There are cases where older legacy components do not meet the solderability requirements for PCB assembly. This could be due to either contamination on the components leads or severe oxidation. Lead tinning describes the tinning or solder coating of SMT, through hole and odd form electronic components to mitigate this lack of solderability. BEST provides such lead tinning services.
Lead tinning for solderability makes sure that the component solderability is acceptable and can be used for placing in to automated assembly equipment including wave , selective or reflow soldering. In many cases the oxidation or contaminated layer needs to be removed and or cleaned prior to the lead being dipped in to the processing alloys. When the process is ably controlled a uniform , solderable surface finish is presented and it can then be used in the automated assembly process. Part of the retinning process in these cases involves the cleaning of the parts, inspection and re-packing them in to reel/tape, matrix trays or other packages.
In many cases the refurbishing of legacy components via lead tinning is accomplished after a design of experiments augmented by the company’s experience is performed. This leads the process engineers to the correct flux chemistries and subsequent cleaning and process parameter selection in order to make this process sustainable. Legacy components may have been in storage for many years and may require process development steps for the refurbishing of these legacy components. Lead tinning for solderability improvements will refurbish these legacy component surface finishes.
A common example of how this lead tinning refurbishment service works is that a customer, having to go ahead with building a very old design using obsolete and excess inventory, opens the component packaging only to find that the leads have a severe oxide layer formed around them. This oxide layer is thick enough such that the leads do not meet the solderability requirements. A wetting balance measurement, made per IPC J-STD-002 is made to confirm the lack of solderability. In other cases unauthorized distributors can send parts in to the user only that the user discovers that they have unsolderbale components. The refurbishment of these legacy components begins by running samples using a variety of different flux and cleaning solutions followed by hot solder tin dipping them in the appropriate soldering alloy with the intention of replacing the old finish with a fused intermetallic finish. Finally, after the lead tinning process is “dialed in” the wetting balance test confirms an increase in wettability.