Leadframe Surface Layout for Solvent Wetting Control
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Solution Overview
Problem
Existing techniques are inadequate in preventing the wetting and spreading of solvent components on leadframes, which reduces adhesion between the leadframe and resin in semiconductor devices, leading to potential failures due to thermal expansion and contraction.
Innovation Solution
A leadframe design featuring a flat film along the outer edge of the mounting region and a roughened film inside, where the flat film has a flatter surface than the roughened film, formed by laser processing to prevent solvent component wetting and spreading, thereby maintaining adhesion with the resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of the leadframe is roughened to increase adhesion between the leadframe and resin, then the adhesion between leadframe and resin is improved, but the solvent component in adhesive is likely to wet and spread over the surface, reducing adhesion
Solution Approach 1:
The patent applies different surface properties to different regions: the first region (peripheral area) has a roughened surface for strong resin adhesion, while the second region (mounting area) has a flattened surface to prevent solvent spreading. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The leadframe surface is divided into two distinct regions with different surface characteristics. The segmentation allows the peripheral region to provide strong adhesion through roughness while the mounting region prevents solvent wetting through flattening, thus resolving the contradiction between adhesion strength and solvent resistance.
2Reliability
If the surface of the leadframe is roughened to prevent solvent wetting and spreading, then solvent spreading is reduced, but the adhesion between leadframe and resin may be insufficient
Solution Approach 1:
Different surface qualities are assigned to different functional regions: the peripheral first region maintains roughness for solvent resistance, while the mounting second region is flattened to prevent solvent spreading. This resolves the contradiction by applying appropriate surface properties where needed.
Solution Approach 2:
The surface is segmented into a peripheral region for solvent resistance and a mounting region for preventing solvent spreading. This segmentation allows both requirements to be satisfied simultaneously in their respective zones.
3Reliability
If the entire surface of the leadframe is flattened to prevent solvent spreading, then solvent wetting and spreading is prevented, but the adhesion between leadframe and resin is reduced
Solution Approach 1:
Instead of uniform flattening, the patent applies flattening only to the peripheral first region where solvent resistance is needed, while maintaining roughness in the mounting second region for strong adhesion. This localized approach resolves the contradiction.
Solution Approach 2:
The surface is segmented into a peripheral flattened region for solvent resistance and a mounting roughened region for adhesion. This segmentation prevents the adverse effect of complete flattening while maintaining the benefit of solvent spreading prevention.
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 solution effectively prevents solvent component wetting and spreading, ensuring strong adhesion between the resin and the roughened film, enhancing the reliability of semiconductor devices by minimizing the impact of thermal expansion and contraction.
Implementation Method 1
a surface of the leadframe is roughened to increase the adhesion between the leadframe and the resin
Implementation Method 2
The solvent component may reduce the adhesion between the leadframe and the resin. Therefore, various techniques for preventing the wetting and spreading of the solvent component have been studied
Implementation Method 3
formed by laser processing to prevent solvent component wetting and spreading
Data Source
AI summary
A leadframe includes a die pad having a surface that includes a region for mounting a semiconductor chip, and a flat film and a roughened film on the surface of the die pad. In a plan view, the flat film is along and outside the outer edge of the region and the roughened film is inside and outside the flat film. The roughened film includes a roughened plating film and a plating film on the roughened plating film. The plating film follows the shape of the roughened plating film to have a roughened surface. The flat film has a flatter surface than the roughened film, and includes a first metal film formed of the same material as the roughened plating film and a second metal film on the first metal film. The second metal film is an alloy film including metals of the roughened plating film and the plating film.