Reading time words. Any components not lead-free approved were verified by X-ray fluorescence testing on receipt. Alternatively, the component change could be rejected and remedial action taken. The PCN review procedure was extremely useful in indicating industry assembly and material trends. Fox showed a range of component package styles, together with the acceptance tests and mitigation strategies for each type, including PCB design rules defining minimum component lead spacing. He also discussed the attributes of a range of conformal coatings: acrylic, polyurethane, silicone and parylene.
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Reading time words. Any components not lead-free approved were verified by X-ray fluorescence testing on receipt. Alternatively, the component change could be rejected and remedial action taken. The PCN review procedure was extremely useful in indicating industry assembly and material trends.
Fox showed a range of component package styles, together with the acceptance tests and mitigation strategies for each type, including PCB design rules defining minimum component lead spacing. He also discussed the attributes of a range of conformal coatings: acrylic, polyurethane, silicone and parylene.
Returning to the subject of component finishes, he commented on the debate as to whether the reflow process reduced or increased the propensity of tin to whisker, and concluded that if there was any doubt or there was a contractual obligation not to use tin, then refinishing of components was justified, using a controlled solder dip process that met the requirements of GEIA-STD Dr Mark Ashworth returned to deliver his second presentation on research at Loughborough, this time focused on post-plating mitigation methods.
Three different techniques had been investigated. The coupons had been periodically inspected for whisker growth using a stereo microscope. An order of magnitude reduction in whisker growth had been demonstrated and the increased-thickness oxide layer had been observed to be still effective at mitigating whisker growth after three years. The third approach reported by Dr Ashworth was atomic layer deposition, a proprietary thin film coating method using a self-limiting gas-phase chemical reaction to achieve thicknesses at the nanometre level.
A range of pre-treatments and process conditions had been investigated. Coated and control samples had been inspected over a month period using optical and scanning electron microscopy and significant reductions in whisker growth had been observed. There had been several mentions of component refinishing during the seminar, in the context of the requirements of the GEIA-STD standard. Addressing the issues of continuation of supply and development of best practice, Mark Walmsley described how Micross Components had set out to develop and qualify an automated process for hot solder dipping electronic components that was compliant to the GEIA specification.
The outcome was a seven-axis, multi-functional robotic machine with controlled pre-heat and the capability to manipulate and position its robotic arm to within 0. The machine offered a choice of conventional wave, side wave or flat pot soldering, with control of depth, dwell, entry and exit speed, solder angle and exit angle, followed by controlled cool-down and in-line washing.
The qualification of process and equipment to the GEIA standard was undertaken in partnership with the University of Greenwich for mathematical modelling of package reliability, and National Physical Laboratory to investigate terminal finish and reliability. And confocal scanning acoustic microscopy detected no degradation after hot-solder-dip processing.
NPL selected 25 devices from RoHS-compliant sources, representing QFP, BGA and through-hole package types, and these were characterised before and after re-termination by X-ray fluorescence spectroscopy, micro-sectioning and optical microscopy, solderability testing, BGA ball shear measurement, scanning electron microscopy and scanning acoustic microscopy. The re-terminated components showed solderability equal to or better than the original components.
Ball shear results for BGA components were acceptable, scanning acoustic microscopy did not locate any differences between original and re-terminated components, and thermal cycle solder joint reliability was improved for re-terminated components compared with tin plated originals.
Micross had undertaken a two-year exercise with six industrial partners and two academic institutions to develop a European source for hot solder dipping. A number of technical papers had been published, and the overall conclusion was that hot solder dipping components was not a major risk to electronic components. The presenters were happy to be interrupted with questions and many interesting points of discussion were raised. And the coffee and lunch breaks presented abundant networking opportunities.
To contact Starkey, click here. Remember me. Resend confirmation instructions. Toggle navigation. The new chapter is just the latest addition to this global effort from 23 working groups contributing expert input from all aspects of the electronics industry. Increased digitalization and greater connectivity have been driving miniaturization and more complex and integrated designs in electronics. As the real estate on PCBs shrinks, so does the size of packages. However, the drive for finding design solutions for increased performance has continued to expand.
The solder joint is an essential part of assemblies for electronic devices as it provides electrical, thermal, and mechanical connections. Therefore, soldering materials have been evolving to enable such a technological revolution. All rights reserved. Close Menu.
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Pb-Free Electronics Risk Management (PERM) Council