Ag-Plated Lead Frame Layout for Mold Adhesion Reliability
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Solution Overview
Problem
The existing semiconductor packages with silver (Ag) plated surfaces suffer from poor adhesion to mold compounds, leading to delamination and potential corrosion, which complicates the assembly process and reduces package integrity.
Innovation Solution
A semiconductor package design that expands the Ag plated area beyond conventional design rules to cover more of the lead frame surface within the mold body, combined with an Ag oxide adhesion promotion layer, ensuring improved adhesion and reduced delamination without altering the standard assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ag plated area is minimized to reduce delamination risk, then adhesion reliability is improved, but lead frame flexibility for different die sizes deteriorates
Solution Approach 1:
The lead frame is segmented into fixed Ag-plated interconnection zones and variable non-plated zones. The non-plated areas can be adjusted in size and shape to accommodate different die sizes and package configurations, while the Ag-plated zones maintain consistent dimensions for reliable interconnection. This segmentation preserves both adhesion reliability and design flexibility.
Solution Approach 2:
The lead frame design incorporates dynamic adaptability through the non-plated areas that can be configured differently for various die sizes and package types, while the Ag-plated interconnection areas remain static and standardized. This dynamic configuration capability maintains versatility without compromising adhesion reliability.
2Reliability
If Ag strike plating is added over entire lead frame surface to improve adhesion, then mold compound adhesion is improved, but assembly process complexity deteriorates
Solution Approach 1:
The Ag strike plating is extracted from the entire lead frame surface and applied only to the specific interconnection areas where it is needed for die bonding and wire bonding. This selective application eliminates the need for additional Ag strip processes on lead terminals and prevents mold flash adhesion issues, thereby reducing assembly process complexity while maintaining adhesion reliability.
Solution Approach 2:
Ag strike plating is applied locally only to the interconnection areas rather than the entire lead frame surface. This localized treatment provides the adhesion promotion where needed for bonding operations while leaving the lead terminals and mold contact areas free of Ag plating, avoiding the complexity of additional processing steps.
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 design enhances package integrity and solderability during board mounting by maintaining the Ag plating within the package boundaries, eliminating mold flash issues and maintaining standard assembly complexity.
Implementation Method 1
The layer, which is essentially Ag-oxide, will then provide a better adhesion to the mold compound. This surface oxidation can be achieved by appropriate chemistry in one step of the lead frame manufacture process.
Data Source
AI summary
A semiconductor package including a lead frame, an Ag plated surface positioned on the lead frame, an adhesion promotion layer positioned on the top of the Ag plated surface, and mold body covering the top of the lead frame is provided. The Ag plated surface covers a significant part of an interconnection area of the lead frame surface, and the Ag plating surface does not exceed the area of the mold body.