Vertical Probe Head Shifted Guide Holes Eliminate Scrub
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Solution Overview
Problem
Vertical probe heads exert significant shear forces on semiconductor wafers during testing, causing unwanted lateral shifts due to the simultaneous scrub mechanism of contact probes, which can damage the wafer and affect the accuracy of the test.
Innovation Solution
The probe head is designed with guides having shifted guide holes to cancel out scrub movement, with a further lower guide absorbing the shear forces, ensuring each contact probe exerts no force on the wafer, thereby eliminating shear forces and maintaining probe bending functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the probe head uses a conventional guide configuration with parallel guides, then the structure is simple and easy to manufacture, but significant shear forces are exerted on the wafer causing lateral shifts during testing
Solution Approach 1:
The single guide structure is segmented into multiple guides (first guide, second guide, third guide) with progressively shifted guide holes. This segmentation allows the shear force to be distributed and neutralized across multiple components rather than concentrated in a single guide, eliminating lateral forces on the wafer while maintaining manufacturing feasibility.
Solution Approach 2:
The guide holes are shifted not only in the horizontal direction but also arranged at different vertical levels (first guide at upper level, second guide at intermediate level, third guide at lower level). This three-dimensional arrangement creates a more complex force distribution that effectively neutralizes shear forces while allowing probe bending to occur in the vertical air gap.
2Reliability
If the contact probes are allowed to bend freely in a large air gap, then proper contact with contact pads is achieved, but lateral scrub movement causes unwanted shear forces on the wafer
Solution Approach 1:
Different guides provide different local constraints: the first guide allows initial probe positioning, the second guide provides intermediate constraint with horizontal shift, and the third guide provides final constraint with additional horizontal shift. Each guide's guide holes are strategically positioned to provide the specific local constraint needed at that stage, collectively eliminating lateral scrub while maintaining vertical bending freedom.
3Object-affected harmful factors
If multiple guides with shifted holes are used to eliminate shear forces, then wafer stability is improved, but the device complexity increases
Solution Approach 1:
Multiple guide functions (support, alignment, shear force neutralization, probe constraint) are merged into a single integrated guide assembly consisting of three guides. Rather than using separate components for each function, the shifted guide holes in the three guides collectively perform all necessary functions, simplifying the overall structure while achieving the goal of eliminating lateral forces.
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 eliminates shear forces on the wafer, preventing lateral shifts and ensuring precise and reliable testing without damaging the probes or contact pads, while allowing for proper bending and contact with the device under test.
Implementation Method 1
the contact probes undergo, during said pressing contact, a bending inside the air gap between the guides
Implementation Method 2
said probes being usually made of wires of special alloys with good electric and mechanical properties... slidingly housed in said guide holes
Data Source
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AI summary
A probe head (20) for testing a device under test integrated on a semiconductor wafer (26) comprises a plurality of contact probes (21), each provided with a first end (21a) and a second end (21b), said first end (21a) being adapted to contact pads (25) of the device under test, and at least one first lower guide (22) and one second lower guide (23) at the first end (21a), said guides (22, 23) being parallel to each other and provided with a respective plurality of first and second guide holes (22h, 23h) for slidingly housing the contact probes (21), wherein the second guide holes (23h) of the second lower guide (23) are shifted with respect to the first guide holes (22h) of the first lower guide (22) along a first direction (Dir1). Suitably, the probe head (20) comprises at least one third lower guide (24), which is substantially parallel to the first lower guide (22) and to the second lower guide (23) and is provided with a plurality of third guide holes (24h) for slidingly housing the contact probes (21), wherein the second lower guide (23) is arranged between the first lower guide (22) and the third lower guide (24), and wherein the third guide holes (24h) of the third lower guide (24) are shifted with respect to the second guide holes (23h) of the second lower guide (23) along a second direction (Dir2) opposite the first direction (Dir1), the shift of the third guide holes (24h) being such as to eliminate a scrub movement of the first ends (21a) of each contact probe (21) of the probe head (20).