Lead Finger Z-Direction Obstruction for Fine-Pitch Pullout Resistance
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Solution Overview
Problem
The reduction in lateral spacing between conductive lead ends and die pads in fine pitch electronic device packages increases the risk of lead pull out due to mechanical forces, which can result in damage or disconnection, and existing laterally extending features become less effective as pitch spacing decreases.
Innovation Solution
Incorporating vertical obstruction features, such as indents or raised features, on the conductive leads that extend into the package structure to engage with the molded material and prevent lead movement outward, allowing for finer pitch spacing and larger die pads while maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If laterally extending features (mushroom head structures) are incorporated into lead fingers to mitigate lead pull out, then lead stability is improved, but the size and effectiveness of these features are reduced as lead pitch spacing decreases
Solution Approach 1:
The patent transitions from lateral obstruction features (mushroom head structures extending in the x-direction) to vertical obstruction features extending in the z-direction. This dimensional change allows the obstruction feature to engage the molded package material effectively without requiring large lateral dimensions, thereby maintaining lead stability in fine-pitch applications where lateral space is constrained.
2Productivity
If the lateral spacing between conductive lead ends and die pads is reduced to achieve finer pitch spacing, then device size is reduced, but the risk of lead pull out increases
Solution Approach 1:
By extending the obstruction feature vertically in the z-direction rather than laterally in the x-direction, the patent enables effective lead anchoring even when lateral spacing is minimized. The vertical extension engages the molded material depth-wise, providing sufficient resistance to pull-out forces without requiring increased lateral dimensions.
Solution Approach 2:
The patent changes the geometric parameters of the obstruction feature from lateral dimensions to vertical dimensions. Specifically, the obstruction feature extends a distance in the z-direction that is sufficient to engage the molded package material, while maintaining minimal lateral footprint to accommodate fine-pitch spacing requirements.
3Area of stationary object
If the area available for mold lock features is reduced to accommodate larger die pads, then more die pad area is available, but the effectiveness of mold lock features is reduced
Solution Approach 1:
The patent creates vertical obstructions on the lead fingers that extend into the molded package material in the z-direction. This vertical engagement provides effective mold locking without requiring large lateral areas, thereby preserving die pad area while maintaining reliable mechanical interlocking between the lead frame and package structure.
Data Source
AI summary
An electronic device with a conductive lead having an internal first section and an external second section extending outside a molded package structure, the first section having an obstruction feature extending vertically from a top or bottom side of the conductive lead and engaging a portion of the package structure to oppose movement of the conductive lead outward from the package structure.