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Electronics (Electroplating, Coating, CVD)

Electronics
Precious Metal Compounds for Surface Coating and Plating
Metals can be deposited on surfaces in the form of thin layers. These serve various purposes (partly in combination), such as:
• Resistance to oxidation and corrosion
• Mechanical protection, due to hardness
• Electrical conductivity.
Such requirements are mainly found in the fields of electronics.


Precious metals, mainly the platinum group metals (PGM's) platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), and the metals gold (Au), and silver (Ag), meet most of these requirements.
For example, the following fields use precious metal chemicals for deposits:
• Plating
• Thick-film technology
• Thin-film technology
Plating is the deposition of metals from aqueous solutions ("electrolytes") of their compounds ("salts") in a micrometer range by reducing the metal ions.
These electrolytes contain the metals in oxidized states. Reduction to the elements and deposition are only practicable either with a direct current flow ("Electroplating") or with chemical reducers ("Electroless Plating").
For electroplating, the parts to be metallized are submerged in the electrolytes as cathodes (reduction site). The anodes (oxidation site) are often made of platinized titanium or of the metal itself ("Sacrificial Anodes" of gold or silver, e.g. for cyanide baths). Depending on the types of the parts, the plating units use racks or barrels for holders.
Electroless plating is mainly suitable for workpieces of high complexity. The chemical reducer can be either a chemical compound (e.g. formaldehyde) or the non-noble workpiece itself.
For a better adhesion there is often need for an intermediate plating with base metals (e.g. nickel). And for specific physical requirements (color, hardness, etc.), the electrolytes themselves often contain further metals or additives.
Precious metal compounds serve to manufacture these plating electrolytes, but also to replenish just the metals that deposit from these electrolytes.


Furthermore, coatings are feasible in a silk-screen process with pastes containing precious metals. Then these deposits are fixed with heat (firing). This method is called thick-film technology and is mainly applied to electronics.


Thin-film technology is based on physical processes (e.g. sputtering); it plays a decisive part in electronics.
With "CVD" (Chemical Vapor Deposition) metals can be deposited from the vapor phase by applying highly volatile materials. If organometallic compounds are used, this method is called "MOCVD". Such processes are gaining importance in the field of precious metals.
Our Chemical Products business unit manufactures suitable compounds and their solutions as core products, which serve for the production and the replenishing of plating electrolytes, but also for thick-film technology, and for CVD processes.
• Platinum (Pt)
Pt forms comparatively thick deposits. In thick-film technology, Pt serves e.g. for the manufacture of lambda probes, which control the air-fuel ratio of engines. Organoplatinum compounds are conceivable for CVD.

For coating and plating with platinum, Heraeus manufactures important starting materials, e.g.:

• Dihydrogen hexachloroplatinate(IV) hydrate, H2[PtCl6]•nH2O ("CPA")
• cis-Diamminedinitritoplatinum(II) solutions, cis-[Pt(NO2)2(NH3)2] (solutions of "Pt-P Salt")
• Bis(acetylacetonato)platinum(II), [Pt(acac)2]
• Tetraammineplatinum(II) chloride hydrate, [Pt(NH3)4]Cl2•nH2O
• Dihydrogen hexahydroxoplatinate(IV), H2[Pt(OH)6]
• Potassium hexahydroxoplatinate(IV), K2[Pt(OH)6]
• Ammonium hexachloroplatinate(IV), (NH4)2[PtCl6]
• Potassium tetranitritoplatinate(II) K2[Pt(NO2)4]
• Palladium (Pd)
Pd plays an important part in the electroplating of relays, IC's (= integrated circuits), etc. For example, deposits of Pd alloyed with nickel show extraordinary resistance to corrosion, and therefore are used as primers to connectors. Furthermore, palladium can serve as an activator for top coats of base metals. Baths for electroless Pd plating are applied, too.

In thick-film technology, a large amount of Pd is used for the production of multi-layer ceramic capacitors ("MLCC's") and – analogous to platinum - of lambda probes.

Heraeus offers you for plating with palladium e.g.:

• Diamminedinitritopalladium(II) solution, [Pd(NO2)2(NH3)2] (solution of "Pd-P Salt")
• Tetraamminepalladium(II) chloride hydrate, [Pd(NH3)4]Cl2•nH2O
• Palladium(II) chloride, PdCl2
• Diamminedichloropalladium(II), [PdCl2(NH3)2]
• Palladium(II) sulfate solution, PdSO4
• Tetraamminepalladium(II) sulfate solution, [Pd(NH3)4]SO4
• Rhodium (Rh)
Rh is applied for industrial as well as decorative purposes in various types of electroplating soutions. Rhodium's very high white remission makes it ideal for plating frames of spectacles, and jewelry. Due to its hardness and corrosion resistance, rhodium protects silver and is used for top plating of sliding contacts and of reed relays (= relays containing protective gas).

Heraeus supplies you with chemicals and concentrate of rhodium electrolytes , e.g.:

• Rhodium(III) sulfate solution, Rh2(SO4)3
• Rhodium(III) phosphate solution, RhPO4
• Rhodium bath "DK20"
• Rhodium bath "DK80"
• Rhodium bath „RE“
• Ruthenium (Ru)
Ru is mainly used for electronic thick-film resistors, which are based on ruthenium(IV) oxide (RuO2). Also, reed relays are plated with Ru because of its extraordinary resistance to abrasion.

Heraeus, your partner for coating e.g. with the following Ru compounds:

• Ruthenium(III) chloride hydrate, RuCl3•nH2O
• Ammonium µ-nitrido-bis[aquatetrachlororuthenate(IV)], (NH4)3[{RuCl4(H2O)}2(µ-N)]
• Gold (Au)
There is a large number of Au electrolytes on the market, which meet the various requirements of gold plating (hardness, adhesion, etc.).

Strongly acid electrolytes are based on trivalent gold. Most of the gold baths that are weakly acid or even neutral contain the monovalent metal, which is replenished in the form of "Gold Salt" [chemical term: potassium dicyanoaurate(I)]. The main fields of application are printed circuits, connectors, diodes, etc.

Ceramic circuit boards based on thick-film technology contain gold, too. Organometallic Au(I) compounds are conceivable for CVD methods.

Heraeus's starting materials for your gold plating are e.g.:

• Hydrogen tetrachloroaurate(III) hydrate, H[AuCl4]•nH2O
• Potassium dicyanoaurate(I), K[Au(CN)2]
• Potassium tetracyanoaurate(III), K[Au(CN)4]
• Silver (Ag)
Ag is an excellent electric conductor and therefore the basis of conducting pastes for electronic thick-film switches. Ag plating baths are used on the basis of "Silver Salt" [chemical term: potassium dicyanoargentate(I)].

Heraeus offers you Ag chemicals for coating and plating, e.g.:

• Potassium dicyanoargentate(I), K[Ag(CN)2]
• Silver(I) nitrate, AgNO3
• Silver(I) cyanide, AgCN
We look forward to your enquiries and are at your disposal at any time. Should you not find the product you are searching for, please feel free to contact us.
Our company also offers you the recovery of precious metals from e.g. spent electrolytes. For this, please, visit the web page of our Recycling business unit.

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