Methods for Forming 3DIC Package

A method comprising:

• placing a first package component over a lower jig, wherein the first package component covers a through-opening extending from a top surface to a bottom surface of the lower jig;
• placing an upper jig over the first package component, wherein the upper jig secures the first package component on the lower jig;
• bonding a second package component onto the first package component;
• dispensing an underfill between the first package component and the second package component;
• and
• curing the underfill, wherein at a time between a starting time and an ending time of the step of curing the underfill, an action selected from the group consisting essentially of vacuuming and air blowing is performed, and wherein the action causes a force to be generated and applied on the first package component through the through-opening.

A method comprising:

• placing a first package component and a second package component on a top surface of an air-pressure boat to block a through-opening at the top surface of the air-pressure boat;
• vacuuming the air-pressure boat when the through-opening is blocked by the first package component and the second package component;
• dispensing an underfill into a gap between the first package component and the second package component;
• and
• curing the underfill during the step of vacuuming.