Leadframe Insulating Coating for Semiconductor Device Short Circuit Prevention
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Solution Overview
Problem
Current methods for manufacturing semiconductor devices, such as leadframes, face challenges with undesired lead displacement and electrical short-circuits during package molding and material handling, which existing solutions like lead locking tape (LLT) fail to adequately address, especially in high-voltage and space-constrained environments, and are costly.
Innovation Solution
Applying an electrically-insulating material like copper oxide or OSP to the vertical sides and bottom of leadframe leads to prevent electrical contact between adjacent leads or wires, which can be integrated into existing manufacturing processes through masking and coating steps, ensuring high temperature resistance and compatibility with reflow processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead locking tape (LLT) is used to prevent lead displacement, then lead stability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent removes the lead locking tape component entirely and replaces it with an integrated insulating coating applied directly to the leadframe leads. This extraction of the separate LLT component simplifies the overall structure while maintaining lead stability through the insulating material that prevents lead displacement during molding and handling.
Solution Approach 2:
The patent combines the lead stability function and electrical insulation function into a single integrated solution. The insulating coating serves dual purposes: preventing lead displacement (stability) and providing electrical isolation between adjacent leads, thereby eliminating the need for separate LLT and reducing structural complexity.
2Reliability
If lead locking tape (LLT) is used to prevent lead displacement, then lead stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts the separate LLT component and replaces it with a coating process that can be integrated into existing manufacturing workflows. This eliminates the need to purchase, handle, and apply separate locking tape materials, thereby reducing manufacturing costs while maintaining lead stability.
Solution Approach 2:
The insulating coating is applied directly to the leads in a manner that provides self-contained lead stabilization. The coating material itself performs the stabilizing function that previously required separate LLT components, making the system self-sufficient and reducing overall manufacturing complexity and cost.
3Reliability
If lead locking tape (LLT) is used to prevent lead displacement, then electrical short-circuit prevention is improved, but adaptability to high-voltage and space-constrained environments deteriorates
Solution Approach 1:
The patent merges the electrical insulation function with the lead stabilization function into a single insulating coating. This integrated approach provides electrical short-circuit prevention while maintaining adaptability to high-voltage environments and space-constrained designs, as the coating does not add significant bulk or complexity.
Solution Approach 2:
The insulating coating is applied locally to the leads where needed, providing electrical isolation and stability precisely at the critical interfaces between adjacent leads. This localized application ensures adaptability to space-constrained environments while effectively preventing electrical short-circuits.
4Reliability
If existing coating methods are used on leadframe leads, then electrical insulation is provided, but adhesion to package molding compound deteriorates
Solution Approach 1:
The patent employs a composite coating structure consisting of a copper oxide layer combined with an organic solderability-preserving (OSP) layer. This composite material provides both electrical insulation and strong adhesion to the package molding compound, resolving the contradiction between insulation and bonding strength.
Solution Approach 2:
The patent changes the chemical and physical parameters of the coating material by using copper oxide and OSP materials with specific properties. These parameter changes enable the coating to simultaneously achieve electrical insulation, thermal stability during reflow, and strong adhesion to both the leadframe and molding 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
This solution effectively prevents electrical short-circuits and reduces costs compared to LLT, while being applicable to high-voltage conditions and space-constrained designs, enhancing the reliability and quality of semiconductor devices like Quad Flat Packages.
Implementation Method 1
coating the leadframe (by dipping in a chemical bath, for instance) with electrically-insulating material such as copper oxide or an OSP-like material
Implementation Method 2
electrically-insulating material such as copper oxide
Data Source
AI summary
A leadframe for a semiconductor device includes an array of electrically-conductive leads. The electrically-conductive leads have mutually opposed lateral (vertical) surfaces. An electrically-insulating material is formed over the mutually lateral opposed surfaces to prevent short circuits between adjacent leads. The electrically-insulating material may further be provided at one or more of the opposed bottom and top surfaces of the electrically-conductive leads of the leadframe.