Dimpled Plate Interconnections for Semiconductor Package Alignment
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Solution Overview
Problem
Existing semiconductor packages face issues with misaligned interconnections due to floating patterned plates or clips during solder reflow, leading to short circuits and thermal expansion mismatches that cause die cracking, while also requiring complex assembly processes and high electrical resistance.
Innovation Solution
The semiconductor package employs dimpled plate interconnections between leadframe source and gate contact areas, using Ni/Au metalized areas to restrict solder flow and ensure precise placement, with dimples on the plates aligning with metalized areas to prevent floating and enhance mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If patterned plate or clip interconnections are used to connect semiconductor device contacts to leadframe leads, then electrical connection is achieved, but the plates or clips may float during solder reflow causing misalignment and short circuits
Solution Approach 1:
The patent applies preliminary action by forming dimples on the plates or clips before the soldering process. These dimples are pre-positioned to align with the semiconductor device contact areas, ensuring that the plates cannot float or shift during solder reflow. This preliminary structural preparation eliminates misalignment issues without adding complexity to the assembly process.
Solution Approach 2:
The patent uses curvature by forming dimples (concave spherical or cylindrical surfaces) on the plates or clips. These curved surfaces mechanically engage with the solder material during reflow, preventing the plates from floating and ensuring stable alignment. The spherical/cylindrical geometry of the dimples provides natural mechanical locking that maintains interconnection precision.
2Reliability
If larger contact area plates or clips are used to reduce electrical resistance, then electrical resistance decreases, but thermal expansion mismatch stress increases causing die cracking
Solution Approach 1:
The patent applies local quality by creating dimples at specific locations on the plates or clips that correspond to the semiconductor device contact areas. This localized structural modification allows the plates to have larger overall contact area for low resistance while the dimpled regions specifically accommodate thermal expansion differences, preventing stress concentration that would cause die cracking.
Solution Approach 2:
The patent changes the physical parameters of the plates by introducing dimples with specific depth and diameter ratios. These parameter changes allow the plate structure to flex and accommodate thermal expansion mismatch while maintaining large contact area for low electrical resistance. The dimple geometry parameters are optimized to balance electrical performance with mechanical stress relief.
3Strength
If smaller plates or clips are used to reduce thermal expansion stress, then die cracking is prevented, but electrical resistance increases
Solution Approach 1:
The patent applies segmentation by dividing the plate or clip contact area into multiple smaller contact regions separated by dimples. This segmentation allows each local region to accommodate thermal expansion independently while the overall plate maintains sufficient total contact area for low electrical resistance. The segmented structure prevents stress concentration while preserving electrical performance.
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 reduces the incidence of short circuits and die cracking, improves thermal dissipation, and simplifies the assembly process by ensuring precise clip placement and location assurance, while maintaining low electrical resistance and mechanical stability.
Implementation Method 1
U.S. Pat. No. 6,040,626 discloses a semiconductor package which employs a mixed connection between a MOSFET top surface comprising a low resistance plate portion for connecting to a source and a wire bond for connecting to a gate.
Implementation Method 2
a first lead assembly, formed from a semi-rigid sheet of conductive material, has a lead assembly contact attached to one of the contact areas of the semiconductor chip
Implementation Method 3
The leads are alloyed to the electrode bumps in a heating furnace and the solder bumps may spread during heating and create undesirable shapes.
Data Source
AI summary
A semiconductor package is disclosed. The package includes a leadframe having drain, source and gate leads, a semiconductor die coupled to the leadframe, the semiconductor die having a plurality of metalized source areas and a metalized gate area, a patterned source connection having a plurality of dimples formed thereon coupling the source lead to the semiconductor die metalized source areas, a patterned gate connection having a dimple formed thereon coupling the gate lead to the semiconductor die metalized gate area, a semiconductor die drain area coupled to the drain lead, and an encapsulant covering at least a portion of the semiconductor die and drain, source and gate leads.