Vertical Probe Head Impedance Matching via Local Quality
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Solution Overview
Problem
Conventional vertical probe heads face challenges in achieving good impedance matching for high-speed differential pairs due to large probe gaps, leading to inconsistent contact force and instability in elasticity, especially when probes are widened to accommodate larger pitches.
Innovation Solution
The design incorporates a vertical probe head with a distinctive probe configuration, where the body portion width is smaller than the head portion installation part, and the body portion centerline is deviated from the head portion installation part centerline, allowing for closer proximity of body portions while maintaining appropriate contact force and preventing excessive width, thus achieving better impedance matching and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the probes are widened to accommodate larger pitch for high-speed differential pairs, then the impedance matching is improved, but the contact force becomes inconsistent and elasticity stability deteriorates
Solution Approach 1:
The probe is designed with non-uniform width: the body portion has a smaller width for stable elasticity and consistent contact force, while the head portion installation part has a larger width to accommodate the larger pitch of high-speed differential pairs. This local differentiation allows each section to optimize its function independently.
Solution Approach 2:
The probe is divided into distinct segments with different width characteristics: the body portion (smaller width) and the head portion installation part (larger width). This segmentation enables the probe to simultaneously satisfy the requirements for elastic stability and impedance matching by assigning different geometric properties to different segments.
2Manufacturing precision
If the probes are widened to accommodate larger pitch, then the gap between probes is reduced, but the body portion thickness must be decreased to very thin extent, causing instability in elasticity
Solution Approach 1:
The probe employs local quality differentiation where the body portion maintains a smaller width (and thus greater thickness) to ensure elastic stability, while the head portion installation part has a larger width to reduce the gap and improve impedance matching. This prevents the need to make the entire probe body extremely thin.
Solution Approach 2:
By segmenting the probe into body portion and head portion installation part with different width specifications, the design avoids the constraint that would require the entire body to be very thin. The body portion can maintain sufficient thickness for elastic stability while the head portion accommodates the larger pitch requirement.
3Length of moving object
If the body portion width is increased to match larger pitch, then the coupling capacitance is reduced, but the contact force becomes too large and inconsistent
Solution Approach 1:
The body portion is designed with a smaller width to maintain appropriate coupling capacitance and prevent excessive contact force, while the head portion installation part has a larger width to match the larger pitch of high-speed differential pairs. This local differentiation resolves the contradiction between maintaining physical properties and accommodating geometric requirements.
Solution Approach 2:
The probe is segmented into body portion and head portion installation part with different width characteristics. The body portion's smaller width ensures stable contact force and appropriate coupling capacitance, while the head portion's larger width accommodates the larger pitch, allowing independent optimization of each function.
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
This configuration ensures consistent contact force and improved impedance matching for high-speed differential pairs by allowing the head portion contact parts to match the larger pitch of the device under test while maintaining the body portion's smaller center-to-center distance for increased coupling capacitance, enhancing probing accuracy and stability.
Implementation Method 1
when the test is performed and the body portions 136 of the probes 13 are deformed elastically, the contact force of each probe 13 is controllable
Data Source
AI summary
A vertical probe head includes upper and lower die units having upper and lower through holes, and probes each including a body portion between the die units, tail and head portion installation parts in the upper and lower through holes respectively, and a head portion contact part for electrically contacting a device under test. The probes include a pair of signal probes including at least one distinctive probe, for which, the body portion is smaller in width than the head portion installation part, and a body portion center line is deviated from a head portion installation part center line toward the probe paired thereto. For the paired probes, a head portion contact part pitch is larger than a body portion pitch for matching a large-pitch high-speed differential pair of the device under test, great impedance matching effect, and consistent contact force and stable elasticity of the probes in operation.