Probe Card Flatness via Embedded Posts and Interposer
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Solution Overview
Problem
The challenge is to maintain accurate flatness and parallelism of a probe card used in semiconductor wafer testing, especially when the substrate undergoes deformation such as warp and waviness, which affects the contact resistance and testing efficiency.
Innovation Solution
The probe card design includes a reinforcing member, an interposer, a space transformer, and post members that are strategically embedded and fastened to maintain the flatness and parallelism, ensuring stable contact resistance regardless of substrate deformation. This design includes a probe head with probes, a substrate with a wiring pattern, and a leaf spring for uniform pressure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the substrate size is increased to accommodate more probes for testing more dies, then the productivity increases, but the substrate deformation (warp and waviness) increases which deteriorates the flatness and parallelism accuracy
Solution Approach 1:
The probe card is divided into multiple independent probe groups (first probe group and second probe group), each mounted on separate mounting surfaces. This segmentation allows each group to be independently positioned and adjusted, compensating for substrate deformation and maintaining testing precision across large substrates with increased die capacity.
Solution Approach 2:
Reference surfaces are introduced as intermediary elements between the substrate and the probe groups. These reference surfaces provide stable mounting planes that are not affected by substrate deformation, enabling accurate positioning of probes relative to the semiconductor wafer even when the substrate warps or waves.
2Adaptability or versatility
If the stroke of probes is increased to accommodate substrate deformation, then the adaptability to deformation improves, but the contact resistance stability deteriorates
Solution Approach 1:
The probe card is pre-adjusted during setup to establish accurate initial positions of all probe groups relative to the semiconductor wafer. This preliminary positioning compensates for expected substrate deformation, allowing the system to maintain stable contact resistance without requiring excessive probe stroke adjustment during operation.
Solution Approach 2:
The probe card design allows for dynamic adjustment of probe group positions relative to the substrate. Mounting surfaces and reference surfaces enable repositioning of probe groups to compensate for substrate deformation, maintaining optimal contact conditions while preserving contact resistance stability.
3Productivity
If multiple probe groups are mounted on the substrate to test more dies collectively, then the productivity increases, but the difficulty of maintaining parallelism across all probes increases
Solution Approach 1:
Multiple mounting surfaces are provided on the substrate, each with its own reference surface, creating equipotential mounting planes for different probe groups. This ensures that all probe groups can be positioned with consistent accuracy relative to their respective reference surfaces, simplifying the alignment process while maintaining parallelism across all probes.
Solution Approach 2:
Reference surfaces act as intermediary alignment elements between the substrate and multiple probe groups. These reference surfaces provide stable, accurately positioned mounting planes that facilitate precise positioning of each probe group, reducing the overall alignment complexity despite the increased number of probes.
Data Source
AI summary
A probe card includes probes that are made of a conductive material and come into contact with a semiconductor wafer to receive or output an electric signal; a probe head that holds the probes; a substrate that has a wiring pattern corresponding to a circuit structure for generating a signal for a test; a reinforcing member that reinforces the substrate; an interposer that is stacked on the substrate for connection of wires of the substrate; a space transformer that is stacked between the interposer and the probe head and transforms intervals among the wires; and a plurality of first post members that have a height greater than the thickness of the substrate, and are embedded in a portion of the substrate on which the interposer is stacked.