Variable-Thickness Flexible Membrane Probe Card for RF Power Testing
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Solution Overview
Problem
Existing probe cards face challenges in carrying high-frequency and high-power RF signals due to conductive tracks melting and probe stiffness issues, leading to device damage and malfunction.
Innovation Solution
A flexible membrane with varying thickness areas, featuring thicker conductive tracks and thinner contact probe areas, allowing for controlled impedance and reduced stiffness, enabling effective signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of contact probes is reduced to carry high-frequency signals, then self-inductance is limited, but the stiffness of probes increases dramatically
Solution Approach 1:
The probe card is divided into distinct functional zones: a central portion with thin flexible membrane for low stiffness and high-frequency signal transmission, and peripheral portions with thicker membrane for mechanical support and damping. This segmentation allows different regions to optimize for different functions simultaneously.
Solution Approach 2:
The flexible membrane has non-uniform thickness distribution where the central area is thinner to reduce stiffness for probe flexibility, while peripheral areas are thicker to provide mechanical strength and damping. This local variation in material properties resolves the contradiction between probe flexibility and structural strength.
2Reliability
If the length of contact probes is reduced, then self-inductance is limited, but the force exerted on contact pads increases causing breaking
Solution Approach 1:
Damping structures are pre-positioned in the peripheral portions of the flexible membrane to cushion and absorb excessive contact forces before they can be transmitted to the contact pads. This prevents pad breaking while maintaining the reduced probe length needed for high-frequency operation.
3Power
If conductive tracks are made thicker to carry high-power RF signals, then signal transmission capability is improved, but the risk of track fusion increases
Solution Approach 1:
The flexible membrane has localized thicker regions in peripheral areas that provide mechanical support and heat dissipation pathways for high-power RF signal transmission, while the central area remains thinner to maintain flexibility. This local thickening allows high-power signal transmission without causing overall stiffening that would lead to track fusion.
4Ease of operation
If the flexible membrane is made thinner to reduce stiffness, then probe flexibility is improved, but mechanical strength decreases
Solution Approach 1:
The flexible membrane is segmented into central and peripheral portions with different thicknesses. The central portion is thin to maximize probe flexibility and accommodate micro contact probes, while the peripheral portion is thicker to provide mechanical strength and support for damping structures.
Solution Approach 2:
The flexible membrane is constructed as a composite structure with varying material properties across different regions. The central area uses thinner material for flexibility, while peripheral areas use thicker material for strength, creating a composite structure that simultaneously satisfies both flexibility and strength requirements.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A flexible membrane (30) adapted to carry high-frequency power signals is described, the membrane comprising a plurality of contact pads (31A, 31B) adapted to electrically connect with a plurality of micro contact probes (25) and made in a central portion (30A) of the flexible 5 membrane (30) and a plurality of contact structures (31C) adapted to electrically connect with a support plate (24) and made in a peripheral portion (30C) of the flexible membrane (30), as well as a plurality of conductive tracks (33A, 33B) made in the flexible membrane (30), each of these conductive tracks (33A, 33B) electrically connecting one of the 10 contact pads (31A, 31B) with one of the contact structures (31C), this flexible membrane (30) further comprising an intermediate portion (30B) arranged and connected between the central portion (30A) and the peripheral portion (30C). Suitably, the elastic membrane is divided into a first area (34A) having a first total thickness (HA) and into a second area 15 (34B) having a second total thickness (HB), the first area (34A) being contiguous and adjacent to the second area (34B), the first total thickness (HA) having a value which is lower or equal to 75 μm and the second total thickness (HB) having a value which is greater than the value of the first total thickness (HA). Furthermore, the first area (34A) of the membrane 20 (30) extends at the central portion (30A) and comprises the plurality of contact pads (31A, 31B). A probe card (20) for testing electronic devices comprising this flexible membrane (30) is also described.