The occurrence of poor coating quality is mostly due to abnormalities in plating conditions, plating equipment or plating solution, and human negligence It is usually easier to identify the cause and overcome it when defects occur on site, but it is more challenging to wait for a period of time after electroplating before defects occur However, in the future, it is also necessary to pay attention to the accelerated oxidation and corrosion caused by contact with acidic gases, oxygen, moisture, etc. in the environment The following chapter will explore and explain the causes and improvement measures of poor electroplating
1. Surface roughness: refers to an uneven, non shiny surface, usually in a coarse white shape
(1) Possible reasons: (2) Improvement measures:
1. The surface of the material is severely rough, and the coating cannot cover it evenly. 1. If the material is severely rough, immediately stop production and notify the customer
2. The surface of the metal transmission wheel is rough and the compression is too tight, resulting in compression damage. 2. If the transmission wheel is rough, it can be replaced with a substitute and the compression tightness can be checked
3. The current density is slightly high, and some surfaces are not shiny or rough (not yet burnt). 3. Calculate whether the current density is too high, and if so, reduce the current
4. If the bath temperature is too low, nickel plating usually occurs. 4. Wait for the clarity to improve before turning on the machine, or reduce the current and immediately check the temperature control system
5. If the pH value is too high or too low, nickel plating or gold plating (not too low) will generally occur. 5. Immediately adjust the pH to the standard range
6. Pre treatment solution corrodes the substrate. 6. Check the pre-treatment solution, dilute the solution, or replace the solution
2. Adhesion of foreign objects: Refers to the dirt attached to the surface of the terminal
(1) Possible reasons: (2) Improvement measures:
1. Unclean washing or poor water quality (if there are microorganisms). 1. Clean the sink and replace it with new water
2. Mechanical oil stains occupying the receiving system. 2. Cover the areas with oil stains
3. The material contains a gel like substance that cannot be removed in the pre-processing process. 3. It must be soaked in a solvent first
4. When receiving materials, if they come into contact with soil or dirt. 4. Avoid falling to the ground. If soil has already been attached, blow air to clean it. If there is a lot of soaking, it is recommended to clean it again
5. Tin lead crystal adhesion 5. Immediately remove the crystal
6 brush plated wool? Fiber silk 6. Replace wool? And check the contact pressure
7. Dissolve fiber filaments in paper tape. 7. Clean the groove
8. Belt shedding debris. 8. Replace the belt
3. Poor adhesion: Refers to the peeling of the coating Peeling, blistering and other phenomena
(1) Possible reasons: (2) Improvement measures:
1. Poor pre-treatment, such as nickel stripping. 1. Strengthen pre-treatment
2. Discharge due to poor cathode contact, such as nickel stripping, nickel stripping of gold, nickel stripping of tin and lead. 2. Check for poor cathode contact and adjust accordingly
3. The plating solution is severely contaminated. 3. Replace the solution
4. If the production speed is too slow, the bottom layer will oxidize again, such as nickel layer oxidation (or gold reduction) in the gold bath, tin and lead stripping. 4. Before electroplating, it must be reactivated
5. Poor water washing. 5. Replace with new water and clean the sink if necessary
6. The material is severely oxidized, such as oxidation spots, and the oxide film is formed after heat treatment. 6. Rust removal and oxide film removal must be carried out first, usually using chemical polishing or electrolytic polishing
7. Shutdown caused by chemical displacement reaction. 7. Must not shut down or remove defective products
8. If the operating voltage is too high, the cathode conductive head and plated parts will heat up, causing oxidation of the coating. 8. Reduce the operating voltage or check the contact condition of the wires
9. Poor bottom plating (such as burning), causing the next layer to peel off. 9. Improve the quality of bottom plating
10. Serious 10. Refer to NO12 treatment measures for the peeling caused by burning
4. Exposed copper: Copper or yellow black color can be clearly seen at low current areas (grooves)
(1) Possible reasons: (2) Improvement measures:
1. Poor pre-treatment, grease, oxides Foreign objects have not been removed, and the coating cannot precipitate. 1. Strengthen pre-treatment or reduce production speed
2. The operating current density is too low, resulting in low current areas where the coating cannot precipitate. 2. Recalculate the plating conditions
3. Excessive nickel gloss agent, resulting in low current areas and inability to precipitate the coating. 3. Treatment solution, remove excessive gloss agent or renew
4. Severe scratches causing exposed copper. 4. Check the electroplating process (refer to NO5 for reference)
5. Not plated. 5. Adjust the current position
Scratch: Refers to horizontal lines, which are generally more likely to occur on tin lead coatings
(1) Possible reasons: (2) Improvement measures:
1. The material itself may be scratched during stamping. 1. Stop production and contact the customer
2. Scratches on metal tools in electroplating equipment, such as cathode heads, oven locators, guide wheels, etc. 2. Check the electroplating process and adjust equipment and tools as necessary
3. Scratched by electroplated crystals. 3. Stop production and immediately remove the crystals
6. Deformation (scraping): Refers to the terminal shape deviating from its original size or position
(1) Possible reasons: (2) Improvement measures:
1. The material itself undergoes deformation during stamping or transportation. 1. Stop production and contact the customer
2. The electroplating equipment and tools are scraped off (such as blowing air, locator, oscillator, groove, rotating wheel). 2. Check the electroplating process and adjust the equipment and tools in a timely manner
3. The plate is too small or poorly wound, causing it to scrape off during feeding and discharging. 3. Stop production and adjust the plate as needed
4. The transmission wheel is misaligned. 4. Correct the transmission wheel or change the transmission mode
7 compression injury: refers to irregularly shaped concave holes
Possible reasons: Improvement measures:
1) During the punching process, it was already damaged and the coating could not be covered smoothly
2) Loose or faulty transmission wheels causing damage during compression: 1) Stop production and contact the customer
2) Check the transmission mechanism or replace spare parts
8. White mist: refers to a layer of cloud like coating on the surface of the coating, which is not shiny but smooth
Possible reasons: 1) Poor pre-processing
2) The plating solution is contaminated
3) The tin lead layer is prone to acid corrosion, such as being corroded by tin lead liquid during shutdown
4) The temperature of tin lead solution is too high
5) Tin lead current density too low
6) Insufficient gloss agent
7) Spread the word that the wheels are dirty and dirty
8) The improvement measures caused by the long-term progress of tin lead electricity and foam adhesion: 1) Strengthen pretreatment
2) Replace the medicine and purify the contaminated liquid
3) Avoid shutdown, and if unavoidable, remove any defects
4) Immediately check the temperature control system and reset the temperature
5) Increase current density
6) Supplement the non detergent transmission wheel
7) Clean the transmission wheel
8) Remove foam immediately
9 pinholes: Refers to clusters of small circular holes (resembling a bell shaped pattern)
Possible reasons: Improvement measures:
1. The current density of the operation is too high. 1. Reduce the current density
2. The surface tension of the electroplating solution is too high and the wetting agent is insufficient. 2. Add moisturizer or check the solution.
3. Poor stirring effect during electroplating time. 3. Strengthen mixing.
4. The temperature of the tin lead bath is too low. 4. Adjust the bath temperature
5. The electroplating solution is contaminated. 5. Purify the medicine or update it.
6. Poor pre-processing. 6. Strengthen the pre-treatment effect.
10. Tin lead remelting: Refers to the surface of the coating having a flat, mountainous terrain (resembling bubbles, but with good adhesion), which only occurs in tin lead coatings.
(1) Possible reasons: (2) Improvement measures:
1. The tin lead cathode overheats (voltage is too high), causing the tin lead layer to remelt. 1. Reduce the voltage and understand why the bath voltage is too high before adjusting the plating conditions.
2. The oven temperature is too high and the baking time is too long, causing the tin lead layer to remelt. 2. Reduce the oven temperature and check the temperature control system.
11. Terminal melting: Refers to the formation of concave holes on the surface due to heating, usually caused during copper material (before nickel plating) or tin lead electroplating.
(1) Possible reasons: (2) Improvement measures:
1. Poor cathodic contact before nickel plating or between tin lead electroplating can cause discharge sparks to melt copper into concave holes. 1. Check the cathode and adjust it in a timely manner.
12. Burnt coating: Refers to the surface of the coating being severely dark, rough, and carbon colored. (referring to high current density areas)
(1) Possible reasons: (2) Improvement measures:
1. The operating current density is too high. 1. Reduce the current density.
2. The bath temperature is too low. 2. Increase the bath temperature and check the temperature control system.
3. Poor mixing. 3. Increase the mixing effect.
4. Insufficient gloss agent. 4. Supplement the gloss agent.
5. The pH value is too high. 5. Adjust the pH value to the standard range.
6. Improper selection of plating position. 6. Revise the plating position and pay attention to the current distribution line.
7. Poor filtering of rectifier. 7. Check if the filtering degree meets the standard. If there is any deviation, the rectifier must be sent for repair.
13. Excessive plating thickness: Refers to the actual plating thickness exceeding the expected thickness.
(1) Possible reasons: (2) Improvement measures:
1. The transmission speed slows down, becomes inaccurate or unstable. 1. Check the transmission system and calibrate the production speed.
2. The current is too high, inaccurate or unstable. 2. Check the rectifier and anode and cathode, and make timely corrections.
3. Selection of plating position variation. 3. Check if the plating position deviates and readjust.
4. When the concentration of metal in the medicine increases, gold plating is generally more sensitive. 4. Adjust the current or transmission speed.
5. The pH value of the medicine is too high. 5. Adjust the pH value to the standard range.
6. The fluorescence film thickness tester deviates or the testing method is incorrect. 6. Calibrate instruments or determine testing methods.
7. The bath temperature is too high. 7. Check the temperature control system.
14. Insufficient plating thickness: Refers to the actual plating thickness being lower than the expected thickness
(1) Possible reasons: (2) Improvement measures:
1. The transmission speed becomes faster, inaccurate or unstable. 1. Check the transmission system and calibrate the production speed.
2. The current is too low, inaccurate or unstable. 2. Check the rectifier and anode and cathode, and make timely corrections.
3. Selection of plating position variation. 3. Check if the plating position deviates and readjust.
4. The concentration of metal in the medicine decreases or the medicine is diluted. 4. Adjust the current or transmission speed, and stop production if necessary.
5. The pH value of the medicine is low. 5. Adjust the pH value to the standard range.
6. The fluorescence film thickness tester deviates or the testing method is incorrect. 6. Calibrate instruments or determine testing methods.
7. The bath temperature is too low. 7. Check the temperature control system and stop production if necessary.
8. There is gold deposition in the coating structure, which consumes some of the current. 8. Remove metal deposits or replace fixtures.
9. Mixing of electroplating solution, uneven circulation or insufficient metal replenishment. 9. Improve the circulation or replenishment of medication.
15. Uneven plating thickness: refers to the actual thickness of the plated film being high or low, or unevenly distributed.
(1) Possible reasons: (2) Improvement measures:
1. Unstable transmission speed. 1. Check the transmission system and calibrate the production speed.
2. Unstable current. 2. Check the rectifier and anode and cathode, and make timely corrections.
3. The terminal is severely deformed, causing instability in the plating position. 3. Check if the plating position is deviated. If the material is severely deformed and the process cannot be improved, production must be stopped.
4. The terminal structure causes uneven distribution of high and low currents. 4. Adjust the plating position to increase the stirring effect.
5. Poor mixing effect. 5. Increase the mixing effect.
6. There is an issue with the location of the film thickness test, resulting in significant errors. 6. The testing location needs to be recalibrated.
7. The plating mechanism is unstable. 7. Improve the plating selection mechanism.
16. Dark red coating: usually refers to a golden color that is darker and redder.
(1) Possible reasons: (2) Improvement measures:
1. The gold plating solution deviates. 1. Adjust the electroplating solution again.
2. The coating is rough, and when burned white and covered with a gold layer, it turns red. 2. Improve the defect of nickel layer.
3. Poor water washing can cause redness. 3. Replace the washing water.
4. The plated parts are not completely dry and will oxidize red in the future. 4. Check the drying system to ensure that the plated parts are dry and the terminals that have turned red can be cleaned with dilute cyanide.
17. Interface black line, fog line: This phenomenon usually occurs at the interface of the semi tinned lead layer.
(1) Possible reasons: (2) Improvement measures:
1. The cathodic reaction is too large, and a lot of hydrogen foam floats on the liquid surface. 1. Reduce the current.
2. Poor cathode stirring. 2. Adjust the frequency and amplitude of the oscillator.
3. Uneven adjustment of plating height. 3. Check the plating height and make corrections again.
4. The plating tank is poorly designed, resulting in foam remaining on the liquid level of the plating tank, which cannot be eliminated. 4. Improve the plating tank structure.
5. White mist in the low current area of tin lead solution. 5. Adjust the tin lead solution to the optimal slot condition.
6. Poor filtering of rectifier. 6. Measure the filtering degree with an oscilloscope, and if the filtering is poor, repair the rectifier.
18. Poor soldering: Refers to the poor ability of the tin lead coating to adhere to tin.
(1) Possible reasons: (2) Improvement measures:
1. Tin lead electroplating solution is contaminated. 1. Replace the tin lead solution.
2. Excessive amount of gloss agent causes excessive carbon content in the coating. 2. Immediately perform activated carbon filtration or replace the solution.
3. Poor post-treatment after electroplating (residual acid solution, poor water quality, salt formation, foreign matter adhesion). 3. Improve processes and enhance water quality
4. Poor adhesion. 4. Solve the problem of poor adhesion.
5. Excessive voltage during electroplating can cause thermal oxidation and passivation of the plated parts. 5. Improve conductive equipment.
6. Excessive current density leads to poor coating structure. 6. Reduce current density.
7. Poor mixing leads to poor coating structure. 7. Increase the mixing effect.
8. Excessive bath temperature leads to poor coating structure. 8. Immediately lower the bath temperature and check the cooling system.
9. Due to poor storage environment and prolonged use, the coating may oxidize and age. 9. Strengthen packaging and improve storage environment.
10. The coating is too thin. 10. Increase the thickness of the plating layer.
11. The soldering temperature is incorrect. 11. Check the soldering temperature.
12. The influence of the shape and structure of the plated parts. 12. Change the judgment method.
13. Excessive impurities in the solder flux. 13. Replace the solder flux.
14. The influence of plating material (tin>tin lead>gold>copper>phosphor bronze>brass) 14. Explore the material.
15. There are foreign objects on the surface of the plated part, such as oil stains. 15. Remove foreign objects.
16. The bottom layer is rough. 16. Improve the flatness of the bottom layer.
19. Blackening of coating: Excluding burnt black and black lines at the tin lead interface.
(1) Possible reasons: (2) Improvement measures:
The tin lead coating originally had white mist, but later turned black. 1. Refer to Section 8 for countermeasures to deal with tin lead white mist.
2. The nickel tank has been contaminated and there will be a black coating in the low current area. 2. Perform activated carbon treatment or weak electrolysis treatment.
3. The plated parts are severely oxidized, blackened, and corroded. 3. Analysis and exploration of the reasons are necessary.
4. Shutdown causes corrosion or reduction. 4. Eliminate defects and avoid downtime.
5. The tin lead coating was blackened by sparks released from the cathode conductive head. 5. Adjust the cathode conductive head to ensure good contact with the terminal.
20. Tin slag: refers to the intermittent and fine tin lead metal on the surface of the tin lead layer, usually most commonly found at the material strip.
(1) Possible reasons: (2) Improvement measures:
1. Tin lead solution is severely crystallized in the cathode conductive seat. 1. Improve the dispensing of medication and strengthen the cleaning process.
2. Rubbing in the oven and scraping off high-temperature metal objects. 2. Adjust the fixtures inside the oven to avoid rubbing against the terminals, and adjust the oven temperature.
