How to efficiently solve the problem of Kelvin test pin selection for high-precision resistors in PCBA?

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How to efficiently solve the problem of Kelvin test pin selection for high-precision resistors in PCBA? [Copy link]

Kelvin Four -terminal sensing is also known as four-terminal detection (4T detection, 4T sensing), four-wire detection or 4-point probe method. It is an electrical impedance measurement technology that uses separate electrodes for current and voltage detection, which can perform more accurate measurements than traditional two-terminal (2T) sensing. The key advantage of four-wire detection is the separation of current and voltage electrodes, which eliminates the impedance of wiring and contact resistance. It is widely used in high-precision resistance detection in the PCBA manufacturing industry, such as automotive electronics, instrumentation, communication products, etc.

It uses a special bridge in the test instrument to achieve high-precision measurement, and is usually used in the measurement of small resistance and high-precision resistance. For example, if a resistor has a resistance of 2.5 ohms, using the traditional measurement method, the cumulative loss of the contact resistance and the measurement line can reach several ohms, so accurate measurement cannot be achieved. At this time, the Kelvin test method is needed.

The Kelvin test method requires the following PCB circuits: the network connected to each pin of the resistor to be tested needs to have two test points, so one resistor needs four test points; while in the common test method, the network of each pin of a resistor only needs one test point, that is, one resistor only needs two test points. The following figure is a schematic diagram of the test points for a resistor to be measured with four wires.

Figure 1

In order to meet the requirements of four-wire detection, it is first necessary to select points in the circuit network connected to the pins of the target test component to meet the required number of test points. If engineers are to find test points that meet the conditions in the network where the resistors and their pins are located one by one, it will not only be a large workload, but also difficult. Therefore, manual point selection is inefficient and the selected pin points may not be optimal, which may lead to higher ICT fixture costs.

High efficiency and low cost are the competitive advantages of enterprises, and are also the goals that enterprises are constantly pursuing. Vayo has been focusing on the field of electronic process design industrial software for 16 years, and has developed a series of electronic system digital design -manufacturing industrial software to help enterprises improve quality and reduce costs, improve high reliability, and help enterprises upgrade their smart manufacturing. Among them, VayoPro-TestExpert software can solve the above problems for users very well. Next, I will show you how Vayo Test Expert software can efficiently handle the selection of test points for precision resistors Kelvin.

First, define the components that need to be measured in four-wire mode in the software. For example, if the four-wire measurement object is a resistor with a value of 0Ω<R≤10Ω, then click "Add" in the Find Component dialog box in the second figure below and select a device of type RES*.

Figure II

Set the search condition parameters in Figure 3 below;

Figure 3

The above steps can complete the Kelvin distribution of resistor elements. The search results are shown in Figure 4 below;

Figure 4

Now that the component definition is complete, you can then perform automatic point selection in the software. The software will automatically select two test pin points for each pin network of all the selected resistor components. Details can be viewed in the pin selection result report interface.

Note: The default point selection rules have been configured in the software for Kelvin test conditions, see Figure 5 below. If the point selection rules are added by the user, please confirm whether there are the following KELVIN test pin point quantity requirements, otherwise you need to add them first and then perform automatic point selection.

Figure 5