Interposer Package Stiffener Structure for PoP Warpage Control
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Solution Overview
Problem
The semiconductor industry faces challenges in reducing warpage and thermal resistance in Package-on-Package (PoP) devices due to coefficient of thermal expansion (CTE) mismatch between semiconductor dies and molding compounds, which affects the reliability and performance of these devices.
Innovation Solution
Incorporation of stiffener structures at the edges of molded stacked die structures to act as barriers during thermal processes and reduce stress, using materials with similar CTE to the wafer, thereby reducing warpage and thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If semiconductor dies are stacked in PoP configuration to increase integration density, then component density and functionality are improved, but warpage increases due to CTE mismatch between dies and molding compound
Solution Approach 1:
A stiffener structure is introduced as an intermediary element between the semiconductor dies and the molding compound. This stiffener has a CTE that is intermediate between the high-CTE molding compound and the low-CTE semiconductor dies, acting as a thermal expansion mediator that reduces the overall warpage of the stacked package while enabling high integration density through PoP configuration.
2Ease of manufacture
If traditional molding compound is used to encapsulate stacked dies, then manufacturing simplicity is maintained, but thermal resistance increases affecting device performance
Solution Approach 1:
The molding compound is formulated as a composite material containing thermally conductive particles (such as aluminum oxide, boron nitride, or metal particles) dispersed within the polymer matrix. This composite structure maintains the ease of manufacturing through standard molding processes while significantly improving thermal conductivity to reduce thermal resistance in the stacked die package.
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 stiffener structures effectively reduce warpage by about 33% and thermal resistance by about 3%, enhancing the mechanical and thermal performance of the package structure while improving process handling and enabling functional customization.
Implementation Method 1
coefficient of thermal expansion (CTE) mismatch between semiconductor dies and molding compounds
Implementation Method 2
reducing thermal resistance by about 3%
Data Source
AI summary
A package structure and a method of forming the same are provided. A method includes forming first electrical connectors and second electrical connectors on a first side of an interposer wafer. An integrated circuit die is bonded to the first side of the interposer wafer using the first electrical connectors. A stiffener structure is attached to the first side of the interposer wafer adjacent the integrated circuit die. The stiffener structure covers the second electrical connectors in a plan view. The integrated circuit die and the stiffener structure are encapsulated with a first encapsulant. The interposer wafer and the stiffener structure are singulated to form a stacked structure.