Leadframe Die Pad Through-Slot Structure for Delamination Control
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Solution Overview
Problem
Existing semiconductor packages, particularly QFN and QFP-ep packages, face issues with delamination between the molding compound and the die pad, leading to compromised package hermeticity and reliability.
Innovation Solution
The introduction of a through slot on the die pad periphery, formed by overlapping upper and lower half-cut patterns, enhances the adhesion between the die pad and the molding compound, thereby reducing delamination and improving package hermeticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional die pad structure is used without additional anchoring features, then the manufacturing process is simple, but delamination occurs between the molding compound and die pad leading to poor package hermeticity
Solution Approach 1:
The die pad structure is segmented by introducing a through slot that divides the die pad into distinct regions. This segmentation creates separate anchoring zones that independently secure the molding compound, preventing delamination while maintaining overall structural integrity. The slot effectively breaks up the continuous die pad surface into functional segments.
Solution Approach 2:
The through slot introduces a vertical dimension to the adhesion mechanism by creating overlapping half-cut patterns that extend through the die pad thickness. This dimensional change transforms a surface-level adhesion problem into a volumetric anchoring solution, with the molding compound locking into the slot structure from multiple depths.
2Reliability
If surface treatments or under etching are applied to improve adhesion, then bonding strength increases, but delamination can still occur compromising package hermeticity
Solution Approach 1:
The through slot is formed in the die pad before the molding compound is applied. This preliminary structuring of the die pad with pre-defined anchoring features ensures that when the molding compound is subsequently applied, it automatically locks into the slot structure, providing inherent adhesion without requiring additional surface treatments or etching steps.
3Strength
If the die pad is completely surrounded by molding compound, then structural support is maximized, but adhesion failure can still occur at the interface
Solution Approach 1:
The through slot acts as an intermediary structure between the die pad and molding compound. Instead of relying solely on the interface contact, the slot provides a mechanical interlocking mechanism where the molding compound physically engages with the die pad structure, creating a positive anchor that mediates the stress transfer between the two materials.
Data Source
Figure 1~2B
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AI summary
A leadframe (10) for semiconductor devices, the leadframe (10) comprising a die pad portion (14) having a first planar die-mounting surface (14a) and a second planar surface (14b) opposed the first surface (14a), the first surface (14a) and the second surface (14b) having facing peripheral rims jointly defining a peripheral outline of the die pad (14), wherein: the die pad (14) comprises at least one package molding compound receiving cavity (18) opening at the periphery of said first planar surface (14a), the peripheral rims of said first surface (14a) and said second surface (14b) are mutually offset to provide a stepped peripheral outline of the die pad (14) with the periphery of said first planar surface (14a) having a peripheral region protruding with respect to the second planar surface (14b), wherein said at least one package molding compound receiving cavity (18) is provided at said protruding region of the first planar surface (14a), and the at least one package molding compound receiving cavity (18) partially overlaps and goes through said stepped peripheral outline of the die pad (14).