Half-Etched Leadframe Package for Side-Solderable Contacts
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Solution Overview
Problem
The existing manufacturing process for leadless semiconductor packages requires step cutting and plating, which increases manufacturing work and cost, as it necessitates sawing through leads to expose side surfaces for electroplating, complicating the packaging process.
Innovation Solution
A leadframe design that employs half-etching to create side solderable surfaces without the need for step cutting, allowing for electroplating during the manufacturing process before encapsulation, ensuring side surfaces remain exposed and solderable without additional processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If step cutting is used to expose side surfaces for electroplating, then solder wettablity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The leadframe is pre-plated with a wettable material layer before encapsulation, so that the side surfaces of the contact already have solder wettablity before the packaging process begins. This eliminates the need for subsequent step cutting and plating operations, resolving the contradiction by performing the plating action in advance rather than requiring complex post-encapsulation processing.
Solution Approach 2:
The leadframe structure is designed with specific geometric features (such as angled contact surfaces or positioned contact regions) that naturally expose the plated side surfaces after encapsulation without requiring additional cutting steps. This local structural modification allows the plated surfaces to be accessible for soldering while maintaining package integrity, thus improving solder wettablity without increasing overall device complexity.
2Reliability
If step cutting and plating are performed, then side solderable surfaces are created, but manufacturing time and cost increase
Solution Approach 1:
The wettable material plating is performed on the leadframe contacts before the encapsulation process, so that when the package is completed, the side surfaces already possess solder wettablity. This preliminary plating action eliminates the need for subsequent step cutting and re-plating operations, thereby reducing total manufacturing time and improving productivity while maintaining reliable side solderable surfaces.
Solution Approach 2:
The leadframe fabrication process is merged with the plating process by integrating the plating step into the leadframe manufacturing sequence before encapsulation. This consolidation of operations (leadframe formation + plating + encapsulation) into a streamlined sequence eliminates separate step cutting and plating operations, reducing manufacturing complexity and improving overall production efficiency.
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 simplifies the packaging process by eliminating the need for sawing and reduces costs, while ensuring reliable solder fillet formation and visual inspection capabilities through exposed, plated side surfaces, enhancing the reliability and efficiency of semiconductor device assembly.
Implementation Method 1
Electroplating is the more desirable plating method because a thicker and faster metal deposition occurs. The thicker metal layer provided by electroplating provides a more reliable solder fillet
Data Source
AI summary
A leadframe is formed by chemically half-etching a sheet of conductive material. The half-etching exposes a first side surface of a first contact of the leadframe. A solder wettable layer is plated over the first side surface of the first contact. An encapsulant is deposited over the leadframe after plating the solder wettable layer.