Interposer Pad-Free Layout for Void-Free Semiconductor Molding
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Solution Overview
Problem
The existing 2.5D semiconductor package manufacturing process faces challenges with void formation due to the reduced fluidity of molding material between the interposer and semiconductor devices, leading to incomplete filling and reduced package reliability.
Innovation Solution
Incorporating a pad-free region with a cross-shaped structure on the interposer, which serves as an injection passage for the molding material, ensuring complete filling of gaps between the interposer and semiconductor devices without the need for separate underfill processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafer-level molding process is used, then manufacturing efficiency is improved, but molding material fluidity is reduced causing voids
Solution Approach 1:
The interposer surface is segmented into pad-free regions and pad regions, where pad-free regions serve as injection passages for molding material. This segmentation allows the molding material to flow through designated pathways, ensuring complete filling while maintaining manufacturing efficiency.
Solution Approach 2:
The pad-free region acts as an intermediary structure that facilitates the flow of molding material between the mold cavity and the bonding pads. By providing this intermediate pathway, the molding material can reach all necessary areas without being blocked by bonding pads, thus preventing void formation.
2Reliability
If bonding pads are placed in all mounting regions, then electrical connectivity is improved, but molding material flow is blocked causing incomplete filling
Solution Approach 1:
The mounting region is divided into pad-free regions and pad regions. Bonding pads are exclusively placed in pad regions, while pad-free regions remain clear to allow molding material flow. This spatial segmentation resolves the conflict between electrical connectivity and material flow.
Solution Approach 2:
Different regions of the interposer are assigned different functions: pad-free regions provide fluid passage for molding material, while pad regions provide electrical connectivity. This local differentiation allows each region to optimize its specific function without compromising the other.
3Reliability
If separate underfill process is added, then void prevention is improved, but manufacturing complexity increases
Solution Approach 1:
The functions of molding and underfilling are merged into a single molding process. The pad-free regions enable the molding material to simultaneously perform both encapsulation and gap-filling functions, eliminating the need for a separate underfill process and reducing manufacturing complexity.
Solution Approach 2:
The molding material serves multiple functions: it provides mechanical protection, electrical insulation, and void prevention. By designing the pad-free regions, the same molding process achieves what would traditionally require separate underfilling, demonstrating multi-functionality.
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.