Interposer Design for Reliable Semiconductor Packages
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Summary
Problems
The mismatched coefficients of thermal expansion (CTE) between flip chip and package substrate components in semiconductor packages cause mechanical stress due to thermal cycling, and the limitation of contact pad pitches hinders direct mounting of flip chips onto package substrates, affecting package reliability and performance.
Innovation solutions
An interposer with a redistribution layer and vias filled with reflowed conductive material is used to couple the flip chip to the package substrate, providing a medium with similar CTE to the flip chip and allowing for finer pitched die contacts to be connected to the package pads, reducing mechanical stress and enabling mounting despite pitch limitations.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
If flip chip is directly mounted onto package substrate, then mounting process is simple, but CTE mismatch causes mechanical stress and reliability issues
Why choose this principle:
An interposer is introduced as an intermediary component between the flip chip and package substrate. The interposer has a CTE that matches the flip chip, thereby reducing mechanical stress caused by CTE mismatch during thermal cycling. The interposer includes contact pads that interface with the flip chip solder bumps and package pads that connect to the substrate, effectively mediating the connection and resolving the reliability issue while maintaining relatively simple mounting procedures.
Principle concept:
If contact pad pitch on package substrate is increased to accommodate flip chip, then direct mounting is enabled, but I/O pad pitch cannot be reduced for higher performance
Why choose this principle:
The interposer enables pitch transformation by redistributing connections across multiple dimensions. The fine-pitch I/O pads on the flip chip are connected to the interposer contact pads, which are then redistributed to larger-pitch package pads on the substrate through the interposer's internal routing. This dimensional redistribution allows the flip chip to maintain its high-performance fine pitch while the package substrate uses larger, more manufacturable pitch dimensions.
Application Domain
Data Source
AI summary:
An interposer with a redistribution layer and vias filled with reflowed conductive material is used to couple the flip chip to the package substrate, providing a medium with similar CTE to the flip chip and allowing for finer pitched die contacts to be connected to the package pads, reducing mechanical stress and enabling mounting despite pitch limitations.
Abstract
An interposer is presented. The interposer includes an interposer base having first and second surfaces. A redistribution layer is disposed on a first surface of the interposer base. The interposer has at least one interposer pad coupled to the redistribution layer. It also includes at least one interposer contact on the second surface. The interposer contact is electrically coupled to the interposer pad via the redistribution layer. The interposer also includes at least one interposer via through the interposer base for coupling the interposer contact to the redistribution layer. The interposer via includes reflowed conductive material of the interposer contact.