Lead Frame Dimple Geometry for Resin Adhesion
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Solution Overview
Problem
Existing semiconductor packages with lead frames face inadequate adhesion of sealing resin on the backside of the die pad due to insufficient dimple design, leading to reduced reliability and performance.
Innovation Solution
A lead frame manufacturing method involving the formation of specific dimples on the die pad, including first dimples with inclined and standing side surfaces, and second dimples with reversed inclined side surfaces, which enhance the anchor effect and resin adhesion by altering the surface geometry to improve resin sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large number of dimples are provided on the backside of the die pad by stamping, then adhesion of sealing resin is improved, but adhesion is not always sufficient with conventional dimple shapes
Solution Approach 1:
The patent changes the geometric parameters of the dimples by providing multiple types with different shapes (first dimples with inclined side surfaces, second dimples with substantially vertical side surfaces, and third dimples with curved side surfaces). This variation in dimensional parameters creates different anchoring effects for the sealing resin, improving overall adhesion beyond what single-shaped dimples can achieve.
Solution Approach 2:
The patent applies local quality by distributing different dimple types in specific regions on the backside of the die pad. Each dimple type is strategically placed to optimize resin adhesion in different local areas, creating a non-uniform but functionally optimized surface structure that enhances overall sealing reliability.
2Ease of manufacture
If conventional single-type dimples are used on the die pad backside, then manufacturing is simple, but resin adhesion and anchor effect are insufficient
Solution Approach 1:
The patent segments the dimple structure into multiple types (first, second, and third dimples with different geometries) rather than using a single uniform dimple design. This segmentation allows each dimple type to serve a specific function in resin anchoring, collectively providing superior adhesion while maintaining compatibility with conventional stamping manufacturing processes.
3Ease of manufacture
If the die pad backside remains flat, then manufacturing is simplest, but sealing resin adhesion is inadequate
Solution Approach 1:
The patent introduces curved surfaces by providing third dimples with curved side surfaces in addition to inclined and substantially vertical dimple types. These curved geometries create effective anchor points for the sealing resin, transforming the flat backside into a multi-featured surface that significantly enhances resin adhesion while remaining manufacturable through stamping.
Data Source
AI summary
A method of manufacturing a lead frame, includes forming a rectangular first dimple includes, first inclined side surfaces inclined to a depth direction, and arranged in two opposing sides in one direction, and standing side surfaces standing upright to a depth direction, and arranged in two opposing sides in other direction, on a backside of a die pad by a first stamping, and forming a second dimple having second inclined side surfaces inclined on the backside of the die pad by a second stamping, such that a second inclined side surfaces of the second dimple are arranged in side areas of the standing side surfaces of the first dimple, wherein the standing side surfaces are transformed into reversed inclined side surfaces inclined to a reversed direction to the first inclined side surfaces, and a front side of the die pad is semiconductor element mounting surface.