Lead Frame Nanoparticle Oxidation for Mold Compound Adhesion
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Solution Overview
Problem
In semiconductor packaging, the poor adhesion of mold compound to lead frames leads to delamination, causing damage to wire bonds and electrical opens due to inadequate bonding between the mold compound and the lead posts.
Innovation Solution
The surface of the lead posts is treated by depositing conductive nanoparticles, which are then oxidized and coated with a photoactive material. Exposure to radiation or plasma creates hydrophilic groups, enhancing the adhesion of the mold compound by forming chemical bonds with polar groups, thereby improving the bonding between the mold compound and the lead frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lead frame packaging is used with standard plating, then the manufacturing process is simple, but the mold compound delaminates from the lead posts causing wire bond damage
Solution Approach 1:
The lead post surface is pre-treated with nanoparticle deposition and oxidation before mold compound application. This preliminary surface modification creates hydrophilic groups that enhance adhesion, preventing delamination issues that would otherwise require complex post-processing or redesign
Solution Approach 2:
The surface chemistry of the lead post is fundamentally changed by depositing conductive nanoparticles (silver, copper, or nickel) and oxidizing them to create hydrophilic surfaces. This parameter change in surface properties (from hydrophobic to hydrophilic) dramatically improves mold compound adhesion without requiring complex structural modifications
2Reliability
If the lead post surface is treated with nanoparticles and oxidation, then adhesion is improved, but the manufacturing process becomes more complex
Solution Approach 1:
Standard plating processes are replaced with nanoparticle deposition and oxidation treatments that fundamentally change the surface chemistry. This creates hydrophilic groups on the lead post surface, improving mold compound adhesion by forming chemical bonds with polar groups in the mold compound
Solution Approach 2:
Conductive nanoparticles (silver, copper, or nickel) serve as an intermediary layer between the lead post and mold compound. These nanoparticles, when oxidized, create hydrophilic surface groups that act as a chemical bridge, enabling strong adhesion between the metallic lead post and the organic mold compound
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 increased adhesion between the mold compound and the lead frame reduces delamination, ensuring the integrity of wire bonds and preventing electrical opens, with silver nanoparticles demonstrating improved adhesion compared to regular plated silver.
Implementation Method 1
oxidizing the nanoparticles; and forming wire bonds between contacts on a semiconductor die and the nanoparticles on the lead posts
Implementation Method 2
a photoactive material is formed over the nanoparticles which, after attaching the die and forming the wire bonds but prior to forming mold compound, the lead frame with the photoactive material is exposed to illumination to active or create hydrophilic groups
Implementation Method 3
the nanoparticles are exposed to a plasma to provide oxidation
Implementation Method 4
The hydrophilic groups include, for example, amino groups (NH2) and hydroxyl groups (OH). The hydrophilic surface increases adhesion
Data Source
AI summary
A method of manufacturing a packaged semiconductor device includes patterning and plating silver nanoparticles in bonding areas of a lead frame, forming a hydrophilic group while oxidizing the silver nanoparticles, forming wire bonds on the silver nanoparticles, and encapsulating the wire bonds and the silver nanoparticles.