Incorrect Nickel Plating Thickness 1

[rockey1]

Hi.

My company has recently started silver plating aluminium and after microsectioning a batch of work pieces we have found that the nickel plating layer we have set down before the silver is coming out at a maximum of 16% above our maximum theoretical tollerance.

So. I have set about trying to find out where we have gone wrong. Making our calculations a bit more accurate reduced the error by about 3% and we are now plating a test piece so we can see how much ally comes off with the Nickel when we chemically remove it to try and find out how far the Nickel is getting into the ally to see if we need to alter our plating thickness calc.

My question, to anyone who can help, is "am i missing anything?". I am a newb to this sort of work and am building up my understanding as i go so any help would realy be appreciated.



Kind regards and thanks

Keiven Smith

http://www.credowan.co.uk/

 

[belowzero]

I am a little confused on one hand you mention that you are sectioning the test piece and then on the other stripping the nickel off.
The two are obviously very different.
I summize that it was on the cross sectioned part you found the 16% discrepancy!
Are these round pin like components and is that 16% overall or on the one side?
B

 

[rockey1]

belowzero.

Thanks for getting back to me. Sorry if i was unclear.

We make waveguides. Basically just hollow tubes connected together with flanges and joints. We have taken cross sections of various waveguides: 2 accross a flange joint; 2 accross a lap joint on a collar; and 1 cross section through the tube itself, on each waveguide we have tested.

Analysing these sections we have found that our nickel plating thickness is always on the top end of our tolerance and often over. We are aiming for 20 microns +/- 5 and finding that our minimum is 21.8 and our maximum is 29. This discrepancy is fairly evenly distributed over the microsectioned flange joints, lap joints and the internal and external surface of the tube.

I mentioned we are running a test piece through plating and it is this test piece only which we are chemically stripping the nickel layer off. This is to establish how far the nickel is getting into the alluminium to see if it is something we need to consider.

I am thinking that our submersion time in our baths is slightly off and am trying to figure out why.

Kind regards and thanks

Keiven Smith

http://www.credowan.co.uk/

 

[belowzero]

Most of my silver plating experience is with a base of Beryllium copper on connector pins and other electrical components, Plus lots of other types of plating.
If the plating has a uniform thickness throughout and this is higher than you require then obviously the components need less time, however you did state that your minimum was 21.8 which means that you can only go down 6.8 microns before you compromise your minimum (15.0, this would make your maximum 22.2 but your sailing close to the wind for rejects and re-plating expense on the lower side. Do you have a reliable plating process working for other components?
I would suggest more is better than less, as your components are quite large anyway, can you work out the additional cost of silver and add this to the component cost before you compromise the component with a under spec thickness?
B

 

[rockey1]

belowzero,

Thank you for your help over the last couple of days. I realy appreciate it.

I have now found the problem.

I found out some information which would have been realy helpfull to me from the srart but nobody here decided to tell me until i asked the right questions. The Nickel we use is not pure Nickel. Maybe i should have assumed this from the start but as i said i am new to this. The Nickel we used in the past was a low level Phosphorous doped alloy and we recently changed to a higher level of Phosphorous doping because the lower level is quite brittle and was forming cracks during certain calibrations.

We were using the density value for the purer Nickel in our calculations which was throwing our values for how long we keep the items in our baths off by the ammount i mentioned before. Altering our calculations to follow reality should put our range of values back within spec. I should find out whether the alteration has had the desired effect at some point today.



Kind regards and thanks

Keiven Smith

http://www.credowan.co.uk/