a second composite filler;

melt-mixing a second prepolymeric material with the second composite filler to form a second composite material comprising the second prepolymeric material and the second composite filler; and

dispensing the second composite material between the die and the package substrate.

11 . The method of claim 10 , further comprising:

pulverizing the first composite filler prior to melt-mixing the first prepolymeric material with the first composite filler.

12 . The method of claim 10 , wherein, melt-mixing the first prepolymeric material with the first composite filler is performed such that a ratio of a weight of the first composite filler to a weight of the first composite material is in a range from about 10% to about 85%.

13 . There method of claim 10 , wherein the first 1D nanomaterial comprises cellulose nanofibrils.

14 . The method of claim 10 , wherein the second composite material has a higher electrical conductivity than the first composite material.

15 . The method of claim 10 , wherein the first 2D material comprises hexagonal boron nitride, and the second 2D material comprises graphene.

16 . A method for fabricating a package structure, comprising:

premixing carbon nanotubes and a hexagonal boron nitride in a first solvent to form a first solution, wherein a weight of the carbon nanotubes to a weight of the hexagonal boron nitride define a first premixing weight ratio;

removing the first solvent from the first solution to form a first composite filler;

pulverizing the first composite filler;

mixing a first prepolymeric material with the first pulverized composite filler to form a first composite material;

encapsulating a die using the first composite material, the first composite material comprising the carbon nanotubes and the hexagonal boron nitride;

attaching the die to a package substrate;

premixing a 1D nanomaterial and graphene in a second solvent to form a second solution, wherein a weight of the 1D nanomaterial to a weight of the graphene define a second premixing weight ratio different than the first premixing weight ratio of the weight of the carbon nanotubes to the weight of the hexagonal boron nitride;

removing the second solvent from the second solution to form a second composite filler;

pulverizing the second composite filler;

mixing a second prepolymeric material with the pulverized composite filler to form a second composite material; and

depositing the second composite material comprising the 1D nanomaterial and the graphene over the package substrate and the die.

17 . The method of claim 16 , wherein removing the first solvent from the first solution comprises:

evaporating the first solvent.

18 . The method of claim 16 , wherein removing the first solvent from the first solution is performed such that the first composite filler is in solid form.

19 . The method of claim 16 , wherein after depositing the second composite material, the second prepolymeric material is cured to be a polymeric material, and the graphene has an in-plane thermal conductivity greater than a thermal conductivity of the polymeric material.

20 . The method of claim 16 , wherein the 1D nanomaterial and the graphene form a network in the second composite material.