Semiconductor Package Lead Barb Structure for PCB Alignment
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Solution Overview
Problem
Semiconductor modules face misalignment issues due to component shifting during transport and soldering, leading to increased thermal resistance.
Innovation Solution
The semiconductor package incorporates external leads with barb portions that interlock with the PCB, preventing shifting and warpage, ensuring precise alignment and reducing thermal resistance by maintaining a thinner thermal interface material layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional external leads without barb portions are used, then the manufacturing process is simpler, but component misalignment occurs during transport and soldering
Solution Approach 1:
The external lead features an asymmetric barb portion with a wider section that creates a mechanical interlock with the PCB. This asymmetric geometry prevents the lead from being inserted backward and provides a locking mechanism that resists displacement during transport and soldering, directly improving component alignment precision.
Solution Approach 2:
The barb portion is pre-formed on the external lead before mounting, creating a preliminary mechanical engagement structure. This pre-configured feature ensures that once the lead is inserted through the PCB, the barb automatically locks into place, preventing subsequent misalignment without requiring additional alignment steps during assembly.
2Temperature
If PCB warpage is not countered, then the structure remains simple, but thermal resistance increases due to misalignment
Solution Approach 1:
The barb portion is formed with a curved or bent geometry rather than a straight configuration. This curved shape allows the barb to flex and conform to the PCB surface, creating a mechanical constraint that counters warpage and maintains contact between the semiconductor package and PCB, thereby reducing thermal resistance.
Solution Approach 2:
The barb portion changes the mechanical parameters of the lead-PCB connection by introducing a flexible, interlocking structure. This structural parameter change allows the connection to accommodate and counteract PCB warpage, maintaining optimal thermal contact and reducing thermal resistance despite variations in PCB flatness.
3Reliability
If barb portions are added to external leads, then component alignment and thermal contact are improved, but the manufacturing complexity increases
Solution Approach 1:
The external lead is segmented into distinct functional portions: a shaft portion for insertion, a barb portion for mechanical interlocking, and a bent portion for electrical connection. This segmentation allows each portion to be optimized for its specific function and facilitates manufacturing through processes like stamping or forming, where different sections can be created in sequence.
Solution Approach 2:
The lead structure utilizes parameter changes in geometry (width, curvature, angle) to create the barb portion. These geometric parameters can be controlled during manufacturing processes such as stamping or bending, allowing the complex-looking barb feature to be produced efficiently without significantly increasing manufacturing difficulty.
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
The solution effectively maintains component alignment, reduces thermal resistance, and minimizes material and energy consumption by eliminating misalignment-related issues.
Implementation Method 1
the barb portion being configured to interlock with a surface of the printed circuit board around the through hole
Implementation Method 2
the barb portions pull the printed circuit board against the second side of the molded body such that a warpage of the printed circuit board is countered
Data Source
Figure 1A~2
Figure 3~4
Figure 5~6
AI summary
A semiconductor package comprises: a semiconductor die, a molded body encapsulating the semiconductor die, and a plurality of external leads exposed from the molded body, the external leads being leadframe parts, wherein at least a first one and a second one of the plurality of external leads comprise a barb portion, the barb portion having a greater width than an innermost portion and a through hole portion of the respective external lead, the innermost portion extending from the molded body to the through hole portion, the through hole portion extending between the innermost portion and the barb portion, the through hole portion being configured to extend through a through hole of a printed circuit board, and the barb portion being configured to interlock with a surface of the printed circuit board around the through hole.