Advanced Materials for Electronics

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. a standard 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