The plated parts are easy to float, and the place where they are in contact with the hanger is easily burnt. Because the specific gravity of the plastic is small, it is easy to float in the solution. The shape of the lampshade is like a small disk. The inner surface is recessed and there are two small holes on the side. At first, only one copper wire is used to plate the two holes. Due to the release of gas in the plating, the lamp cover is easily separated from the copper wire, and the copper wire is also light, which is insufficient for the lamp cover to be immersed in the solution. Later, heavy objects were attached to the copper wire to solve the floating problem. The contact point between the copper wire and the lampshade is burnt and the plastic is exposed, which is caused by poor electrical conductivity. In order to solve the floating and conductive problems of the workpiece, we designed a special fixture. The clip has a certain weight, no longer floats after the upper lamp cover, and then two wide conductive sheets are stuck on the holes of the lamp cover, so that the current is uniform everywhere, and the contact points are not burnt.
Bubbles appear in the electroless copper plating of the lampshade, the bubbles become larger after electroplating, and the process of plastic plating can be lifted: degreasing→water washing→roughening→water washing→sensitization→tap water washing→deionized water washing→activation→water washing→chemistry Copper plating→water washing→electroplating→water washing→drying. From the above, it can be seen that any problem in any step before electroless copper plating causes bubbling. There are many reasons for the poor bonding, and the problems that often occur are the degreasing process and the roughening process. If the oil is not completely removed, it will cause peeling and falling off. The lampshade is chemically degreased (plastic parts are not suitable for degreasing with organic solvents). During operation, the temperature rises to 65-70 ° C, and the workpiece is continuously shaken until the water is not washed. Coarsening is an important process in aBS plastic plating. Insufficient coarsening, the bonding force is reduced; excessive coarsening causes the pores to become large and the bonding force is also reduced.
Since the ferrous tin in the sensitizing solution is extremely unstable, the sensitizing liquid is liable to fail, and if it is not adjusted, the activation failure may occur. Insufficient activation will result in incomplete deposition of the electroless plating layer; and excessive activation will cause the active metal to be excessively reduced on the surface to form a discontinuous film layer, which will also lower the bonding force. From the beginning of degreasing, we strictly checked the oil formulation and operating conditions, and checked the time and temperature of the roughening process. A new sensitizing solution and an activation solution were prepared. As a result, bubbles still appeared after electroless copper plating. Several trials and repeated trials, the results are the same, and finally concluded that bubbling is not caused by degreasing, roughening, sensitization, activation. At this time, it is suspected that there is a problem with the composition of the material and the molding process, because the composition and molding process of the aBS plastic has a direct relationship with the plating.
The aBS particles are easy to absorb water, and the moisture content before injection is less than 0.1%. It must be dried in a hot air drying oven at 80 °C for 2 to 4 hours, and the surrounding environment must also be dried. No other ingredients can be mixed in the aBS plastic. We found through investigation that the injection molding plant piled a large number of formed aBS plastic parts on the wet warehouse floor, and the raw materials before injection were not dried. Under our guidance, the raw materials to be injection molded are dried at 80 ° C for 2 to 4 hours, and then tested after meeting the plating requirements. The problem of bubbling after the improved lampshade plating did not occur again.
After the lampshade is electroplated, black spots appear on the surface. After the electroless copper plating of the matt lampshade, it is transferred to the electroplating process. The process used by us is: nickel plating→copper plating→plating bright nickel→chrome plating. The copper plating solution is relatively stable. The main problem is that the copper anode is prone to copper powder (Cu2O) during electroplating, and the copper powder entering the plating solution causes the coating to be rough. We wrapped the anode with a corrosion-resistant anode cloth and placed it in the anode casing. After plating, it was often cleaned. Therefore, the surface after plating was bright and detailed without any problems. After the parts are bright nickel, the surface is dull, and there are dark spots. After adding the brightener, the problem is still not eliminated, and the content of each component is within the range.
After the bath was left overnight, the supernatant was all poured into the spare tank, and a yellow-brown mud-like precipitate was found at the bottom of the plating tank. The analysis is due to the high temperature of the nickel plating solution and the decomposition of the brightener. During the electroplating, the air agitation device turns the sludge at the bottom of the tank and deposits it with the nickel ions on the coating, causing burrs and dark spots. Later, it was found that due to the use of a set of conductive rods for nickel plating and chrome plating, the conductive rods were provided with chromic anhydride left by chrome plating. When nickel plating, chrome was easily introduced into the nickel bath; and since the hangers were not insulated, plating Copper impurities are introduced into the nickel solution, which are the cause of blackening. Copper impurities can be removed by electrolysis at a current density of 0.5 a/dm2. To remove hexavalent chromium, first adjust the pH of the plating solution to about 3 with sulfuric acid, then add 0.2-0.4 g/L of sodium sulfite, stir to reduce the hexavalent chromium to trivalent chromium, and then remove the trivalent chromium with a low current density.
Finally, the organic impurities were removed by filtration with activated carbon. After the bath was treated, no black spots appeared after nickel plating. When chrome is set, the concave part of the lampshade adopts a pictographic anode, and the lampshade finally plated is bright and detailed, which meets the product requirements.
The composition and molding process of plastic parts cannot be ignored, which is often a problem that plating workers are not aware of.
Design special hangers when plating.
Care is taken to maintain the bath so that the ingredients remain within the process specifications.
Strengthen the cleaning between processes and do not bring other impurities into it.
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