Molded Underfill for Package on Package Devices
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Solution Overview
Problem
The semiconductor industry faces limitations in reducing the total thickness of package on package (PoP) devices due to the solder ball joint height between the top and bottom packages, which restricts further integration density and miniaturization in electronic components.
Innovation Solution
The implementation of a molded underfilling process, where a mold is used to apply a nonconductive material, such as epoxy or resin, between the die and the interposer substrate, filling the spaces between mounting conductors and allowing for the coining of package and die mounts to achieve a reduced profile, enabling thinner packages while maintaining electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If traditional PoP technology is used with solder ball joints, then electrical connectivity between top and bottom packages is achieved, but the total package thickness cannot be reduced further due to the fixed solder ball joint height
Solution Approach 1:
The patent changes the physical state and form of the connection material from spherical solder balls to molded underfill material that flows and cures to create direct die-to-substrate contact. This parameter change eliminates the fixed height constraint of solder balls while maintaining electrical connectivity through the conductive properties of the underfill material
Solution Approach 2:
The patent extracts the solder ball joint layer from the package structure and replaces it with a molded underfill process that directly bonds the die to the substrate. This removal of the intermediate solder ball layer enables significant reduction in package thickness while preserving electrical connection functionality
2Productivity
If the package thickness is reduced to achieve denser integration, then integration density improves, but the solder ball joint height becomes insufficient to maintain reliable electrical connections
Solution Approach 1:
The patent transforms the connection architecture from fixed-height solder balls to a flowable molded underfill material that can adapt to reduced thickness configurations. The underfill material's ability to flow during molding and then cure provides reliable electrical connections even when the overall package thickness is minimized for higher integration density
3Reliability
If underfill material is applied to fill spaces between mounting conductors, then mechanical support and electrical connectivity are improved, but the package profile cannot be reduced due to the height required for proper underfill application
Solution Approach 1:
The patent applies preliminary action by forming the molded underfill material with precise height control before final package assembly. The molding process pre-establishes the optimal underfill height that provides sufficient mechanical support and electrical connectivity while minimizing the overall package profile, eliminating the need for additional height compensation
Solution Approach 2:
The patent changes the application method of underfill material from traditional dispensing (which requires excess height for proper coverage) to molded application (which provides precise height control). This parameter change in the application process enables the underfill to provide full mechanical and electrical functionality at a reduced package profile
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
This approach allows for a significant reduction in package thickness, enabling denser integration of electronic components without compromising electrical connections, thus overcoming the thickness limitations of traditional PoP devices.
Implementation Method 1
a molded underfilling process, where a mold is used to apply a nonconductive material, such as epoxy or resin, between the die and the interposer substrate, filling the spaces between mounting conductors
Data Source
AI summary
Presented herein are a package-on-package device having a molded underfill and a method for forming the same, the method comprising applying a package mount mounting a die to the first side of a carrier package. A molded underfill may be applied first side of the carrier package, and be in contact with a portion of the package mount a portion of a sidewall of the die. A top package having at least one land may be mounted to the first side of the carrier package above the die, and, optionally separated from the top of the die. The package mount may be coined prior to, during or after applying the molded underfill to optionally be level with the underfill surface. The underfill region contacting the package mount may be below or above the surface of the underfill region contacting the die sidewall.