Multi-Plane Lead Frame Etching for Source-Down Semiconductor Packages
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Solution Overview
Problem
The production of semiconductor packages is hindered by the costly and difficult process of using metal clips for interconnection, which require bending to compensate for height differences, and the restrictions in copper etching/stamping processes complicate the integration of multiple dies and flipped chip assemblies.
Innovation Solution
A method involving a two-step etching process is used to create lead and clip frames with multiple planes, allowing for the integration of semiconductor dies with a source-down configuration by forming transition regions and redistribution structures, eliminating the need for complex bending and copper pillar connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal clips are used for interconnection of semiconductor dies, then electrical connection is achieved, but the process becomes costly and complex due to required bending operations
Solution Approach 1:
The patent extracts the bending operation from the clip assembly process by integrating the bending function directly into the lead frame structure through multi-depth etching. The lead frame is etched to different depths to create pre-bent transition regions, eliminating the need for separate bending operations on attached clips and simplifying the overall manufacturing process.
Solution Approach 2:
The patent introduces depth as an additional dimension in the lead frame structure by etching different regions to different depths. This creates three-dimensional transition regions that naturally accommodate height differences between dies and lead frame, replacing the need for mechanical bending of two-dimensional clip structures.
2Productivity
If clip frames with multiple metal clips are used, then production efficiency is improved, but manufacturing precision deteriorates due to large clip height variation
Solution Approach 1:
The patent applies local quality by etching different regions of the lead frame to different depths according to their specific functional requirements. Each region receives the appropriate etching depth locally, creating precisely controlled transition regions that accommodate varying height requirements while maintaining uniformity within each specific region.
3Ease of manufacture
If conventional copper etching/stamping processes are used, then manufacturing simplicity is maintained, but the ability to integrate flipped chip assemblies is restricted
Solution Approach 1:
The patent segments the etching process into multiple steps with different depths, allowing different regions of the lead frame to be structured independently. This segmentation enables the lead frame to accommodate multiple die orientations and configurations, including flipped chip assemblies, while still using conventional copper etching/stamping processes.
4Strength
If thick base metal lead frames are used for chip embedding, then structural strength is improved, but flipped chip assembly becomes difficult due to height restrictions
Solution Approach 1:
The patent uses depth variation within the thick base metal lead frame to create localized transition regions. The overall lead frame maintains its structural strength from the thick base metal, while specific etched regions provide the necessary depth accommodation for flipped chip assemblies, effectively adding a vertical dimension to solve the height restriction problem.
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 method simplifies the production of semiconductor packages by reducing costs and complexity, enabling efficient integration of multiple dies and flipped chip assemblies while maintaining optimal performance.
Implementation Method 1
performing a first etching process during which first regions of a metal sheet are not masked and etched to a first depth from a first surface of the metal sheet; and after the first etching process, performing a second etching process during which second regions of the metal sheet are not masked and etched to a second depth from the first surface of the metal sheet
Data Source
AI summary
A method of producing a clip or lead frame includes: performing a first etching process during which first regions of a metal sheet are not masked and etched to a first depth from a first surface of the metal sheet; and after the first etching process, performing a second etching process during which second regions of the metal sheet are not masked and etched to a second depth from the first surface of the metal sheet, wherein the first regions are not masked during the second etching process such that the first regions are etched to a cumulative depth that corresponds to the first depth plus the second depth, wherein the first regions and the second regions delimit clip or lead frame features. Semiconductor packages that use the clip or lead frame and methods of producing such semiconductor packages are also described.