Leadframe Die Pad Isolation Through Trench Sawing in MCM Packages
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Solution Overview
Problem
Conventional semiconductor devices using pre-molded or pre-taped leadframes are expensive and require additional support for multiple die pads during fabrication, which increases production costs.
Innovation Solution
A method involving mounting semiconductor dies on a leadframe with preformed leads, electrically connecting them, forming a molding structure, and creating a trench between the dies to separate the die pad into isolated portions, thereby reducing the need for pre-molded leadframes and minimizing material removal during fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If pre-molded or pre-taped leadframes are used to provide sufficient die pad support during fabrication, then die pad support is improved, but manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by forming a recess in the die pad before mounting the semiconductor dies. This pre-prepared structure provides mechanical support and isolation during fabrication without requiring expensive pre-molded or pre-taped leadframes. The recess is created in advance to receive the dies, ensuring proper support during subsequent processing steps.
Solution Approach 2:
The patent replaces expensive pre-molded or pre-taped leadframes with a simpler, cheaper die pad structure that has a recess formed directly in it. This disposable-like approach uses a basic leadframe with the recess feature instead of costly pre-prepared leadframes, achieving the same support function at lower cost.
2Reliability
If a trench is formed in the molding structure to separate die pad portions, then die pad isolation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by forming a trench that divides the die pad into separate portions, each supporting an individual semiconductor die. This physical separation isolates the die pads electrically and mechanically, improving reliability. The trench creates distinct segments within the otherwise continuous die pad structure.
Solution Approach 2:
The trench acts as an intermediary element between adjacent die pads. Rather than directly modifying the die pads themselves or using complex isolation structures, the trench serves as a mediating feature that provides isolation while maintaining the simplicity of the overall manufacturing process.
3Productivity
If the die pad thickness is reduced to minimize material removal during sawing, then tool life is improved, but structural support may be compromised
Solution Approach 1:
The patent applies local quality by creating a recess in specific locations of the die pad where semiconductor dies will be mounted. This localized modification provides structural support exactly where needed (under the dies) while keeping the overall die pad thickness reduced for easier sawing. The recess depth and positioning are optimized to provide support only in the critical areas.
Solution Approach 2:
The patent addresses the thickness issue by moving from a uniform thickness approach to a dimensional variation approach. The recess creates a localized depth variation in the die pad, allowing the overall structure to be thinner for easier processing while maintaining adequate support through the recess features that extend downward to provide reinforcement where dies are mounted.
Data Source
AI summary
A method of making a semiconductor device includes mounting at least two semiconductor dies to a die pad of a leadframe in spaced apart relation to each other, the leadframe having a plurality of preformed leads, electrically connecting each semiconductor die to at least one preformed lead of the leadframe, forming a molding structure including at least part of the semiconductor dies and the preformed leads of the leadframe, and forming a trench in the molding structure in a space between the at least two semiconductor dies, the trench separating the die pad into first and second die pad portions.