Probe Card Loopback Impedance Layout for High-Frequency Signal Integrity
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Solution Overview
Problem
High-frequency test signals in semiconductor devices experience impedance mismatch and signal integrity issues due to mismatched characteristic impedances in the probe device and system impedance, leading to poor signal quality and integrity, especially at frequencies above 10 GHz.
Innovation Solution
The probe card design includes a wiring substrate, connection carrier board with a loopback path, and probe device, where the loopback path impedance is adjusted to match the system impedance, forming a differential pair to improve signal integrity by reducing impedance mismatch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the loopback path length is reduced to improve signal integrity at high frequencies, then impedance mismatch is reduced, but the spatial distribution of contact points cannot be sufficiently enlarged
Solution Approach 1:
The patent applies local quality by creating different impedance characteristics in different sections of the loopback path. Specifically, the loopback path includes a first section with first impedance and a second section with second impedance, where the impedances are deliberately different to achieve overall impedance matching with the probe device while maintaining compact dimensions. This allows the path to have locally optimized electrical characteristics without requiring uniform geometry.
Solution Approach 2:
The patent changes electrical parameters (impedance values) along the loopback path to resolve the contradiction. By setting the first impedance and second impedance to specific values that satisfy the matching condition with the probe device characteristic impedance, the patent achieves improved signal integrity at high frequencies while maintaining a compact loopback path length that does not compromise the spatial distribution of contact points.
2Reliability
If the characteristic impedance of the probe device is matched to the system impedance, then signal integrity is improved, but the design flexibility of the probe card is reduced
Solution Approach 1:
The patent segments the loopback path into multiple sections with different impedance characteristics. The loopback path is divided into a first section with first impedance and a second section with second impedance, allowing each section to be independently designed and optimized. This segmentation enables impedance matching to be achieved through configuration rather than constraining the entire probe device to a single fixed impedance value, thereby preserving design flexibility.
Solution Approach 2:
The patent introduces dynamic adjustability in the impedance configuration of the loopback path. By using different impedance values in different sections that can be configured based on specific application requirements, the system can adaptively match various probe device impedances without being locked into a fixed design, thus maintaining both signal integrity and design flexibility.
3Speed
If high-frequency test signals are used to increase test speed, then testing capability is improved, but impedance mismatch and signal integrity issues worsen
Solution Approach 1:
The patent applies preliminary anti-action by pre-configuring the loopback path with specific impedance characteristics that counteract the impedance mismatch problems that would otherwise occur at high frequencies. The first and second impedances are designed in advance to satisfy the matching condition with the probe device characteristic impedance, preventing signal integrity degradation before high-frequency testing begins. This proactive impedance matching enables high-speed testing without suffering from the typical high-frequency signal integrity issues.
Data Source
AI summary
A probe card, a method for designing the probe card, a method for producing a tested semiconductor device, a method for testing an unpackaged semiconductor by the probe card, a device under test, and a probe system are provided. The probe card includes a wiring substrate, a connection carrier board, and a probe device. At least two probes electrically connected to a loopback path of the connection carrier board to form a test signal loopback path. The probe device has a probe device impedance on the test signal loopback path. The loopback path has a loopback line impedance on the test signal loopback path. A difference between the probe device impedance on the test signal loopback path and the loopback line impedance on the test signal loopback path is in an impedance range.