Letter 42045

Through hole plating of PCBs

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Dear Sir,

I am W.A.P.L Wijesinghe (an Engineer)working in the Engineering Design Centre of University of Moratuwa, Sri Lanka. We basically carry out industrial automation projects and develop appropriate technologies for the country. Most of them involves high end electronic designs which incoperates so called surface mount components. But we are suffering from problems in manufacturing quality PCBs . The most severe problem is through hole plating. I searched a lot in the net and found some clues regarding the matter but that is not organised information. I collected enough information on the process information of different process.( I thank you,really a lot of information from your site disscussions as well) One method is silver activated ( not Paladium since it is too expensive and cannot be found in Sri Lanka) electroless copper plating. and the other is using a conductive ink to paint holes and electroplate ( acid/copper)later. If you can provide me with the correct concentrations of the silver/borate activation bath and the electroless copper bath. Or if you can provide me a chemical formula for making a conductive ink which can be applied to the drill holes of the PCBs and electroplate them later.

Thanks

Best Regards.

Wijesinghe Arachchige Pradeep Lanka Wijesinghe
University of Moratuwa - Sri Lanka

For cheaper PTH process, you can consider to apply either conductive carbon or conductive polymer follow by electrolytic copper. However, these processes may not have good reliability for high aspect ratio holes (thick panel and small diameter hole).

In fact, palladium catalyzation is not that expensive even though Pd metal price is much higher than silver due to the catalyst concentration is very low (~50-100 ppm Pd). Sometimes 0.1% more scrap rate on output is already cost more than saving on cheaper catalyzation. If you want to produce high end product, I strongly recommend to use Pd catalyst plus electroless Cu.

David Shiu
- Singapore

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