Modular WLCSP Daisy Chain for Multi-Size Testing
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Solution Overview
Problem
Current wafer level chip scale package (WLCSP) daisy chain designs require new tooling for each die/package size change, leading to increased costs and time consumption, and fail to test wafer fab structures under the solder ball area, limiting board level reliability testing efficiency.
Innovation Solution
A modular die daisy chain design that allows singulation of dies into various sizes and shapes from a single mask design, with pairs of solder balls electrically connected by metal pads, enabling testing without additional tooling and allowing assessment of wafer fab structures under the solder ball area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If current WLCSP daisy chain designs are used, then board level reliability testing can be performed, but new tooling is required for each die/package size change which increases cost and time consumption
Solution Approach 1:
The patent implements a universal daisy chain test vehicle design that can accommodate multiple die/package sizes through a standardized substrate with configurable interconnection patterns. The test vehicle includes a substrate with multiple connection regions that can be electrically interconnected in series to form daisy chains, allowing the same hardware platform to test different WLCSP package sizes without requiring new tooling for each size variation.
Solution Approach 2:
The test vehicle is segmented into modular components including a substrate with multiple connection regions, interconnection structures, and configurable electrical pathways. This segmentation allows flexible configuration of the test vehicle to match different die/package sizes by selectively activating or deactivating specific interconnection regions, eliminating the need for complete tooling redesigns.
2Reliability
If current WLCSP daisy chain designs are used, then reliability testing can be performed, but complete new WLCSP tooling sets are required for each new die/package size which is costly and time consuming
Solution Approach 1:
The patent creates a single universal test vehicle platform that maintains full board level reliability testing capability across multiple die/package sizes. The substrate includes multiple connection regions with interconnection structures that can be configured to test different package dimensions, eliminating the need to manufacture separate tooling sets for each size and significantly reducing manufacturing costs.
Solution Approach 2:
The test vehicle incorporates dynamically reconfigurable electrical interconnections that can be programmed or configured to match different die/package size requirements. This dynamic adaptability allows the same physical hardware to be reused across multiple product variants, reducing the need for expensive custom tooling manufacturing while maintaining full testing capability.
3Reliability
If current WLCSP daisy chain designs are used, then testing can be performed, but wafer fab structures under the solder ball area cannot be tested
Solution Approach 1:
The patent extends the test vehicle design to include access to wafer fab structures in the solder ball area by incorporating additional connection regions and interconnection pathways that reach beneath the solder ball locations. This dimensional extension of the test vehicle allows electrical access to previously unreachable structures, enabling comprehensive testing of the complete interconnection architecture including under-ball regions.
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
Enables efficient board level reliability testing across multiple die/package sizes with reduced tooling costs and time, allowing for flexible testing of different shapes and sizes without additional equipment investment, while ensuring connectivity and resistance continuity in the daisy chain.
Implementation Method 1
The pairs of solder balls are electrically connected in a daisy chain on the test PCB
Implementation Method 2
an electrical change in resistance in the connection signifies a failure
Data Source
AI summary
A method to fabricate a modular die daisy chain design for wafer level chip scale package (WLCSP) board level reliability testing is described. A wafer is provided having pairs of solder balls electrically connected to each other by underlying metal pads. The wafer is singulated into dies of any of a plurality of sizes as required for testing. Thereafter one of the singulated dies is mounted to a test printed circuit board (PCB). The pairs of solder balls are electrically connected in a daisy chain on the test PCB.