Pre-Molded Die Pad Anchoring for Pull and Press Resistance
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Solution Overview
Problem
Conventional pre-molded leadframes face challenges in resisting both pressing and pulling forces during assembly and operation due to limited adhesion between the sculptured conductive structure and the pre-mold resin, with slot-like anchoring structures providing inadequate pulling resistance.
Innovation Solution
A die pad design featuring an alternation of 'fingernail-like' anchoring structures on the top and bottom sides of the die pad, which are formed through standard half-etching before pre-molding, providing balanced resistance to both pulling and pressing forces by enhancing adhesion with the pre-mold resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If anchoring structures are added to improve adhesion, then force resistance is improved, but pad area available for die attachment is reduced
Solution Approach 1:
The anchoring structures extend into the thickness dimension of the leadframe, utilizing the Z-axis (depth) rather than consuming pad area on the X-Y plane. By creating interdigitated fingers that extend vertically and laterally within the leadframe thickness, the design achieves enhanced adhesion without reducing the horizontal pad area available for die attachment.
Solution Approach 2:
The interdigitated anchoring fingers are nested within the leadframe structure itself, with metal fingers extending from opposite surfaces and interlocking with the resin matrix. This nested configuration integrates the anchoring function within the existing leadframe geometry, adding strength without requiring additional space that would reduce pad area.
Data Source
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Figure 3A~4
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AI summary
A method of manufacturing a pre-molded substrate for semiconductor devices comprises providing a sculptured, electrically conductive (e.g., copper) laminar structure (10) having spaces therein. The laminar structure includes one or more die pads (10) having a first die pad surface configured to have semiconductor chips (C1) mounted thereon. A pre-mold material (12) molded onto the laminar structure (10) penetrates into the spaces therein and provides a laminar pre-molded substrate (10, 12) including the first die pad surface left exposed by the pre-mold material (12). An alternation of first (200A) and second (200B) anchoring formations to the pre-mold material (12) is provided along the peripheral edge of the die pad (10). The first anchoring formations (200A) are configured to counter first detachment forces inducing displacement of the die pad (10) with respect to the pre-mold material (12) in a first direction from the second die pad surface (10B) to the first die pad surface (10A). The second anchoring formations (200B) configured to counter second detachment forces (F2) inducing displacement of the die pad (10) with respect to the pre-mold material (12) in a second direction from the first die pad surface (10A) to the second die pad surface (10B).