Surface Mount Package Coupling Recesses Resonant Frequency
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Solution Overview
Problem
Existing surface mount packaging techniques for semiconductor devices, such as gull-wing leaded packages, often fail to achieve the desired minimum natural resonant frequency, particularly in automotive applications like airbag sensors, due to undesired movements of the gull-wing leads.
Innovation Solution
Incorporating additional coupling elements, such as coupling recesses and solder dams, between the package and the circuit board to restrict movements in three-dimensional space, thereby increasing the mechanical resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gull-wing leaded packaging is used, then the package structure is simple and easy to manufacture, but the mechanical resonant frequency is insufficient (below 45 kHz)
Solution Approach 1:
The package structure is segmented into multiple functional components: the encapsulation body, gull-wing leads, and additional coupling elements (solder dams and coupling recesses). This segmentation allows each component to serve specific functions - the coupling elements independently restrict lead movements while the encapsulation provides protection, thereby increasing resonant frequency without compromising manufacturability
Solution Approach 2:
Coupling elements (solder dams and coupling recesses) are introduced as intermediary structures between the gull-wing leads and the circuit board. These intermediaries restrict the undesired swinging movements of the leads by providing additional mechanical support and coupling points, thereby increasing the mechanical resonant frequency to above 45 kHz while maintaining the overall package architecture
2Reliability
If additional coupling elements are added to increase resonant frequency, then the mechanical resonant frequency increases (above 45 kHz), but the manufacturing process becomes more complex
Solution Approach 1:
The coupling elements are merged with the existing encapsulation molding process. The coupling recesses are formed as integral features of the encapsulation body during the same molding operation, and the solder dams are applied as part of the standard soldering process. This merging allows the additional functionality to be achieved without requiring separate manufacturing steps or additional assembly operations
Solution Approach 2:
The coupling recesses are pre-formed in the encapsulation body during the molding process, before the actual assembly and soldering operations. This preliminary action ensures that the structural features for restricting lead movements are already in place, allowing the subsequent soldering process to simply fill these pre-defined recesses with solder material, thereby simplifying the overall manufacturing flow
Data Source
AI summary
A surface mount package of a semiconductor device, has: an encapsulation, housing at least one die including semiconductor material; and electrical contact leads, protruding from the encapsulation to be electrically coupled to contact pads of a circuit board; the encapsulation has a main face designed to face a top surface of the circuit board, which is provided with coupling features designed for mechanical coupling to the circuit board to increase a resonant frequency of the mounted package. The coupling features envisage at least a first coupling recess defined within the encapsulation starting from the main face, designed to be engaged by a corresponding coupling element fixed to the circuit board, thereby restricting movements of the mounted package.