COTS components in Space applications
Space is becoming a more and more competitive sector, asking for higher performance but reducing the overall Cost of the Missions.
In parallel, Electronic, Electrical and Electromechanical (EEE) parts designed for terrestrial application such as Automotive sector show High Reliability levels in the targeted applications when produced in massive quantities and while being the subject to ad-hoc qualification schemes (e.g. AEC-Q).
Although we could see a solution matching a need, there is still a big gap between space and terrestrial application of components, and proper methodologies have still to be developed
and approved in order to allow a more systematic usage of Commercial Off The Shelf (COTS) components and modules for Space applications.
Terrestrial components are inherently COTS components. As such to utilize the latest software, apps, capabilities in space applications (especially manned missions), the
hardware must be compatible with the terrestrial package.
The main reasons of using COTS components and modules in Space :
- Performance advantage if the performance is not obtainable by classical Hi-Rel components
- Lack of Hi-Rel components for performing that function
- Availability of production capability of supply chain for terrestrial use (in terms of modules)
- Shorter lead times and lower risk of part unavailability (not necessarily true, depending on procurement scheme, taking into account of quick obsolescence cycle of COTS components and their limited shelf life). Also limited regulatory control might help shorter lead times.
- Cost advantage, only for large volumes or low reliability/low radiation application where important risks might be taken.
- Terrestrial components rely inherently on COTS components. As such to utilize the latest software, apps, capabilities in space applications (especially manned missions), the hardware must be compatible with the terrestrial package.
The usage of COTS (Commercial Off The Shelf), PEM / PED (Plastic Encapsulated Microcircuits) of Electronic, Electrical and Electromechanical (EEE) parts in High Reliability applications offers many benefits.
However, it is important to calculate the Total Cost of Ownership of the parts, which consists of the procurement cost and the costs associated testing and upgrading to meet Program Reliability requirements.
For Commercial encapsulated active Monolithic parts (Integrated circuits and Discrete) the ECSS-Q-ST-60-13C can be adopted while, PEM / PED device’s the Mechanical, Environmental and Electrical testing, as well as Construction Analysis shall be based on NASA Documents :
- PEM-INST-001 (Instructions for PEM Selection, Screening and Qualification)
- EEE-INST-002 (Instructions for EEE Parts Selection, Screening, Qualification and Derating).
Automotive Grade EEE Parts are qualified in accordance with Automotive Electronics Council (AEC) specifications “AEC Q” :
- AEC-Q100 Stress test qualification for integrated circuits
- AEC-Q101 Stress test qualification for discrete semiconductors
- AEC-Q200 Stress test qualification for passive components
Justification Documents (JD) with Part detailed Quality / Reliability analysis to obtain information regarding design, workmanship, counterfeit:
- PPAP (Production Part Approval Process)
- Constructional Analysis (C.A.) systematically per lot
- Radiation test report for sensitive active devices
- Dispositions to prevent Tin whiskers induced failures.
- Special design rules (Derating)
Use of COTS Main Issues
- Generally no traceability, quality inspections, temperature range etc.
- But manufacturer reliability data are often very good COTS built for Automotive/Aero/Defense markets can have good reliability features and are a good starting point.
- Typically need incoming lot screening and tests
- Mounting process
- Typically plastic packages, often BGA, Flip Chip, etc.
- Finish problems (tin whiskers)
- Low experience in the qualification of processes
- Radiation effects
- COTS need radiation behavior assessment, which is a long, costly and uncertain process Total dose is not a great concern: often the requirements are limited (10-20 Krad)
- SEE effects are the major problem, in particular SEU/SEFI for digital devices.
- SEE tests are expensive and difficult to perform and interpret the results
- SEE are not destructive, but generate transient errors that affect the availability of the computer
- COTS are not designed to be SEE hard. Different mitigation methods can be implemented, but at last a quick reset and restart can be needed.
- When using COTS computers, it must be born in mind that full SEE immunity, i.e. 100% availability, which is typical of classical P/F computers, cannot be realized.
MICROREL offers Consulting Services in Partnerships with external Certified Laboratories specialized in High-Reliability EEE Parts Procurement services for the Electronic Components and RF Microwave parts to the Military Standards requirements from Program Management to Parts Engineering for Military and Aerospace application requirements.