TRANSENE SULFITE GOLD – TSG-250
Gold Electroplating Solution for Electronic and Aerospace Applications
DESCRIPTION:
TSG-250 is a ready-to-use, cyanide free stabilized gold sulfite electroplating solution which deposits soft satin-bright electrodeposits. The solution exhibits a slightly acid or neutral pH for applications where high pH is undesirable. TSG-250 meets Type IIIA of Mil-G-45204 C requirements.
OPERATING CONDITIONS:
| Temperature | 110-160°F (140° F optimum) |
| Current Density | 1-8 ASF (2-4 recommended) |
| Anode | Platinized |
| Anode to Cathode Ratio | 1:1 minimum |
| Agitation | 100% efficiency-vigorous |
| pH | 6.0-7.0 |
| SPG | 10-30° Baume |
| Tank | Polypropylene, Glass, Fiberglass |
| Hardness | 60-70 knoop as plated (may be annealed) |
| Gold Content | 1 Troy ounce per gallon |
| Plating Rate | 0.25 micrometers/minute at 4 ASF |
APPLICATIONS:
TSG-250 is ideal for applications where high pH plating solutions react with exposed materials or if a non-cyanide bath is desired. One troy ounce of gold is plated every four amp-hours. The specific gravity of the bath rises with use. Above 30o Baume precipitate sulfate using calcium acetate or barium acetate to lower the SPG to a working range.
ANALYSIS:
TSG-250 is a sulfite gold plating solution with a slightly acidic pH. Without additives, the solution deposits soft, bright or satin-bright films adhering to Type III A of Mil-G-45204 C. Additives are available to adjust brightness and hardness.
Replenishment:
Add 1 troy ounce TSG-250 Concentrate every 4 ampere-hours.
pH Adjustment:
Raise pH using 30% sodium hydroxide solution
Lower pH using TSG-250 Acidifier.
Specific Gravity:
Above 30o Baume, reduce the specific gravity by adding calcium acetate to precipitate sulfate. Filter to remove the precipitate.
Brightener:
TSG-250 Brightener is added to the bath at a loading of 10 grams/gallon. A bright deposit with similar hardness results.
Hardener:
TSG-250 Hardener both hardens and brightens the deposit. At 10 mL/gallon, the only effect observed is brightening. At 100 mL /gallon, a hard, bright deposit is obtained.
Analysis for Sulfite:
The nominal concentration of sulfite (Na2SO3) for TSG-250 is 6 ounces per gallon. Anhydrous sodium sulfite replenishes the sulfite content. When replenishing sulfite, 3 grams TSG-250 Stabilizer/ounce anhydrous sodium sulfite is required.
To analyze for sulfite content, dilute 2 mL plating solution to 500 mL using deionized water; mix. Determine the absorbance of the solution vs. standards at 266 nm. The acceptable absorbance range is 10-60 grams/gallon.
Absorbance: 0.5 1.0 1.5 2.0 2.25 2.5
Concentration (g/gal): 10 25 40 50 60 65
TROUBLESHOOTING:
| PROBLEM | LIKELY CAUSE | RESPONSE |
| Gold Precipitation | Low stabilizer or excess voltage | Add 0.24 mL stabilizer/L; reduce voltage |
| Poor Adhesion | High current density | Reduce current density |
| Brown Deposit | High current density; high pH; low temperature | Reduce current density; adjust pH; increase temperature |
| Dull/Rough Deposit | pH out of range; insufficient agitation; high temperature | Adjust pH, increase agitation, reduce temperature |
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