74CJ-APT-KS-SR Low Noise Coaxial Holder with Series Resistor


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The Flexible Low Current Design with easily replaced coax probes. The probe holder is provided with dual SSMC connectors that allows for variety of test measurements required for semiconductor test.  The second SSMC connector with a series resistor provides an easy accessible point for sensing voltage or current, guarding, grounding, termination and LCR four wire measurements. Designed with an industry standard form-factor that easily retrofits to almost any probe station or custom application.  The replaceable 50 ohm coaxial probe has a tungsten core that is electrochemically etched to the desired radius ranging from 0.5um to 20um with options to 50 micron. The replaceable probes can also be ordered with custom shapes and bends to meet any custom requirements.  An assortment of accessories and options for shielding, grounding, guarding, series resistors, terminations, high voltage, and high frequency can be ordered and configured.


Very Low Current Design to less than 10 fA. Dual SSMC connections for Quasi Kelvin connection for SMU and LCR use. Replaceable Coax Probe design for easy replacement of damaged probes or to replace with a different radius size.

Applications include

  • Low current (SMU) (<10fA)
  • LCR (<10fF)
  • Signal Integrity
  • Pulse source/sense
  • TLP (<10nS rise with 76LWA ground return)

*Identical to 74CJ Series with the addition of series resistor between SSMC's.



Video Courtesy: Grund Technical Solutions


Also see: 

73CT-APTA Series Replaceable Coaxial Probes

       74CJ-APT-KS Low Noise Coaxial Probe Holder with replaceable coax probes

74CJ-APT-KS-SR Low Noise Coaxial Probe Holder with replaceable coax probes & series resistor

74CJA-APT-KS Series Coaxial Probe that accepts standard 20 mil DC probes

73APT-100K Kelvin Probe

73APT-100K-SR Kelvin Probe with Series Resistor

76CPC-SSMC Coaxial Cables

76LPC-SSMC Low Noise Coaxial Cables

86LPC-SSMC Low Noise Triaxial Cable

What size probe should I use?

The typical recommendation is to use a probe diameter that is half to two thirds the size of the contact. Remember, APT's probes are sold by the radius, so you must double the number to determine the diameter. It is normally found that a radius larger than 20 microns does not yield lower contact resistance. An example is: The contact pad is 10 microns, using the recommendation, you would then use a probe with a radius of 2.5 - 3.5 microns. (5- 7 micron diameter)

Product Specifications:


Material: Type II Gold plated brass/copper Connectors: Two SSMC connectors connected in parallel to create a Quasi-Kelvin connection within the probe holder body Mounting Shank: 0.124" ~ 0.125" Probe: Accepts a 0.034" O.D. semi rigid coaxial probe (73CT-APTA, 73CT-CMIA, 73CT-SMTA) Probe lock: The coaxial probe is held in place by two 0x80 pan head screws tighten the holder clamp


Current leakage: < 10 fA. Frequency: > 150 MHz Capacitance (Guarded): < 10 fF Impedance: 50 Ohm Power Handling: > 125 Watts @ 18-21 Deg. C Voltage Rating: > 250 Volts RMS @ sea level

The series resistor is mounted between the two SSMC connectors within the probe holder body.  The standard resistor is an SM-603, 1/16 watt with other wattages available upon request. 


Click here for dimensional drawing of this product


Reference Documents

Contact resistance Data (Preliminary Analysis) The data was collected using a programmable load and power supply connected to a 74CJ-APT-KS/100 coaxial probe with a 10 micron radius. The target was a hard gold plated copper plate.

74CJ-APT-KS probe contact resistance

The test results can be viewed here

You will note an anomaly at about 400 mA where the probe station was accidently bumped causing the probe contact to be somewhat damaged. This damage resulted in higher contact resistance as noted.