Leadframe Pad Groove Structure for Die Attach Adhesive Control
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Solution Overview
Problem
Roughened surfaces in semiconductor packages lead to increased flow of die attach adhesive, causing reduced fillet height and resin bleed, which can result in delamination issues due to poor adhesion between the mold compound and the leadframe.
Innovation Solution
Incorporating a groove with a surface roughness less than the surrounding roughened surface on the leadframe pad to restrict adhesive flow and resin bleed, thereby enhancing adhesion and fillet height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leadframe surface is roughened to improve adhesion between the leadframe and mold compound, then adhesion is improved, but die attach adhesive flows more readily across the surface causing reduced fillet height
Solution Approach 1:
The patent applies different surface characteristics to different regions of the leadframe: the first region (die attach area) has a smooth surface to control adhesive flow and maintain fillet height, while the second region (mold compound contact area) has a roughened surface to improve adhesion between the leadframe and mold compound. This local differentiation resolves the contradiction by allowing each region to have the surface property needed for its specific function.
2Reliability
If the leadframe surface is roughened to improve adhesion, then adhesion is improved, but resin bleed from die attach adhesive increases causing delamination
Solution Approach 1:
The patent creates a smooth first region on the leadframe surface where die attach adhesive is applied, which restricts resin bleed and prevents delamination. The roughened second region is separated from the adhesive application area, allowing improved adhesion to the mold compound without causing harmful resin bleed. This spatial separation resolves the contradiction between improving adhesion and preventing harmful resin bleed.
3Reliability
If chemical etching is used to roughen the leadframe surface, then adhesion is improved, but the process becomes material-intensive and expensive
Solution Approach 1:
The patent uses selective masking to apply roughening treatment only to the second region of the leadframe that contacts the mold compound, while leaving the first region (die attach area) smooth. This selective approach reduces material consumption and processing costs compared to treating the entire surface, while still achieving the necessary adhesion improvement in the critical mold compound contact area.
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 groove effectively controls adhesive flow and resin bleed, improving the robustness and reliability of semiconductor packages by maintaining a stable adhesive thickness and enhancing adhesion between the mold compound and the leadframe.
Implementation Method 1
the groove having a surface roughness less than a surface roughness of the roughened surface of the metallic pad
Data Source
AI summary
A semiconductor package includes a metallic pad and leads spaced from the metallic pad by a gap, the metallic pad including a roughened surface. The semiconductor package further includes a semiconductor die including bond pads, and an adhesive between the roughened surface of the metallic pad and the semiconductor die, therein bonding the semiconductor die to the metallic pad, wherein the adhesive includes a resin. The metallic pad further includes a groove surrounding the semiconductor die on the roughened surface, the groove having a surface roughness less than a surface roughness of the roughened surface of the metallic pad.