Planar Leadframe Downset for Mold Flow Control
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Solution Overview
Problem
Existing leadframe technologies face challenges in controlling the flow velocity of mold material during overmolding, leading to potential external voids and quality control issues in the final package, while also requiring significant adhesive for die pad attachment.
Innovation Solution
Incorporating downsets with defined interior volumes and openings on the leadframe substrate to slow down the mold material flow, creating tortuous paths and allowing precise control of the flow velocity, thereby reducing void formation and adhesive usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If mold material flows rapidly during overmolding, then productivity is improved, but external voids form and manufacturing precision deteriorates
Solution Approach 1:
The patent introduces a downset structure that extends below the bottom surface of the die pad, creating a three-dimensional flow control feature. This vertical dimension allows the mold material to be redirected into a cavity below the main plane, where flow velocity can be reduced and controlled, preventing void formation while maintaining overall process efficiency
Solution Approach 2:
The downset acts as an intermediary structure between the incoming mold material flow and the die pad area. It provides a transition zone where the high-velocity flow is converted to a slower, more controlled flow pattern, mediating between the conflicting requirements of fast molding and void-free filling
2Manufacturing precision
If downset structure is added to control flow velocity, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The downset is integrated with the leadframe substrate and die pad structure, merging the flow control function into the existing mechanical support structure. This consolidation avoids adding separate, complex flow control devices while achieving the desired velocity regulation
Solution Approach 2:
The downset modifies the flow characteristics by changing geometric parameters (creating a cavity with specific volume and opening configuration) rather than introducing active control mechanisms. This passive geometric approach controls flow velocity through physical constraints rather than complex systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The downsets effectively control mold material flow velocity, reducing voids and adhesive requirements, enhancing product quality and reducing assembly costs without compromising wire bond reliability.
Implementation Method 1
The downset includes at least one wall defining an interior volume for receiving a flow of the mold material to reduce the velocity of the mold material flow through the downset
Data Source
AI summary
A leadframe for encasing in a mold material includes a plurality of interconnected support members. A die pad is connected to the support members and includes a bottom surface. The die pad is configured to receive a die. A downset is connected to the die pad and positioned below the bottom surface. The downset includes at least one wall defining an interior volume for receiving a flow of the mold material to reduce the velocity of the mold material flow through the downset.