Leadframe Structural Integrity via Differential Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing leadframe technology for no lead semiconductor packages faces challenges in forming multi-row terminals, leading to issues with strength and structural integrity during manufacturing, which affects yield and quality, and the use of additional substrates increases costs and delays.
Innovation Solution
A method of fabricating leadframes by partially etching metal sheets to form contact pads, die pads, and connecting bars, with masking patterns applied before etching, allowing for the removal of connecting bars post-encapsulation using chemical etching, laser cutting, or sawing, and singulating individual packages from a molded sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If etched leadframe technology is used to form multi-row terminals, then leadless packages can be manufactured, but the strength and structural integrity of the leadframes deteriorate during handling and wire bonding processes
Solution Approach 1:
The leadframe manufacturing process is segmented into two distinct etching operations: first etching the contact pads and die pad areas, then separately etching the connecting bars. This segmentation allows each component to be optimized independently - contact pads maintain full thickness for strength while connecting bars are thinned for flexibility and cost-effectiveness.
Solution Approach 2:
Different regions of the leadframe are given different properties through selective etching. The contact pads and die pad areas retain their full metal thickness for maximum strength and structural integrity, while the connecting bars are etched to reduced thickness to provide flexibility and reduce material costs without compromising overall leadframe strength.
2Strength
If additional plastic substrate is used to provide strength and structure during manufacture, then structural integrity improves, but manufacturing cost and time delay increase
Solution Approach 1:
The invention extracts and removes the unnecessary additional plastic substrate from the manufacturing process. By optimizing the leadframe itself through differential etching to provide the required structural integrity, the patent eliminates the need for extra substrate layers, thereby reducing manufacturing complexity, cost, and time delays while maintaining adequate strength during the manufacturing process.
3Device complexity
If connecting bars are removed after encapsulation, then package complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The connecting bars are etched in advance during the leadframe fabrication process itself, before encapsulation occurs. This preliminary action prepares the connecting bars for subsequent removal by creating etched patterns that define where material should be removed. The pre-etched patterns guide the final removal process, making it more precise and controllable while reducing the complexity of the overall package 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
This approach enhances the structural integrity of leadframes during manufacturing, improves yield and quality, and eliminates the need for additional substrates, reducing costs and time delays while enabling efficient production of no lead semiconductor packages.
Implementation Method 1
The lead frame is fabricated by partially etching a metal sheet to form the upper portions of the die pad, contact pads, and/or connecting bars
Implementation Method 2
Before the surfaces of the metal sheet are etched, some embodiments apply a masking pattern to the surfaces of the metal sheet. The masking pattern typically covers the areas where the contact pads and/or the die pad of the leadframe are to be formed
Implementation Method 3
the removal of these connecting bars is performed by using various methods, such as, for example, chemical etching
Implementation Method 4
The removal of these connecting bars is performed by using various methods, such as, for example, chemical etching, and/or cutting with a laser or a saw blade
Implementation Method 5
The removal of these connecting bars is performed by using various methods, such as, for example, chemical etching, and/or cutting with a laser or a saw blade
Data Source
AI summary
A leadframe for use in fabricating a no lead semiconductor package contains connecting bars between individual electrical contact pads. For embodiments having a die pad, the leadframe further includes connecting bars between the contact pads and the die pad. The lower surfaces of the connecting bars are coplanar with the lower surfaces of the contact pads and/or the die pad, and the upper surfaces of the connecting bars are recessed with respect to the upper surfaces of the contact pads and/or the die pad. The semiconductor package is fabricated by encapsulating the die and the leadframe in a molding compound and then removing the connecting bars. The leadframe is typically formed by half etching a metal sheet to form the connecting bars. The connecting bars are removed from the encapsulated package by a selected cutting, sawing, or etching means, based on a predetermined pattern.