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The method to solve the black sheet duplication failure in the PCB board is introduced as follows:
1. Problem: The width of all wires of the reproduced black and white negative film becomes thin and uneven
reason:
(1) Improper selection of exposure process parameters
(2) Poor quality of the original film
(3) There is a problem with the silicon control during the reworking process
Solution:
(1) First, check whether the positive or negative flip is over-exposed, and it should be corrected according to the actual situation.
(2) Check the optical density of the original film, especially whether the "shading density" is too low.
(3) Check the developer concentration and device.
2. Problem: The width of the outer wire of the overturned film becomes thin or irregular
reason:
(1) PCB exposure equipment verification expired
(2) The light source is too close to the larger size film
(3) The distance and angle of the light source reflector are out of adjustment
Solution:
(1) Re-check according to the process requirements to check whether the energy of the light source is within the technical requirements
(2) Re-adjust the distance of the light source or switch to a large exposure machine
(3) Readjust the distance and angle of the "reflective cover"
3. Problem: The resolution of the reproduced film is not ideal, and the edges of the whole film are not sharp
reason:
(1) Poor quality of the original film
(2) Poor functionality of the vacuum system of the exposure machine
Solution:
(1) Check the edge condition of the original film wire
(2)A: In particular, check whether the tightly connected part is sealed and the tightly connected part of the film
B: If the suction is insufficient, check whether the suction hose is damaged
4. Problem: The local resolution of the reproduced film is poor
reason:
(1) Poor quality of original film
(2) Poor functionality of the vacuum system of the exposure machine
(3) There are bubbles between the negatives during the exposure process
Solution:
(1) Check the bad condition of the lead edge of the original film
(2) A: Check the tight joint of the vacuum system
B: Check if there is any damaged part of the air hose
(3) There are dust particles on the surface of the exposure machine, and the air extraction system must be strengthened.
5. Problem: The optical density of the reproduced film is insufficient (mainly refers to the insufficient degree of shading in the dark area)
reason:
(1) The development process of the reproduced film is incorrect
(2) Poor storage conditions of the original film
(3) Deterioration of the function of the developing device
Solution:
(1) Check the developing process conditions and developer concentration
(2) It needs to be stored in a room that meets the process requirements, especially to avoid exposure to light.
(3) Inspection and repair, especially temperature and time control system
6. Problem: Pinholes or holes appear on the graphic surface of the reproduced film
reason:
(1) Dust or particles on the surface of the exposure machine
(2) Poor quality of original film
(3) Poor quality of original film substrate
Solution:
(1) The original film and the exposure table should be cleaned carefully.
(2) Check the surface condition of the original film, if necessary, you can try to turn over the second film for comparison inspection
(3) Perform a trial inspection to observe whether there are pinholes or voids on the black surface of the dark area after the entire film is exposed and developed.
7. Problem: The circuit pattern of the reproduced film is deformed
reason:
(1) The temperature and humidity of the PCB working environment are not correct
(2) The drying process is incorrect
(3) Improper pretreatment of the negative film to be reproduced
Solution:
(1) Operating environment temperature and humidity control: temperature 20-27 degree Celsius, humidity 40-70% RH, the operating humidity should be controlled at 55-60% RH for the film with high precision requirements.
(2) The film is placed horizontally and blow-dried for 1-2 hours for the thick (100um) film, and 6-8 hours for the film with a thickness of 175um.
(3) It needs to be placed in the film room environment for at least 24 hours for stability treatment
8. Problem: The transparent area of the film is insufficient or the film base appears cloudy
reason:
(1) There are inclusions in the original film substrate
(2) The original film base surface is poor
(3) The original film is of poor quality
(4) There are problems in the exposure and development process
Solution:
(1) Choose high-resolution and high-quality original film
(2) Ensure the temperature and humidity control of the storage environment
(3) First of all, we must test the performance and quality of the original film
(4) Inspect and adjust the conditions of the equipment, developer, fixer and PCB production process conditions.
