» TEST & QUALITY
» TEST & QUALITY ASSURANCE Source: Omron Electronic Components Europe The company says its G3VM-MT MOSFET module offers maintenance-free operation and a simplified design that saves on board space Solid-state modules for test applications Minimizing leakage current with T-circuit MOSFETs There have long been concerns about the performance of solid-state relays – particularly with regard to leakage current – when used in test applications. Gabriel Sikorjak, Technical Sales Manager at Omron Electronic Components Europe explains how the newest solid-state modules address these technical drawbacks, and advocates for their wider adoption. MOSFETs are superior to reed relays in many respects. Those continuing to use traditional relays because of their low current leakage are missing the benefits offered by alternative solid-state components. Benefits of MOSFET relays MOSFET relays deliver substantial benefits for test equipment. They take up less space on boards, offer faster switching times, and provide longer service life than traditional reed relays. Many applications also benefit from the lower power requirements, stable on-resistance and better resistance to shock/vibration they provide. One of the key benefits of MOSFET relays is their package size. Reed relay packages, placed in high volumes on PCBs, require much more space. Increasing demands from the semiconductor industry, test equipment with a more advanced design, and higher integration needs all affect the number of inspection channels. All these extra requirements are transferred into a larger number of switching components. Using more compact MOSFET relays can thus make a huge difference in terms of the amount of board space utilised. Then there is the question of reliability which, in turn, translates into operating life. In test applications, reed relays need to be regularly maintained. Mechanical relays have generally been preferred in the semiconductor industry (as well as for other test equipment) – in part due to their isolation characteristics. They do, however, have a shorter lifespan due to abrasion of the contacts – which reduces equipment durability over time. When used intensively, mechanical relays need to be regularly replaced – pushing up maintenance costs. Moreover, replacement is necessary as soon as contact resistance goes 46 EPP Europe » 11 | 2022
G3VM-21MT reference design board testing result (DUT: FJH1100) above a specified threshold, and this end-of-life moment is not easy to predict or evaluate. Alternative solid-state relays provide incomparable electrical endurance and, when used with semiconductors, do not suffer from mechanical contact wear. There is thus no need for maintenance. Nonetheless, there are still some performance trade-offs when using these alternative relays. These are summarised in the table on p. 56. Leakage current – a barrier to adoption? Though used advantageously in many applications in test equipment, MOSFET relays, like reed relays, are stretched to their limits by increasingly demanding test requirements. Despite boasting exceptional reliability and tiny packages, to meet the needs of the T&M industry, they must also deliver in terms of performance. One of the most critical ratings for semiconductor components is leakage current. During DC parametric testing in automatic test equipment (ATE), for example, minimizing leakage current at the test line is a key factor to ensure accurate measurement. Increasing drain-source voltage results in increased leakage currents. This creates issues with performance values. In circuit designs where multiple lines are used, such as semiconductor devices switching various DUTs and measurement pins, MOSFET relays can reach their limit. Are T-modules the solution? Using T-circuit solid-state modules, however, it is possible to address leakage current issues associated with MOSFET relays. These modules are based on a T-circuit built on three MOSFET pairs (as shown in A T-circuit configuration can dramatically reduce leakage current from MOSFET relays Source: Omron Electronic Components Europe Source: Omron Electronic Components Europe EPP Europe » 11 | 2022 47
