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Nickel sulfamate bath problem

Q. We manufacture printed circuit boards and our nickel bath is having an issue. When the boards come out they have crusty nickel at the knee of the holes. This is random and it will completely fill small holes. It looks like burnt nickel and will come off if you pick at it with an exacto knife ⇦this on eBay or Amazon [affil links] . There is nicely plated nickel under it so I believe this does not start as soon they are put in the bath.

Skip Mora
Manufacturer - Dallas, Texas, USA
February 25, 2009

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A. You have a high current density area at the sharp corner of the hole that you called a knee. This will form a surface that somewhat resembles cauliflower. A lower current applied will reduce this effect, but will lengthen your plating time. Do you have an option of putting a slight bevel on the hole. This will spread out the current density. An unpleasant thought is the use of shields or robbers. Electroless nickel may be your answer, but it is expensive. James Watts - Navarre, Florida February 26, 2009 A. We do not understand the build-up on the "knee" but assuming you mean the right angle between the thru-hole and the flat, you are describing what the industry calls "treeing". If you are agitating paddle-wise where you are forcing the solution rapidly thru the holes - that will favor the formation of "trees". Low pH favors trees, use 4.0 to 4.3. High ammonium ion from the breakdown of the sulfamate molecule will favor treeing. Metallic contamination causes trees. Be sure to "dummy-out" the copper contamination that comes from (1) your boards, and (2) the nickel anodes. Lower temperature, I favor 120 F, but 110 F is better for tree retardation. The list goes on - you need a complete analysis of the impurities. Robert H Probert Robert H Probert Technical Services Garner, North Carolina February 26, 2009 A. It could be a number of things but since you mention the nickel comes out burnt in those HCD areas sounds like a localized pH raise due to current density or agitation problem. How much boric do you have? Are you using chlorides or bromides for anode dissolution? Guillermo Marrufo Monterrey, NL, Mexico February 27, 2009

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Nickel Sulfamate bath -- pH dropping, anode going passive

January 16, 2019

Q. Hello,

I'm new to the forum and I'am having some issues with my plating bath. From reviewing past posts it seems everything should be going according to plan. But I'm constantly struggling to keep the pH from dropping and having the anode going passive on me. After the first batch deposition the pH rises as intended but following the first batch the anode begins to become passive and the pH begins to drop (3.8-->2.8). From my understanding the Nickel Bromide Ions in solution from the manufacturer should inhibit the anode from going passive. Is there a rate at which the Nickel Bromide leaves solution? Requiring the need to input more into the solution after the bath has been used for a given time? Perhaps this is the reason our anode is going passive? The electrical connection seems to be optimal, operating voltage low, the anode/cathode surface area is definitely above the recommended 1:1 or 2:1 but not too high as suggested against. When observing anode after 1 to 3 runs, a brown film is noticeable.

Additional Information:

-400 mL Nickel Sulfamate bath
-Per chemical MSDS - contains Bromide & Boric Acid
-Anode/Cathode ratio 4:1
-soluble S-Nickel anode
-Operating at room temperature 21 °C
-stir bar agitation
-pH from manufacture -> 3.8 - 4.2

Procedure
-HCl:DI = 1:1 - anode etch start of day for 10 min
-operating current @ .60 amps
-Electroplating operating time -> 30 min
-layer thickness -> 15 microns

Phil Dichero
- Houston, Texas

adv.  

"The Sulfamate Nickel How-To Guide"

by David Crotty, PhD
& Robert Probert

published Oct. 2018
$89 plus shipping