National Physical Laboratory

Improving Electronic Reliability - Through Product & Process Qualification at NPL - Downloads of past webinars - 2015

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Coating Protection Performance under Condensing Conditions
Monday 30 November 2015

As electronics are applied into increasingly harsh conditions, conformal coatings are being increasingly used across a wide range of applications to mitigate against electrochemical failures. Humidity testing in combination with SIR (Surface Insulation Resistance) testing is used to characterise coatings, however a more severe test where a liquid layer is formed is finding popularity. The new test is required because it is more challenging to achieve coating coverage over right angle edges than for flat areas. These edges on the termination provide active sites on which electrochemical corrosion can proceed.

The new tests aim to achieve condensing conditions where a liquid layer is formed. This is a more aggressive test for a coating, yet is representative of typical failure modes. Humidity cabinets are engineered to achieve stable temperature and humidity conditions and to expressly avoid condensation occurring in them. Rapid transitions between conditions may cause condensation, but the occurrence and level is not predictable or repeatable. To improve the capability of creating condensation, separate injection of moisture into the environment is currently being used, but again the effect is not predictable on circuit test board.

CAF Conductive Anodic Filaments - How to Avoid Failure
Monday 16 November 2015

Conductive Anodic Filamentation (CAF) is a subsurface failure mode for woven glass-reinforced laminate (FR4) materials, in which a copper salt filament grows and results in a consequential electrical short between plated through-hole (PTH) walls or adjacent copper planes. In this webinar we covered FR4 laminates, in the form of high PTH density multi-layer test circuits, exposed to different manufacturing conditions and studied for resistance to CAF initiation and growth. CAF performance was assessed using high temperature and humidity conditions to promote failures, with a voltage applied across adjacent vias. By application of a range of voltages and via geometries, the basis for a performance map for laminates was obtained for use in materials comparison. The changes due to exposure of laminates to lead-free temperatures and other processing steps were then examined using the technique, and a number of important recommendations made regarding minimising the possibility of CAF initiation and growth. A new approach to characterise CAF processes has been developed using a Simulated Test Vehicle (STV). The STV, can be easily built under controlled condition in the laboratory using different glass fibres and resin power to investigating effect of different variables on CAF separately. The advantage of STV was described and examples of material studies that can be undertaken presented.

This webinar covered: What is CAF?  |  How does failure occur?  |  Testing techniques  |  Testing performance  |  Failure modes  |  Design and its impact on CAF  |  Latest research work on CAF


The Future of High Temperature Interconnect
Wednesday 16 September 2015

The ELCOSINT collaborative R&D project has focused on high temperature electronics aiming to have a significant impact on energy efficiency and the environment. Over the last three years the project partners Microsemi, NPL and Gwent Electronic Materials (GEM) have successfully developed innovative materials specifically designed to offer an alternative for high Pb content materials to further increase the operating temperature of electronic assemblies. These materials will be suitable for operating at temperatures above 250 ºC utilising standard manufacturing processes which until now have been a road block for high temperature interconnects in, for example, SiC applications.

This webinar covered: Development of Materials  |  The Demonstrator Product  |  Testing and Results

Practical Applications of Carbon Based Nanomaterials in Electronics
Monday 14 September 2015

The extraordinary properties exhibited by metallic carbon nanotubes (CNT), which arise from their perfect self-organised crystal structure, make these materials attractive candidates for electrical interconnects. This webinar looked at methodologies being developed for implementation of CNT interconnect systems, synthesised at low temperature, in accordance with the ITRS roadmap. Another key aspect for industrial take-up is the development of dependable tests of performance and reliability which, due to the unique material properties, will require innovative metrology. The challenges in this area were presented and the possible solutions discussed, and included advances made in this area to date.

This webinar covered: Properties of CNTs  |  Adhesion of CNTs to surfaces  |  Conditioning of CNTs in order to improve adhesion  |  Wetting of CNTs with solder  |  Interconnections using sintered silver  |  Reliability testing of CNTs  |  Health and safety: what are the risks?

Tin Whisker Mitigation Measurements using a Test Vehicle based on a Printed Circuit Assembly
Monday 13 July 2015

Conformal coating of assemblies has been pursued as a mitigation strategy for tin whiskers by a number of organisations across avionics, space and other high reliability applications. NPL has led a number of collaborative projects with industry to develop test vehicles to enable measurement of the effect of applying mitigation strategies to tin-plated copper. NPL, along with 15 industrial partners, has developed a new test vehicle based on specially plated SOIC components mounted onto PCBs, allowing the coating challenges of an actual surface mount assemblies to be tested. During trials on test vehicle assembly methods, the effect of different thermal profiles on whisker formation has been determined. The project is now in the final phase of long-term testing of a range of mitigation strategies. Over 2,500 components have been coated for the study using 20 different conformal coatings covering acrylics, polyurethanes, urethane acrylates, paraxylenes, fluorocarbons and silicones. Analysis of the uncoated control assemblies and early prototypes has given valuable data on how whiskers cause shorts and intermittents to develop on unprotected printed circuit assemblies. The importance of the frequency of testing has also been determined. Details of early failures in coated samples are also given.

Characterisation and Life-time Prediction of Printed Electronics Interconnects
Monday 11 May 2015

The Electronics Interconnect Group of the National Physical Laboratory has been involved with characterising printed electronics systems for more than a decade. Initially evaluating conductive adhesives for SnPb replacement, this led to collaborative projects in developing highly recyclable printed circuit assemblies (ReUSE) based on printed conductor tracks, dielectrics and conductive component attachment. Subsequent collaborative research has included performance and lifetime testing of carbon, silver and graphene printed inks on flexible substrates such as PET and PEN. More recently, we have been investigating methods for interrogating wet inks to determine their fully cured electrical performance and also looking at printed electronics defect characterisation and detection. Current projects include characterisation of electrochemical inks and investigating methods of defect detection for high-speed printed electronics manufacture. Examples of our work over the last decade in developing a suite of measurement techniques for characterising printed electronics systems were given. Details of the characterisation and testing services for printed electronics interconnect that are available at NPL were detailed.

Smart Textiles for Wearable Technology
Monday 16 March 2015

There is an increasing demand for wearable electronics from industries such as sport and fitness, consumer electronics, medical and healthcare applications. Smart textiles with wearable technology have the potential to change the way we manage our health, respond to emergency, communicate and entertain ourselves.

Currently, weaving or knitting a metal wire is the most commonly-used method for making a conductive textile. However, true wearable technology should be integrated within the clothing with maximum comfort and minimum visibility. The conductive textile solution we present here could make this possible. Currently, there are significant challenges for wearable electronics which needs to be overcome, e.g. a critical performance metric for future smart textiles is the ability to withstand multiple wash cycles. Also, there are environmental concerns regarding the release of metals in the form of nanoparticles.

This webinar covered: Why wearable technology?  |  Market opportunities  |  Limitation of existing processes  |  Available manufacturing techniques  |  Advance techniques fabric technology

Laser & Robotic Iron Soldering for Electronics Assembly
Monday 19 January 2015

Over the past few years there has been a lot of discussion on the need for higher temperature materials and expanding the use and knowledge of high temperature assembly techniques. In many industries there is also increasing interest in automating these soldering processes, rather than the traditional manual soldering techniques for small and medium volume. When we start to talk about high temperature electronics, it is not just the solder alloy, but all of the materials that go to produce an electronic assembly. Substrates, components, connectors, cables and solder need to be examined; the needs of the assembly process also require careful consideration.

Often, due to the smaller volumes, many companies who require high temperature capability have used manual soldering techniques, particularly for through hole. Typically, the industries affected by these hostile working conditions include aerospace, automotive, petrochemical and military. Laser soldering and robotic iron systems are increasingly being investigated for use in factories and, due to the limited availability of information, NPL has started looking at the benefits of these techniques.

This webinar covered: Reasons for laser and robotic soldering  |  Equipment considerations  |  Soldering with high temperature solder alloys  |  Intermetallic formation  |  Impact of ageing  |  Inspection of solder joints  |  Common process defects

Last Updated: 1 Dec 2015
Created: 20 Jan 2015


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