Cross-Shaped Pad-Free Interposer Layout for Void-Free Package Molding
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Solution Overview
Problem
In semiconductor packaging, the fluidity of molding material between the interposer and semiconductor devices is often reduced during the wafer-level molding process, leading to incomplete filling and the formation of voids, which compromises package reliability and productivity.
Innovation Solution
A semiconductor package design featuring a pad-free region with a cross-shaped structure on the interposer, allowing the molding material to flow through and fill gaps effectively, eliminating the need for separate underfill processes and enhancing the filling of small spaces between the interposer and semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafer-level molding process is used, then productivity is improved, but molding material fluidity is reduced causing voids
Solution Approach 1:
The mounting region is segmented into a pad region and a pad-free region. The pad-free region acts as a dedicated fluidity enhancement zone that allows molding material to flow more easily and fill gaps between the interposer and semiconductor devices, preventing voids while maintaining high productivity through wafer-level molding.
Solution Approach 2:
The pad-free region is created with different local properties compared to the pad region. This localized area without bonding pads provides enhanced fluidity for molding material specifically where needed for gap filling, while the pad region maintains its bonding function. This local quality change resolves the contradiction by improving material flow only in the critical area without affecting overall process productivity.
2Reliability
If bonding pads are placed in all mounting region areas, then electrical connection is improved, but molding material flow is blocked causing incomplete filling
Solution Approach 1:
The mounting region is divided into two functional segments: a pad region where bonding pads are located for electrical connection, and a pad-free region where no pads are present to allow molding material flow. This segmentation enables both electrical connectivity and complete filling without compromise.
Solution Approach 2:
The pad-free region serves as an intermediary zone that mediates between the electrical connection requirement (pad region) and the filling completeness requirement. By providing a pad-free pathway, it allows molding material to flow through and fill gaps while the pad region maintains electrical connectivity, resolving the contradiction between these two requirements.
3Reliability
If separate underfill process is added, then gap filling is improved, but process complexity is increased
Solution Approach 1:
The pad-free region design merges the gap filling function into the main molding process. By creating a pad-free region that enhances molding material fluidity and flow, the need for a separate underfill process is eliminated. The molding material naturally fills gaps through the pad-free region during the standard molding process, combining multiple functions into one step and reducing process complexity.
Solution Approach 2:
The pad-free region enables the molding material to self-fill the gaps between the interposer and semiconductor devices without requiring additional underfill processing. The enhanced fluidity in the pad-free region allows the molding material to automatically flow and fill gaps during the normal molding process, making the system self-sufficient and eliminating the need for separate underfill steps.
Data Source
AI summary
A semiconductor package includes a package substrate, an interposer on the package substrate, semiconductor devices in individual mounting regions on a first surface of the interposer, respectively, first conductive connection members, and a molding member on the interposer. The interposer has first bonding pads in the individual mounting regions, respectively. The semiconductor devices each have chip pads electrically connected to the first bonding pads. The first conductive connection members are between the first bonding pads and the chip pads. The molding member covers the semiconductor devices and fills gaps between the first surface of the interposer and the semiconductor devices. At least one of the individual mounting regions includes a pad-free region with a cross shape and pad regions defined by the pad-free region, and the first bonding pads are in the pad regions.