Premolded Clip Block Assembly for Small Power QFN Packaging
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Solution Overview
Problem
In power semiconductor devices, the small size and elongated shape of clips used for electrical coupling pose challenges in stamping and handling, leading to fragile pins and critical dimensions, which complicates the manufacturing process and increases production costs, while alternative materials may degrade electrical performance.
Innovation Solution
The use of premolding technology to form clip blocks with a featured volume, where photoetching processes shape metallic material into sculptured structures with embedded conductive formations, allowing for easier centering and electrical connections between semiconductor dice and leads, and optionally incorporating cut-outs for wire coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If clips are stamped from flat material with pins for centering, then electrical coupling is achieved, but the pins become fragile and reach critical dimensions in small power QFNs
Solution Approach 1:
The invention extracts the centering function from the pin structure and relocates it to the leadframe through recesses. The pin becomes a simple attachment element without the burden of providing centering, thereby eliminating the fragility issue while maintaining clip reliability and electrical coupling functionality.
Solution Approach 2:
The recess in the leadframe acts as an intermediary element that facilitates centering. Instead of relying on the pin to provide both attachment and centering functions, the recess mediates the centering process, allowing the pin to focus solely on attachment and thereby improving its structural integrity.
2Volume of moving object
If clip dimensions are reduced for small power QFNs, then device size is reduced, but manufacturing becomes more difficult and pins become too fragile
Solution Approach 1:
The invention extracts the centering function from the pin and assigns it to the leadframe recess. This allows the pin to be simplified in design and manufacturing, as it no longer needs to incorporate centering features, thereby improving ease of manufacture while maintaining reduced clip dimensions for small power QFNs.
Solution Approach 2:
The recess is pre-formed in the leadframe before clip attachment. This preliminary action of creating the recess ensures that centering is established beforehand, simplifying the subsequent clip attachment process and improving overall manufacturability of the reduced-dimension clips.
3Adaptability or versatility
If multiple channels are integrated in small power QFNs, then device functionality is enhanced, but clip handling and singulation become more difficult
Solution Approach 1:
The invention segments the centering function from the clip structure and assigns it to the leadframe recess. This segmentation allows each clip to be independently handled and attached to its corresponding recess, simplifying the handling and singulation process for multi-channel devices while maintaining enhanced device functionality.
Solution Approach 2:
The recess in the leadframe provides self-aligning and self-centering capabilities during clip attachment. This self-service mechanism eliminates the need for complex handling tools or procedures, thereby improving ease of operation for clip handling and singulation in multi-channel small power QFNs.
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 manufacturing efficiency and reliability of electrical coupling in power semiconductor devices by reducing the complexity of clip handling and stamping, maintaining electrical performance, and potentially lowering production costs.
Implementation Method 1
a clip with determined shape is formed starting from metallic (e.g., copper) material via photoetching technology
Data Source
Figure 1~2
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Figure 7~9
AI summary
A semiconductor die (14) is arranged on a die pad (12A) in leadframe (12) and electrically coupled with one or more electrically conductive leads (12B) in the leadframe (12) arranged peripherally of the leadframe (12) with an electrical coupling member (clip block, 100) applied onto the semiconductor die (14) arranged on the leadframe (12). The electrical coupling member (100) comprises a planar body (24, 102, 104) configured to cover the semiconductor die (14) as well as the electrically conductive lead or leads (12B). The planar body of the electrical coupling member (100) comprises electrically insulating material (24) having embedded therein at least one strip-like, electrically conductive formation (102, 104) having a first end (102) configured to contact (SM) the semiconductor die (14) as well as a second end (104) configured to contact (SM) the electrically conductive lead or leads (12B).