Full Bright Acid Tin Plating Process For Electrical Parts And Trimmings

MDT-LS Full Bright Acid Tin Plating Process

(Low Foam, No Formaldehyde)

Applications and advantages

We developed brand-new full bright acid tin plating process with two agents which are Make up solution agent and Supplementary agent. These additives has advantages of low foams and the plated parts are easy to be cleaned up. They can make the deposit have good discoloration-resistance ability and solderability. This process could be widely used in electrical parts and trimmings. It is the optimal additive in racking plating thick tin, barrel plating electrical parts, and high-current strike plating thin and pure tin.

Bath Composition and Working Conditions

Preparation of bath solution

1. Pour calculated amount of deionized water into the bath.
2. Stir fast and add needed sulfuric acid very slowly and carefully.
3. Stir fast and add calculated amount of stannous sulfate into bath. Stir continuously until it is dissolved.
4. Cool the liquid until the temperature is within the required range (under 20℃, add required amount of Make up solution agent and supplementary agent, stir evenly.
5. Supply deionized water to the required volume, stir adequately and filter the solution. Electrolyze the liquid with low current for 4-8 hours. Then it could be put into production after trial plating.

Please note: The Make up solution agent cannot be added into baths above 30℃.

Process flow

Removing oil→Sulfuric acid pickling→Washing twice→Tin plating (reference: when the current density is 1-2 A/dm², rack plating for 10-15 minutes; when the current density is 1A/dm², barrel plating for 20 minutes)→Wash several times→Dry the parts→Discoloration-resistant treatment.

The replenishment of bath solution and the maintenance

1. Control the tin content within the operation range. The replenishment of tin is in the form of stannous sulfate. The tin ion concentration will increase 1g/L when every 2g/L stannous sulfate is added.
2. If the plating outcome is not satisfactory as the bath solution is left there for a long time, a proper amount of make up solution agent and supplementary agent can be added into the bath. Electrolyze for a short time, the plating liquid will be back to normal.
3. When in normal plating, the additives should be added in small amount for several times. The given consumption amount is just a reference value, especially the supplementary agent,the added amount for each time should not exceed 1ml/L, or the plating layer may not attach. Once the above situation appears, the only resolution is to electrolyze for several hours until normal electroplating.
4. The chloride ion may affect the dispersion of low-current density area in plating layers, so preimpregnation of 10% sulfuric acid is needed before parts enter into baths. Bright tin cannot be directly plated on zinc alloy and bronze parts, as the zinc may proliferate into the tin layer, decreasing tin layer’s corrosion-resistant ability and weldability. Therefore, zinc alloy and bronze parts tin plating need advanced copper or nickel plating.
5. Tin plating parts can increase its corrosion-resistant ability by a treatment of potassium bichromate. The formula is listed below:

Trisodium phosphate: 30-50g/L

Tin off-color Prevent Agent: 20-50ml/L (make up in 50℃ purity water)

Temperature: 50-60℃

Processing time:30-60 seconds

Packing and Storage

Packed in 25kg plastic drums, stored in cool and dry place.

Product Display

Declaration:

The recommendations among the content of this instruction is based on the trials and tests, as well as the related documents which are credible to our company. As the operating practices and equipment differ from each other, we will not hold responsible for any negative outcomes. The content of this instruction could not serve as evidence of copyright infringement.