Semiconductor Package UBM Layer Adhesion and Crack Resistance
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Solution Overview
Problem
Current semiconductor packages face challenges in achieving stable electrical connections and reliability due to limitations in the under-bump metallurgy (UBM) layer design, which affects the adhesion and crack propagation between the UBM layer and connection bumps.
Innovation Solution
The semiconductor package incorporates a UBM layer with a UBM pad and via structure, where the UBM pad has a specific diameter and thickness, and the UBM via penetrates the insulating layer, accompanied by an adhesive layer, to enhance adhesion and reliability, and the UBM layer is formed using a copper foil layer with a different crystal structure than the redistribution layer, facilitating improved connectivity and manufacturing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UBM layer uses a conventional design with limited adhesion enhancement, then the manufacturing process is simpler, but the reliability and adhesion between UBM layer and insulating layer deteriorate
Solution Approach 1:
The UBM layer is segmented into multiple functional components: UBM pad, UBM via, and adhesive layer. This segmentation allows each component to be optimized independently for its specific function, improving overall adhesion and reliability without requiring complex integration
Solution Approach 2:
The adhesive layer is applied in advance between the UBM pad and insulating layer before final assembly. This preliminary action ensures optimal adhesion from the outset, preventing future failures without requiring complex post-processing steps
2Reliability
If the UBM via has the same diameter as the UBM pad, then the manufacturing process is simpler, but the adhesion and crack propagation resistance deteriorate
Solution Approach 1:
The UBM via is designed with a smaller diameter than the UBM pad, creating a localized quality difference. This configuration concentrates stress distribution in a specific pattern that enhances crack propagation resistance while maintaining manufacturability through standard patterning processes
3Reliability
If the UBM pad upper surface is higher than the insulating layer lower surface, then the connection bump attachment is easier, but the adhesion between UBM layer and insulating layer deteriorates
Solution Approach 1:
The adhesive layer is applied in advance to bridge the UBM pad and insulating layer, ensuring optimal adhesion before connection bumps are attached. This preliminary bonding action maintains reliability while allowing flexible connection bump placement
Solution Approach 2:
The adhesive layer acts as an intermediary between the UBM pad and insulating layer, providing a bonding interface that maintains strong adhesion while accommodating variations in UBM pad height relative to the insulating layer
Data Source
AI summary
A semiconductor package includes a redistribution portion including an insulating layer, a redistribution layer, and a redistribution via, an under-bump metallurgy (UBM) layer below the redistribution portion and including a UBM pad on a lower surface of the redistribution portion and a UBM via on the UBM pad to penetrate through the insulating layer, a semiconductor chip on an upper surface of the redistribution portion and electrically connected to the redistribution layer, an adhesive layer between the UBM layer and the insulating layer and including a conductive material, and a connection bump below the UBM pad and connected to the UBM layer. The UBM pad has a first diameter, and the UBM via has a second diameter, less than the first diameter, and an upper surface of the UBM pad is located on the same level as, or a level lower than, a lower surface of the insulating layer.