Advantages of using aluminum substrates for aerospace electronics

Electronic assemblies lie at the heart of virtually every aerospace system and mission and have resided there since the earliest days of NASA. Presently electronic assemblies are arguably the most mission-critical aspect of every aerospace mission. Currently and for the past more than half-century traditional organic epoxy resin laminates have served at the substrate of first choice for printed circuits, with solder-based interconnection technologies universally used to join and interconnect components on virtually every electronic assembly in use today. Unfortunately, as electronics reliability engineers can attest, nearly every failure in an electronic system can be traced back to a faulty solder joint. The challenge to electronic reliability maintenance has been exacerbated by the European Union's decision to eliminate the use of lead in electronics solders which require process temperatures up 40C higher than tin-lead alloys. While aerospace and the military are exempt from EU regulations, they are not immune to the impact of such, as leadfree solders have become nearly ubiquitous making escape from them nearly impossible. If leadfree solders more reliable, this would not be a problem. However, the reality is that the reliability of leadfree solders is extremely uncertain and moreover that certain types of defects which were once under control, such as tin whiskers, have been seen to rise since the broad scale implementation was forced upon the industry. With that background, this paper will describe a new way of manufacturing electronic assemblies using aluminum as a substrate while completely bypassing the soldering process and all of the problems associated with the venerated yet problematic technology. Aluminum, it will be shown is a highly attractive material for use in the manufacturing of electronic assemblies for a number of important reasons. It is at once, low cost, light weight, a good thermal conductor and dimensionally stable. Unfortunately, it is not easy used when solder is required to make interconnections to components due to its innately effective thermal spreading ability, requiring higher temperature soldering, which results in increased potential for thermal damage to both components and assemblies. This paper will also, for the edification of the reader, show and describe ways to manufacture electronic assemblies using aluminum as a base and eschewing the use of solder. This new approach it is believed will enable aerospace companies around the world to take on new and more challenging missions through the implementation of a manufacturing method which eliminates the primary cause of failure in electronic systems, the ubiquitous yet unquestionably vulnerable solder joint.