What is Near Continuous LLCR?
Near Continuous LLCR is the frequent, periodic monitoring of Low Level Circuit Resistance (LLCR) in the test environment. Typically, LLCR measurements are taken from 1 to 5 minutes apart, non stop, during the duration of the test. Measurements may be taken on only a few samples, with a dozen or so data points, or many samples with hundreds of data points. Temperature measurement are taken along with the LLCR measurements to track the affects of temperature change on the readings.
Why Would I Use Near Continuous LLCR?
In a conventional environmental test, LLCR measurements are taken at the beginning and at the end of the test, manually, at ambient conditions. These readings show the accumulated effect of a test environment, but give little insight into the performance of a connector during the exposure. A connector which passes LLCR at ambient conditions before and after a test, may fail miserably during the environment exposure.
In contrast, Near Continuous LLCR allows frequent, automatic, periodic measurements of the samples within the chamber, under test conditions. This gives the test engineer better data on connector performance during the exposure.
If a test sponsor is concerned about the functionality of a connector under test conditions, especially during temperature transitions, Near Continuous LLCR is a good measuring technique to use.
How is Near Continuous LLCR Performed?
Sample test points must be wired to a harness which extends outside the environmental chamber. Thermocouples are also placed in the chamber and/or on the samples. The wiring harness and thermocouples are then connected to a scanner / meter system under the control of a computer. The harness is usually constructed by Contech Research personnel. Sometimes, test boards are designed and manufactured to facilitate testing.
A Real World Example.
A large computer manufacturer wanted to test the performance of Land Grid Array (LGA) sockets under an accelerated temperature test profile, which simulated the power up and power down phases of their system. They were interested in determining the LLCR of socket contacts during temperature ramp up and ramp down, as well as during the constant "soak" temperature.
Contech Research set up a Near Continuous LLCR test which measured 300 contact chains in the LGA test boards, once every 3 minutes. Over the course of the 1500 hour test, Contech provided updates of LLCR and temperature data to the customer, allowing them to evaluate the performance of the connectors during the test.
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