Leadframe Clip Immobilization for Small Power Semiconductor Packages
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Solution Overview
Problem
The manufacturing of power semiconductor devices with small dimensions and multiple channels faces challenges in clip production and handling due to small recess dimensions, leading to uneven pads and increased production costs, and existing solutions either complicate the process or degrade electrical performance.
Innovation Solution
The use of additive manufacturing techniques, such as Laser Induced Forward Transfer (LIFT), to form clips with pins that utilize peripheral features of the leadframe for centering, eliminating the need for additional recesses on the pads and allowing for more efficient clip placement and electrical coupling between semiconductor dies and leads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If recesses are created on leadframe pads to center clips, then clip centering is improved, but pad flatness deteriorates and manufacturing complexity increases
Solution Approach 1:
The patent introduces a tie bar as an intermediary element that provides peripheral features (notches, openings, or protrusions) for clip centering, rather than modifying the pad surface directly. This mediator approach allows clips to be centered accurately while preserving the flatness and integrity of the pad surfaces, resolving the contradiction between ease of operation and manufacturing precision.
Solution Approach 2:
The invention moves the centering function from the two-dimensional pad surface to the peripheral dimension through tie bars. By placing notches, openings, or protrusions on the peripheral tie bars rather than on the pad surfaces, the solution utilizes another spatial dimension to achieve clip centering without compromising pad flatness.
2Adaptability or versatility
If more pads are added for multiple channels in small packages, then functionality is improved, but recess dimensions become smaller and harder to manufacture
Solution Approach 1:
The patent segments the centering function from the pad structures and assigns it to peripheral tie bars. This segmentation allows each pad to remain simple and flat while the complex centering features are concentrated in the peripheral tie bar region, making manufacturing easier even as the number of channels increases.
Solution Approach 2:
The tie bars serve multiple functions: they provide structural support, enable clip centering through peripheral notches/openings/protrusions, and facilitate assembly. This multi-functionality eliminates the need for separate centering features on each pad, simplifying manufacturing while supporting multiple channels.
3Ease of manufacture
If clips are stamped from flat material with pins, then clip formation is simplified, but handling and centering in small packages becomes difficult
Solution Approach 1:
The patent applies local quality by providing specific geometric features (notches, openings, or protrusions) only at the peripheral locations of tie bars where clip engagement is needed. The rest of the pad surfaces remain flat and simple, optimizing both clip formation ease and handling in small packages.
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 manufacturing process, reduces production costs, and maintains electrical performance by using clips with sculptured distal portions that engage leadframe notches for immobilization, facilitating easier handling and assembly in small package devices.
Implementation Method 1
Pins are also created extruding the material by punching with the purpose of centering the clip on the leadframe
Implementation Method 2
additive manufacturing technique, optionally Laser Induced Forward Transfer (LIFT)
Data Source
AI summary
A semiconductor die is arranged at a die mounting location of an electrically conductive substrate. The electrically conductive substrate includes an array of electrically conductive leads having openings at the periphery of the electrically conductive substrate. An electrically conductive clip is arranged in a bridge-like position between the semiconductor die and an electrically conductive lead in the array of electrically conductive leads to provide electrical coupling therebetween. The electrically conductive clip has an end coupled to the electrically conductive lead, wherein the end includes: a planar proximal portion configured to contact the electrically conductive lead proximally of the openings, and a distal portion projecting beyond the proximal portion distally thereof, the distal portion provided with sculpturing configured to engage the openings to facilitate immobilizing the electrically conductive clip in the bridge-like position between the semiconductor chip and electrically conductive lead.