Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

contaminated components



contaminated components | 10 May, 2004

We are trying to solder a Surface mount relay having lead free finish on the leads. The leads are not getting soldered down during the reflow. The leads also look oxidized (failed our solderability test) but we don't have an option but to use these relay. Is there any way we can remove the oxidation (chemical etc??). Please advise.

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contaminated components | 10 May, 2004

The three basic methods you can use to restore solderability on components are: * Highly active fluxes in a retinning operation. * Surface stripping chemistry and then a standard retinning operation. * Electrochemical conversion chemistry and then a standard retinning operation.

Keep in mind that none of the three basic methods work on everything and all are highly dependent on just what/amount of finish remains on the component lead and the amount of oxidation/corrosion that is on the component lead. * Highly active fluxes are good, but residues from poor removal methods can cause problems later on in the assembly. * Surface stripping chemistries (eg, Kester SolderNu) work well, but require protection to prevent the stripping chemistry from attacking component bodies. Stripping chemistries are specific to the surface (eg, copper, nickel, or alloy 42, etc.) to be stripped. * Electrochemical conversion is great, but level of cleanliness and some surface materials (eg, iron) can contaminate the electrochemical cell. ROSA cathode grids have an iron tolerance on the that requires periodic maintenance schedule attention.

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