Buffer Dam for PoP Delamination Prevention
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Solution Overview
Problem
In conventional Package-on-Package (PoP) processes, stress from the curing of the molding compound and through-assembly vias (TAVs) causes delamination of the device die from the release layer due to shrinkage, leading to reliability issues and integration challenges.
Innovation Solution
A dam member made of a soft material with specific thermal expansion and mechanical properties is introduced between the device die and TAVs, absorbing shrinkage stress and preventing delamination, formed using techniques like photolithography or printing methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the molding compound is cured to complete the packaging process, then the packaging structure is formed, but shrinkage stress causes the device die to delaminate from the release layer
Solution Approach 1:
A buffer dam is introduced as an intermediary element positioned between the device die and the molding compound. This buffer dam absorbs the shrinkage stress generated during curing, preventing direct stress transmission to the device die-release layer interface and thereby preventing delamination while maintaining bonding reliability
Solution Approach 2:
The buffer dam is formed in advance before the molding compound is applied and cured. It is strategically positioned to cushion and absorb the shrinkage stress that will be generated during the curing process, preventing delamination before it can occur
2Adaptability or versatility
If through-assembly vias are formed to enable package interconnection, then integration level is increased, but stress from TAVs contributes to device die delamination
Solution Approach 1:
The buffer dam serves as a mediator between the through-assembly vias and the device die. It absorbs stress generated by both the curing molding compound and the TAVs, preventing this combined stress from causing delamination while maintaining the integration benefits of TAVs
Solution Approach 2:
The buffer dam is selectively positioned at specific locations where stress concentration occurs, particularly around the through-assembly vias. This localized stress management allows the TAVs to maintain their interconnection function while preventing delamination at critical stress points
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The dam member effectively reduces stress and enhances the reliability of the PoP structure by preventing delamination, improving the integration process and bonding margin between packages.
Implementation Method 1
Due to shrinkage of the molding compound following the step of curing, stress from the cured molding compound and the TAVs may cause the device die to delaminate from the release layer
Implementation Method 2
A dam member made of a soft material with specific thermal expansion and mechanical properties is introduced between the device die and TAVs, absorbing shrinkage stress and preventing delamination
Data Source
AI summary
Package-on-Package (PoP) structures and methods of forming the same are disclosed. In some embodiments, a method of forming a PoP structure may include: plating at least one through-assembly via (TAV) over a peripheral region of a conductive seed layer; forming a dam member over a central region of the conductive seed layer; and placing a die over the central region of the conductive seed layer. The dam member may be laterally separated from the die and disposed between the die and the at least one TAV. The method may further include encapsulating the die, the dam member, and the at least one TAV in a polymer material.