PCB Tech - How to remove poor nickel plating

How to remove poor nickel plating

PCB manufacturers: How to remove poor nickel plating
It is more difficult to remove the nickel-plated layer than the electroplated nickel layer, especially for the high-corrosion-resistant nickel-plated layer. Unqualified nickel plating should be removed before heat treatment, otherwise it will be more difficult to remove the plating after passivation. It is required that the deplating solution must be non-corrosive to the substrate, and then factors such as the thickness of the coating, the speed of the deplating, and the cost of the deplating must be considered.

1. Electrolytic deplating method

The formula is: NaNO3 100g/L, nitrilotriacetic acid 15g/L, citric acid 20g/L, thiourea 2g/L, sodium gluconate 1g/L, sodium lauryl sulfate 0:1g/L, pH=4, Room temperature, DA=2～10A/dm2, cathode 10# steel, SK:SA=23:1.

Two, chemical stripping method:

The chemical stripping method does not cause the workpiece to be corroded, and is suitable for workpieces with complex geometric shapes, and can achieve uniform stripping.

Formula 1: Concentrated HNO3, 20～60 degree Celsius. This solution has low cost, fast speed of 30-40μm/h, and low toxicity. It is suitable for the deplating of workpieces with low requirements for precise dimensions, to prevent water from being brought into, and after the deplating is completed, it is quickly washed in hydrochloric acid and then cleaned with running water.

Formulation 2: Ammonium nitrate 100g/L, nitrilotriacetic acid 40g/L, hexamethylenetetramine 20g/L, pH=6, room temperature, 1/5min deceleration rate, low cost.

Formula 3: Sodium m-nitrobenzene sulfonate 110～130g/L, sodium cyanide 100～120g/L, sodium hydroxide 8～10g/L, trisodium citrate 20～30g/L, 80～90 degree Celsius, applicable Removal of the nickel-plated layer of precision steel parts.

Formula 4: Sodium m-nitrobenzene sulfonate 100g/L, NaOH 100g/L, ethylenediamine 120ml/L, sodium lauryl sulfate 0:1g/L, 60～80 degree Celsius. Adding sodium nitrosulfonate during adjustment can restore the deceleration to 80% of the maximum deceleration.

Formula 5: HNO31: 20～40 degree Celsius, fast retreat speed 10μm/5～6min, suitable for stainless steel.

Formulation 6: concentrated HNO3 1000ml/L, NaCl 20g/L, urea 10g/L to inhibit the formation of NOX gas, hexamethylenetetramine 5g/L, room temperature, deceleration rate 20μm/h.

Formulation 7: sodium m-nitrobenzene sulfonate 60～70g/L, sulfuric acid 100～120g/L, potassium thiocyanate 0:5～1g/L, 80～90, suitable for deplating and deplating of copper and copper alloy workpieces When the plating surface is dark brown, clean it thoroughly after taking it out, and then remove the brown film NaCN 30g/L and NaOH 30g/L at room temperature.

Formula 8: HNO3:HF=4:1 volume ratio, proper heating in winter, fast retreat, and iron matrix does not corrode. But HF must be equipped with analytical pure industrial grade HF, which is prone to explosion.

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