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Guru
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Masking Nickel Plate

03/01/2012 5:09 AM

I am looking at a part we need to make in thin molybdenum sheet. We want to braze this part to some metallised ceramics which we can do if we apply a nickel flash to the surface.

My problem is that there will be an area in the centre which will have a series of fine slots, like a venetian blind, these will be in the order of 40µm wide bars at an angle through the thickness of the sheet which is 125µm. The bars are on a pitch of 160µm.

As you can imagine, this area is quite delicate but has to be coated in a substance which can not be deposited onto nickel or have nickel covering it so it has to be masked during plating. Whatever mask is used will have to be removed to UHV standards of cleanliness but we won't be able to abrade or blast it without causing damage.

Does anyone know of a masking system that might work?

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#1

Re: Masking nickel plate

03/01/2012 5:36 AM

I'm completely guessing here, but it may get you on the right track.

I'm thinking along the lines of sheetrock mud. I think you call it spackling in the UK. Something along those lines that could be applied, heat won't bother it, you could fill the fine slots with it, and simply rinse it off with water when you're done.

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#2

Re: Masking nickel plate

03/01/2012 6:09 AM

I don't know anything about this sort of thing, but, I believe that Nickel plating needs to be done at high temperature, which could make many masking techniques fail.

I did a search for Kynar tape which is used to mask gold edge connectors on PCBs when flow soldering, and, found this stuff:-

http://www.mocap.co.uk/high-temp-poly-tapes.html

It might be worth talking to them.

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#3
In reply to #2

Re: Masking nickel plate

03/01/2012 6:46 AM
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#4

Re: Masking nickel plate

03/01/2012 7:29 AM

3M makes a line of platers tapes that I've used before. I don't know if they would work for you.

Here's two:

  1. Circuit Plating Tape 1280: 3M™ Circuit Plating Tape 1280
  2. Greenback Circuit Plating Tape 851: 3M™ Greenback Circuit Plating ...
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#5

Re: Masking Nickel Plate

03/01/2012 10:48 AM

There are masks available for nickel but the ones I have seen are lacquers & need to be removed by abrasion. My concern is for the delicate structure in the centre of our component. We use adhesive tape masks when we evaporate chrome & copper onto optics & have found it quite hard to completely remove the adhesive.

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#6
In reply to #5

Re: Masking Nickel Plate

03/01/2012 10:59 AM

Looks like you are going to earn your pay on this one.

Doesn't sound too easy.

Good luck.

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#7
In reply to #6

Re: Masking Nickel Plate

03/01/2012 7:08 PM

We don't do easy.

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#8
In reply to #7

Re: Masking Nickel Plate

03/01/2012 7:17 PM
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#9

Re: Masking Nickel Plate

03/01/2012 10:34 PM

If the slots etc. are machined in, could you plate the moly sheet or partially finish the moly component and plate before machining the slots in?

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#10
In reply to #9

Re: Masking Nickel Plate

03/02/2012 5:12 AM

It's a possibility. There are conflicting process requirements, the slots are laser cut & have to be done by holding a whole sheet of moly. The nickel could be applied to the whole sheet before cutting. I know that the chamber used for the other coating process is quite small & will only hold a few components at a time. I would have to check if there is likely to be any adverse chemical reaction to the nickel but it's a path worth investigating.

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#11

Re: Masking Nickel Plate

03/02/2012 8:16 AM

You might consider using a photo-resist like the semiconductor industry uses. It can be spun or sprayed onto the moly, exposed to light through a mask, and washed away where you want the plating. After plating, the remaining resist that protected the slots can be removed chemically or in a plasma cleaner.

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#12

Re: Masking Nickel Plate

03/03/2012 2:34 PM

Looks like the method we will try is to nickel plate the whole moly sheet first. Still not sure if the nickel will interfere with the later process applied to the laser cut slots but we only need the later coating on the angled faces of the slots so it won't matter if it does not take on the sheet faces. It will probably take a couple of months to get through all the processes but I'll try to remember to post the results.

As always, thanks for all the good advice.

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