Pre-plated Leadframe Copper Die Pad Adhesion
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Solution Overview
Problem
The existing methods for enhancing adhesion between encapsulation molding compound (EMC) and nickel-palladium-gold pre-plated leadframes are costly and prone to quality issues due to the need for selective plating and masking, which can lead to delamination and solder non-wetting problems.
Innovation Solution
A method involving a base leadframe material plated with multiple layers of nickel, palladium, and gold, followed by selective copper plating on unmasked areas for enhanced adhesion, with an optional oxidation treatment to form copper oxide for improved EMC adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If selective masking and plating are used to enhance adhesion, then adhesion strength is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts the adhesion enhancement function from the complex selective plating process and concentrates it on the die pad area only, where it is most critical for wire bonding. By applying copper plating selectively only to the die pad rather than across the entire leadframe, the patent achieves improved adhesion strength while significantly reducing manufacturing complexity and masking requirements.
Solution Approach 2:
The patent applies different plating treatments to different areas of the leadframe based on local requirements. The die pad receives copper plating for enhanced adhesion, while other areas maintain their original nickel-palladium-gold plating structure. This local quality approach ensures adhesion enhancement is applied only where necessary, reducing overall manufacturing complexity.
2Strength
If repeated masking is used for selective plating, then adhesion is enhanced, but alignment precision deteriorates
Solution Approach 1:
The patent extracts the adhesion enhancement function from the complex selective plating process and concentrates it on the die pad area only, where it is most critical for wire bonding. By applying copper plating selectively only to the die pad rather than across the entire leadframe, the patent achieves improved adhesion strength while significantly reducing manufacturing complexity and masking requirements.
Solution Approach 2:
The patent performs preliminary masking and plating operations during the leadframe manufacturing process itself, before the leadframe is assembled into the final package. By establishing the copper-plated die pad structure early in the manufacturing sequence, the patent eliminates the need for subsequent masking and re-plating operations that would compromise alignment precision.
3Strength
If copper oxide layer is formed to enhance adhesion, then EMC adhesion is improved, but delamination risk increases due to loose oxide
Solution Approach 1:
The patent carefully controls the oxidation parameters of the copper plating process to form a copper oxide layer with optimal properties. By adjusting oxidation time, temperature, and chemical composition, the patent creates a copper oxide layer that provides strong EMC adhesion while maintaining sufficient structural integrity to prevent delamination, thus optimizing both adhesion strength and reliability.
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
This approach provides a cost-effective solution with enhanced adhesion strength between the EMC and the leadframe, reducing delamination and solder non-wetting issues while maintaining consistent quality.
Implementation Method 1
plating the base leadframe material with multiple layers of nickel, palladium, and gold
Implementation Method 2
plating the unmasked areas with a layer of copper
Implementation Method 3
the copper strike is exposed to an oxidizing agent to form a layer of cupric oxide (CuO) that promotes adhesive bonding between the plastic mold and the leadframe
Data Source
AI summary
A process for producing a pre-plated leadframe that has enhanced adhesion by molding compound is provided, wherein a base leadframe material is first plated with multiple layers of metallic material. Thereafter, the plated base leadframe material is covered with a mask, so as to expose selected surfaces thereof at unmasked areas where enhanced adhesion of molding compound is desired. The said unmasked areas are plated with a layer of copper before removing the mask. Optionally, the layer of copper may further be oxidized to form a layer of specially controlled copper oxide.