Semiconductor Module Lead-Frame Step Structure for Void-Free Sealing
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Solution Overview
Problem
In semiconductor modules, unfilled states (voids) of the sealing material can occur, leading to performance drops, particularly due to the thickness and distribution of the sealing material, which is not adequately addressed by existing techniques.
Innovation Solution
A semiconductor module design featuring a lead frame with a die stage where the sealing material is thinner on the lower side of the die stage than on the semiconductor element and lead, incorporating a bent portion with a step and groove configuration to ensure even sealing, and a manufacturing method that deforms the lead frame to control the sealing material flow and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the sealing material is made thinner on the lower side of the die stage to enable miniaturization, then the module size is reduced, but unfilled states (voids) occur in the sealing material
Solution Approach 1:
A bent portion is formed in advance in the lead frame at the position corresponding to the lower side of the die stage. This preliminary structural preparation creates a step that guides the sealing material flow during the sealing process, ensuring complete filling even when the sealing material thickness is reduced for miniaturization.
Solution Approach 2:
The bent portion creates a step structure that introduces a vertical dimension variation in the lead frame. This step forms a flow path for the sealing material, transforming the sealing process from a simple horizontal filling to a controlled multi-level filling process that prevents voids.
2Manufacturing precision
If the sealing material thickness is reduced on the lower side of the die stage, then the module is miniaturized, but the sealing material may not fill properly
Solution Approach 1:
The bent portion is pre-formed in the lead frame to create a step structure. This preliminary action establishes a controlled flow path that guides the sealing material, making the thin sealing process easier to execute without improper filling.
Solution Approach 2:
The bent portion creates a localized step structure at the critical area (lower side of die stage) where the sealing material needs to be thin. This local structural modification allows precise control of sealing material thickness and flow in the specific region without affecting the entire sealing structure.
3Reliability
If a bent portion with step structure is added to the lead frame, then unfilled states are suppressed, but the lead frame structure becomes more complex
Solution Approach 1:
The bent portion is formed as a preliminary structural feature in the lead frame manufacturing process. This single pre-formed element simultaneously creates the step structure and defines the sealing material flow path, suppressing unfilled states without requiring multiple separate components or complex assembly steps.
Data Source
AI summary
In one aspect of the semiconductor module, the sealing material on the lower side of the die stage is thinner than the sealing material on the upper side of the semiconductor element, a bent portion that forms a step with respect to vertical direction in the first lead is provided in a region sealed by the sealing material in the first lead, the side where the die stage is present of the step is positioned below the side where the die stage is not present of the step due to the step, the side where the die stage is not present of the step in the first lead protrudes from one end side of the sealing material, and a groove is provided on an upper side surface, a lower side surface, or both of them of the bent portion of the first lead.