Recessed Lead Leadframe Packages for High Voltage Isolation
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Solution Overview
Problem
Conventional chip-on-lead packages with high voltage leads experience premature failure due to failure of die bonding material under high voltage conditions, as small air bubbles and metal pieces create conduction paths leading to isolation breakdown.
Innovation Solution
Incorporating a thinned lead with a portion adjacent to the semiconductor chip that is not mechanically coupled through die bonding material, using mold compound for isolation, which has better high voltage properties and reduces proximity to the chip, allowing the lead to carry high voltage signals without bond-related heating issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If die bonding material is used to mechanically couple leads to the semiconductor chip, then mechanical support is achieved, but high voltage isolation reliability deteriorates due to conduction paths through air bubbles and metal pieces
Solution Approach 1:
The lead structure is segmented into two distinct portions: a thinned portion that does not contact the chip and a thicker portion that provides mechanical support. This segmentation allows the lead to fulfill both mechanical support and high voltage isolation functions simultaneously, with the thinned portion maintaining isolation reliability while the thicker portion provides structural strength.
Solution Approach 2:
Different portions of the lead have different cross-sectional dimensions optimized for their specific functions. The thinned portion has reduced dimensions to minimize conduction paths and improve isolation, while the thicker portion has increased dimensions to provide adequate mechanical support. This local quality variation resolves the contradiction between mechanical strength and electrical isolation.
2Ease of operation
If leads are positioned close to the semiconductor chip, then electrical connection is achieved, but high voltage isolation deteriorates due to proximity effects and conduction paths
Solution Approach 1:
The solution moves the critical isolation dimension from the horizontal plane to the vertical dimension by creating a thinned portion that extends closer to the chip in the horizontal direction but maintains adequate vertical spacing. This dimensional transition allows electrical connection while preserving high voltage isolation through the reduced material volume that minimizes conduction paths.
3Reliability
If thinned lead portion is used for high voltage connection, then high voltage isolation is improved, but mechanical strength deteriorates
Solution Approach 1:
The lead is divided into functional segments where the thinned portion handles electrical connection and isolation while the thicker portion provides mechanical support. This segmentation allows each portion to be optimized for its specific function without compromising the other, resolving the strength-isolation contradiction.
Solution Approach 2:
The lead structure serves multiple functions through its varied cross-section: the thinned portion provides electrical connection and high voltage isolation, while the thicker portion provides mechanical support. This multi-functionality allows a single component to satisfy both isolation reliability and mechanical strength requirements.
Data Source
AI summary
Leadframes for semiconductor packages. Implementations may include a plurality of leads extending inwardly into an opening surrounded by the plurality of leads where the plurality of leads except for at least one are configured to mechanically couple at a surface of a semiconductor chip. The at least one of the plurality of leads that is not configured to mechanically coupled at the surface of the semiconductor chip be configured to electrically couple with the semiconductor chip.