Lead Frame Trenches for Semiconductor Package Stability
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Solution Overview
Problem
The increasing integration density of wiring in semiconductor packaging processes complicates the packaging of semiconductor chips, and existing methods like wire bonding are inefficient, leading to issues such as tilting and stress on the chip during the reflow process, which can result in reduced reliability due to uneven solder distribution.
Innovation Solution
A lead frame with trenches in the bonding part, where the semiconductor chip is bonded, including a first trench along a central axis and second trenches perpendicular to it, filled with a different material, which prevents molten solder from flowing and tilting, ensuring the chip's stability and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is used to connect semiconductor chip and substrate, then connection is achieved, but integration density of wiring increases and packaging becomes more difficult
Solution Approach 1:
The bonding part is segmented into multiple regions by forming first trenches extending along a first central axis and second trenches extending along a second central axis that vertically intersects the first central axis. This segmentation divides the bonding part into multiple regions, allowing independent control of solder distribution and chip positioning in different areas, thereby resolving the packaging complexity while maintaining connection reliability
Solution Approach 2:
Different regions of the bonding part are given different properties through the trench structure. The first trenches and second trenches create zones with distinct solder flow characteristics and mechanical support properties. This local differentiation allows optimized solder distribution and chip stabilization without affecting the entire bonding part uniformly, addressing both connection reliability and packaging simplicity
2Reliability
If solder bumps are formed on entire surface for flip-chip bonding, then direct connection is achieved, but solder distribution becomes uneven and chip tilting occurs
Solution Approach 1:
The trenches are formed in the bonding part before the reflow process to preemptively counteract the harmful effects of uneven solder distribution and chip tilting. The first trenches and second trenches create physical barriers that prevent solder from flowing into unwanted areas, thereby maintaining even solder distribution and preventing chip tilting before the bonding process completes
Solution Approach 2:
The trenches act as intermediary structures between the solder bumps and the chip. By introducing these intermediate features into the bonding part, the system gains control over solder flow paths and chip positioning without directly modifying the chip or solder bumps themselves, thus maintaining connection reliability while improving position stability
3Reliability
If trenches are formed in bonding part, then chip tilting is prevented and solder distribution is maintained, but manufacturing process becomes more complex
Solution Approach 1:
The formation of first trenches and second trenches is combined into a single integrated manufacturing process. By simultaneously creating both sets of trenches with orthogonal orientations, the patent achieves comprehensive chip stabilization and solder distribution control without requiring separate manufacturing steps for each trench type, thereby improving operating reliability while minimizing the increase in manufacturing complexity
Data Source
AI summary
A lead frame includes a bonding part to bond to a semiconductor chip, a first trench in the bonding part along a first central axis, the first central axis dividing the bonding part into two parts, and second trenches in the bonding part along a second central axis, the second central axis dividing the bonding part into two parts, and the first and second central axes vertically intersecting each other.