Introduction

TinStar 405 is a bright pure tin plating process, particularly suitable for electroplating electronic components. Thanks to its unique additive system, it produces a uniform and stable coating morphology across a wide operating temperature range. The deposits are highly lustrous, exhibit excellent solderability, and contain very low levels of organic impurities.

Characteristics

TinStar 405 complies with and exceeds relevant testing standards in the electronics industry (including MIL-STD-202F, 208F test methods, as well as MIL-STD-883C, Method 2003).

Required Materials

Required Equipment

A. Plating

Polypropylene groove or rubber

a) Alkali

Ordinary

Heavy Oil

Dissolve the above chemicals with water in the tank, and follow the safe operation for strong alkaline chemicals. Raise the temperature of the solution to 52℃ and continue for 6 hours. Most electroplating processes are alkali resistant and can be used under these conditions. After 6 hours, pump the solution out of the tank. The bottom is about 2.5cm deep. Brush the tank wall with the remaining solution.

b) Rinse with cold water

Thoroughly rinse the alkaline solution from the first step. Fill the plating tank with water and then pour it out. After repeating this twice, rinse for another 5 minutes.

c) Acid

TinStar A-70 acid concentrate: 10%, v/v

Mix TinStar A-70 acid concentrate with water in the tank and follow the safety operating procedures for strong acidic chemicals. Heat to 55℃ and cycle in the electroplating system for 8 hours.

d) Rinse with cold water

Follow the same as in step b.

e) Rise with deionized water

Rinse with deionized water or distilled water filtered by activated carbon before use. If the plating tank is not used temporarily, cover it properly to avoid further contamination. In addition to the plating tank, other sources of pollution must also be eliminated to ensure that no pollutants are brought into the plating solution.

The polar bag, filter bag, and filter element need to be soaked in boiling water for 30 minutes to wash away the adhesive on top. The new anode needs to be degreased and washed with alkali. Deionized water made from ion exchange resin still needs to be activated. Carbon filtration removes organic matter from it. In short, any object in contact with the plating solution may cause contamination and must be treated appropriately.

B. Cooling

Appropriate cooling equipment is required.

C. Stirring

Stirring can make the coating uniform and increase the working current. Mechanical stirring is recommended. Air stirring cannot be used because it may cause excessive bubbles and the formation of tetravalent tin.

D. Ventilation

A ventilation system compliant with local safety regulations is required.

Operating Parameters

It is recommended to use pure tin anodes, and soluble anodes should use anode bags. When high brightness is required, try to reduce the temperature as much as possible to achieve a large amount of strip output. It is recommended to use high tin and low acid.

Solution Preparation

A. Chemical Composition‍‍‍‍

B. Tank Setup Procedure

Preparation of 1 L Plating Solution:

a) Add 300 mL of deionized (DI) water into a clean tank.

b) While stirring, slowly add 200 mL of TinStar A-70 acid concentrate.

c) Add 167 mL of TinStar A-300 tin concentrate.

d) Add 70 mL of TinStar 405A additive.

e) Add 10 mL of TinStar C2 additive.

f) Top up with DI water to the final volume and mix thoroughly.

g) Analyze the tin, additive, and acid concentrations, and adjust to target values.

h) Perform test plating in the lab to determine the optimal solution composition and operating parameters (e.g., plating rate, deposit thickness) based on process and product requirements.

Process Optimization

The recommended values for the above solution composition will not always deliver optimal performance under all circumstances. The following guidelines can help achieve desired results.

A. Tin Metal Concentration

The metal concentration in the plating bath depends on a balance between deposition rate, agitation, and minimum drag-out loss.

If the current density is too high, causing the deposit to "burn" (resulting in dark/black nodules or powdery deposits), the following corrective actions can be taken within specified limits:

● Reduce current density

● Increase tin concentration

Enhanced solution agitation and elevated temperature can also help increase the upper limit of allowable current density.

B. Additive Concentration

The optimal additive concentration depends on operating conditions and product requirements. If operating conditions significantly deviate from the recommended range, adjustments to additive levels may be required. For specific guidance, consult technical support.

C. Process Control

Stable plating performance relies on comprehensive process control. The recommended operating ranges provided in the manual should serve as guidelines. To maintain consistent bath composition, we advise regular chemical analysis and timely replenishment. This ensures all solution components remain within specified parameters.

D. Tin Supplementation and Control

Due to drag-out losses, the metal concentration must be regularly monitored. If the metal concentration falls below 40 g/L, it should be adjusted back to 50 g/L.

E. Acid Concentration and Control

The acid concentration should be maintained within the range of 150–225 ml/L.

F. Temperature Control

The recommended operating temperature range is 14–35°C. When the plating solution temperature exceeds 35°C, cooling is required.

G. Coating Appearance

The consistency of the plated part's appearance depends on the following conditions:

a. Stable agitation control

b. Stable temperature control

c. Stable current density control

d. Determination of optimal parameters for each product (establishing an ideal control point for every product type)

H. Additive Concentration and Control

The TinStar 405 process exhibits a broad tolerance range for additive concentration variations. However, it is still recommended to maintain additive concentrations through analytical monitoring. If frequent analysis is not feasible, additions should be made based on Amp-Hour (AH) consumption, with periodic analysis conducted.

Regular analysis helps verify whether the current addition rate is correct and determines if adjustments are required. Before the addition rate is precisely established, the following guidelines are suggested:

● TinStar 405R supplement: 150–300 ml/1000 AH

● TinStar 405A additive: Added in appropriate amounts to compensate for drag-out losses

● TinStar C2 additive: 20 ml/1000 AH

For strip plating, the dosage of TinStar 405A additive should be increased to offset higher drag-out losses.

I. Maintenance

To ensure the highest quality coating throughout the bath's service life, the following practices are recommended:

a. Ensure thorough pre-cleaning to prevent contaminants or residues from entering the plating solution.

b. Pre-dip parts in 10% TinStar A-70 acid concentrate before entering the TinStar 405 plating process.

c. Regularly monitor tin, free acid, and additive concentrations.

d. Routinely inspect and replace anodes as needed.

e. Periodically check and control temperature.

If the coating quality remains unsatisfactory despite these measures, activated carbon treatment should be performed. This treatment can be conducted in-line or as a batch process.

J. In-Line Activated Carbon Treatment

The effectiveness of in-line activated carbon treatment depends on the amount of activated carbon used and the number of times the plating solution passes through the filter.

a. Retain a sample of the original solution for comparative analysis.

b. Use approximately 20 g of granular activated carbon per liter of plating solution.

c. Ensure the entire solution passes through the filter at least 20 times. The filtration duration depends on the pump capacity and flow rate.

d. After treatment, analyze the composition and adjust all parameters back to the operational range.

K. Batch Activated Carbon Treatment

The following activated carbon treatment procedure should be performed in a dedicated treatment tank equipped with mechanical agitation and a filtration system:

a. Retain a sample of the original solution for comparative analysis.

b. Transfer the plating solution to the treatment tank.

c. While stirring, add 8–20 g/L of granular activated carbon and continue agitation for 6 hours.

d. Allow the activated carbon to settle for 2 hours.

e. Filter the solution into another tank using diatomaceous earth as a filter aid.

● If the solution returns to its original color, it can be transferred back to the plating tank.

● If not, a second filtration is recommended.

● If fine activated carbon particles remain in the filtrate, use a finer filter aid.

f. Take a sample and conduct a composition analysis.

g. Replenish additives and other components as needed.

h. Perform a Hull Cell test (HCHC or standard) to adjust bath composition and ensure satisfactory plating quality.

Plating Solution Analysis

A. Analysis of Tin

The tin content is analyzed by titration with an iodine solution using starch as an indicator.

a. Materials and Reagents

b. Solution Preparation

c. Analytical Procedure

i. Sample Preparation:

● Transfer 2 mL of the plating solution into a 250 mL conical flask.

● Add 100 mL of deionized water.

ii. Acidification & CO₂ Generation:

● Add 20 mL of 20% hydrochloric acid (HCl) solution.

● Slowly introduce 1–2 g of sodium bicarbonate (NaHCO₃) to avoid excessive foaming.

iii. Titration:

● Add 2–4 mL of starch solution as an indicator.

● Titrate with 0.1 N iodine solution until a persistent blue endpoint (lasting at least 30 seconds) is reached.

d. Calculation

Tin (g/L) = Volume of 0.1N iodine solution (mL) × 2.97

B. Analysis of TinStar A-70 Acid Concentrate

The acid concentration is determined by titration with sodium hydroxide (NaOH). Initially, the pH changes minimally. However, when the pH reaches approximately 2.2, a sharp increase in pH is observed upon further addition of NaOH. Sodium sulfate (Na₂SO₄) is added to mitigate interference from lead ions.

(Note: It is recommended to first test this method with a sample of known concentration for validation.)

a. Materials and Reagents

b. Analytical Procedure

i. Sample Preparation:

● Pipette 5 mL of the sample solution into a 250 mL beaker.

● Add 20 mL of 15% sodium sulfate (Na₂SO₄) solution and mix thoroughly.

ii. Dilution:

● Dilute the mixture with deionized water (DI water) to a total volume of 100 mL.

iii. Initial Titration:

● While stirring continuously, titrate with 1N NaOH standard solution until the pH reaches 1.8–2.0.

iv. Rinsing:

● Rinse the inner walls of the beaker with DI water to ensure no residual sample interferes with the titration.

v. Incremental Titration & pH Monitoring:

● Continue titration by adding 0.2 mL increments of 1N NaOH.

● After each addition:

● Rinse the beaker walls with DI water.

● Record the pH value.

vi. Endpoint Determination:

● Due to variations in metal content, the endpoint occurs between pH 2.2–2.8.

● Identify the sharpest pH jump (greatest change per 0.2 mL NaOH) as the final endpoint.

c. Calculation

TinStar A-70 Acid Concentrate (mL/L) = NNaOH × VNaOH (mL) × 20.8

C. Analysis of TinStar 405 Additive

The TinStar 405A additive is analyzed by extracting the wetting agent component from the plating solution using methylene chloride (CH₂Cl₂). The extract reacts with a water-soluble complexing agent to form a blue-colored complex. The absorbance of the separated blue methylene chloride layer is measured at 620 nm.

A calibration curve is prepared using plating solutions of known concentrations, allowing the TinStar 405A additive concentration in the working solution to be determined from the curve.

(Note: The developed color remains stable for 2 hours.)

a. Materials and Reagents

b. Preparation of Standard and Blank Solutions

Prepare 100 mL standard solutions containing 5 mL, 7 mL, and 10 mL of TinStar 405A additive (equivalent to 50 mL/L, 70 mL/L, and 100 mL/L TinStar 405A solutions, respectively). The metal concentration in the standard solutions must match that of the working bath solution.

Typical Standard Solution Composition:

c. Complexing Agent (TinStar Color Developer)

Important Note:

Ammonium thiocyanate (NH₄SCN) has extremely high solubility and causes significant solution volume expansion during dissolution. To prevent overflow, do not add excess water initially.

Dissolution Process:

● The solution will cool down during mixing (endothermic reaction).

● To ensure complete dissolution, gentle warming to room temperature may be required.

d. Procedure

i. Sample Preparation: Pipette 5 mL of TinStar 405 plating solution (or TinStar 405 standard solution) into a separatory funnel.

ii. Extraction: Add 15 mL of methylene chloride (CH₂Cl₂) to the funnel and cap it securely.

iii. Mixing & Phase Separation: Shake vigorously for 3 minutes, then let stand for 1–2 minutes for clear layer separation.

iv. Organic Layer Transfer: Drain the bottom CH₂Cl₂ layer into a 60 mL polyethylene bottle.

v. Color Development: Add 3 mL of TinStar color developer and a 1-inch stir bar, then cap immediately.

vi. Reaction & Separation: Stir for 15 minutes, then allow phases to separate again.

vii. Sampling for Analysis: Using a pipette, transfer the bottom blue CH₂Cl₂ layer into a 1 cm cuvette.

viii. Prevention of Evaporation: Seal the cuvette immediately to avoid solvent evaporation.

ix. Absorbance Measurement: Measure absorbance at 620 nm against a blank solution.

● Blank preparation: Follow the same steps but replace the 3 mL color developer with 3 mL DI water.

x. Calibration Curve: Plot absorbance vs. TinStar 405A additive concentration (mL/L) using standard solutions.

xi. Concentration Determination: Determine the TinStar 405A concentration in the working solution from the calibration curve.

Disclaimer

All proposals or suggestions regarding our company's products in this manual are based on experiments and data that our company trusts. Due to the inability to control the actual operations of other practitioners, our company cannot guarantee or be responsible for any adverse consequences.