iTHOP preshrinkage issue

 The actual shrinkage rate of iTHOP is higher than anticipated, influenced by the smile warpage behavior. The inspection of iTHOP from mark to mark distance was validated that its value is smaller than actual design value. 

Based on our observation, the larger warpage , longer distance between mark to mark, which exhibits more expansion which was validated by the stage DOE experiment from Shinko & PTI. The inner flip chip pad showed that it has higher shrinkage rate, making alignment with the bumping from HBM side challenging.

The thinner organic interposer is more likely to be influenced by the properties of interposer material, it tend to be expand more freely even though vacuumed by the stage, but once bonded, it will be more easily pulled and conformed by ABF substrate.

-->Understanding the interactions can help in optimizing the design to achieve the desired alignment.