Sven Lamprecht

An investigation of the recommended immersion tin thickness for lead‐free soldering

Purpose – This paper describes the different thickness measurement techniques that enable reliable thickness assessments, and the determination of the recommended immersion tin thickness for lead‐free soldering.Design/methodology/approach – Immersion tin layers were prepared with systematically varying layer thicknesses. The samples were annealed at different reflow profiles, used in assembly for tin/silver/copper (SAC‐alloy) soldering. The layers were characterized with X‐ray fluorescence, electrochemical stripping coulometry, and by examining the cross sections using a scanning electron microscope. The solderability of the samples was determined with a solder balance (Solderability Tester Menisco ST60) using a SAC‐alloy (melting point 217°C) with T(max) at ΔT=28°C and ΔT=43°C above melting.Findings – If all pure tin is converted into the Sn/Cu IMC, so that no pure tin is left as solderable layer, the wetting behaviour will decrease dramatically. Especially for multiple soldering processes, two times ref...

“Green” PCB production processes

Purpose – The purpose of this paper is to show production process developments and innovations that resolve many of the issues faced with certain process steps for printed circuit board (PCB) manufacturing following “green” practices.Design/methodology/approach – Several key PCB manufacturing processes have been developed or studied with respect to new environmental legislations and practises.Findings – The introduction of new legislations designed to protect the environment require changes to laminate materials, solders, and PCB manufacturing techniques. The effect of new laminate materials on the desmearing and metallising processes have been assessed and recommendations given. The effect of increased thermal stress on plated copper has been assessed. Developments in adhesion enhancement for black oxide alternatives have been made and are presented with their suitability for the newer green laminate materials. The development of a new laminate manufacturing technique to reduce environmental impact is in...