Nickel Sulfamate Electroforming

A. "snac-am", no such animal. Snap-am is sulfamate nickel anti pit, air mechanical. It controls pitting, not stress. Air mechanical is for heavy agitation and is used rather than regular snap which foams badly under those conditions. A stalagmometer is required to control anti pit level. Wire rings can be used on plain snap.

Snap does not control pH, SNAC, sulfamate nickel acid compound which is sulfamic acid is used to lower the pH. A properly operated tank will always rise, requiring acid to lower. A pH of 4 is desired. 4.0 ± 0.1 is not hard to maintain if it is attended to daily. Lower than 4 slows down the plate rate. Higher than 4 plates a little faster, but tends to cause problems.

Separation from your mandrel could be caused by stress or difference in the coefficient of expansion of the two materials. No adhesion from bad prep will also cause it. Porosity of the material has to be looked at. Normally, it would cause a problem or surface roughness of the plate or it could be picking up chemicals from the prep tanks and leaching out wherever possible causing terrible adhesion.

Heavy tarnish, I will interpret as darker plate. This could be caused by dissolved silver or copper or cadmium or a few other metals. This will normally be darker in lower current density areas.

There is a serious problem with sulfamate nickel if it comes out like a mirror. Proper parameters will give a nice bright matte or satin finish. ASF, agitation and temperature will affect the look some. Not knowing the shape of your part, it is difficult to comment on why tape appeared to give the results that it did.

One thing that could cause apparent porosity is pH. The boric acid is a buffer in the solution to control pH in the diffusion layer, a couple of millionths thick layer of solution surrounding the part. Plating tends to raise the pH significantly which forms nickel hydroxide which looks dark and porous in the normal plate. Check the pH procedures. A shocking amount of people do not properly care for their pH probe, so it gives wrong answers. Leaving the probe in nickel solution will allow nickel ions to permeate the frit giving a green look to the solution surrounding in inner "tube". This messes up the chemical reaction; that gives a bad pH reading. The pH of a hot solution is not valid unless you calibrated the probe at the same temp. Constant exposure to high temp shortens the life of the probe also.

Recheck your boric acid level. I guess that it is low.

Try to get copies of the old Barret papers or reprints that Allied Kelite did. Jerry Lightenen authored numerous papers on sulfamate nickel in his days with AK. Sorry Jerry, I forgot how to spell your name. I am sure that all of this passed to MacDermid when they took over AK. I disposed of mine when I moved and sort of retired.

A. Stochastic +"diffusion-layer" "normally"-current density areas . . model in Mathematics, that being Mathematical (statistical) Models to analyze the "epitaxial": diffuse-layers for Chemical-Engineers to normally be left unsearched in too many 'results' in or with current search-algorithms for the density of epitaxial-layers and related areas of research.

A. Hello,
I would make sure normal filtration is adequate. After a few filter tube changes, install a carbon pack (filter) and run for 2 hours then another carbon filter for the same time period. If the silver from the photoresist did not dissolve into the bath these measures should work. If there is silver in solution dummy plate at a low current density 3-5 ASF for 4-6 hours. After dummy plating the bath should get a full analysis to ensure any organic additives are within range.