Packaging and function tests for package-on-package and system-in-package structures

A method comprising:

• bonding a plurality of dies onto a package substrate strip to form a bottom package component comprising a plurality of bottom units, wherein the package substrate strip comprises a plurality of package substrates;
• after the bonding the plurality of dies, placing the bottom package component onto a jig;
• placing a plurality of upper component stacks onto the bottom package component, wherein each of the plurality of upper component stacks is placed on one of the plurality of bottom units;
• and
• performing a reflow to join the plurality of upper component stacks with the plurality of bottom units, wherein after the reflow, the package substrate strip remains not bonded to the jig.

A method comprising:

• bonding a plurality of dies onto a package substrate strip to form a bottom package component comprising a plurality of bottom units, wherein the package substrate strip comprises a plurality of package substrates;
• performing a first function test on the bottom package component;
• after the first function test, placing the bottom package component onto a jig;
• selectively placing a plurality of upper component stacks onto a first one of the plurality of bottom units, wherein the first one of the plurality of bottom units passes the first function test;
• and
• performing a reflow to join the plurality of upper component stacks with the plurality of bottom units, wherein when the reflow is performed, a second one of the plurality of bottom units has no upper component stack placed thereon, and the second one of the plurality of bottom units fails the first function test.