Semiconductor Package Wettable Slot Structures for Solder Joint Inspection
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Solution Overview
Problem
Current semiconductor packages with solder joints are not consistently formed and are often undetectable by visual inspection systems, making them unsuitable for high reliability applications like automotive systems where proper electrical connections need to be verified.
Innovation Solution
A semiconductor package with a substrate featuring multiple slot structures that provide large wettable surfaces, encouraging the formation of solder joints with solder fillets that extend outward, facilitating easy detection by inspection systems and enhancing the reliability of the electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional leads are used for mounting semiconductor packages, then the device can be soldered to PCB, but the solder joints are not consistently formed and are undetectable by visual inspection systems
Solution Approach 1:
The substrate surface is segmented into multiple discrete slot structures distributed across the mounting surface. Each slot structure acts as an independent solder joint formation zone, ensuring that solder is consistently formed in multiple locations rather than relying on a single lead structure. This segmentation provides both consistent solder joint formation and multiple detectable points for visual inspection.
Solution Approach 2:
The slot structures extend vertically from the substrate surface, creating a three-dimensional feature that protrudes outward. This dimensional change allows solder to form fillets that extend beyond the substrate plane, making the solder joints visible to automated optical inspection systems while maintaining reliable electrical connection.
2Difficulty of detecting and measuring
If traditional leads are used for mounting, then the structure is simple, but the solder joints do not extend outward enough to form detectable fillets
Solution Approach 1:
Instead of adding complex three-dimensional lead structures, the solution segments the substrate surface into multiple simple slot features. Each slot is a basic geometric structure that can be easily manufactured, yet collectively they provide the necessary solder joint formation and detectability without significantly increasing overall device complexity.
Solution Approach 2:
The slot structures utilize vertical dimensionality by extending slightly above the substrate surface, creating protruding features that facilitate solder fillet formation. This approach achieves detectable solder joints through simple vertical extrusions rather than complex multi-dimensional lead geometries.
3Difficulty of detecting and measuring
If slot structures with large wettable surfaces are used, then solder fillets extend outward improving detectability, but the manufacturing process becomes more complex
Solution Approach 1:
The substrate fabrication process is segmented into standard steps: forming recesses or grooves in the substrate surface, applying conductive material to line the slots, and completing the mounting surface. This segmentation into discrete, manageable steps makes the manufacturing process systematic and controllable, reducing overall complexity despite the enhanced functionality.
Solution Approach 2:
The slot structures are pre-formed during substrate fabrication before the semiconductor die is mounted. This preliminary action ensures that the solder joint formation features are already in place when the package is assembled, eliminating the need for additional post-assembly steps and simplifying the overall manufacturing workflow.
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 slot structures ensure consistent formation of solder fillets, improving the strength and detectability of solder joints, making the semiconductor package suitable for high reliability applications by allowing easy verification of proper electrical connections.
Implementation Method 1
The slot structures, compared to traditional leads, provide multiple, large wettable surfaces that encourage the formation of solder joints
Data Source
AI summary
The present disclosure is directed to a semiconductor package including a substrate having a lower surface with a plurality of slot structures. The plurality of slot structures are multi-layer structures that encourage the formation of solder joints. The semiconductor package is desirable for high reliability applications in which each solder joint termination should be checked by visual systems to ensure a proper electrical connection has been made.