Lead Frame Particle Roughening for Semiconductor Adhesion
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Solution Overview
Problem
Packaged semiconductor devices often experience reliability failures due to poor adhesion between the molding compound and the lead frame, leading to delamination issues.
Innovation Solution
The surface of the lead frame is roughened using particle-containing polymeric materials, such as polyimide or epoxy resin, applied via ink jet or screen printing, and a reflow wall is formed to surround the solder joint, enhancing adhesion and reducing stress from thermal expansion mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lead frame surface is left smooth, then the manufacturing process is simple, but the adhesion between molding compound and lead frame is poor
Solution Approach 1:
The lead frame surface is pre-treated with particle-containing polymeric material before molding compound application. This preliminary surface modification creates a roughened topology that enhances mechanical interlocking, resolving the adhesion problem without requiring complex post-processing or specialized equipment during the molding stage.
Solution Approach 2:
The surface morphology of the lead frame is changed from smooth to roughened by applying particle-containing polymeric material. This parameter change in surface topology increases the surface area and creates mechanical interlocking features, significantly improving adhesion between the molding compound and lead frame while maintaining a relatively simple manufacturing process.
2Reliability
If the solder joint height is increased, then the stress from thermal expansion mismatch is reduced, but the device occupies more vertical space
Solution Approach 1:
A reflow wall is pre-formed on the lead frame before solder joint creation. This preliminary structure provides mechanical support and stress distribution during thermal cycling, allowing the solder joint to achieve greater effective height for stress resistance without proportionally increasing the overall device vertical envelope.
Solution Approach 2:
The reflow wall extends the solder joint support structure in a lateral dimension rather than purely vertical. By creating a stepped or extended configuration, the effective solder path length increases for stress resistance while the overall device height increase is minimized through horizontal expansion of the support structure.
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 improved adhesion significantly reduces delamination failures and increases the reliability of solder joints by creating a stronger bond between the molding compound and the lead frame, while also reducing stress on the solder joint through increased height and reinforcement.
Implementation Method 1
The particle roughened surface may aid in adhesion between the molding compound and the lead frame
Implementation Method 2
a reflow wall is formed to surround the solder joint, enhancing adhesion and reducing stress from thermal expansion mismatches
Data Source
AI summary
A packaged semiconductor device with a particle roughened surface on a portion of the lead frame that improves adhesion between the molding compound and the lead frame. A packaged semiconductor device with a particle roughened surface on a portion of the lead frame that improves adhesion between the molding compound and the lead frame and with a reflow wall that surrounds a portion of the solder joint that couples the semiconductor device to the lead frame. A packaged semiconductor device with a reflow wall that surrounds a portion of a solder joint that couples a semiconductor device to a lead frame.