„Choosing the correct switching device can go a long way to making a successful test system.“
If there are particular areas you need help with, feel free to skip to any of the following sections:
Introduction
What Are the Critical Test Parameters
Choosing the Correct Switching Device
Which Reed Relays Are Used in Pulsed High Current Testing?
Additional Resources
Conclusion
Introduction
Test Equipment and Automated Test Equipment (ATE) systems are used to test discrete semiconductors. A switching device such as a relay is often required that can carry high-pulsed currents without distortion. Pulsed currents are used to verify that the device under test can handle high and/or surge currents without lowering performance. The high current pulse verifies that the chip is adequately bonded to its substrate. Also, at the same time, high voltages may be needed to hold off high switching voltages. Next, we evaluate reed relays, electromechanical, and semiconductor relays along with factors used for choosing the correct switching device.
What Are the Critical Test Parameters
When testing discrete semiconductors, particularly power devices (Fets, mosfets, etc), high current testing is a very important parameter. Multiple tests occur for each component, requiring different voltages, currents and detection devices. Therefore, high voltage isolation between components is another critical factor. Switching reliability is another key factor. Over its lifetime, the switching device will need to be turned on and off hundreds of millions of operations. So, choosing the correct switching device can go a long way to making a successful test system.
Choosing the Correct Switching Device
To choose the right device, we need to compare how electromechanical, semiconductor, and reed technology meets the critical requirements. Electromechanical relays do well for carrying high currents but begin to wear mechanically after 1 million operations. Semiconductor relays generally cannot support both high currents and high voltages in one chip. Therefore, semiconductor devices don’t meet these kinds of switching requirements. A single reed relay can pulse high currents and isolate high voltage. Plus, using high voltage reed relays achieves the goal of billions of successful pulsed operations. As a result, designers have turned to Standex Electronics’ high voltage reed relays containing one or more reed switches for meeting the above test requirements.
Standex Electronics‘ 1 kVDC high voltage reed relays for Test & Measurement
In fact, Reed relays have numerous traits that are valuable for test and measurement:
- Very high off resistance
- Very low on resistance
- Very high isolation resistance
- Reliably switch micro to medium loads
- Billions of operations including pulsed carry currents
- Small Size
- No mechanical wear
- Ability to carry pulsed currents up to 5 Amps
- Ability to Switch up to 1000 Volts
- Dielectric strength across the contacts 3000 volts
- Contacts dynamically tested
Which Reed Relays Are Used in Pulsed High Current Testing?
Standex Electronics’ Standard-in-line High Voltage (SHV) Series was designed for this very requirement. The SHV relay can switch low level signals for billions of operations. All, while carrying high current pulses for an equal number of times. Making the SHV ideal in pulsed high current test applications.
Furthermore, the SHV high voltage relay series can carry 3 amps continuously and can carry 5 amps pulsed currents for up to 5 milliseconds through the relay. No distortion to the leading or trailing edge will occur. This reed relay series can also switch up to 1000 volts, and Standex Electronics uses an evacuated reed switch to ensure the dielectric strength of 3000 volts minimum. For the higher pulsed currents, it is recommended to wait at least 5 msec after the coil has been energized before applying the high pulsed current. The pulsed currents allow the designer to determine the integrity of the chip and to make sure it is properly placed on its substrate for efficient operation.
Pulsed high current testing using a high voltage Reed Relay; depicts a perfect square wave pulse of 5 Amps traveling across the closed reed switch contact surface which remains undistorted.
Conclusion
While electromechanical and semiconductor relays meet some of the critical requirements of pulsed high current testing, reed relays present the best choice for overall performance. No other switching device can handle all the switching needs in a single device for the extended lifetime. Standex Electronics’ reed relays use hermetically sealed reed switches that are further packaged in an environmentally robust housing, ensuring no loss of reliability. Finally, the reed relay is an excellent choice because it can operate reliably over a wide temperature range and represents an economical way to carry out billions of switching operations.
If your application requires one of the standard relays from our catalog, that’s clearly the best approach and the quickest solution to satisfying your design requirement. However, more than half of our shipped relays are from special requirements. Since many switching and sensing requirements are unique, working with customers on their special applications is expected. Send us your requirements!
Because at Standex, “custom is standard.”
Additional Resources
Download the Pulsed High Current, Automated Test Equipment Application writeup or the Test & Measurement brochure to explore more switching solutions and applications with superior functionality, longevity, and reliability.
