SBOA344A July 2019 – September 2022 LMX2694-SEP , SN55HVD233-SEP , SN65C1168E-SEP , TL7700-SEP , TLV1704-SEP , TPS73801-SEP , TPS7H1111-SEP , TPS7H1210-SEP , TPS7H2140-SEP , TPS7H2201-SEP , TPS7H2211-SEP , TPS7H2221-SEP , TPS7H3302-SEP , TPS7H4003-SEP , TPS7H4010-SEP , TPS7H5005-SEP , TPS7H5006-SEP , TPS7H5007-SEP , TPS7H5008-SEP , TPS7H5020-SEP , TPS7H6005-SEP , TPS7H6015-SEP , TPS7H6025-SEP
Historically, satellite programs have used space grade, hermetically sealed, QML-V qualified components for enhanced reliability and radiation hardness. With the emergence continued growth in constellation and low-earth orbit satellite launches for new commercial and government programs, there is a growing need for smaller components that can meet strict budgets. As a result, there has been more interest in using plastic encapsulated microcircuits (PEM) in space for a variety of reasons. PEMs become more attractive because leading edge products are not available as space qualified products and PEMs generally have smaller footprints and are lighter than the ceramic packages used in space qualified products. It has been recognized that there is a quality and reliability risk in using commercial-off the shelf (COTS) products and some space programs have been investigating using automotive grade AEC-Q100 products with more stringent qualification requirements. However, the extra qualification steps in Q100 parts do not meet all the requirements of a space application, even for those space applications with reduced requirements. For instance, commercial low earth orbit (LEO) applications with a projected three year life still have to meet radiation goals that many PEM products do not survive. One of the biggest challenges for a satellite program is finding and then testing those products that meet the radiation goals.
Although radiation performance may be biggest obstacle to using some COTS or automotive products in space, there are a number of other risks and factors to consider, such as tin whiskers, copper bond wires, rated temperature range, and package outgassing. Finding a device that can withstand the harsh environments of space can prove to be time consuming and challenging.
In addition to Texas Instruments' full line of rad-hard QML-V products for normal and high risk space missions, TI has introduced the rad-tolerant Space Enhanced Plastic (Space EP) product family in PEM packaging to lower the risk of using PEMs for missions with reduced requirements. The Space EP products have the following features:
The risks of using PEMs in space and how TI's Space EP products address these risks are discussed in this application note.
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Different semiconductor technologies have different inherent radiation tolerances (see TI’s Radiation Handbook for Electronics for more details). At the same time, two products using the same process technology or node might have totally different radiation responses due to how the product is designed and which modules in the process are used. As a result, customers need to spend time and resources in order to evaluate the reliability and radiation performance of these devices. To enable shorter development times, Texas Instruments’ Space EP products provide extensive radiation characterization to meet the requirements of LEO missions.
In addition, there are many generalities floating around about radiation tolerance that are not true for all cases. A 65-nm process is likely to be SEL immune, but only for the 1.1-V circuits. If a product uses higher voltage circuits, it is more likely to have SEL. Having an epi or SOI substrate does not necessarily mean that a CMOS product is SEL immune. For most CMOS products, the use of an epi substrate has no impact on SEL susceptibility and SOI only assures SEL immunity if the field oxide (STI) reaches all the way through the active layer down to the buried oxide.
A supplier such as TI has the knowledge of the process used on its products. Using this information, TI can choose products that have a high probability of being radiation tolerant and often uses a process or design change to meet the radiation goal. After choosing a part, TI then verifies the choice with heavy ion, neutron displacement damage (NDD), and total ionizing dose (TID) testing.
TI’s Space EP flow also follows a single production flow and provides radiation lot acceptance testing (RLAT) in order to reduce the risk with lot-to-lot variation. Most wafer fabs do not have monitors or controls in place for radiation tolerance. Modern wafer fabs maintain very tight controls to ensure consistent electrical performance, but the parameters that are controlled are not the same ones that impact radiation tolerance. For instance, the stoichiometry and thickness of passivisation layers have little impact on electrical performance but can be huge variables in radiation tolerance. In an extreme case, there was a product where one lot passed 100 krad(Si) and a lot processed in the same wafer fab a month later only passed 10 krad(Si). That is why radiation lot acceptance testing (RLAT) is so important.
Customers can design with Texas Instruments’ Space EP products to help bring new space systems faster to market and ensure these systems meet the radiation requirements for LEO missions. Each device is radiation tested up front and has TID, SEE and often NDD characterization provided in separate radiation reports available in the product folder. For enhanced radiation reliability, the Space EP products use only one production flow and each lot gets RLAT, eliminating the risks of lot-to-lot variations.
Satellites often experience the extreme hot and cold temperature ranges in space. In order to ensure the reliability of circuit electrical performance in this environment, TI’s Space EP products have a temperature range of -55°C to +125°C, with electrical parameters tested and guaranteed to operate over those conditions. The commercial grade temperature range is typically 0°C to +70°C. For automotive products, there are several specified temperature ranges with the most common being Grade 3 at –40°C to +85°C. While some COTS and automotive products may operate beyond the rated temperature, many others do not. It becomes necessary to test the products at the temperature extremes of the application to determine if a COTS or automotive product would work.
