1. The surface of the parts can not be plated with copper layer; the cause of this type of failure is generally caused by the failure of the sensitizing solution or activation solution, and it may also be that the pH value, temperature, formaldehyde, and copper sulfate content in the electroless copper plating solution are too low Or the content of complexing agent is too high. To deal with this type of failure, first check whether the sensitization solution, activation solution or colloidal palladium solution is normal. Use a small amount of newly prepared sensitizer and activation solution (or colloidal palladium solution). If the roughened plastic parts can be deposited with a copper layer after being treated with the newly prepared sensitizer and activation solution, it proves that the original sensitization solution or activation solution Has expired, these solutions should be adjusted or replaced. If the roughened light-colored plastic parts are treated with the original sensitizing and activating solution, the surface of the part can become brown, indicating that the sensitizing solution and the activating solution have not failed, and the electroless copper plating solution should be checked. When checking the electroless copper plating solution, first check the pH value and temperature of the solution, adjust the pH value of the solution to about 12, control the temperature at about 30°C, and replenish an appropriate amount of formaldehyde before proceeding with trial plating. If the parts still cannot be deposited For the upper copper layer, the color (light color) or composition analysis of the electroless copper plating solution should be used to determine whether the copper sulfate content in the plating solution is low. If the content is low, an appropriate amount of copper sulfate main salt should be added. After such analysis and processing, the phenomenon that the parts cannot be plated with copper can be eliminated.
2. When electroless copper plating. Partially unplated copper layer on the surface of parts is different from partial unplated parts and completely unplated parts. The reason for this failure is: Partially unplated parts on the surface may be incomplete degreasing; poor roughening; sensitization or The activation time is not enough; the plastic parts themselves have stress or the composition of the electroless copper plating solution is out of adjustment. The failure of plating caused by incomplete degreasing of parts only occurs on a few parts and some parts of the parts, and not all parts have oil on the surface. Therefore, this kind of failure phenomenon is rare, and good degreasing can be taken. Measures are eliminated; if the plastic itself is not plated due to stress, it usually appears in similar parts of the parts, a small amount of parts can be heat-treated to remove the stress, and then inspected according to the usual roughening, sensitization, activation and electroless copper plating Eliminate this kind of trouble; the composition imbalance of the electroless copper plating solution is usually manifested as slow copper sinking speed. If during electroless copper plating, the surface of the plastic part starts to sink within 5 minutes, it is not a problem of the composition of the copper plating solution; if there is no copper layer on the surface of the plastic part for more than 15 minutes during chemical copper plating, it may be possible The reason is that the pH value of the electroless copper plating solution is too low, the temperature is low, the formaldehyde content is low, the copper sulfate content is low, or the complexing agent content is too high. The analysis solution can be adjusted in proportion to eliminate this failure. In addition, the content of chromic acid in the roughening solution is insufficient, and the roughening temperature is too low or the time is too short to cause roughening failure, resulting in the partial surface of the parts not being plated with copper.
Different plastics need different coarsening temperature and time. Most domestic ABS plastics only need to be coarsened at 60℃～65℃ and the time is 20min～30min. No matter how high the coarsening temperature is, it is easy to cause coarsening. Excessive melting, deforming plastic parts. However, the temperature of 60℃～65℃ for Japanese electroplating grade ABS plastic is a bit too low, and it is easy to cause poor roughening of parts. Generally, it is better to roughen at 70℃～75℃. Of course, it also depends on whether the parts are deformed. If the parts are easily deformed, the roughening temperature should be lower and the time should be longer. For some parts that are not easily deformed, the roughening temperature can be higher, and the time should be shorter. In some factories, the temperature is controlled at 82℃～85℃ during roughening, and the time is shortened to 2min～5min. In this way, the roughened parts will light up quickly and have good brightness when electroless copper plating is performed on bright copper. Therefore, during roughening, the temperature and time of the roughening solution should be mastered according to different plastic materials to prevent electroplating failure caused by poor roughening. During the electroplating process of plastic signs in a factory, the plastic parts sent by the supporting factory are not regular injection molded parts, but parts that have been machined on the injection molding plate and surface polished. The conventional injection molded parts electroplating process is used for electroplating. It was found that the appearance of the part was normal before roughening, but after the chemical roughening process, several yellow spots appeared on the surface of the part, and the plating layer in this area became black during electroless copper plating, and there was a failure of plating after electroplating. . Although the chemical roughening process has been adjusted many times, the heat treatment time to eliminate internal stress has been extended, and the chemical reduction process has been strengthened, the results have been minimal. After investigating the production process of the plastic blanks, it was learned that the blanks of the ABS injection molding board were not completely cleaned by the injection molding machine, and there were a small amount of black inclusions on the injection molding board. Although there are no defects on the surface of the part after machining and polishing, it is easy to over-roughen and form micro-cracks or looseness due to the large stress in this area during the roughening process. In this way, in addition to the reaction in the activation process, a part of the unreacted solution penetrates into the cracks, which cannot be completely removed even though it is washed with water and reduced with formaldehyde. As a result, the electroless copper plating cannot proceed according to the normal reaction process, and a black non-conductive Cu20 layer is formed in this area, resulting in the occurrence of partial plating leakage. Later, the factory switched to the electroless nickel plating process for metallization of plastic parts, which avoided the occurrence of the above-mentioned failures. This is because the reducing ability of the reducing agent (sodium hypophosphite) in the electroless nickel plating solution is far greater than the formaldehyde in the electroless copper plating solution, thereby eliminating this failure.
In addition, if the time for sensitization and activation is not enough, there is often a phenomenon that the plastic parts cannot be coated with copper. Sometimes the plastic parts that have been sensitized and activated once do not form activated silver atoms locally, and this will happen. The phenomenon of partial failure of copper plating. In order to eliminate this kind of failure, after the first sensitization and activation, the second sensitization and activation treatment can be repeated after washing with water, and even the third and fourth sensitization and activation treatments can be performed to make the roughening process. All parts of the surface of the plastic parts have catalytic silver atoms, which eliminates the phenomenon that the parts cannot be plated with copper.
3. Poor adhesion between the coating and the plastic. Poor adhesion of the coating on the plastic parts is a common failure phenomenon. The general reasons for this failure are: incomplete degreasing on the surface of the plastic parts; improper plastic injection molding conditions; insufficient surface roughness or Excessive roughening; oil in the electroless copper plating solution will cause blistering and peeling of the coating. Incomplete degreasing of general parts is an accidental rare phenomenon. It is possible to use enhanced degreasing measures before plating to avoid this failure; the poor adhesion of the coating caused by improper injection molding conditions often appears in the same part of each part, and it will There are many parts that have this kind of failure phenomenon. Whether this is the reason, you can take a small amount of parts, put them in the oven to remove the stress, then go through roughening, sensitization, activation and electroless copper plating, and observe whether the adhesion of the coating is good after electroplating . The poor adhesion of the coating caused by insufficient roughening of the part often appears on the concave surface of the part. If the coating is peeled off, the plastic surface of these parts is usually smooth, while the poor adhesion of the coating caused by excessive roughening often appears At the tips and edges of the parts, these parts show a rough appearance after the coating is stripped.
The way to check whether the roughening is appropriate is to place the roughened parts in the sun or dry them in an oven. If the surface becomes white after drying, fine powdery substances appear on the tips and edges of the parts. This kind of powdery If the object can be wiped off by hand, it indicates that these parts have been excessively coarsened, and the coarsening temperature should be lowered or the coarsening time should be shortened. If a few parts of the surface of the dried part are white, and most of the surface is still the natural color of the plastic, it indicates that the roughening is insufficient, and the roughening temperature should be increased or the roughing time should be increased.
What kind of roughening temperature and time should be used? It is best to take a small number of parts and test in different roughening temperatures and times in batches to find out that the roughened parts can be hydrophilic and on the surface after drying. It is better to control the roughening temperature and time under such temperature and time to show the uniform whitening temperature and time when there is no powder. The use of air stirring to improve the crystalline structure of the electroless copper plating layer, reduce copper powder, and prolong the service life of the copper plating solution has certain benefits. The hydrogen generated by the reaction in the bath acts as the second reducing agent in the bath, but its presence will cause the activity of the local bath to be too strong; in addition, the air must be strictly purified and stirred. Otherwise, if the air is removed The oil in the compressor is brought into the copper plating solution, which will make the copper plating layer rough and loose, and the bonding force will not be good. Because the electroless copper plating solution is alkaline, if the oil entering the copper plating solution is saponified oil, a saponification reaction will occur to produce soap and glycerin. If the solution entering the solution is non-saponified oil, it will become Partially emulsified, so that bubbles appear in the copper plating bath. Therefore, when it is observed that there is foam in the copper plating solution, and the copper layer is rough and loose at the same time, and the bonding force is not good, check whether the air passing through the copper plating solution is oily. If there is oil, strengthen the air. Purification, in addition, the copper plating solution must be treated with activated carbon to remove oil stains and eliminate the failure of poor plating adhesion.
Checking the bonding force of the coating of plastic parts can use the cross-cut method, that is, use the sharp edge spacing of lmm to draw 10 vertically and horizontally. The scratches must expose the plastic matrix, and then press and stick with the specified adhesive tape. When the adhesive tape is opened, the coating is plated. At least 90% does not fall off or there is no coating sticking off at all to be qualified. In addition, the thermal cycle test can also be used to assess the adhesion of the coating of plastic parts. Generally, it is required to place the plastic plated parts at -30°C for 1 hour, then at room temperature for 1 hour, then at 70°C for 1 hour, and finally to room temperature for 1 hour. Cycle, the requirement of high bonding performance is that no blistering of the coating after 4 cycles is qualified.
4. There is dark brown powder on the copper plating layer. The reason for this failure is: excessive loading of parts during electroless copper plating; excessive roughening; pH or temperature of the copper plating solution is too high; the content of copper salt is too high and complex The content of the agent is too small; the content of the reducing agent is too much or the copper plating solution is contaminated by the activation solution. When analyzing and dealing with such failures, first check whether the electroless plating load of the parts is too much. If the load is really too much, reduce the number of electroless copper plating parts to see if this kind of malfunction can be eliminated; Shorten the chemical roughening time to check whether the plastic parts are excessively roughened. If it is not for the above reasons, check the electroless copper plating solution.
Generally speaking, the pollution of the copper plating solution by the activation solution is different from the abnormal composition and operating conditions of the electroless copper plating solution. The latter usually speeds up the copper plating speed. The speed of copper is not fast, it may be caused by the pollution of the activation solution. From the chemical copper plating solution composition and operating conditions abnormality caused such failures, it is found that the pH value of the chemical copper plating solution is too high, and such failures are prone to occur. Therefore, the pH value of the chemical copper plating solution needs to be strictly controlled (around 12) in production. Do not increase the pH value of the electroless copper plating solution in order to pursue a faster copper plating speed. If the pH value of the electroless copper plating solution is controlled at about 12 and a dark brown powdery copper layer appears, it may be that the electroless copper plating solution needs to be supplemented with a complexing agent, or the plating solution can be appropriately diluted to make the electroless plating The temperature of the copper liquid is controlled below 30°C. These measures are conducive to troubleshooting this failure.
5. There is black powder on the electroless nickel plating layer. The main reasons for this failure are: the temperature of the electroless nickel plating solution is high or the pH value of the plating solution is too high, the content of nickel sulfate and sodium hypophosphite in the electroless nickel plating solution is too high, etc. . These factors will cause the reaction of the electroless nickel plating solution to be violent, causing the solution to decompose rapidly and produce solid nickel particles in the solution, and the inclusion of these particles becomes the black powder in the nickel plating layer. The way to troubleshoot this type of fault is: first need to control the pH value and temperature of the plating solution, then analyze and adjust the solution composition, and then filter the solid particles in the electroless nickel plating solution.
6. Pockmarks of plastic coating (copper or nickel) The main sources of pits on the surface of plastic parts are: base material, pre-electroless plating process, copper plating and nickel plating. Small holes, small spots, inclusions, etc. on the base of plastic parts may cause pitting in the coating; during roughening, there are small spots on the surface of the part that are not wetted, activated to small spots that are not coated after electroless plating, and then electroplated Pockmarks are formed; and these pockmarks exist in the form of pits. Eliminating the pitting produced in this link is to strengthen the pre-plating inspection of the base material and the treatment of the pre-electroless plating process. After electroless plating of plastic parts, copper electroplating and nickel electroplating are also prone to pitting. If the phosphorus content of the phosphorous anode plate used for copper plating is low or too high, the anode will dissolve abnormally and easily produce cuprous oxide particles. , Resulting in pitting of the copper plating layer. In addition, the imbalance of the brightener in the plating solution or the decomposition products of the brightener will cause pitting of the coating, which must be strictly controlled to eliminate the surface pitting of the electroplated copper layer. The pitting of the electroplated nickel layer is related to iron impurities in the nickel plating solution, brightener decomposition products, pH value of the plating solution, insufficient wetting agent, solid particles in the plating solution, etc. It is also necessary to carry out this plating according to the method in Chapter 4 Elimination of pitting faults.