Analysis and troubleshooting of common faults in bright acid copper plating: the coating is not bright in low current density area

Plastic plating-.
Analysis and troubleshooting of common faults in bright acid copper plating: the coating is not bright in low current density area.
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When the bright sulfate copper plating appears that the coating in the low current density area is not bright, if the bright nickel and decorative chromium are then plated, the bright coating can not be easily obtained in the low current density area. The causes of such failures are as follows: rough coating in the area of low current density of pre-coating; poor electrical conductivity of the fixture; low content of N, M brightener or sodium dodecyl sulfate in copper plating bath or too much sodium polydithiodipropane sulfonate (those using other bright additives should be analyzed in accordance with the fault instructions of the process manual); there is more univalent copper in the plating bath. Too high bath temperature and low sulfuric acid content will make the copper plating layer not bright in the low current density area. Although most of these faults are caused by the imbalance of bath composition or impurities in the bath, the quality of the pre-coating and the electrical conductivity of the contact point should be checked first. Sometimes because the coating on the hook of the hanging part is very thick, the conductivity is very poor, or the contact resistance of each contact point of the hanger is large, the real current density on the surface of the part is too small, so that the coating in the low current density area is not bright. The faults caused by these factors have nothing to do with the composition of the plating bath, so check the conductivity of the pre-plating layer and the hanger first, which can prevent the original plating solution from being treated blindly without any problem.

In the actual production, the imbalance of the composition of the bath or the proportion of brightener is adjusted according to the Hall slot test. If the univalent copper in the bath causes the coating in the low current density area to be not bright, an appropriate amount of hydrogen peroxide can be added into the Hall cell to observe whether the brightness of the coating in the low current density area has been improved. If so, it shows that there is more univalent copper in the bath. Otherwise, it is not a problem of univalent copper. If the fault disappears after adding hydrogen peroxide, but the fault occurs again after a while, hydrogen peroxide needs to be added to eliminate the fault. This shows that univalent copper is easily produced in the plating bath, so it is necessary to check the anode. if there is no brown-black film on the surface of the anode at normal current density, it means that the quality of the anode is poor or the phosphorus content is too low, so it should be replaced.

Too high bath temperature (generally bright sulfate copper plating bath above 28 ℃, wide temperature plating bath above 38 ℃) will also make the copper plating layer not bright in the area of low current density. Therefore, cooling measures should be taken.