Ball height control in bonding process

1. A package comprising:

a first package component comprising:

a first surface dielectric layer;

a bond pad in the first surface dielectric layer, wherein a top surface of the bond pad is lower than a top surface of the first surface dielectric layer;

a second package component over the first package component and comprising:

a second surface dielectric layer at a bottom of the second package component;

an Under-Bump Metallurgy (UBM) comprising a first portion in the second surface dielectric layer, and a second portion below a bottom surface of the second surface dielectric layer;

a solder region bonding the bond pad to the UBM; and

a ball-height control stud separating the first package component and the second package component from each other, wherein the ball-height control stud and the first surface dielectric layer are formed of a same dielectric material, with no distinguishable interface existing between the ball-height control stud and the first surface dielectric layer, and the ball-height control stud forms a step with a top surface and an edge of the first surface dielectric layer.

2. The package of claim 1 , wherein the second package component comprises a device die.

3. The package of claim 1 further comprising a plurality of ball-height control studs distributed substantially uniformly along a peripheral of the second package component.

4. The package of claim 3 , wherein the plurality of ball-height control studs comprises four discrete ball-height control studs physically separated from each other, with each of the four discrete ball-height control studs adjacent to a corner region of the first package component.

5. The package of claim 1 , wherein the first package component comprises a printed circuit board, and wherein the second package component comprises a device die.

6. The package of claim 1 , wherein the first package component extends beyond edges of the second package component.

7. A package comprising:

a first package component comprising:

a first surface dielectric layer at a top surface of the first package component; and

a bond pad in the first surface dielectric layer and exposed through an opening in the first surface dielectric layer, wherein in a cross-sectional view of the package, the bond pad is spaced apart from the first surface dielectric layer;

a second package component comprising:

a second surface dielectric layer at a surface of the second package component; and

a surface conductive feature extends into, and in physical contact with, the second surface dielectric layer;

a solder region between and in contact with and bonded to both the bond pad and the surface conductive feature; and

a plurality of ball-height control studs between the first surface dielectric layer and the second surface dielectric layer, wherein the plurality of ball-height control studs contacts, and is not adhered to, the second surface dielectric layer, wherein the plurality of ball-height control studs and the first surface dielectric layer are formed of a same dielectric material, with no distinguishable interface existing between the plurality of ball-height control studs and the first surface dielectric layer, and each of the plurality of ball-height control studs forms a step with a top surface and an edge of the first surface dielectric layer.

8. The package of claim 7 , wherein the plurality of ball-height control studs and the first surface dielectric layer are formed of a polymer.

9. The package of claim 7 further comprising an underfill between the first package component and the second package component, wherein the underfill contacts the plurality of ball-height control studs, and wherein the underfill extends into a space separating the bond pad from the first surface dielectric layer.

10. The package of claim 7 , wherein the plurality of ball-height control studs comprises at least three discrete ball-height control studs physically separated from each other, with each of the plurality of ball-height control studs adjacent to a corner region of the first package component.

11. The package of claim 7 , wherein the first package component comprises a printed circuit board, and wherein the second package component comprises a device die.

12. The package of claim 7 , wherein the first package component extends beyond edges of the second package component.

13. A package comprising:

A package substrate comprising:

four corners;

a top dielectric layer; and

an additional dielectric layer underlying the top dielectric layer;

a device die over and bonded to the package substrate;

an underfill filling a gap between the package substrate and the device die; and

three studs, each disposed adjacent to one of the four corners, wherein each of the three studs comprises:

a top surface in contact with, and not adhered to, a bottom surface of the device die,

wherein each of the three studs comprises two sections joined to each other, each being elongated and having a lengthwise direction parallel to an edge of the package substrate, wherein the three studs and the top dielectric layer are formed of a same dielectric material, with no distinguishable interface existing between the three studs and the top dielectric layer, and each of the three studs forms a step with a top surface and an edge of the top dielectric layer.

14. The package of claim 13 , wherein the top surface of the each of the three studs is coplanar with a top surface of the underfill.

15. The package of claim 13 further comprising a fourth stud at a corner of the package substrate.

16. The package of claim 13 , wherein the three studs are discrete studs separated from each other.

17. The package of claim 13 , wherein each of the three studs is encircled by the underfill.

18. The package of claim 1 , wherein the ball-height control stud and the first surface dielectric layer are formed of a polymer.

19. The package of claim 1 , wherein an entirety of the ball-height control stud is formed of a homogenous material.

20. The package of claim 13 , wherein the package substrate extends beyond edges of the device die.