Lead Frame Inclined-Slit Structure for Semiconductor Bubble Venting
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Solution Overview
Problem
Air bubbles trapped under the lead frame in semiconductor devices can lead to insulation breakdown and decreased reliability due to the insulation distance decreasing and a difference in expansion rates between the air bubbles and the seal material, which is exacerbated by long distances to pass-through slots.
Innovation Solution
Incorporating an inclined portion in the lead frame design with slits at its boundaries to facilitate the extrusion of air bubbles during seal material injection, ensuring the air is less likely to be trapped.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pass-through slot is provided at a lead frame to let out air bubbles, then air bubbles can be released, but air bubbles are less likely to be let out when the distance to the pass-through slot is long
Solution Approach 1:
The lead frame is divided into multiple sections with slits created at specific locations (boundaries between inclined and non-inclined portions). These slits act as localized air bubble escape paths, segmenting the large enclosed space into smaller regions where air bubbles can more easily reach escape openings.
Solution Approach 2:
The solution introduces inclined portions that create a slope in the lead frame structure. This inclination provides a directional path that guides air bubbles toward the slits, effectively using the inclined dimension to shorten the escape distance and improve bubble removal efficiency.
2Reliability
If air bubbles remain under a lead frame when seal material is injected, then insulation breakdown occurs, but providing pass-through slots does not fully prevent bubble trapping
Solution Approach 1:
The slits are pre-formed in the lead frame at strategic locations before the sealing process. The inclined portions are also pre-configured to create favorable flow paths. This preliminary preparation ensures that air bubbles have predetermined escape routes during seal material injection, preventing bubble trapping before it occurs.
Solution Approach 2:
The slits act as intermediary escape channels between the sealed enclosure and the external environment. The inclined portions serve as intermediary structures that facilitate the transition of air bubbles from the enclosed space to the slits, making the bubble removal process more effective.
3Ease of manufacture
If the lead frame connection portion is completely flat, then manufacturing is simple, but air bubbles are trapped under the lead frame
Solution Approach 1:
Instead of making the entire lead frame complex, only specific local regions are modified to include inclined portions and slits. The majority of the lead frame remains flat and simple for easy manufacturing, while the critical connection portions have the necessary inclination and slit features to enable air bubble escape.
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
Prevents insulation failures and maintains reliability by effectively expelling air bubbles, thus enhancing the semiconductor device's performance.
Implementation Method 1
the inclined portion is provided in the lead frame. Thus, air below the inclined portion of the lead frame is likely to be extruded above when the seal material is injected.
Data Source
AI summary
A lead frame connects a metal wiring and an electrode of a case. A seal material is filled in the case. The lead frame includes a first joint portion joined to the metal wiring, a second joint portion joined to the electrode, and a connection portion connecting the first joint portion and the second joint portion. The connection portion includes an inclined portion inclined with respect to the upper surface of the insulating substrate on a cross-section across an extension direction of the lead frame, a first non-inclined portion provided between the inclined portion and the first joint portion, and a second non-inclined portion provided between the inclined portion and the second joint portion. Slits are provided on both sides of the lead frame at a boundary of the first non-inclined portion and the inclined portion and a boundary of the second non-inclined portion and the inclined portion.