National Physical Laboratory

High Temperature Electronics Interconnect

The Electronics Interconnect (EI) Group of the National Physical Laboratory (NPL) is involved with characterising interconnect systems for electronics operating above 150 ºC, which include avionics, oil drilling and automotive.

©iStock.com/Fertnig
©iStock.com/Fertnig

The Group is developing a suite of metrology methods to enable improved manufacturability and lifetime prediction of alternatives to high Pb content alloys. Key process variables in a range of interconnect systems including high temperature conductive adhesives and sintered silver materials are being characterised and combinatorial metrology tools for assessing fitness for purpose are being developed. Methods in identifying degradation in material and electrical properties are being investigated.

The current topics and outputs are:

Practical guide to soldering PCBs with high temperature solder alloys

ELCOSINT project

TAMESSA project

Sintered interconnects

Overview of operating at elevated temperatures


Practical guide to soldering PCBs with high temperature solder alloys

High Temperature Electronics Interconnect - Fig 1

High Temperature Electronics Interconnect - Fig 2

High Temperature Electronics Interconnect - Fig 3

The EI Group has produced a good practice guide to high temperature electronics, which not only considers the solder alloys, but all of the materials that go to produce an electronic assembly. Substrates, components, connectors, cables and solder are considered, as well as the needs of the assembly process.

Download the guide


ELCOSINT project

The ELCOSINT project has developed novel polymeric, sintered interconnection materials for electronic assemblies specifically designed to replace high-Pb content materials and further increase the operating temperature of electronic assemblies. The multi-disciplinary project team (Micro-semi, Gwent Electronic Materials and NPL) has developed the materials and manufacturing process for electronic component interconnection using nano-silver based materials to form joints between components and substrates. The technology is compatible with standard microelectronics manufacturing process enabling fast take-up.

View the webinar : The Future of High Temperature Interconnect

There is also a dedicated website for this project with the partners: http://www.elcosint.co.uk/


Tamessa project

High Temperature Electronics Interconnect - Fig 4

The Tamessa project represents a step change in harsh environment electronic assembly. The project is developing an integrated system that will reduce the need to use expensive and heavy ceramic technologies in applications up to 225 ºC and allow the integration of bespoke through hole components. OEMs will benefit from 30% reduction in board cost, 50% reduction in board weight and 93% reduction in tooling NRE cost. Energy cost associated with manufacture are significantly reduced. The project will develop a novel polymeric, resist and conformal coating materials, together with innovative usage of organic substrates and advanced component interconnect. When combined with MSL's advance manufacturing, the assembly method will allow manufacture of low cost mixed tech organic PCBs capable of operation at >225 ºC. The technology will be demonstrated by the assembly of real-world test cases in a bespoke pilot assembly line commissioned at MSL.


Sintered interconnects

High Temperature Electronics Interconnect - Fig 5

NPL is working in characterising sintered materials for surface mount attach. Preliminary work in this are is described in the NPL Report MAT 64: High temperatures solder replacement to meet RoHS. The report describes assembly issues and characterisation techniques. In the future, NPL will develop tools to measure stress/strain behaviour at elevated temperatures for interconnect structures, and characterise the degradation mechanisms.


Overview of operating at elevated temperatures

©iStock.com/HeliRy
©iStock.com/HeliRy


©iStock.com/Cogal
©iStock.com/Cogal

Electronic circuit assemblies are ubiquitous, and are a contingent part of an incredibly wide range of products and applications. A common feature of electronic assemblies is that the components are attached with solder, a tin-based alloy. The 2006 RoHS 'The Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment Regulations' restricted the use of lead, which resulted in a new family of solder compositions. There were, however, exemptions, and paradoxically an alloy with >85% lead was allowed because of its high melting point, and there being no known alternatives. In 2013, RoHS was recast with modified restrictions and new exemptions and, importantly, it stated for the first time that all exemptions will automatically expire after five or seven years, unless they are renewed. This has put a lot of pressure on industry, which needs certainty in its product portfolios over long time periods. One of the exemptions - 7(a) Lead in high melting temperature type solders (i.e. lead based alloys containing 85% by weight or more of lead) - could therefore be lost. These high temperature solders have long been used in hierarchical soldering for attaching silicon die within components. Furthermore, there has been an increase in the demand for high temperature interconnect solutions at circuit board level joining with recent introductions of high power semiconductors and increased operating temperatures. In addition to the aero engine and downhole applications, important areas for interconnect operation in harsh environments include transportation (automotive and marine engine emission and turbo charger sensors, electric and hybrid vehicle power management systems) and renewable energy power management.


Contact

For more information on high temperature electronics at NPL, please contact Martin Wickham

Last Updated: 29 Sep 2015
Created: 29 Sep 2015

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