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Electroplated gold surface stain/brownish for Flexible Circuits

2003

Guys,

Currently I'm facing a major issue for the electroplated gold finishing.
I'm plating flexible circuit with end use as connectors, ACF and also soldering application.

The chemistry I'm using is nickel sulphamate (semi-bright Enthrone chemistry) and for electrolytic strike and hard gold I'm using Metalor chemistry (previously known as Engelhard).
The issues encountered during production is that the plated finishing is not robust meaning having brownish stain marks after plating.

My end customer controls zero detect and are extremely concerned on the cosmetic finishing.
The hard gold bath analyzed found gold cont :
4.0 g/l, pH :
4.8, Cu cont :
0.5 ppm, Ni cont :
5 ppm, Solution Density :
18 baumé which are the specified controls from the chemical supplier.

We have 2 final DI rinsing with the final rinse being Hot Rinse with the temp of 70°C.
The dryer used is an oven(minimal efficiency of air flow)type with the temperature of 90°C. (no cool air blower before hot air).

Due to our manual unloading procedure some touching into the gold plating area were encountered which also causes the brownish stains.

Would really like to know how to have
: 1) gold plated surface not to have brownish stain after drying.
Any help provided will be extremely valued.

SENTHIL NATH NEELAKANDAN
flexible circuit manufacturer - PENANG, MALAYSIA

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Brown stain is because of Organic contamination in the bath, or organics in the final rinse of DI water so, Carbon Polish the Gold bath and see the final water rinse is of conductivity less than 5 micro siemens. there is another chance , that you need to check the air in the oven whether it is free of oil or any dust etc, keep an filter to the blower, so that hot air is free of any contaminants. Hope this should solve your problem of brownish stains.

Panjala Mukesh
fashion jewelry mfgr.
Hyderabad, India
2003