Lead Frame Connecting Bar Layout for Reliable Contact Plating
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Solution Overview
Problem
Conventional lead frame cutting processes result in isolated metal contacts that cannot be adequately covered with soldering material, leading to poor soldering reliability, electrical conductivity, and thermal conductivity, necessitating costly and inefficient X-ray inspections.
Innovation Solution
A lead frame design incorporating short connecting bars that electrically connect metal contacts to horizontal long connecting bars, ensuring continuous electrical conduction post-cutting, allowing direct visual inspection and application of solderable metal layers without X-ray, thereby enhancing soldering quality and conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lead frame is cut into multiple lead frame units, then the productivity and versatility are improved, but the metal contacts become isolated islands that cannot be covered with soldering material in the rack plating process
Solution Approach 1:
The lead frame is divided into multiple lead frame units through cutting, each unit containing chip package structures with metal contacts. The segmentation is designed so that metal contacts within each unit remain electrically connected to connecting bars, ensuring they can be properly plated while maintaining production efficiency.
Solution Approach 2:
Connecting bars serve as intermediary elements that electrically connect metal contacts to the rack plating system. These connecting bars act as mediators that bridge the gap between the isolated metal contacts and the plating process, enabling soldering material to reach all necessary surfaces including lateral surfaces of metal contacts.
2Ease of manufacture
If conventional cutting process is used, then the manufacturing cost is reduced, but the soldering quality deteriorates requiring expensive X-ray inspection
Solution Approach 1:
Connecting bars serve as visible intermediary elements that enable direct visual inspection of soldering quality. By providing accessible connection points, they allow inspectors to verify soldering without needing expensive X-ray equipment, thus maintaining low manufacturing costs while improving inspection capability.
Solution Approach 2:
The connecting bars and metal contacts are designed to be visually inspectable, potentially using color-coded or visually distinct features that allow direct observation of soldering quality. This eliminates the need for expensive radiographic inspection while maintaining quality control.
3Device complexity
If metal contacts are isolated after cutting, then the device complexity is reduced, but the electrical conductivity and thermal conductivity deteriorate
Solution Approach 1:
The lead frame is segmented into multiple units, but electrical connectivity is maintained through carefully designed connecting bars that bridge metal contacts within each unit. This segmentation reduces structural complexity while preserving essential electrical and thermal conduction paths.
Solution Approach 2:
Connecting bars serve multiple functions: they provide electrical connection, thermal conduction, and mechanical support. This multi-functionality allows the structure to maintain conductivity without adding excessive complexity, as the same element performs multiple roles.
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
The solution ensures reliable soldering, improved electrical and thermal conductivity, and reduces inspection costs by enabling direct visual inspection of soldering quality, thus maintaining electrical conduction and enhancing mechanical stress resistance.
Implementation Method 1
The at least one short connecting bar electrically connects the plurality of metal contacts of one of the plurality of chip package structures to at least one of the plurality of horizontal long connecting bars adjacent thereto
Implementation Method 2
ensuring the solderable metal layer and the solder material to be applied to the metal contacts in the electroplating process
Implementation Method 3
the solderable metal layer and the solder material to be applied to the metal contacts
Data Source
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AI summary
A lead frame (10) including a plurality of chip package structures (2) and a plurality of horizontal long connecting bars (201, 207). The plurality of chip package structures each include a chip solderable area (206), a plurality of metal contacts (203, 204, 205) and at least one short connecting bar (202a, 202b). The plurality of metal contacts is electrically connected to the chip solderable area. The at least one short connecting bar is electrically connected to the plurality of metal contacts. The at least one short connecting bar electrically connects the plurality of metal contacts of one of the plurality of chip package structures to at least one of the plurality of horizontal long connecting bars adjacent thereto.