### 1. ENIG Plating NG
**Cause Analysis of the Problem:**
1.1 Nickel cylinder is too active; high concentration or contamination of activated palladium due to pretreatment (e.g., iron or copper ion contamination, high local temperature accelerating the aging of the liquid), prolonged immersion time, high temperature, or insufficient washing after activation (i.e., before nickel deposition).
1.2 Grinding plates from previous operations may have absorbed excessive palladium. The rollers on the equipment may not be thoroughly cleaned before grinding the plates, and insufficient water pressure may fail to flush remaining copper powder from the edges (not completely etched away). Residual copper and nickel deposits after etching can lead to seepage plating.
1.3 High concentration of colloid-activated palladium was present after PTH pretreatment.
**Corresponding Improvement Measures:**
1.1 Strictly control the nickel cylinder load to between 0.3 and 0.8 dm²/L and use an appropriate stabilizer. Revert the cylinder when the anode protection current exceeds 0.8A.
1.2 Strictly monitor the concentration of the activated tank liquid, immersion time, working temperature, and washing time. Ensure plates are fully washed after activation and minimize contamination of the tank liquid.
1.3 Inspect and etch QC boards before nickelization to ensure no residual copper. Clean brushing equipment thoroughly. Ensure micro-etching depth, abrasive board depth, and water pressure are adequate (1000-1500” for ordinary soft board brushing and 800-1000” for hard board brushing). Maintain consistent appearance and quality using brushing equipment.
1.4 Properly control the concentration of colloid-activated palladium during the pretreatment of copper carbide PTH.
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### 2. Leakage Plating of ENIG
**Cause Analysis of the Problem:**
2.1 The concentration of activated palladium is too low, or immersion activation time, temperature, and activated contamination are insufficient. Plates left in the sink too long before nickel deposition (passivation) can also contribute to leakage plating.
2.2 Copper surface contamination may be due to residual glue, dirty treatment (e.g., tin removal), external contamination, or previous process contamination.
2.3 Excessive amounts of stabilizer in the nickel sink, low temperature, inadequate activity (resulting in a dark nickel layer or dark red gold color after gold sinking), insufficient load, metal or organic pollution, or excessive stirring can lead to leakage plating. Copper surfaces that are badly oxidized or inadequately washed after development, and contamination of the nickel groove pH and copper surface with sulfides or improper additives, can also cause issues.
**Corresponding Improvement Measures:**
2.1 Control the concentration of palladium in the activated fluids, monitor immersion time, working temperature, and reduce contamination of copper ions (replace when copper ion concentration exceeds 100PPM). Ensure plates do not remain in the sink too long before nickel sinking.
2.2 Ensure there is no residue on the copper surface and that the copper surface is thoroughly treated during pretreatment before nickelization.
2.3 Control operational parameters of the nickel reduction groove, ensure adequate pre-nickelization activity, increase the load by adding auxiliary copper plates in the groove, avoid metal or organic pollution, and control stirring to prevent excessive intensity.
3. **ENIG Immersion Gold PCB Nickel Layer “Whitening” (Nickel Layer Sub-layer, Nickel Layer Thickness is Insufficient)**
**Cause Analysis:**
Nickel slot metal nickel ion concentration may be too low or high, temperature may be low, pH value might be low, activity could be insufficient, time might be inadequate, load may be large, phosphorus content might be high (resulting in white lines or holes), or nickel bath liquid may be < or > 4MTO.
**Improvement Measures:**
Adjust nickel ion concentration to the correct range, control temperature, pH value, improve activity, reduce load, and adjust phosphorus content to within the allowable range. Ensure nickel reaches or exceeds 4MTO, and conduct tests to meet quality requirements.
4. **Coarse and White ENIG PCB Layer**
**Cause Analysis:**
4.1. Residual glue or medicinal liquid on copper surface, dirty or rough copper surface, severe oxidation, excessive micro-etching, uneven micro-etching of copper ions, or unclean tin removal; 2. Gold trough contamination (nickel metal impurities) or imbalance (excessive or small load), low temperature, low pH value, low gold concentration, low specific gravity, too many stabilizers, insufficient gold layer thickness, or gold trough medicinal water < or > 4MTO; 3. Poor nickel deposit quality (thin or discolored nickel layer), dark appearance of gold layer, unstable nickel bath liquid activity, excessive local speed of nickel cylinder circulation, local overheating, or excessive nickel stabilizer concentration; 4. Solid particles, whitening, or shedding of welding resistance in chemical nickel solution, minor contamination by palladium or copper; 5. Nickel trough plating solution pH too high or water quality not clean.
**Improvement Measures:**
4.1. Enhance inspection of incoming materials, use high-quality electroplated copper, control micro-etching rate, and ensure thorough tin removal; 2. Control gold bath liquid components within range; 3. Improve nickel deposit quality, ensure uniform filtration and temperature of nickel trough liquid, and maintain nickel stabilizer within range; 4. Strengthen filtration of chemical nickel solution to avoid contamination; 5. Maintain water quality and pH value of nickel trough within range.
5. **Gold Layer “Drop Gold, Drop Nickel Gold” (Copper-Nickel or Nickel Poor Binding with Gold PCB)**
**Cause Analysis:**
5.1. Nickel surface passivation, darkening of nickel layer, excessive nickel content (>5%), imbalance of nickel cylinder accelerator, high phosphorus, or contamination by copper ions; 2. Dirty (oxidized) copper surface, long wash-in time after development/microetching, passivation of palladium layer, excessive activation, poor oil removal, or copper ion contamination in activating solution; 3. Unclean washing between nickel cylinder and gold slot, low pH value of gold liquid, contamination by metal or organic impurities, aggressive gold deposit system, or composition control out of range.
**Improvement Measures:**
5.1. Prevent nickel surface passivation, check nickel layer quality, control nickel addition in small stages, adjust accelerator, reduce phosphorus content, minimize copper ion contamination, and maintain nickel parameters; 2. Improve cleanliness of copper treatment, prevent palladium layer passivation, control activation time and concentration, and improve oil removal and microetching; 3. Enhance washing of gold plates, adjust pH value, detect contamination, and select appropriate gold system.
6. **Immersion Gold Surface PCB “Poor Weldability” (Solderability)**
**Cause Analysis:**
6.1. Gold layer too thin; 2. Poor water quality, high nickel or gold cylinder content, contamination by impurities, inadequate activity, or abnormal nickel appearance; 3. High copper ion content or excessive activation during micro-etching and activation; 4. Nickel and phosphorus content should be 7-12%, and nickel-gold layer deposition rate should be controlled; 5. Long gold deposit time, low gold concentration, low temperature, or contamination by organic/metal impurities.
**Improvement Measures:**
6.1. Maintain gold thickness at 0.05-0.1 μm; 2. Recycle wash gold-deposited plates with pure water, enhance maintenance to minimize nickel or trough medication aging, avoid contamination, and improve nickel layer appearance; 3. Strengthen control of micro-etching and activation parameters; 4. Control phosphorus content to 7-9% and nickel deposition rate; 5. Increase gold concentration or temperature to reduce deposit time, reduce contamination, or replace gold.
7. **Corrosion of Nickel Layer (Black Disc)**
**Cause Analysis:**
7.1. Long gold immersion time; 2. Low pH value, low temperature, or low gold concentration; 3. Uneven distribution of nickel and phosphorus; 4. Difficult or slow gold recovery due to water aging or contamination; 5. Aggressive gold deposit system; 6. Nickel layer too thin (<2 μm); 7. Incomplete cleaning of nitric acid residue; 8. Prolonged exposure to corrosive environments; 9. High pH of nickel slot resulting in low phosphorus content and reduced corrosion resistance.
**Improvement Measures:**
7.1. Control gold deposition rate and thickness (0.05-0.1 μm, not exceeding 8u); 2. Control pH, temperature, and concentration of gold liquid; 3. Improve nickel slot stirring and distribution; 4. Increase gold concentration or replace if needed; 5. Select high-quality gold systems; 6. Maintain nickel layer thickness at 3-4 μm; 7. Eliminate nitrate ion contamination; 8. Transfer plates promptly; 9. Keep nickel slot pH within range, ideally not exceeding 4.8.
8. **Pinhole in Nickel Layer**
**Cause Analysis:**
8.1. Poor exhaust of nickel slot filter, weak stirring, or inadequate oscillation; 2. Soluble particles in nickel solution, poor pretreatment, or organic contamination.
**Improvement Measures:**
8.1. Improve filter exhaust conditions, maintain circulating pipeline, increase oscillation intensity, and optimize mixing conditions; 2. Strengthen filtration of nickel solution, improve pretreatment, and reduce organic contamination.
9. **The Current of the Ejection Protection Device is Too High (Consumes a Lot of Nickel)**
**Cause Analysis:**
9.1. High nickel bath temperature, high pH, local overheating, rapid replenishment, or low tranquilizer; 2. Slot wall passivation; 3. Carrying small amounts of activating liquid; 4. Nickel and gold fragments falling into nickel slot; 5. Abnormal ejection protection device; 6. Improper passivation of stainless steel groove.
**Improvement Measures:**
9.1. Control nickel liquid operating parameters; 2. Prevent groove wall passivation; 3. Avoid carrying small amounts of activating residue into nickel liquids; 4. Regularly inspect and clean hangers; 5. Improve ejection protection device; 6. Re-passivate with nitric acid.
10. **Liquid Nickel “Turbidity”**
**Cause Analysis:**
10.1. High nickel pH or temperature; 2. Excessive carry-out; 3. Leaks from pipes or drugs; 4. High imbalance activity.
**Improvement Measures:**
10.1. Maintain nickel pH and temperature within range; 2. Monitor employee operation (preferably automatic lines); 3. Improve equipment; 4. Enhance solution maintenance and ensure nickel solution activity.
**Cause Analysis of the Problem:**
1.1 Nickel cylinder is too active; high concentration or contamination of activated palladium due to pretreatment (e.g., iron or copper ion contamination, high local temperature accelerating the aging of the liquid), prolonged immersion time, high temperature, or insufficient washing after activation (i.e., before nickel deposition).
1.2 Grinding plates from previous operations may have absorbed excessive palladium. The rollers on the equipment may not be thoroughly cleaned before grinding the plates, and insufficient water pressure may fail to flush remaining copper powder from the edges (not completely etched away). Residual copper and nickel deposits after etching can lead to seepage plating.
1.3 High concentration of colloid-activated palladium was present after PTH pretreatment.
**Corresponding Improvement Measures:**
1.1 Strictly control the nickel cylinder load to between 0.3 and 0.8 dm²/L and use an appropriate stabilizer. Revert the cylinder when the anode protection current exceeds 0.8A.
1.2 Strictly monitor the concentration of the activated tank liquid, immersion time, working temperature, and washing time. Ensure plates are fully washed after activation and minimize contamination of the tank liquid.
1.3 Inspect and etch QC boards before nickelization to ensure no residual copper. Clean brushing equipment thoroughly. Ensure micro-etching depth, abrasive board depth, and water pressure are adequate (1000-1500” for ordinary soft board brushing and 800-1000” for hard board brushing). Maintain consistent appearance and quality using brushing equipment.
1.4 Properly control the concentration of colloid-activated palladium during the pretreatment of copper carbide PTH.
—
### 2. Leakage Plating of ENIG
**Cause Analysis of the Problem:**
2.1 The concentration of activated palladium is too low, or immersion activation time, temperature, and activated contamination are insufficient. Plates left in the sink too long before nickel deposition (passivation) can also contribute to leakage plating.
2.2 Copper surface contamination may be due to residual glue, dirty treatment (e.g., tin removal), external contamination, or previous process contamination.
2.3 Excessive amounts of stabilizer in the nickel sink, low temperature, inadequate activity (resulting in a dark nickel layer or dark red gold color after gold sinking), insufficient load, metal or organic pollution, or excessive stirring can lead to leakage plating. Copper surfaces that are badly oxidized or inadequately washed after development, and contamination of the nickel groove pH and copper surface with sulfides or improper additives, can also cause issues.
**Corresponding Improvement Measures:**
2.1 Control the concentration of palladium in the activated fluids, monitor immersion time, working temperature, and reduce contamination of copper ions (replace when copper ion concentration exceeds 100PPM). Ensure plates do not remain in the sink too long before nickel sinking.
2.2 Ensure there is no residue on the copper surface and that the copper surface is thoroughly treated during pretreatment before nickelization.
2.3 Control operational parameters of the nickel reduction groove, ensure adequate pre-nickelization activity, increase the load by adding auxiliary copper plates in the groove, avoid metal or organic pollution, and control stirring to prevent excessive intensity.
3. **ENIG Immersion Gold PCB Nickel Layer “Whitening” (Nickel Layer Sub-layer, Nickel Layer Thickness is Insufficient)**
**Cause Analysis:**
Nickel slot metal nickel ion concentration may be too low or high, temperature may be low, pH value might be low, activity could be insufficient, time might be inadequate, load may be large, phosphorus content might be high (resulting in white lines or holes), or nickel bath liquid may be < or > 4MTO.
**Improvement Measures:**
Adjust nickel ion concentration to the correct range, control temperature, pH value, improve activity, reduce load, and adjust phosphorus content to within the allowable range. Ensure nickel reaches or exceeds 4MTO, and conduct tests to meet quality requirements.
4. **Coarse and White ENIG PCB Layer**
**Cause Analysis:**
4.1. Residual glue or medicinal liquid on copper surface, dirty or rough copper surface, severe oxidation, excessive micro-etching, uneven micro-etching of copper ions, or unclean tin removal; 2. Gold trough contamination (nickel metal impurities) or imbalance (excessive or small load), low temperature, low pH value, low gold concentration, low specific gravity, too many stabilizers, insufficient gold layer thickness, or gold trough medicinal water < or > 4MTO; 3. Poor nickel deposit quality (thin or discolored nickel layer), dark appearance of gold layer, unstable nickel bath liquid activity, excessive local speed of nickel cylinder circulation, local overheating, or excessive nickel stabilizer concentration; 4. Solid particles, whitening, or shedding of welding resistance in chemical nickel solution, minor contamination by palladium or copper; 5. Nickel trough plating solution pH too high or water quality not clean.
**Improvement Measures:**
4.1. Enhance inspection of incoming materials, use high-quality electroplated copper, control micro-etching rate, and ensure thorough tin removal; 2. Control gold bath liquid components within range; 3. Improve nickel deposit quality, ensure uniform filtration and temperature of nickel trough liquid, and maintain nickel stabilizer within range; 4. Strengthen filtration of chemical nickel solution to avoid contamination; 5. Maintain water quality and pH value of nickel trough within range.
5. **Gold Layer “Drop Gold, Drop Nickel Gold” (Copper-Nickel or Nickel Poor Binding with Gold PCB)**
**Cause Analysis:**
5.1. Nickel surface passivation, darkening of nickel layer, excessive nickel content (>5%), imbalance of nickel cylinder accelerator, high phosphorus, or contamination by copper ions; 2. Dirty (oxidized) copper surface, long wash-in time after development/microetching, passivation of palladium layer, excessive activation, poor oil removal, or copper ion contamination in activating solution; 3. Unclean washing between nickel cylinder and gold slot, low pH value of gold liquid, contamination by metal or organic impurities, aggressive gold deposit system, or composition control out of range.
**Improvement Measures:**
5.1. Prevent nickel surface passivation, check nickel layer quality, control nickel addition in small stages, adjust accelerator, reduce phosphorus content, minimize copper ion contamination, and maintain nickel parameters; 2. Improve cleanliness of copper treatment, prevent palladium layer passivation, control activation time and concentration, and improve oil removal and microetching; 3. Enhance washing of gold plates, adjust pH value, detect contamination, and select appropriate gold system.
6. **Immersion Gold Surface PCB “Poor Weldability” (Solderability)**
**Cause Analysis:**
6.1. Gold layer too thin; 2. Poor water quality, high nickel or gold cylinder content, contamination by impurities, inadequate activity, or abnormal nickel appearance; 3. High copper ion content or excessive activation during micro-etching and activation; 4. Nickel and phosphorus content should be 7-12%, and nickel-gold layer deposition rate should be controlled; 5. Long gold deposit time, low gold concentration, low temperature, or contamination by organic/metal impurities.
**Improvement Measures:**
6.1. Maintain gold thickness at 0.05-0.1 μm; 2. Recycle wash gold-deposited plates with pure water, enhance maintenance to minimize nickel or trough medication aging, avoid contamination, and improve nickel layer appearance; 3. Strengthen control of micro-etching and activation parameters; 4. Control phosphorus content to 7-9% and nickel deposition rate; 5. Increase gold concentration or temperature to reduce deposit time, reduce contamination, or replace gold.
7. **Corrosion of Nickel Layer (Black Disc)**
**Cause Analysis:**
7.1. Long gold immersion time; 2. Low pH value, low temperature, or low gold concentration; 3. Uneven distribution of nickel and phosphorus; 4. Difficult or slow gold recovery due to water aging or contamination; 5. Aggressive gold deposit system; 6. Nickel layer too thin (<2 μm); 7. Incomplete cleaning of nitric acid residue; 8. Prolonged exposure to corrosive environments; 9. High pH of nickel slot resulting in low phosphorus content and reduced corrosion resistance.
**Improvement Measures:**
7.1. Control gold deposition rate and thickness (0.05-0.1 μm, not exceeding 8u); 2. Control pH, temperature, and concentration of gold liquid; 3. Improve nickel slot stirring and distribution; 4. Increase gold concentration or replace if needed; 5. Select high-quality gold systems; 6. Maintain nickel layer thickness at 3-4 μm; 7. Eliminate nitrate ion contamination; 8. Transfer plates promptly; 9. Keep nickel slot pH within range, ideally not exceeding 4.8.
8. **Pinhole in Nickel Layer**
**Cause Analysis:**
8.1. Poor exhaust of nickel slot filter, weak stirring, or inadequate oscillation; 2. Soluble particles in nickel solution, poor pretreatment, or organic contamination.
**Improvement Measures:**
8.1. Improve filter exhaust conditions, maintain circulating pipeline, increase oscillation intensity, and optimize mixing conditions; 2. Strengthen filtration of nickel solution, improve pretreatment, and reduce organic contamination.
9. **The Current of the Ejection Protection Device is Too High (Consumes a Lot of Nickel)**
**Cause Analysis:**
9.1. High nickel bath temperature, high pH, local overheating, rapid replenishment, or low tranquilizer; 2. Slot wall passivation; 3. Carrying small amounts of activating liquid; 4. Nickel and gold fragments falling into nickel slot; 5. Abnormal ejection protection device; 6. Improper passivation of stainless steel groove.
**Improvement Measures:**
9.1. Control nickel liquid operating parameters; 2. Prevent groove wall passivation; 3. Avoid carrying small amounts of activating residue into nickel liquids; 4. Regularly inspect and clean hangers; 5. Improve ejection protection device; 6. Re-passivate with nitric acid.
10. **Liquid Nickel “Turbidity”**
**Cause Analysis:**
10.1. High nickel pH or temperature; 2. Excessive carry-out; 3. Leaks from pipes or drugs; 4. High imbalance activity.
**Improvement Measures:**
10.1. Maintain nickel pH and temperature within range; 2. Monitor employee operation (preferably automatic lines); 3. Improve equipment; 4. Enhance solution maintenance and ensure nickel solution activity.
