Common Causes and Solutions of Alkali Corrosion on PCB

Common Causes and Solutions of Alkali Corrosion on PCB
1 Problem: Etching rate in PCB is reduced
Reason: due to improper control of process parameters
Solution: According to the process requirements, check and adjust the process parameters, such as temperature, spray pressure, solution specific gravity, PH value and ammonium chloride content to meet the process specifications
2. Problem: Etching solution precipitates on PCB
Reason: (1) The content of ammonia is too low;  (2) The water is too diluted;  (3.) The specific gravity of the solution is too large.
Solution:
(1) Adjust the PH value to reach the specified value of the process or appropriately reduce the exhaust air volume.
(2) Strictly follow the regulations of the process requirements or appropriately reduce the exhaust air volume when adjusting.
(3) Discharge part of the solution with high specific gravity according to the process requirements.  After analysis, add aqueous solutions of ammonium chloride and ammonia, and adjust the specific gravity of etching solution to the allowable range of the process
PCB board

3. Problem: PCB with metal anti-corrosive coating is corroded
Reason: (1) the pH value of the thing solution is too low; (2) the chloride ion content is too high.
Solution: (1) Adjust the PH value according to the process regulations;  (2) Adjust the chloride ion concentration to the process regulations.
4. Problem: The copper surface PCB in is black, and the setting does not move
Reason: The sodium chloride content in the etching solution is too low
Solution: Adjust the sodium chloride to the specified value of the process according to the process requirements.
5. Problem: There is residual copper PCB on the surface of the substrate in
Reason: (1) The etching time is not enough;  (2) The film is not clean or there is corrosion-resistant metal.
Solution: (1) Carry out the first test according to the process requirements to determine the etching time (that is, adjust the transmission speed);  (2) Check the board surface according to the process requirements before setting, without residual film and corrosion resistant metal penetration
6. Problem: The etching effect on both sides of the middle substrate PCB is obviously different
Reason:
(1) The nozzle of the etching section of the equipment is blocked;
(2) The conveying rollers in the equipment must be staggered before and after each rod, otherwise it will cause traces on the board;
(3) Water leakage in the nozzle causes the spray pressure to drop (often appearing at the joints of the nozzle and the manifold);
(4) The solution in the preparation tank is inefficient, causing the motor to idle
Solution:
(1) Check the blockage of the nozzle and clean it in a targeted manner;
(2) Re-examine thoroughly and arrange the staggered positions of the rollers of each section of the equipment;
(3) Check each joint of the pipe, repair and maintain it;
(4) Observe frequently and make supplements in time to the positions specified in the process.
7. Problems: PCB leaves some residual copper with uneven surface etching
Reason:
(1) The film removal on the substrate surface is not complete enough, and there is residual film;
(2) The thickness of the copper plating layer on the board surface is uneven when the whole board is copper-plated;
(3) When the board surface is corrected or repaired with ink, it is printed on the drive roller of the etching machine
Solution:
(1) The film removal on the substrate surface is not complete enough, and there is residual film;
(2) The thickness of the copper plating layer on the board surface is uneven when the whole board is copper-plated;
(3) When the board surface is corrected or repaired with ink, it is stained on the driving roller of the etching machine;
(4) Check the unwinding process conditions, adjust and improve them;
(5) According to the identity of the circuit pattern and the accuracy of the wire, and the brushing and flattening process can be used;
(6) The repaired ink must be cleaned
PCB board
8. Problem: After etching the PCB, it is found that the wire is severely corroded
Reason: (1) The nozzle angle is wrong, and the nozzle is out of adjustment;  (2) The spray pressure is too large, causing rebound and serious side erosion
Solution: (1) Adjust the nozzle angle and nozzle to meet the technical requirements according to the instructions;  (2) According to the process requirements, the spray pressure is usually set to 20-30PSIG and adjusted by the process test method
9. Problem: The base plate moves the PCB forward on the conveyor belt
Reason:
(1) The level of equipment installation is poor;
(2) The nozzles in the etching machine will automatically reciprocate left and right.  Some nozzles may not swing correctly;
(3) The damage to the gear of the conveyor belt of the etching machine causes the stop of part of the transmission wheel rod;
(4) The transmission rod in the etching machine is bent or twisted;
(5) The squeezing water stop roller is damaged;
(6) The position of part of the baffle of the etching machine is too low to block the conveying board;
(7) The upper and lower spray pressure of the setting machine is not uniform

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