This Standard has been cancelled and replaced by ECSS-Q-ST-70-38C (31 July 2008).
This Standard defines the technical requirements and quality assurance provisions for the manufacture and verification of high-reliability electronic circuits based on surface mounted device (SMD) and mixed technology.
The Standard defines acceptance and rejection criteria for high-reliability manufacture of surface-mount andmixed-technology circuit assemblies intended to withstanding normal terrestrial conditions and the vibrational g-loads and environment imposed by space flight.
The proper tools, correct materials, design and workmanship are covered by this document. Workmanship standards are included to permit discrimination between proper and improper work.
Requirements related to printed circuit boards are contained in ECSS-Q-70-10 and ECSS-Q-70-11. The substrates covered by this document are divided into five classes in accordance with their average X and Y coefficient of thermal expansion (CTE).
The mounting and supporting of components, terminals and conductors prescribed herein applies to assemblies designed to operate within the temperature limits of -55 ºC to +85 ºC.
Special thermal heat sinks are applied to devices having high thermal dissipation (e.g. junction temperatures of 110 ºC, power transistors) in order to ensure that solder joints do not exceed 85 ºC.
Verification of SMD assembly processes is made on test vehicles (surface mount verification samples). Temperature cycling ensures the operational lifetime for spacecraft. However, mechanical testing only indicates SMD reliability as it is unlikely that the test vehicle represents every flight configuration.