Formance K has been developed to deposit pure, solderable silver layer on copper circuitry in compliance with IPC specification no. IPC-4553A. The deposit satisfies Class 3 final finish durability and is an excellent choice for demanding Pb-free assembly. Formance K is an easy to use product with simple analytical controls and straightforward replenishment that leads to lower running cost. Notably, the chemistry is EDTA- and alkylphenol ethoxylate-free and thus biodegradable.
Formance K is used in a standard immersion line, vertical or horizontal, incorporating the chemical steps of Cleaner, Microetch, Predip and Silver Bath with counterflow rinses in between. It is recommended to use an acidic cleaner appropriate for a final finish line (such as FinClean from RBP). The use of persulfate-based microetch is strongly recommended as it creates a better surface topography for immersion silver plating. An example of such microetch is Circutek ME-515 from RBP. Formance K Predip and Silver Bath are prepared from the components described below.
PreLam Cleaner is a cleaner/microetch/adhesion promoter for use on copper and other metals. It will give optimal resist adhesion both initially and during subsequent processing, where other chemicals can weaken the bond at the copper/photoresist interface. PreLam Cleaner yields a non-traditional looking panel with a bright orange color rather than a more typical matte pink.
A liquid persulfate-based copper microetch that is pre-mixed with sulfuric acid. ME 515L removes copper uniformly, providing good topography for subsequent processing. It can be used wherever a microetch is needed; prior to plating, resist lamination, solder mask over bare copper application, or solder leveling. ME 515L can be used in either soak or spray applications.