NCF Retention Structures for Stacked Semiconductor Assemblies
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Solution Overview
Problem
During the assembly of semiconductor device assemblies with non-conductive film (NCF), the NCF can unpredictably squeeze out from the sides of the device stack when heated and compressed, leading to increased size, potential voids, and prevention of mold material from reaching the sides.
Innovation Solution
Incorporating retention structures on the bottom surface of each stacked device, which are designed to constrain and redirect the flow of NCF, ensuring it fills the desired regions and minimizing squeeze-out to areas where it won't negatively impact the assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-conductive film is applied to fill gaps between stacked devices, then protection and structural integrity are improved, but the film unpredictably squeezes out during heating and compression
Solution Approach 1:
Retention structures are formed on the bottom surface of each stacked device before the non-conductive film is applied. These pre-formed structures create designated pathways that guide the film during subsequent heating and compression, preventing unpredictable squeeze-out while maintaining protection benefits
Solution Approach 2:
The retention structures act as intermediary elements between the stacked devices and the non-conductive film. They mediate the interaction by providing controlled pathways for the film, allowing it to fill gaps effectively while preventing harmful squeeze-out during the bonding process
2Volume of stationary object
If non-conductive film is compressed during assembly, then gap filling and protection are improved, but squeeze-out increases device size and creates voids
Solution Approach 1:
The retention structures segment the bottom surface of each stacked device into distinct regions. This segmentation creates controlled zones that direct the non-conductive film into specific pathways, ensuring gap filling occurs in designated areas while preventing spread to regions that would increase overall device size or create voids
3Strength
If non-conductive film is heated and compressed, then bonding and structural integrity are improved, but mold material cannot reach the sides of the device
Solution Approach 1:
The retention structures create local variations in the bottom surface geometry, providing different functions in different regions. The structures are positioned and sized to allow non-conductive film to be retained in critical bonding areas while leaving peripheral regions open for mold material access, thus achieving both strong bonding and complete mold coverage
Data Source
AI summary
A semiconductor device assembly is provided, which comprises a vertical stack of semiconductor devices, the vertical stack including a plurality of electrical interconnects, a plurality of retention structures, and a non-conductive film (NCF) between each adjacent pair of semiconductor devices of the vertical stack. The plurality of retention structures between each adjacent pair of semiconductor devices is disposed peripherally to the corresponding plurality of electrical interconnects. Each of the plurality of retention structures has a height less than a space between the corresponding adjacent pair of semiconductor devices, and the plurality of retention structures between each adjacent pair of semiconductor devices has a smaller first average pitch between adjacent ones of the plurality of retention structures than a second average pitch between adjacent ones of the corresponding plurality of electrical interconnects.