TVS Package Assembly with Perimeter Ridges for Solder Containment
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Solution Overview
Problem
The packaging of large area semiconductor dies for transient-voltage-suppression (TVS) devices faces challenges with solder paste curing, as it can easily run to the chip edge and cause overflow issues during assembly.
Innovation Solution
A package structure is designed with lead frames and clips that include perimeter ridges forming recessed areas to contain solder, ensuring it remains within the assembly and effectively connects the die pad and chip layer, preventing overflow and improving assembly precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder paste is applied to connect the chip layer to the lead frame, then electrical connection is achieved, but the solder paste runs to the chip edge and causes overflow issues
Solution Approach 1:
The lead frame pedestal is segmented into multiple functional zones: a recessed area that receives and contains the solder paste, and a perimeter ridge that acts as a barrier. This segmentation prevents the solder paste from spreading uncontrollably while maintaining reliable electrical connection between the chip layer and lead frame.
Solution Approach 2:
The recessed area and perimeter ridge structure acts as an intermediary between the solder paste and the chip edge, controlling the solder paste flow and preventing direct contact with the chip edge that would cause overflow. This intermediary structure maintains connection reliability while ensuring precise solder placement.
2Power
If larger semiconductor dies are used to meet power requirements, then current handling capability is improved, but solder paste overflow issues become more severe
Solution Approach 1:
The solution introduces a vertical dimension to solder paste containment by creating a recessed area with depth. This vertical containment structure allows larger die areas to be connected without proportionally increasing solder paste overflow risk, as the recessed area provides three-dimensional confinement rather than relying solely on two-dimensional spread control.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Provided herein are package structures including a first lead frame having a first pedestal and a first lead extending from the first pedestal. A first perimeter ridge defines a first recessed area in a first main side of the first pedestal, wherein a die pad is positioned within the first recessed area. The package structure may further include a chip layer having a first main side opposite a second main side, wherein the second main side is in abutment with the first perimeter ridge of the pedestal of the first lead frame. The package structure may further include a clip including a second pedestal and a lead connector extending from the second pedestal, wherein a second perimeter ridge defines a second recessed area in a second main side of the second pedestal, and wherein the second perimeter ridge is in abutment with the first main side of the chip layer.