Tungsten probe selection: tip radius, shank diameter and a length discrepancy

A request for a “7 µm tungsten probe” needs one more detail: which dimension does 7 µm describe? This MST reading example separates tip geometry from the shaft that fits into the holder. 1. Three rows from the manufacturer selection guide SemiProbe lists the following tip radii: • DC-11006: 7.0 µm. • DC-11008: 10.0 µm. • DC-11013: 20.0 µm. These three rows specify tungsten tips and shanks, with a 20 mil (0.020 in) shank diameter. The differing tip radius does not imply a differing shank diameter. Source: SemiProbe Probe Tip Selection Guide, checked 18 October 2026: https://semiprobe.com/probe-station-product-lines/accessories/probe-tips 2. Work through the units A mil is 0.001 inch. Therefore: 20 mil = 0.020 in = 0.508 mm. 7.0 µm = 0.007 mm. The first value describes the shank diameter; the second is the DC-11006 tip radius. Neither is automatically the diameter of the actual electrical contact patch. Keep the dimension name next to every number in a comparison sheet. 3. An unresolved source inconsistency The manufacturer's table gives overall length as 35 mm (1.25 in). These are not equivalent: 1.25 in is 31.75 mm. Preserve both printed values in your source record, mark the length as unresolved, and request a current drawing or written clarification. Do not silently choose one value or “correct” the manufacturer's specification. 4. A replacement worksheet Compare the existing and proposed probe against the same fields: • Exact probe reference and drawing revision. • Tip material, tip radius and tip shape. • Shank diameter, holder opening and clamping arrangement. • Required installed length, bend geometry and usable reach. • Pad material and dimensions, measurement purpose and operating conditions. • Contact-force or overtravel limits from the relevant equipment/probe documentation. Separate “documented”, “measured on our setup” and “still unknown”. Before qualifying a change, agree how contact repeatability, measurement consistency and pad condition will be checked on representative samples. This is a suggested comparison workflow, not a test report or a process setting supplied by SemiProbe. The same material or a similar model number is insufficient to establish fit or measurement suitability. No interchangeability test was performed for this note. If you have a non-confidential holder drawing or an ambiguous dimension, identify the field in a reply so the discussion can focus on the missing evidence. The related Store reference is: https://store.mst-sg.com/store/tungsten-probe-tips/SC-PROBE-RFQ MST technical editorial | Version 1 | 18 October 2026