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Measuring the reliability of technology demonstrator manufactured with isotropic electrically conductive adhesives.

Wickham, M; Zou, L; Hunt, C P (2006) Measuring the reliability of technology demonstrator manufactured with isotropic electrically conductive adhesives. NPL Report. DEPC-MPR 046

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Electrically conductive adhesives are attracting interest as a possible replacement for solder in the assembly of some electronics equipment. Previous work had demonstrated assembly reliability on test assemblies, and investigated the effects of ageing regimes, component and PCB termination materials. In this phase of the work, a technology demonstrator – a currently offered commercial product (fire detector) – has been manufactured using ICA materials. Subsequently, these assemblies have been subjected to damp heat stressing to ascertain the likely field performance, which has been benchmarked against that of a conventionally soldered system.
Whilst the reliability of the circuits assembled using the two ICA materials did not mirror that of the soldered circuits, their performance was encouraging, and certainly warrants further study. By optimising materials choice and process development, the CAs could find viable applications as a lead-free solder replacement. One ICA material produced joints whose reliability was close to that of the soldered joints - all the assemblies survived 1000 hours at 85%RH/85ºC, although two circuits required reworking of SOT23 components.
Processing yield issues were experienced using the two ICA materials, associated with the formation of shorts under some R0603 components. However, the fact that these were restricted to one component type and three specific locations, strongly suggests that they could be eliminated by normal process optimisation techniques. Components with few leads and small bond areas (e.g. SOT23) would benefit from additional mechanical support to improve their tolerance of mechanical handling.
The work has confirmed the suitability of using damp heat testing as a tool for assessing the reliability of joints made using ICA materials.

Item Type: Report/Guide (NPL Report)
NPL Report No.: DEPC-MPR 046
Keywords: ICAs, processing
Subjects: Advanced Materials
Advanced Materials > Electronics Interconnection
Last Modified: 02 Feb 2018 13:15
URI: http://eprintspublications.npl.co.uk/id/eprint/3689

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