hello everyone
I will be so grateful if someone gives me a solution. I worked on adhesion of decorative coating on faucets and I face a problem. our process is electroplating and Ni shows good adhesion in sharp edges or blind corners while Cr does not deposit in these sites. I tried different direction of immersion but it didn't change at all. on the other hand, I used CAPVD process to deposit TiN after electroplating and the coat doesn't have sufficient adhesion exactly in those spots.
does anyone know that how could I improve the deposition of coating in blind spots and corners?
yours faithfully,
Hi Saba Khoramkhorshid
I don't have any idea about electroplating of Cr,
but about PVD Coating of TiN;
you should use suitable pre cleaning and after that you should use glow discharge cleaning before coating.
if you have done all of this, try to use glow discharge cleaning in more period of time, for example 8 min.
bias power supply is also important that should not be arced ( more current = non voltage).
Mostafa
Dear Saba Khoramkhorshid ,
I can suggest two alternatives.
The first one is another PVD technique: sputtering. You can use a relatively high pressure of argon to sputter titanium or chromium: with high pressure the atoms suffer several collisions before reaching the substrate and as a result they can cover blind spots.
The second route is a chemical one: Atomic layer deposition (ALD), which uses precursors and it is great to obtain conformal films. Although is commonly used to deposit metal oxides, there are processes to obtain pure metals as for instance Cr:
https://doi.org/10.1021/ja407014w
Hello Saba
As far as I know about metal growth, they do not all have the same preferential growth sites or directions. For example, like in your case, having a good adhesion for the Ni does not mean it will also happen with Cr. What I can advice concerning the Cr deposition is performing a surface pre-treatment prior to electroplating. I am more an expert in plasma pre-treatments but you should consider that this pre-treatment should not alter your faucets topography. This pre-treatment will be like a 'surface activation' that could create nucleation sites for your Cr on top of the desired areas and will enhance Cr adhesion (weak bonds, nucleation,...). I am quite sure that such pre-treatments exist in the literature so you can have a look.
As for TiN deposition by CAPVD, before anything check if yourdeposition parameters are well optimized. Because generally adhesion problems of PVD coatings come from using non optimized conditions. I can give you an example that I have faced during gold deposition by PVD: the Ar pressure (in plasma) was too low and there were not sufficient reactive species that are bombarding the target, so the film was thin, dense, fragile and with really bad adhesion. When we increased the Ar pressure, the elaborated films were stable, thicker and with really good adhesion even for elecrochemical tests. So you can perform a little parameters optimization to see if your TiN could be more adherent. Another alternative, since your TiN is deposition, is to perform a post-treatment (like annealing for example). Usually I do not support this step because it can oxidize the film (if the annealing is not exempt of O2), it can induce film sintering or cracking and it could also modify the film's cristallinity.
Well I hope this could help you,
Regards
Loraine
Loraine Youssef
hello dear Loraine
thanks a lot for your noteworthy guide. I will change the used parameters of CAPVD and I will report you the results.
thanks again
Saba
Mostafa Kargar
dear Mostafa Kargar
unfortunately, changing bias voltage does not solve the problem. I will use your advice to increase the time of pre-cleaning
thanks a lot
Saba
Jose-Miguel Garcia-Martin
dear Jose-Miguel Garcia-Martin
I am so grateful for your recommendation. as you recommend, I will change the Ar partial pressure and I will let you know the result. thanks a lot for your cooperation.
best regards
Saba
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