Technical Data sheet

SILVER GLO™ 3K Silver Process For Electronic Finishing Applications

REGIONAL  N. America

PRODUCT AVAILABILITY DESCRIPTION The Dow bright silver process 3K is a simplified process designed to produce bright silver deposits at high current densities 0–7.0 amps/dm2 hull cell (0–70 amps/ft2 hull cell), high efficiency, and with simplicity of control. The 3K solution can be adopted for industrial and electronic applications and rack and barrel operations without radical formula changes. Silver deposits from the 3K bath have exception tarnish resistance. Since the 3K solution is clear, it enables the operator to view the work while plating and to readily view and recover parts that may have fallen to the bottom of the tank.

ADVANTAGES • The 3K solution can be used in industrial and electronic applications, rack, barrel and reel-to-reel operations • Concentrated replenishment

SILVER STRIKE As is customary in silver plating, a silver strike should be used prior to plating. The formulation of the strike solution should be as follows.

Chemicals Required Metric (U.S.) Silver Metal as Silver 1.8–3.0 g/L (0.22–0.37 tr. oz./gal) Cyanide (80.5%)

Free Potassium 75.0–112.5 g/L (10–15 oz./gal.) Cyanide (KNC)

The Strike should be operated at room temperature and 6 volts. For barrel operations, it may be necessary to modify the strike to suit the specific condition. To insure maximum adhesion when plating copper or copper alloys, current should be on when entering tank. The silver strike formula can be modified to suit specific needs. See your Dow service engineer.

RACK AND BARREL Where maximum brightness of the deposit may be desired, it is desirable to substitute sodium carbonate for the potassium carbonate. In such a mixed FORMULATION sodiumpotassium formula, the sodium ion in conjunction with the SILVER GLO™ 3K Silver Process acts as a brightener. For existing solutions that are being converted to the 3K process, this sodium ion may be introduced by substituting sodium cyanide for some of the potassium cyanide. The specific amount of sodium cyanide to be substituted will be recommended by our laboratory.

Where high-purity silver deposits are required with maximum conductivity, for

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example in special electronic devices, use SILVER GLO™ 3K Silver Process upon make-up and SILVER GLO 3K Replenisher or SILVER GLO 33-3X upon replenishment.

BATH MAKE-UP Rack and Barrel Formulation—Metric Chemicals Required Concentration Silver metal as silver cyanide (80.5%) 33 g/L

Potassium carbonate (K2CO3) 15–30 g/L SILVER GLO 3K 10–20 mL/L SILVER GLO TY 5 mL/L Potassium Cyanide 113 g/L

BATH MAKE-UP Rack and Barrel Formulation—U.S. Chemicals Required Concentration Silver metal as silver cyanide (80.5%) 4.4 tr. oz./gal.

Potassium carbonate (K2CO3) 2–4 oz./gal. SILVER GLO 3K 1–2% v/v SILVER GLO TY 0.5% v/v Potassium Cyanide 15.0 oz./gal.

BATH OPERATION Chemicals Required Metric U.S. Silver Metal as 33.0 g/L 4.4 oz./gal. Silver Cyanide (80.5%) Potassium Cyanide 30–135 g/L 4–18 oz./gal. Temperature 21–29°C 70–85°F Agitation 5.5 m/min. 18 ft./min. Current Density Range 0–7.0 amps/dm2 20–70 amps/ft2

HIGH-SPEED Where maximum speed is required for Continuous Strip and Spot Plating of FORMULATION electronic components, the high-speed formulation should be used. BATH MAKE-UP High-speed Formulation—Metric

Chemicals Required Concentration Silver metal as silver cyanide (80.5%) 41–49 g/L

Potassium carbonate (K2CO3) 15–30 g/L Potassium Cyanide 101–135 g/L SILVER GLO™ 3K Brightener 10–20 mL/L

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BATH MAKE-UP High-speed Formulation—U.S. Chemicals Required Concentration Silver metal as silver cyanide (80.5%) 5–6 tr. oz./gal.

Potassium carbonate (K2CO3) 2–4 oz./gal. Potassium Cyanide 13.5–18 oz./gal. SILVER GLO™ 3K Brightener 1–2% v/v

BATH OPERATION Chemicals Required Metric U.S. Silver Metal as 41–49 g/L 5–6 tr. oz./gal. Silver Cyanide (80.5%) Free Potassium Cyanide 101–135 g/L 13.5–18 oz./gal. Temperature 21–29°C 70–85°F Agitation Jet or extremely vigorous Current Density 0–100 ASD 0–1,000 ASF Range depending on depending on agitation agitation Note: No SILVER GLO TY should be added to high-speed formulations.

BATH Silver Metal MAINTENANCE Silver Metal should be maintained using silver cyanide according to the following procedure.

Analytical Procedures for Silver Content in Bright Silver Plating Solution

I. Equipment a) 250 mL Erlenmeyer flask

b) 50 mL burette

c) 10 mL Class A volumetric pipette

d) 100 mL graduated cylinder

II. Reagents Required a) Silver plating solution

b) Concentrated sulfuric acid WARNING! Proper care must be taken to avoid physical contact with sulfuric acid solution as severe burns can result. The use of proper safety equipment is necessary, including chemical goggles, chemical gloves, and suitable protective clothing.

c) Nitric acid WARNING! Proper care must be taken to avoid physical contact with Nitric acid solution as severe burns can result. The use of proper safety equipment is necessary, including chemical goggles, chemical gloves, and suitable protective clothing.

d) Distilled water

e) 2% ferric ammonium sulfate indicator (Fe2(SO4)3(NH4)2SO4 • 24H2O) UNRESTRICTED – May be shared w ith any one ®TM Trademark of The Dow Chemical Company (“Dow ”) or an affiliated company of Dow 886 -00801 10/2014 Page 3 of 8 SILVER GLO™ 3K Silv er Process/ Interconnect Technologies

III. Titrant a) 0.1N sodium thiocyanate (NaCNS) IV. Procedure a) Pipette a 10 mL of the silver plating solution into a 250 mL Erlenmeyer flask.

b) Under a hood (poisonous cyanide fumes are evolved), add 20 mL of concentrated sulfuric acid and 5 cc of nitric acid. Heat to the evolution of white sulfur trioxide fumes. If charring persists, repeat the nitric acid addition and reheat to the evolution of sulfur trioxide fumes. WARNING! Proper care must be taken to avoid physical contact with sulfuric acid solution as severe burns can result. The use of proper safety equipment is necessary, including chemical goggles, chemical gloves, and suitable protective clothing. WARNING! Proper care must be taken to avoid physical contact with Nitric acid solution as severe burns can result. The use of proper safety equipment is necessary, including chemical goggles, chemical gloves, and suitable protective clothing.

c) Cool, then cautiously add 100 mL of distilled water and heat until the white precipitate completely dissolves.

d) Cool to room temperature.

e) Add 2 to 3 mL of 2% ferric ammonium sulfate (Fe2(SO4)3(NH4)2SO4 • 24H2O) indicator and titrate with 0.1N sodium thiocyanate (NaCNS) until a faint pink color appears. Read the burette for volume titrant used and calculate.

V. Calculations a) mL of 0.1N Sodium Thiocyanate (NaCNS) × 0.132 = tr. oz./gal. silver metal (Ag)

b) mL of 0.1N Sodium Thiocyanate (NaCNS) × 1.1 = g/L silver metal (Ag)

c) mL of 0.1N Sodium Thiocyanate (NaCNS) × 0.16 = tr. oz./gal. silver cyanide (AgCN)

d) mL of 0.1N Sodium Thiocyanate (NaCNS) × 1.3 = g/L silver cyanide (AgCN)

Free Potassium Cyanide (KCN) A suggested free KCN concentration is 90 g/L (12.0 oz./gal.). This should be checked periodically. Low free KCN, below 75 g/L (10.0 oz./gal.), will cause fogging and dullness in the low current density areas and higher values, over 120 g/L (16.0 oz./gal.), may slightly reduce the high current density range. Where maximum brightness is desired, some of the potassium cyanide may be substituted by sodium cyanide. The sodium ion introduced by the addition of the sodium cyanide tends to impact additional brightness when used in conjunction with the SILVER GLO™ Brighteners. Such a substitution should be made after consulting with your Dow service laboratory. Sodium cyanide should not be used in high speed formulations.

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Analytical Procedures for Free Cyanide in Bright Silver Plating Solution

I. Equipment a) 5 mL Class A volumetric pipette

b) 250 mL Erlenmeyer flask

c) 50 mL burette

d) 100 mL graduated cylinder

II. Reagents Required a) Silver plating solution

b) Water

c) 10% potassium iodide (KI)

III. Titrant a) 0.1N silver nitrate (AgNO3)

IV. Procedure a) Pipette 5 mL of silver plating solution into a 250 mL Erlenmeyer flask.

b) Add 90 mL of water and 5 mL of 10% potassium iodide (KI).

c) Titrate with 0.1N silver nitrate (AgNO3) solution, shaking the flask slowly until a faint milky turbidity appears. This turbidity should last for 1 minute. V. Calculations a) mL 0.1N AgNO3× 0.262 = oz./gal. free sodium cyanide (NaCN) b) mL 0.1N AgNO3× 1.97 = g/L free sodium cyanide (NaCN)

c) mL 0.1N AgNO3× 0.348 = oz./gal. free potassium cyanide (KCN) d) mL 0.1N AgNO3cyanide (KCN)

Analytical Procedures for Carbonates in Bright Silver Plating Solution

I. Equipment a) 10 mL Class A volumetric flask

b) 250 mL beaker

c) Whatman #30 filter paper

d) 50 mL burette

II. Reagents Required a) Water

b) 10% barium nitrate solution

c) Distilled water

d) Methyl orange indicator (0.2%)

III. Titrant a) 1.0N hydrochloric acid (HCl) WARNING! Proper care must be taken to avoid physical contact with hydrochloric acid solution as severe burns can result. The use of proper safety equipment is necessary, including chemical goggles, chemical gloves, and suitable protective clothing.

IV. Procedure a) Pipette a 10 mL sample into a 250 mL beaker.

b) Add 100 mL water and warm.

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c) Add with stirring 25 mL of 10% barium nitrate solution until no further precipitation forms. Allow precipitate to settle.

d) Filter through Whatman #30 filter paper. Test the filtrate for complete precipitation by adding a few drops of barium nitrate (BaNO3). Wash the precipitate with warm water.

e) Transfer the filter paper and precipitate to the beaker in which the above was performed.

f) Add 50 mL distilled water and 3 to 5 drops of methyl orange indicator (0.2%).

g) Titrate with 1.0N HCl to a pink endpoint. Read burette and calculate.

V. Calculations a) mL of 0.1N HCl × 0.706 = oz./gal. sodium carbonate (Na2CO3)

b) mL of 0.1N HCl × 5.3 = g/L sodium carbonate (Na2CO3)

c) mL of 0.1N HCl × 0.92 = oz./gal. potassium carbonate (K2CO3)

d) mL of 0.1N HCl × 6.9 = g/L potassium carbonate (K2CO3)

SILVER GLO™ Brightener The Replenishing Brightener is SILVER GLO 33-3X for the 3K system. SILVER GLO TY acts as an auxiliary Brightener and Wetting agent. Additions should be made when there is no work in the tank and preferably just before shutdown periods. It is better to make periodic small additions of both chemicals and brighteners rather then a few large additions.

Normal operations will require replenishing at the rate of 5–10 cc of SILVER GLO 33-3X per 25 ampere hours, and 1.5–2 cc of SILVER GLO TY per 25 ampere hours. An overall lack of brightness at all current densities usually indicates the need for an addition of SILVER GLO 33-3X. Large additions of SILVER GLO 33-3X should be avoided since excess quantities of this brightener would cause dullness in the low current density areas.

Deposition Rate Current Density Amps/ft2 10 20 30 40 Deposition Thickness Inches Time in Minutes 0.0001 3.75 1.8 1.3 0.9 0.0002 7.50 3.6 2.6 1.8 0.0003 11.25 5.4 3.9 2.7 0.0004 15.00 7.2 5.2 3.6 0.0005 18.75 9.0 6.5 4.5 0.0006 22.50 10.8 7.8 5.4 0.0007 26.25 12.6 9.1 6.3 0.0008 30.00 14.4 10.4 7.2 0.0009 33.75 16.2 11.7 8.1 0.0010 37.50 18.0 13.0 9.0

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PRODUCT DATA SILVER GLO™ 3K Silver Process Appearance: Clear, colorless liquid

pH: 10.8–13.2

Specific Gravity: 0.098–1.012

SILVER GLO 33-3X Appearance: Clear, colorless liquid pH: 9.5–11

Specific Gravity: 0.995–1.005

SILVER GLO TY Appearance: Clear, colorless to pale yellow liquid

pH: 7.3–8.7

Specific Gravity: 1.003–1.017

Note: These are typical properties, not to be construed as specifications.

EQUIPMENT Anodes: High-purity silver anodes (99.9%) should be used, or 316 stainless steel; the 316 stainless steel inert anodes should be used in the Silver Strike as not to allow the silver metal to rise above the recommended range. Anode bags should be made of 6 ounces cotton duck or dynel

Tanks: Koroseal-lined, polypropylene, or heavy gauge polyethylene; under no circumstances should a fiberglass tank be used for any silver plating solution

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Handling Before using this product, associated generic chemicals or the analytical reagents required for this control, consult the supplier’s Material Safety Data Sheet Precautions (MSDS)/Safety Data Sheet (SDS) for details on material hazards, recommended handling precautions and product storage.

CAUTION! Keep combustible and/or flammable products and their vapors away from heat, sparks, flames and other sources of ignition including static discharge. Processing or operating at temperatures near or above product flashpoint may pose a fire hazard. Use appropriate grounding and bonding techniques to manage static discharge hazards.

CAUTION! Failure to maintain proper volume level when using immersion heaters can expose tank and solution to excessive heat resulting in a possible combustion hazard, particularly when plastic tanks are used.

Storage Store products in tightly closed original containers at temperatures recommended on the product label.

Disposal Dispose in accordance with all local, state (provincial) and federal regulations. Empty containers may contain hazardous residues. This material and its container Considerations must be disposed in a safe and legal manner.

It is the user's responsibility to verify that treatment and disposal procedures comply with local, state (provincial) and federal regulations. Contact your Dow Electronic Materials Technical Representative for more information.

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For Industrial Use Only. This information is based on our experience and is, to the best of our knowledge, true and accurate. However, since conditions for use and handling of products are beyond our control, we make no guarantee or warranty, expressed or implied, regarding the information, the use, handling, storage or possession of the products, or the applications of any process described herein or the results sought to be obtained. Nothing herein shall be construed as a recommendation to use any product in violation of any patent rights.

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