Plug-Socket Wire Interconnects for POP Packages
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Solution Overview
Problem
Conventional semiconductor package on package (POP) technologies face limitations in increasing interconnections between upper and lower packages due to structural constraints, leading to reduced reliability of solder ball connections and potential cracks caused by thermal expansion coefficient differences, which can result in defects in end products.
Innovation Solution
A semiconductor package on package with a plug-socket type wire connection system, where conductive wire connectors with varying thickness and apex shapes are used to increase interconnections and reduce stress-induced cracks by providing a detachable and flexible connection between the upper and lower packages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If solder balls are used to connect upper and lower packages, then electrical connections are established, but the number of interconnections is limited by the structural constraints of the lower package
Solution Approach 1:
The connection system is divided into multiple wire connectors arranged in a grid pattern, with each connector comprising separate plug and socket portions. This segmentation allows for increased interconnection density compared to traditional solder ball arrays, as the wire-based approach is not constrained by the same structural limitations.
Solution Approach 2:
The invention transitions from a two-dimensional array of solder balls to a three-dimensional wire connector system that extends vertically between packages. The wire connectors can be routed through the molding compound and apex structures, utilizing the vertical dimension to achieve higher interconnection counts without increasing the footprint area.
2Reliability
If solder balls are used for connection, then electrical connectivity is achieved, but thermal expansion coefficient differences cause cracks and reduce reliability
Solution Approach 1:
The invention changes the physical parameters of the connection system by using wire connectors with varying thicknesses and apex structures instead of uniform solder balls. The wire connectors can be designed with different diameters, lengths, and flexibility characteristics to better accommodate thermal expansion differences between the PCB, solder balls, and package substrates, thereby reducing stress-induced cracks.
Solution Approach 2:
The wire connectors are formed as composite structures comprising conductive core wires surrounded by insulation layers and apex structures. This composite design allows the connection system to accommodate differential thermal expansion by providing both mechanical strength and flexibility, reducing the harmful effects of thermal stress on connection reliability.
3Quantity of substance
If more solder balls are arranged to increase interconnections, then connection density increases, but the structural limitations of the lower package prevent further increases
Solution Approach 1:
The wire connector system utilizes the vertical space between packages and the volume within the molding compound to achieve higher interconnection density. Instead of being limited to the surface area of the package footprint, the wires can be routed through the third dimension, allowing significantly more connections within the same footprint area.
Solution Approach 2:
The wire connectors are nested within the molding compound structure, with wires routed through the encapsulant material and apex structures. This nesting approach allows the connection system to utilize the internal volume of the package structure rather than being constrained to the external surface area, enabling higher density interconnections.
Data Source
AI summary
A semiconductor package on package includes a tower package, an upper package stacked over the lower package, a plug wire combined to any one of an upper portion of the tower package and a lower portion of the upper package, and a socket wire combined to any one of the upper portion of the lower package and the lower portion of the upper package. The plug wire is plugged into the socket wire to electrically connect the upper and lower packages.