FEATURE TEST & COMPLIANCE
Reed relays: the perfect fit
Robert King, technical engineer at Pickering Electronics explores the technical specifications behind the world’s smallest high voltage reed relay, developed for new semiconductor test equipment
I
n switching systems for test and measurement applications, reed relays
are often the best solution thanks to their small size, high isolation resistance, hermetically sealed contacts, fast operate time and long-life expectancy. Whilst a number of companies offer a range of high voltage reed relays suitable for such applications, there are instances where a customer has a new requirement. One example occurred when ON Semiconductor needed to develop new semiconductor test equipment. Pickering Electronics was formed over 50
years ago to design and manufacture high quality reed relays, intended principally for use in Instrumentation and Test equipment. Today, Pickering's single-in- line (SIL/SIP) range is by far the most developed in the relay industry with devices 25% the size of many competitors. These small SIL/SIP reed relays are sold in high volumes to large ATE and semiconductor companies throughout the world. Many of Pickering’s reed relays are born
out of customer requirements; one example is the recently introduced Series 131 high voltage devices. When developing a new test rig, globally renowned chip maker, ON Semiconductor – a long- standing customer of Pickering - identified the need for a reed relay with a higher stand-off voltage of 400VDC, whilst maintaining the same small size of the device it was replacing, Pickering’s Series 112 SIL relay which can be closely- mounted on a 3.7mm x 2.54mm pitch. Initially, Pickering offered its Series 119
device which has a voltage stand-off of up to 3kV in 1 Form A configuration, and has a footprint of 3.7x20.1mm and stands 6.6mm tall. However, despite being the smallest high voltage reed relay available on the market at that time, the Series 119 device was too large for the application. What ON Semiconductor really needed was a combination of the Series 112 footprint and pin configuration but with the same specifications as the Series 119. This posed a real challenge, since the
internal clearance constraints required by the uprated specs would not fit the
32 SEPTEMBER 2020 | ELECTRONICS
package size of the Series 112 device, but because Pickering has all elements of relay design and manufacture in house, the engineering team was able to accommodate the increased isolation distance requirements within a package with a footprint of 3.7x12.5mm – only slightly larger than the Series 112 device – and a height of 6.6mm. After a 7-week period of research and development, the first prototypes were sent to ON Semiconductor for prototype test. After further refinement and
development and ON Semiconductor’s feedback, a new reed relay family, the Series 131, was launched by Pickering. Housed in the mini-SIL/SIP package, the new reed relays deliver a minimum stand- off of 1500V and are now the smallest device of their type on the market. Featuring a choice of 3, 5 or 12 volt coils,
with optional internal diode, Series 131 reed relays are available in the 1 Form A (energize to make) SPST N.O. configuration, and can switch up to 0.7 amps, 10 watts. Devices are ideal for cable testers, mixed
Figure. 1: The latssor
signal/semiconductor testers, backplane testers, high voltage instrumentation, in- circuit test equipment or other HV applications. The reed relays utilise vacuumed,
Figure 1:
Pickering Series 131 high voltage reed relay
sputtered ruthenium reed switches which have a superb low-level performance, making them an excellent choice where a wide range of signals are involved. Devices are 100% tested for dynamic contact resistance and incorporate an internal mu- metal magnetic screen – another Pickering innovation - to enable high packing density. Pickering’s SoftCenter construction is employed to protect the reed switch. The Series 131 not only solved ON
Semiconductor’s requirement for this particular application, but additionally, these same reed relays can be used in high voltage testing applications ranging from 800 - 1000VDC, so now ON Semiconductor can develop high voltage testers with even more reed relays on each PCB, resulting in equipment with added capabilities and/or smaller size. As a final bonus, ON Semiconductor’s high voltage testers are usually coloured red to highlight the presence of high voltage, so as an additional safety warning for its end customers, Pickering changed its standard reed relay text printing colour from white to red. Pickering offers many customisation
Figure: 2:
Pickering’s Series 131 solved ON Semiconductor’s requirement for high voltage application
options for its wide range of standard series reed relays; for example, different test specifications or pin configurations can be offered. A reed relay, designed with high quality in mind and with no compromise on methods or materials, delivers the greatest performance and reliability.
WATCH THE DEVELOPMENT IN PROGRESS A new video is available on Pickering’s website detailing the development of the Series 131 high voltage relay at
pickeringrelay.com or free Series 131 evaluation samples can be requested at
pickeringrelay.com/samples.
Pickering Electronics
www.pickeringrelay.com
/ ELECTRONICS
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