Plating of ABS Plastics; palladium and electroless nickel issues

A. Dear sir,
Your name is very familiar to me. For many years one respectable gentleman worked with me -- hope you are him.
For plating of polyester with palladium method, some precautions should be considered:
1 - polyester is usually filled with calcium carbonate which increases the pH of the solutions especially Pd sol'n. So it precipitates causing decreasing acidity.
2 - because of insufficient activation, platers tend to increase the reducing agent which is the main factor of instability.
3 - also they tend to increase the temperature, adding another reason of instability.
So if you are him please advise; in my next response I will tell you about a very economical and direct method to plate resin even if it's filled with calcium carbonate.

Regards

Raafat

A. Dear sir:

1 -If you insist on using silver nitrate in activation bath:
1a -It is not recommended to put it in the palladium bath because it will precipitate as silver chloride.
1b -The formula for using silver in activation bath is: silver nitrate: 2 gm/l sodium borates: 20 gm/l.
1c -In this case you have to use electroless copper or special types of electroless nickel.

2. Instability of new E.N bath may be due to:
a -insufficient amount of sodium citrate (complexing agent)
b -over amounts of reducing agent (hypophosphite)
c -overheating the bath
d -unsuitable stabilizer (we use lead nitrate)

So you have the word now.

Best regards,

A. Michael, I have no private formula for electroless nickel but it's my understanding that:

1-The activation metal [Ag ,Pd] it is very important to know the relation between the metal and the reducing agent in the electroless bath. Example, silver is not catalytic to the electroless nickel when hypophosphite is not catalytic to initiate or start the reaction but in borane (NaHB, Di methyl hydrogenborane [DMHB]) it will be catalytic. So the reducing agent plays a very important role.

2-The plating procedure for non conductors using silver in activation is as follows: 1-degreasing 2-etching 3-activation 4-electroless plating 5-electroplating.

Thanks and best regards,

A. Dear sir,

No need for sensitizing with [SnCL2] and the solution is very stable and there is no chance for explosive action.

Thanks and best regards,

A. Dear sir, Sodium borate is borax, which has the formula of [Na2B4O7.10H2O]. The activation cycle is simple:

1-etching
2-neutralization
3-activation in silver bath
4-rinsing [distilled water]
5-rinsing
6-electroless copper
7-electroplating

Thanks and best regards,

A. Dear sir,

1- Yes it is tetra borate deca hydrate.
2- Formaldhyde type is OK.
3- Never use HCl before any silver borate because there will be some traces of [Cl-] ions which will precipitate silver as silver chloride and that spoils the solution. And simply no need for that because [HCHO] will reduce silver [Ag⁺¹] to [Ag⁰] which is able to initiate the electroless reaction.

Thanks,

Dear sir,

I don't understand your response.

Best regards

Dear Raffat,

I mean in the conventional process when use fulminate silver as activator must use sensitizer step (SnCl2/HCl) to enhance absorption of fulminate silver (in fact reduce Ag(I) to Ag(0) ) and go to electroless copper. So if the sensitizing step is omitted the Ag species that absorbed on the plastic is Ag(1) and go to electroless copper (formaldehyde in electroless will reduce Ag(I) to Ag (0) ) so the activity will slow (covering time)? So I will ask that it has any process chemical to promote absorption instead of SnCl2/HCl or not?

Best regards,

A. Dear sir, we talk too much on this subject. Why don't you try to test our claims and tell me the results.

Best regards,

A. Dear sir,

Try to get ready-made silver borate because what you mentioned mean that [SILVER TRACES] found in the solution when you made activation.

Thanks and best regards,

A. Dear friends,

Sorry for lateness.

For first friend:
what silver activator added to us:
1-it is not expensive
2-it gives us ability to plate other kinds of plastics rather than ABS [polyester-p.v.c p.s high impact] etc.
3-not sensitive to changes of pH
4-it is very stable
5-no need for sensitizing with [SnCl2]

For second friend:
My formula [actually it is not my invention] is:
copper sulphate ⇦this on eBay or Amazon [affil links] 5 gm/L
triethanol amin 10 gm/L
formaldehyde 20 ml/L
pH>12 [adjusted with NaOH]
temp. room

You couldn't use this activator with E.N because silver is not catalytic to nickel when hypophosphite is the reducing agent

Thanks & best regards,

A. Dear Murat:

If you used bi-distilled water then no problem 2-if we used silver nitrate with ammonia ⇦this on eBay or Amazon [affil links] this a very strong complex [especially with excess of ammonia] unfortunately this complex is explosive and not safe so get pure borate & bi-distilled water and work safely.

Thanks,

A. Hi, Ti Na.

Lead chloride is never used as a catalyst as far as I know, and it would certainly fail RoHS requirements. There was probably a typo, and you probably mean palladium chloride, but get back to us if that is not the case.

In plating on ABS plastic, the plastic is etched for good tooth, then dipped in PdCl2 or a mix of PdCl2-SnCl2 or the two in sequence. These metals are catalysts for electroless copper or electroless nickel plating solutions, so that when the plastic is subsequently put into those solutions, the Pd molecules act as seed points to begin the plating. Electroless copper and electroless nickel are auto-catalytic, so as soon as the deposition starts, it will continue.

Please hunt for a copy of ASEP's "Standards and Guidelines for Electroplated Plastics" as it is a book that tells all. Good luck.
Regards,

A. Dear Ti Na
Etching:
As you know ABS contains butadiene, which is mostly Rubber. So when it is put in acids (chromic-sulfuric) it is dissolved. Butadiene is distributed in ABS as very nice and complete spheres, so it leaves spherical holes after etching.
Activation:
Palladium & tin chloride go inside this spherical hole, but only palladium is catalytic to Electroless Ni & Cu, so we have to remove the tin and that is what they call "acceleration".
Now the palladium atom is inside the spherical hole and it is catalytic to electroless Ni & Cu, so when it attaches to electroless solution. metal starts to deposit on it so the hole will be closed with metal and start to deposit out side the hole so we can get a continuous metal layer after some time; it will be layers because of autocatalytic nature of the deposit to the electroless solutions. So now it is conductive, and we can go to electrical baths, and good adhesion since the hole is a sphere.
Hope I was clear and you got some help.
Best regards,

Raafat

A. Dear Mr Sheikh
What we talk about is the oldest way for plating of plastic.
Mr. Ted explained one of the best and most popular methods, but now you can find direct metallization (without electroless plating) replaced with what is called (copper link); also you can find direct metallization with semi conductors method without palladium and without electroless baths too -- who knows what will happen in the next hour. My advice to you is to use this method on not smooth substrate (polyester, fiber glass, etc.), but if you insist to use this method then use silver nitrate without any added salt -- just with distilled water. Then tell me what happen. BEST WISHES
Raafat

---

Thanks for coming back to update us, Raafat! My knowledge of current technology is mostly "book knowledge", as I don't get out in the field a lot like I used to. I've been following the subject of direct metallization in the trade press, but did not realize that it was so widely implemented already.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Thank you Mr Ted. It is my pleasure to be here.

Raafat Albendary
national techniecs - Cairo-Egypt (but now I'm in Riyadh, Saudi Arabia)
May 2, 2012

Hi Naveed. Please explain your situation. I don't want to misunderstand the question. Thanks.

Regards,

A. pH is usually kept above 11 or 11.5.

Welcome, Sonu. Please contribute a Q or A.

Regards,

A. Hi Yogesh,

I can't stress this strongly enough, but get a consultant in to help you. You are just beginning the journey and you cannot be expected to know all there is to know about electroless nickel plating.

Saying that you need to tell us the conditions you are currently using for us to be able to really help (in as much as an anonymous website can help). You need to let us know concentrations, operating times and temperatures, any potential delay times between steps etc before any sensible advice can be given.

Finally, get hold of a couple of good books on the subject and read up about the subject. If you go to the library section of this website you will find a list of good books/recommended reading for electroless nickel.

Best of luck.

A. Dear Sir
1- When plastic part comes from the injection machine it has electrostatic charge; this charges adsorbs dust particles, also hand grease because of handling. All these contaminants need to be degreased so degreaser bath is needed.

2- Etching solution will dissolve the Butadiene so it will make a cavity; some chrome atoms will stick inside this
cavity so it should be removed or at least reduced to be easy to remove before activation. Otherwise it will affect the adhesion (50 gm/L of sodium bisulphite will work).

3- Before activation it's maybe better to put HCl bath in the same concentration as activation bath to precipitate or react with any impurities that will harm the activation bath.
4- I'm not understanding what is the "wiping", so please advise.
5- Reading EN bath it's better to read the beginning of this question.
Thanks & best regards
Raafat

A. Not because I work for a supply house, but plating on plastic should not be "home brew". Palladium is too expensive for trial and error.
The supplier will also give you the required backup, plan the plating cycle (which is a long one for POP), etc.

A. This is to respond to whether there is an alternative to PdCl2 (Palladium activator) --
On many research paper and patents, it has been found that a few other metals are just as good as palladium for activating the surface. The least expensive that offers the same performance is Silver nitrate (Silver chloride is insoluble in water). Silver can be used as an activating surface both as colloidal solution (about 0.5 grams per liter) after sensitizing the surface with stannous chloride, or by reducing the silver amine complex (think about silver mirrors or The Brashear process). It does not need to be a thick coat of silver -- just enough to render the surface active enough. If it takes 5 grams of silver nitrate per litter to have a good quality mirror than by using 2 instead will render the surface active enough.

For activating colloidal solution: 0.5 grams per litter of DI water. This solution should go after the stannous chloride sensitizer(5 grams of SnCl2 add 20ml of HCl per litter of DI water) rinse and rinse again, the proceed to the plating tank (the piece should never be allowed to dry).