Lead Frame Scale Structure for Void-Free Resin Sealing
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Solution Overview
Problem
Conventional resin sealing methods for semiconductor devices often result in voids due to air entrapment, which reduce the device's insulation, moisture-proof, and heat dissipation properties, and require costly and time-consuming mold modifications to address unexpected voids.
Innovation Solution
A semiconductor device with a scale-like portion on the lead frame across the resin boundary, allowing air to be discharged during the resin sealing process, eliminating the need for air vents in the mold and enabling high-function, high-reliability devices at lower costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air vents are provided in the mold to discharge voids during resin sealing, then void occurrence is reduced, but mold complexity and manufacturing cost increase
Solution Approach 1:
The air vent function is extracted from the mold and transferred to the lead frame itself. The scale-like projections on the lead frame surface serve as air vents, eliminating the need for corresponding vent structures in the mold while maintaining void discharge capability.
Solution Approach 2:
The lead frame is designed to provide its own air venting function through the scale-like projections on its surface. This self-service approach allows the lead frame to discharge voids during resin sealing without requiring external assistance from the mold structure.
2Reliability
If air vents are provided in the mold to discharge voids during resin sealing, then void occurrence is reduced, but manufacturing time and cost increase due to mold working
Solution Approach 1:
The scale-like projections are pre-formed on the lead frame surface before resin sealing. These projections are created during lead frame manufacturing processes such as stamping or rolling, so no additional time is required during mold preparation or resin sealing operations.
Solution Approach 2:
The lead frame provides its own air venting function through pre-formed scale-like projections, eliminating the need for time-consuming mold modifications or adjustments during the resin sealing process.
3Ease of manufacture
If conventional resin sealing is performed without scale-like portions, then manufacturing process is simple, but voids occur due to air entrapment reducing device performance
Solution Approach 1:
The scale-like projections are applied locally to the lead frame surface, specifically in regions where void formation is most likely during resin sealing. This localized approach maintains overall manufacturing simplicity while providing targeted void inhibition where needed most.
Solution Approach 2:
The surface morphology of the lead frame is changed by creating scale-like projections, transforming the flat surface into a textured surface with specific geometric features that facilitate air entrapment and void discharge during resin sealing.
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 scale-like portion effectively inhibits voids during resin sealing, maintaining high device performance and reliability while reducing manufacturing costs by avoiding mold modifications.
Implementation Method 1
the scale-like portion is provided over both sides across a resin boundary portion which is a boundary between inside and outside of an area sealed by the resin on the lead frame
Data Source
AI summary
In a semiconductor device, on a heat dissipation portion of a lead frame opposite to a mounting portion on which a semiconductor element is mounted, a thin molding portion having a thickness of about 0.02 mm to 0.3 mm is formed by a second molding resin which is a high-heat-dissipation resin. A scale-like portion on which scale-shaped projections are consecutively formed is provided over both sides across a resin boundary portion of the heat dissipation portion. The scale-like portion reaches abutting surfaces of an upper die and a lower die of a mold used in a molding process. Thus, the same void inhibition effect as with an air vent is obtained.