SILVER GLO™ 3K Silver Process for Electronic Finishing Applications
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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 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 1 of 8 SILVER GLO™ 3K Silv er Process / Interconnect Technologies 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 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 2 of 8 SILVER GLO™ 3K Silv er Process/ Interconnect Technologies 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. 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 4 of 8 SILVER GLO™ 3K Silv er Process/ Interconnect Technologies 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.