Products & Services

Precious metal products

Silver powder

Silver powder at the highest purity and different properties is used in many applications: In production of silver-contained contact materials, carbon brushes, diamond tools, on the growth markets of the wind and solar industry, as a basis for, e.g., ECG- / EEG electrodes in the medical technology and in innovative applications such as antibacterial coatings. Silver powder is also used for conductive preparations such as pastes, varnishes and glues in electrical engineering and electronics.

DODUCO closely cooperates with the customers to develop special silver powder for demanding applications and has a broad range of different production procedures in order to meet these requirements.

Applications of silver powder:

  • Manufacture of silver-based contact materilas
  • Base material for ECG and EEG electrodes and antibacterial coatings in medical devices
  • Carbon brushes for electric motors and generators
  • Electromagnetic shielding, e.g. conductive sealants and adhesives
  • As a conductive pigment in polymer systems in the electronics and electrical industries, e.g. in conductive paints, adhesives and pastes
  • Diamond tools

Spraying liquid silver

This produces a silver powder with a high tap density, mostly made up of spherical silver particles.

Silver powder-electrolyse

This produces dentritic to crystalline grain shapes.

Chemical precipitation

This method covers a large bandwidth of desired properties, such as very fine silver particles with large specific surfaces.

       
Silberpulver chemisch gefällt
Klopfdichte: 1,4 – 2,5 g/cm³
Korngröße: 95% < 63 µm Ag-Gehalt: 99,9 %
Silberpulver elektrolytisch abgeschieden
Klopfdichte: 1,6 – 2,5 g/cm³
Korngröße: 95% < 63 µm Ag-Gehalt: 99,9 %
Silberpulver schmelzverdüst
Klopfdichte: 4 – 7 g/cm³
Korngröße: < 40 / < 70 µm Ag-Gehalt: 99,9 %
Silberflakes
Klopfdichte: 2,1 – 2,5 g/cm³
Korngröße: < 4 / < 15 µm Ag-Gehalt: 99,9 %
Versilbertes Kupferpulver Mikroskopansicht

Silver-plated copper powder

DODUCO also offers silver-plating of various copper powders. This surface treatment permits elementary improvement of the properties of the basic material of copper, in particular corrosion resilience, electrical conductivity and soldering capacity of the material.

The possible uses of the powder are determined by factors such as grain size, grain shape, bulk density and silver content. Of course, the powders named below are only examples. Specific powders can be implemented according to the customer’s requirements.

Coarse powders have diverse uses in the production of carbon brushes.

Finer, electrolytic powders, in contrast, are found rather in electrically conductive silicones, plastics, varnishes, paints and pastes that can be used, among others, for electromagnetic shielding.

Thus, refined copper powders not only offer the option of substituting pure copper to improve the product properties, but may also permit an additional more cost-efficient alternative for pure silver powder, depending on application.

Silver bars and granules

Competence in Silver

The DODUCO precious metal refinery, with almost 100 years’ experience in the processing and recovery of precious metals, was included in the “Good Delivery List of Acceptable Refiners” of the London Bullion Market Association (LBMA) as an internationally certified refinery and manufacturer of silver bars, and is an Associated Member of the organization.
DODUCO’s precious metal refinery, which currently has an output of some 500 metric tons per year, counts among the leading silver refineries in Europe. With broad experience and know-how DODUCO offers silver to customers and traders as investments and raw material. Fully recycled, 99.99% pure fine silver is available in different sizes of bars as well as in granules.

Protecting values

Due to increasing demand for silver alongside limited natural resources,“urban mining” is of particular importance. DODUCO’s goal is to satisfy the needs of the market with high-quality recycled silver coming from jewelry and industrial production scrap. Through consistent research and development, DODUCO has continually increased process efficiency. For nearly 100 years, DODUCO has always prioritized its responsibility to the environment. As a symbol of environmental commitment, DODUCO has received all of the necessary industry certifications and approvals. All fine silver used for bars placed on the market by DODUCO is recovered by in-house recycling processes. There is an explicit guarantee that no mined silver has been used in these products.
DODUCO is proud to actively contribute to sustainable secondary recovery. As a visible sign DODUCO bars are marked with the logo “Recycling-Silver”.
1Kg Silberbarren von vorne

Wire blanks

DODUCO also supplies high-purity fine silver in the form of wire blanks – perfectly suited for your anode baskets. The blanks are approximately 10 x 15 mm in size and have an outstandingly uniform structure. Of particular interest is the high level of purity of the silver – 99.99% – which guarantees an extremely low carry-over of contamination in the electroplating bath and a perfect finish. The standard packaging unit of 10 kg in tearproof plastic sacks is also practical and in line with occupational safety concerns. The wire blanks are available from stock at short notice.

With respect to environmental protection you also have a distinct advantage with DODUCO:

All precious metals used for DODUCO products originate from an in-house LBMA-certified recycling process. This conserves natural resources and reduces the burden on the environment.

Precious metal salts

DODUCO is a reliable, LBMA certified German manufacturer of silver salts (silver cyanide and potassium silver cyanide) and gold salts (potassium gold cyanide or potassium dicyanoaurate) and other precious-metal-containing slats and solutions with nearly a century of experience.

Silver and gold salts are used often in galvanotechnical processes and galvanochemicals or galvanic baths. DODUCO supplies the products listed here to commercial purchasers, such as galvanisation plants, only, but not to private end consumers.

Precious metal salts by DODUCO are characterised by highest purity and a particularly good pourability.

Resource-protecting and conflict-free

The fine gold used for production of the gold salts is guaranteed to come from conflict-free origins and was produced in DODUCO’s own cfsi-certified precious metal recovery process.

Silver cyanide

DODUCO’s products for use in galvanisation include the following silver cyanides (cyanide salts of silver):

  • Silver cyanide| AgCN
  • Potassium silver cyanide | potassium dicyanoargentate | K[Ag(CN)]₂

Silver cyanide properties

Silver cyanides (silver salts of cyanide) are characterised by a very high purity and good pourability.

The 80.5% silver cyanide is a white, powder-like product that will not form lumps. Mixed with potassium cyanide at sufficient amounts will make it dissolve well in water.

The 54% potassium silver cyanide, also a white salt, forms fine crystals that will dissolve well in water even without any extra addition of potassium cyanide.

Both silver cyanide and potassium silver cyanide are mostly used to prepare and improve galvanic silver baths or pre-treatment electrolytes in galvanisation plants.

Gold cyanide

DODUCO’s products for use in galvanisation include the following cyanide salts of gold:

  • Potassium gold cyanide | potassium dicyanoaurate| K[Au(CN)₂]
  • Potassium tetracyanoaurate| K[Au(CN)₄]

The cyanidic gold salts by DODUCO are characterised by a particularly high purity and even structure.

Both the monovalent potassium gold cyanide (potassium dicyanoaurate) and the trivalent potassium tetracyanoaurate are fine-crystalline white salts with good pourability that are very well water soluble.

DODUCO’s gold cyanides are mostly used as galvanochemicals for preparing and improving cyanidic gold baths that are used in galvanisation plants to gold-plate less precious metals.

Cyanide-free precious metal solutions

DODUCO’s products for use in galvanisation plants include the following cyanide-.free precious metal concentrates:

  • RHODIOR® 2 | Rhodiumkonzentrat | Rhodium sulfate solution | Rh(SO₄)₃ x H2O
  • Gold solution | Sodium gold sulfite solution | Gold trisodium disulfite | Trinatriumgoldsulfitlösung | Na₃(AuSO₃)₂ x H₂O

The previous metal solutions (rhodium sulphate solution and sodium gold sulphite solution) by DODUCO are marked by high purity. In application as precious surface coatings, e.g. when rhodinating or gold-plating. high grip resistance and brought discharge of the precious metal layer must be emphasized. Rhodium sulphate solutions are often used with other additives in rhodium baths.

Precious-metal-preparations

With nearly 100 years of experience, DODUCO is a reliable, LBMA-certified German manufacturer of precious-metal-containing products. One of its product categories are precious-metal-containing conductive preparations (silver-pigmented) and precious-metal-free conductive preparations (graphite-pigmented), such as varnishes, pastes and glues.

The silver contained in silver-pigmented conductive preparations is produced in DODUCO-specific processes as silver powder or silver flakes.

Depending on composition of the conductive preparation, the resulting properties and the technical requirements, these products are often used in many different electrical and electronic areas where conductive layers are needed.

DODUCO precious metal preparations and graphite preparations are characterised by higher purity, particularly good homogeneity and long-term stability (durability).

Precious metals from your production wastes can be recovered in DODUCO’s recycling processes. The resulting highly pure precious metals are also offered on the market as silver granules, gold granules or silver ingots.

Silver conductive varnishes

DODUCO’s silver-pigmented conductive varnishes are liquid, solvent-containing, physically drying varnishes. Depending on the area of application (carrier material, drying requirements), there are mostly two types distinguished:

  • Conductive varnishes on acrylate-resin basis and
  • Conductive varnishes on nitrocellulose basis

At a silver share of approx. 40 % silver (exceptions are possible) in the form of silver powder or silver flakes from own production, DODUCO’s silver conductive varnishes are characterised by high electrical conductivities at low viscosities. The liquid conductive varnishes can be applied to the carrier materials by brush, roller or submersion. If a spray application is desired, the conductive varnish should be mixed with the corresponding diluent (information on the diluent is available on request). Drying takes place by evaporation of the solvents contained in the temperature range between 20-100°C (on demand, higher temperatures are possible as well).

The benefit of the silver conductive varnishes as compared to the pastes is in simple processing and quick drying. Furthermore, they have a strong, good adhesion to the base and very good electrical and thermal conductivity.

DODUCO’s silver-pigmented conductive varnishes are used in:

  • shielding of electromagnetic waves in the area of electrical engineering and electronics
  • Production of a contact in the area of electrical engineering and/or hobby electronics (e.g. electronic toys)
  • Repair of conductor tracks / improvement of printed circuits
  • Repair of heating conductors (rear window heatings)
  • Repair of antennas
  • Metallisation of non-conductive bases for galvanic further processing

Silver conductive pastes

The also physically drying silver-pigmented conductive pastes of DODUCO’s range have a much higher viscosity than the conductive varnishes. This is caused by higher shares of silver (approx. 60%) and use of polymer basic components for formation of polymer compounds / design of the polymer structure. The silver used in the silver conductive pastes in the form of silver powder or silver flakes is also from the DODUCO-internal production.

The silver-pigmented polymer thick-film pastes are characterised by good electrical and thermal conductivity as well as good adhesion and bending resistance while being highly flexible. The application of conductive pastes preferably takes place by screen printing, with selection of the mesh size varying depending on printing pattern, layer thickness and base. Drying and curing may take place in circulation air dryers, IR-dryers or special tunnel furnaces.

On remand, the silver-pigmented conductive pastes can also be adjusted to different processing techniques (e.g. pad printing). The chemicals required for this may be purchased from DODUCO on request.

The benefit of silver conductive pastes as compared to the varnishes is in the better adhesion to plastic bases as well as films. I spite of high demands by increased flexibility, the layers remain stable and retain their very good conductivity.

DODUCO’s silver-pigmented conductive pastes are used in:

  • production of conductor tracks on membrane keyboards
  • production of circuits on PCBs

Silver conductive glue

In addition to silver conductive varnishes and silver conductive pastes, DODUCO also produces silver conductive glues. Silver-pigmented conductive glues are used to apply construction elements to different carrier materials with conductive contacts. The adhesive technique offers essential benefits as compared to soldering, since lower curing temperatures permit connecting even heat-sensitive parts to each other conductively. Additionally, the higher flexibility of the bonding improves ageing behaviour of the material/part.

DODUCO’s delivery range contains two types of silver-pigmented conductive glues:

  • Single-component conductive glue
  • Two-component conductive glue

Single-component conductive glues are ready-to-use systems with long processing times. Curing takes place within 15-60 min. at temperatures between 120-200°C. In two-component conductive glues, in contrast, are mixed directly before use and then must be processed speedily. The processing time is approx. 4 hours, depending on ambience conditions. Curing can be thermally sped up.

Silver-pigmented conductive glues are applied by screen printing or dispenser.

Special features of DODUCO’s silver-pigmented silver glues are:

  • very good conductivity
  • low-stress properties
  • high strength
  • good heat conductivity
  • no solvents
  • temperature stability

Graphite-containing conductive preparations

Similar to silver-pigmented conductive preparations, precious-metal-free, graphite-pigmented conductive preparations are also based on decades of experience in production. The close cooperation with the customer has enabled DODUCO as producer to develop a selection of precious-metal-free conductive preparations that cover a broad area of use.

DODUCO’s range of precious-metal-free graphite-pigmented conductive preparations includes:

  • Graphite conductive varnishes
  • Graphite conductive pastes
  • Diluent

Packaging sizes of 1 kg product per unit have proven their worth for practical use. The diluents can be delivered in different amounts as well depending on your needs and upon request.

Both DODUCO’s graphite conductive varnishes and graphite conductive pastes are sold under the brand name of GRAPHAROL®. Both product groups are made conductive by the addition of a special graphite pigment. Thus, the product will often have enough conductivity and offer a cost-efficient alternative for precious-metal-containing products. However, if you have any greater requirements to the conductive layer, you should use a silver-containing conductive product.

Similar to the silver conductive preparations, graphite conductive preparations adhere well to many plastics and other carrier materials. The solvents contained permit quick drying even at low temperatures and simple processing.

The thinly liquid graphite conductive varnishes are usually applied by spraying or with a brush. More viscose graphite conductive pastes are recommended for screen printing. Additional of a suitable diluent (information available on request) permits variation of the viscosities as required.

Depending on the area of application (carrier material, drying requirements), there are mostly two types distinguished:

  • Graphite preparations on acrylate resin basis and
  • Graphite preparations on acrylate-polymer basis

DODUCO’s graphite-pigmented conductive varnishes und conductive pastes are used for/in:

  • antistatic equipment of containers and tubes
  • Heating and warmth conductors
  • Production of high-ohmic printed circuits and contact bridges in PCB production
  • Printing over silver conduction tracks to increase corrosion and migration resistance

EKG-/EEG-electrodes based on silver/silver chloride

DODUCO has developed its experience and expertise in manufacturing of EKG and EEG electrodes for the medical technology over the past decades.

It is based on the in-house manufacturing of proprietary silver/silver chloride powders used in a variety of special blends. This material is the well proven base material of choice for EKG and EEG electrodes.

DODUCO manufactures electrodes in different diameters and thicknesses with and without silver pins already incorporated. Both, the material blend composition and the dimensions are mostly specified by our customers and can be customized to meet their specific requirements.

DODUCO produces these electrodes in pill or disc form, allowing our customers to further integrate them into their design during manufacturing into their end product.

Do You Have Questions?

Drei-Personen-Symbol rot
Mr. Fabian Gall
Sales Manager – Precious metal products

Tel.: + 49 (0) 7231 602-586
Mail: fgall@doduco.net