Causes and Solutions of PCB Alkaline Etching Common Problems

Home » Causes and Solutions of PCB Alkaline Etching Common Problems
  1. Problem: The etching rate in the printed circuit is reduced

the reason:

Due to improper control of the process parameters

Solution:

According to the process requirements to check and adjust the temperature, spray pressure, solution specific gravity, PH value and ammonium chloride content of the process parameters to the process specified value.

  1. Problem: The etching solution in the printed circuit appears to precipitate

the reason:

(1) ammonia content is too low

(2) water dilution excess

(3) the proportion of solution is too large

Solution:

(1) adjust the PH value to reach the process requirements or appropriate to reduce the amount of ventilation.

(2) adjust the strict requirements in accordance with the provisions of the process or appropriate to reduce the amount of air to implement.

(3) according to the process requirements of the discharge of some parts of the high proportion of the solution after the addition of ammonium chloride and ammonia solution, so that the proportion of the etching solution to adjust the scope of the process.

 

  1. Problem: The metal resist plating layer in the printed circuit is etched

the reason:

(1) The pH of the etchant is too low

(2) chloride ion content is too high

Solution:

(1) according to the provisions of the process to adjust to the appropriate PH value.

(2) adjust the chloride ion concentration to the process specified value.

  1. Problem: Printed copper surface in the circuit is black, etching does not move

the reason:

The content of sodium chloride in the etching solution is too low

Solution:

According to the process requirements to adjust the sodium chloride to the process requirements.

  1. Problem: Printed circuit in the substrate surface residual copper

the reason:

(1) Etching time is not enough

(2) to the film is not clean or corrosion metal

Solution:

(1) according to process requirements for the first test, determine the etching time (that is, adjust the transmission speed).

(2) before etching should be checked according to process requirements board, requiring no residual film, no corrosion metal plating.

  1. Problem: printed circuit in the substrate on both sides of the etching effect is obvious

the reason:

(1) The etch section of the device is blocked

(2) the conveyor wheel within the equipment to be staggered in front and rear of the column, otherwise it will cause the board surface traces

(3) nozzle leakage caused by spray pressure drop (often out of the nozzle and manifold joints)

(4) liquid solution in the liquid tank is insufficient, causing the motor to idle

Solution:

(1) check the nozzle blockage, targeted to clean up.

(2) to thoroughly check and arrange the wheel staggered position of each section of the equipment.

(3) check the pipe joints and repair and maintenance.

(4) regular observation and timely added to the process of the provisions of the location.

  1. Problem: printed circuit board uneven etching so that part of the residual copper left

the reason:

(1) the surface of the substrate is not complete enough, there are residual film

(2) the whole board copper plating caused the thickness of the copper layer is not uniform

(3) When the plate is repaired or repaired with ink, it is touched on the roller of the drive of the etching machine

Solution:

(1) the surface of the substrate is not complete enough, there are residual film.

(2) the whole board copper plating caused the thickness of the copper layer is not uniform.

(3) When the plate is repaired or repaired with ink, it is touched on the roller of the drive of the etching machine.

(4) check the film process conditions, to be adjusted and improved.

(5) According to the density of circuit graphics and wire accuracy, to ensure the consistency of the thickness of the copper layer can be used to brush grinding process.

(6) The repaired ink must be cured and inspected and cleaned.

  1. Problem: Printed circuit board after etching found serious wire side erosion

the reason:

(1) nozzle angle is wrong, nozzle imbalance

(2) spray pressure is too large, resulting in a rebound and serious side erosion

Solution:

(1) according to the instructions to adjust the nozzle angle and nozzle to meet the technical requirements.

(2) according to the process requirements usually spray pressure set 20-30PSIG, and through the process test method to adjust

  1. Problem: The substrate on the conveyor belt in the printed circuit is inclined

the reason:

(1) equipment installed its level is poor

(2) the nozzle inside the etching machine will automatically swing back and forth, there may be part of the nozzle swing is not correct, resulting in uneven board spray pressure caused by substrate slanting

(3) Etching machine conveyor belt gear damage caused by part of the transmission wheel to stop working

(4) The actuator rod in the etch machine is bent or twisted

(5) squeeze water stop roller damage

(6) The position of the part of the burner is too low to block the conveyed plate

(7) Etching machine spray pressure from top to bottom uneven, under pressure will be too high when the board

Solution:

(1) according to the equipment manual to adjust, adjust the horizontal angle of the wheel and arrangement, should meet the technical requirements.

(2) to check the details of each section of the nozzle swing is correct, and according to the equipment manual to adjust.

(3) should be carried out in accordance with the process requirements to check, will damage or damage to the gear and roller replacement.

(4) After a detailed inspection, replace the damaged drive rod.

(5) Damaged accessories should be replaced.

(6) after inspection should be in accordance with the equipment instructions to adjust the angle and height of the baffle.

(7) appropriate to adjust the spray pressure.

  1. Problem: printed circuit board copper line is not completely copper, part of the edge left residual copper

the reason:

(1) dry film is not removed (it may be due to the two copper and tin-lead coating is too thick to cover a small amount of dry film and lead to tearing difficult)

(2) The conveyor belt is too fast

(3) tin plating lead bath into the bottom of the dry film caused by very thin coating stained dry film, so that the speed of copper erosion at the edge of the formation of wire leaving residual copper.

Solution:

(1) check the situation of the film, strictly control the thickness of the coating to avoid coating extension.

(2) Adjust the speed of the conveyor belt according to the etching quality.

(3) A check the film program, select the appropriate film temperature and pressure, improve the dry film and copper surface adhesion

B check the front surface of the film before the micro-coarsening state.

  1. Problem: Printed circuit on both sides of the board etching effect is not synchronized

the reason:

(1) the thickness of copper on both sides is inconsistent

(2) upper and lower spray pressure uneven

Solution:

(1) A according to the thickness of the two sides of the coating up and down spray pressure (copper layer down);

B using single-sided etching only to start the next nozzle pressure.

(2) A According to the quality of the etching board, check the upper and lower spray pressure and adjust;

B Check whether the nozzle in the etch section of the etch machine is blocked and use the test plate to adjust the upper and lower spray pressure.

  1. Problem: The alkaline etching solution in the printed circuit is excessively crystallized

the reason:

When the pH value of the alkaline etching solution is less than 80, the solubility is deteriorated to cause the formation of copper salt to precipitate and crystallize

Solution:

(1) Check that the amount of sub-liquid in the spare tank is sufficient.

(2) check the sub-liquid to add the controller, piping, pumps, solenoid valves, etc. are blocked exception. (3) to check whether excessive ventilation, resulting in a large number of ammonia escape Y caused by lower. (4) to detect the function of the PH meter is normal.

  1. Problem: The etching rate of the continuous etching in the printed circuit is reduced, but if the time is stopped, the etching rate can be restored

the reason:

The amount of ventilation is too low, resulting in insufficient oxygen supplement

Solution:

(1) through the process test method to find the correct amount of ventilation.

(2) should be in accordance with the instructions provided by the supplier to debug, to find the correct data.

  1. Problem: photoresist off (dry film or ink)

the reason:

(1) PH value of the etching solution is too high, alkaline water-soluble film and ink is very easy to be destroyed

(2) sub-liquid supply system out of control

(3) the type of photoresist itself is not correct, alkali resistance is poor

Solution:

(1) Adjust the value according to the process specification.

(2) to detect the PH value of the sub-liquid, to maintain proper ventilation, do not let ammonia directly into the board to transport the area.

(3) A good dry film can withstand PH = 9 or more.

B using process test method to check the dry film alkali resistance or replace the new photoresist brand.

  1. Problem: The printed circuit in the etching of excessive wire thinning

the reason:

(1) conveyor belt transmission speed is too slow

(2) PH is too high will increase the lateral erosion

(3) The specific value of the etching solution is lower than the specification setting value

Solution:

(1) Check the relationship between the thickness of the copper layer and the transmission speed and set the operating parameters.

(2) to detect the pH of the etching solution, such as higher than the scope of the process can be used to strengthen the ventilation until the return to normal

(3) to detect the specific gravity, if less than the set value, you should add copper salt and stop the sub-liquid supplement , So that the specific gravity of the process to rise within the scope of the provisions.

  1. Problem: Printed circuit in the lack of etching, too small enough

the reason:

(1) conveyor belt transmission speed too fast

(2) the etching solution PH is too low (its value has little effect on the etching speed, but when the PH decreases when the lateral erosion will be reduced, but the foot becomes larger)

(3) the specific gravity of the etching solution exceeds the normal value (the proportion of the etching rate has little effect, but the proportion increases, the lateral erosion will be reduced)

(4) The temperature of the etching solution is insufficient

(5) lack of spray pressure

Solution:

(1) Check the relationship between the thickness of the copper layer and the speed of the etching machine, and find the optimum operating conditions by the process test.

(2) to detect the PH value of the etching solution, when the value is less than 80 when the need to take improved methods, such as adding ammonia or accelerator solution to supplement and reduce ventilation and so on.

(3) A detect the specific value of the etching solution, and add more sub-liquid to reduce the specific gravity to the process range.

B Check if the sub-fluid supply system is malfunctioning.

(4) Check the heater function is abnormal.

(5) A check the spray pressure, should be adjusted to the most short-haired state.

B Check if the pump or tubing is abnormal.

C The water level in the tank is too low, causing the pump to idling, check the level control, add the operating procedures with the discharge pump.

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