With the ever increasing complexity of electronic systems used in aerospace applications, the design, fabrication, performance and monitoring of printed circuit boards (PCBs) and components become more important with each cycle of development.

Reliability modelling, based on individual constituent materials and devices is the first step in the design and fabrication of circuits suitable for use in aerospace applications. Surface preparation techniques play an important role in the use of electronic materials; as does device performance.

For many uses, circuits and systems are subjected to extreme conditions and environments where their reliability and performance must be continually monitored and analysed in real-time. The performance of interconnects and solders must also be considered.

This Emerald Aerospace Briefing introduces aspects of PCB design, testing, materials preparation and testing relevant to all electronic systems in use in the aerospace sector.

Contents:

Modelling of multi-layer circuit boards by using a model of bi-phase and elasto-plastic plies

This paper presents a method for multi-layer PCB modeling at both the micro-structure and board levels. It provides a way to individually design the fabric types and the properties of glass fibers, epoxy resin, and copper foil in PCBs, to meet specific reliability requirements. With the proposed modeling, the static and shock responses of optimized PCBs can be analyzed with less computation.

Originally published in Circuit World Volume 33 Number 3, 2007

Failure analysis of electronic components and interconnection systems

Several examples of the failure analysis of electronic components and interconnection systems are presented. These illustrate the broad range of work undertaken and the nature of many of the failures investigated by the Product Assurance Response Centre (PARC). The information gained is fed back to the manufacturing units in order to prevent a re-occurrence of the fault, and so enhance product reliability. This has resulted in savings to BAE SYSTEMS of several million pounds in terms of the decrease in lost productivity, poor quality and customer returns over the lifetime of the PARC. The return on investment in 2005 was in excess of four million pounds.

Originally published in Circuit World Volume 33 Number 1, 2007

The evaluation of sonochemical techniques for sustainable surface modification in electronic manufacturing

The electronics industry has always had a requirement for adhesion promotion on a vast array of dielectric substrates and, with the emergence of printed electronics, the choice of substrate will increase still further. The surface modification of polymers and plastics is important in the traditional manufacture of printed circuit boards (PCBs) but will become even more so for polymer electronics, printed electronics, radio frequency identification technology, etc. Increasing environmental and health and safety legislation means that the use of “clean and green” technologies for such processes needs to be re-evaluated; one such technology is sonochemistry. This paper sets out to give an introduction to sonochemistry and the effects brought about by the application of ultrasound that might be useful in surface modification; and to show the feasibility of sonochemical surface modification in water on a range of materials employed in electronic manufacturing.

Originally published in Circuit World Volume 33 Number 3, 2007

Hot carrier injection in VDMOSFET for improvement of commutation process

This paper has value in terms of engineering applications where the speed of electronic devices is one of the most valuable parameters in the communication and information technology fields. This work highlights the evolution of the switching times parameters of commercial vertical diffuse metal oxide semiconductor field effect transistors after a hot carrier injection in the reverse bias pn junction. The experimental results show that the device rise time decreases significantly for the first period of stress time at room temperature, which increases the speed of the device during this turn-on switch.

Originally published in Microelectronics International Volume 24 Number 3, 2007

Strain range fatigue life assessment of lead-free solder interconnects subject to temperature cycle loading

The transition to lead-free solder has renewed interest in methods for modeling the life expectancy of solder interconnects in electronic hardware. The ability to model fatigue life is important and for most solder fatigue models, life (damage) is related to a selected stress metric in the form of a power law. For temperature-cycle-induced fatigue, cyclic strain range and cyclic strain energy are often used. This paper details a temperature cycle fatigue life model and constants that allow engineers to predict field life expectancy and determine the acceleration factor between temperature cycle testing and field use conditions.

Originally published in Soldering & Surface Mount Technology Volume 19 Number 2, 2007

High-cycle fatigue testing of Pb-free solder joints

This paper explores the high-cycle fatigue performance of Pb-free alloys and compare them to Sn-Pb. In doing this, it also aims to demonstrate the viability of a new testing method. The results obtained are of interest to high-reliability electronics sectors such as aerospace, defence and automotive, where vibrations in service are encountered. Very little work exists on the subject of solder high-cycle fatigue performance and to the author's knowledge none comparing Pb to Pb-free alloys in an objective manner.

Originally published in Soldering & Surface Mount Technology Volume 19 Number 2, 2007