Metal Finishing Guide Book

2013

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troubleshooting, testing & analysis TROUBLESHOOTING ELECTROLESS NICKEL APPLICATIONS BY JAMES WETHERALD, TECHNICAL SALES REPRESENTATIVE, ELECTROLESS NICKEL DIVISION OF RONATEC, C2C, INC., CARLSBAD, CALIF. Q: I have been told that passivating 13-8ph material prior to electroless nickel plating will cause problems with adhesion. Is this true, and if so, why? A: I am very familiar with electroless nickel plating over stainless steel. I have always passivated with HCL prior to plating. I would like to see a Woods nickel strike used between passivation and electroless nickel plating. If you are trying to activate bare stainless in the electroless nickel tank, you will need to use an electrolytic start for a few seconds so the stainless surface will begin plating. Q: Can a gold pattern with isolated features on a ceramic substrate (Pd activated) be electroless nickel plated and pass tape test? A: Please note that you cannot plate EN top of gold. Gold, like lead, is a poison to EN and it is not autocatalytic. Putting palladium on top of gold may make it plate, but adhesion will be poor. Q: Could you point me to a method for determining the % phosphorous in a thickness test panel from the electroless nickel process? A: 1. Analyzing phosphorus percent with ICP and AA are very inaccurate due to interferences and the form that phosphorus is in (phosphides). We have both seen very low and very high (chemically impossible) phosphorus levels from these methods. 2. X-ray analysis also gives inconsistent values due to the localized non-uniform distribution of the nickel phosphide complexes at the surface-meaning two local areas could have a higher and one lower phosphorus content, when the average of the Ni-P matrix is somewhere in between those two values. 3. All major EN suppliers have found that there is only one consistent way to analyze phosphorus percent. Using a spectrophotometer, the light absorbance of phosphorus is measured, which has a linear relationship to the percent of phosphorus in the deposit. This method is accurate and repeatable. Q: I am trying to find out the proper way to activate Thermcon 83 prior to placing part in an electroless nickel tank. The material is 25% copper and 75% tungsten. Do you have any suggestions? A: I am assuming you are using a RoHS-compliant electroless nickel (doesn't have lead or cadmium)? Tungsten can be tricky, and my experience has been limited with it when combined with copper. With that said, copper should act as a conductor once "set off " so I would suggest either an electrolytic strike (Woods) prior to your electroless nickel tank or electrolytically charging the electroless nickel by running negative current to the part and positive current to the solution with a 565

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