Purpose -The purpose of this work is to undertake a comparison of accelerated test regimes for assessing the reliability of solder joints, in particular those made using lead-free solders. Design/methodology/approach -Identical samples of 1206, 0805 and 0603 resistors were subjected to six different cycling regimes to investigate the effect of thermal excursions, ramp rates and temperature dwells. Findings -The most damage to joints was found to be caused by thermal cycling between 255 and 1258C, with a 108C/min ramp rate and 5 min dwells. Large thermal excursions were shown to give faster results without compromising the failure mode.Research limitations/implications -Similar degrees of damage in the lead-free solder joints were experienced from thermal shock regimes with ramp rates in excess of 508C/min. However, these regimes, although faster to undertake, appeared to cause different crack propagation modes than observed with the thermal cycling regimes. However, these differences may be small and thermal shock testing may still be used to differentiate between, or enable ranking of, the effects of changes to materials or processes on the reliability of the solder joints. Hence, it is envisaged that if a wide range of conditions are to be tested a first sift can be completed using thermal shock, with the final work using typical thermal cycling conditions. Practical implications -The difference between the SAC (95.5Sn3.8Ag0.7Cu) and SnAg (96.5Sn3.5Ag) solder alloy results across all types of cycles showed very little difference in the rates of joint degradation. Originality/value -This paper compares relative reliability (remaining shear strength) of three chip components soldered with two lead-free alloys based on various thermal cycling conditions.

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An increase in the market growth of conductive inks for flexible and printed electronics is predicted to increase from $2.3 billion to $3.2 billion by 2025 (Savastano 2015 Printed Electronics Now). For quality and process control, in order to maintain output yield and reduce waste, it is critical that we are able to verify the electrical properties of printed electronics. This work explores a non-contact technique developed to measure the electrical properties of the printed structures during manufacture in a rollto-roll process. Inductive sensors are used to measure the electrical response of electrically conductive printed samples. The impedance of the inductive sensors are affected by the eddy currents induced in the printed samples. Six sensor designs, each operating at a unique measurement frequency are discussed. The effect of the measurement frequency on the measurement of a variety of samples with varying values of sheet resistivity is investigated. For implementation into a roll-to-roll process, the system must operate at high speed, therefore a low-cost method to achieve this is introduced and demonstrated. REVISED

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