Packages with multiple types of underfill and method forming the same

1. A method comprising:

bonding a first package component over a second package component;

dispensing a first underfill between the first package component and the second package component, wherein the first underfill comprises a capillary underfill;

bonding a third package component over the second package component, wherein a second underfill is between the third package component and the second package component, and wherein the second underfill comprises a first non-conductive film, and wherein both of the first underfill and the second underfill directly contact a top surface of the second package component;

attaching a second non-conductive film on a fourth package component;

after the second non-conductive film has been attached to the fourth package component, placing the fourth package component over the second package component, with the second non-conductive film being in physical contact with the fourth package component, wherein solder regions of the fourth package component are fully inside the second non-conductive film, and the solder regions are spaced apart from the second package component by a layer of the second non-conductive film; and

bonding the fourth package component over the second package component, wherein the solder regions penetrate through the layer of the second non-conductive film to join the second package component.

2. The method of claim 1 , wherein the capillary underfill comprises a portion overlapping a portion of the first non-conductive film.

3. The method of claim 1 further comprising:

attaching the first non-conductive film on the third package component, wherein the third package component is bonded to the second package component after the first non- conductive film is attached, and wherein the first non-conductive film fills a gap between the third package component and the second package component.

4. The method of claim 3 , wherein the first non-conductive film is a solid film when the first non-conductive film is attached.

5. The method of claim 1 further comprising molding the first package component and the third package component in a molding compound.

6. The method of claim 5 , wherein the second underfill comprises a molding underfill, and the method further comprises dispensing the molding underfill between the third package component and the second package component.

7. The method of claim 1 , wherein the first underfill and the second underfill have different coefficient of thermal expansion.

8. The method of claim 1 , wherein the first underfill and the second underfill are in direct contact with each other.

9. A method comprising:

attaching a non-conductive film to a first package component;

after the non-conductive film is attached to the first package component, bonding the first package component over a second package component, wherein electrical connectors of the first package component penetrate through the non-conductive film to electrically connect to the second package component, and wherein the non-conductive film fills a first gap between the second package component and the first package component;

bonding a third package component to the second package component;

dispensing a underfill in a second gap between the third package component and the first package component, wherein the underfill is different from the non-conductive film, and wherein the underfill directly contacts the non-conductive film to form an interface, and wherein a portion of the underfill is in the second gap and contacts a first sidewall of the first package component and a second sidewall of the third package component; and

dispensing a molding compound into the second gap, wherein the molding compound is over and contacting the portion of the underfill in the second gap.

10. The method of claim 9 , wherein the underfill comprises a capillary underfill or a molding underfill.

11. The method of claim 10 , wherein the underfill comprises a first extension portion outside of the second gap, and the first extension portion comprises a concave sidewall, and the non-conductive film comprises a second extension portion outside of the first gap, and the second extension portion comprises a convex and curved sidewall.

12. The method of claim 10 , wherein the molding compound encapsulates the underfill, the non-conductive film, and the first package component and the third package component therein, wherein the molding compound has a composition different from compositions of both of the underfill and the non-conductive film.

13. The method of claim 9 further comprising:

before the first package component is bonded over the second package component, placing the first package component over the second package component, wherein the electrical connectors of the first package component are in the non-conductive film and spaced apart from the second package component by a layer of the non-conductive film; and

pressing the first package component against the second package component, so that the electrical connectors penetrate through the layer of the non-conductive film to electrically connect to the second package component.

14. The method of claim 9 , wherein the underfill directly contacts a sidewall of the first package component.

15. A method comprising:

pressing a first underfill layer that is solid onto a wafer, wherein the wafer comprises a first die, and wherein a first plurality of solder regions of the first die is pressed partially into the first underfill layer;

sawing the wafer to separate the first die from other dies in the wafer;

bonding the first die to an interposer through the first plurality of solder regions, wherein a first portion of the first underfill layer is located between the first die and the interposer, and wherein the first underfill layer surrounds the first plurality of solder regions;

bonding a second die to the interposer through a second plurality of solder regions;

dispensing a second underfill layer between the second die and the interposer, wherein the second underfill layer surrounds the second plurality of solder regions, wherein the first underfill layer is attached to the first die before the first die is bonded to the interposer, and the second underfill layer is dispensed after the second die is bonded to the interposer; and

dispensing an encapsulant to encapsulate the first die and the second die therein, wherein the encapsulant further surrounds the first underfill layer and the second underfill layer.

16. The method of claim 15 , wherein the encapsulant comprises a material different from materials of both of the first underfill layer and the second underfill layer.

17. The method of claim 15 further comprising pressing the first die against the interposer, so that the first plurality of solder regions of the first die penetrate through a layer of the first underfill layer that is solid to penetrate through the first underfill layer.

18. The method of claim 15 , wherein the second underfill layer comprises a capillary underfill that is dispensed through capillary, and the first underfill layer is a non-conductive film.

19. The method of claim 18 , wherein the capillary underfill further extends to a top surface of the first die.