Summary for toc levels in acid copper baths Discussion
TOC levels in PCB acid copper baths are discussed in response to a PCB manufacturer asking whether a vendor’s suggested 5000–6000 ppm operating range is acceptable, since the user had only seen guidance below 4000 ppm. David explains that there is no absolute TOC tolerance for an acid copper bath because the effect depends on the specific organic contaminants present. He notes that some harmful organics can damage the bath at under 100 ppm, while some harmless organics may be present above 1000 ppm without significantly affecting plating. His advice is to determine the acceptable TOC level for the specific process by testing the actual sources of organic leach-out, such as dry film photoresist and plating additive by-products, and then running reliability checks like elongation/tensile strength, Hull Cell, and IST at different TOC levels to find where performance degrades.
Q. Hello,
We are a large PCB mfg. We are currently reviewing our plating procedures and are discussing TOC levels in the baths. I an familiar with TOC levels being maintained below 4000 ppm but one of our vendors is recommending 5000 to 6000 ppm as a normal operating range. Does this sound acceptable? I have been unable to find any information where baths were maintained at such high levels.
Jason Svoboda
PCB mfg – Samutsakhon, Thailand
October 2, 2012
A. Hi Jason,
There’s no absolute TOC (total organic carbon) tolerance of acid copper bath because it depends on what kinds of organic contamination. Some harmful organic contaminants even present in very small qty (<100 ppm) can spoil the bath while some harmless organic contaminants even above 1000 ppm may not affect plating performance significantly. Therefore, you need to base it on your own process (those can cause organic leach out into your acid copper bath such as dry film photoresist, plating additive by-product, etc.) to figure out TOC tolerance (you need to perform reliability test such as elongation/tensile strength, Hull Cell ⇦ huh?
, IST, etc., at different TOC levels and define TOC tolerance at which reliability performance will turn bad when TOC reach such tolerance level).
Regards,
David
David Shiu
– Singapore
October 21, 2012