FPC imaging, etching and film stripping principle

FPC imaging:pcbdown、cn

Principle: Imaging is the process of treating a board with a dry film that has already been exposed to light with a developing solution (7.9g/L sodium carbonate solution) to wash away the dry film that has not been exposed to UV light, while retaining the dry film that has undergone polymerization reaction under UV light irradiation to form the circuit.
Factors affecting the quality of imaging operations:
1. Composition of developer solution
2. Development temperature
3. Development pressure
4. Uniformity of developer distribution.
5. The speed at which the machine rotates.
Process parameter control: drug solubility, development temperature, development speed, spray pressure.
Key points for quality control of imaging operations:
There should be no water droplets on the discharge outlet wrench, and it should be blown clean
2. There must be no un torn dry film protective film
3. The imaging should be complete, and the circuit should not be jagged, bent, or tapered.
4. After imaging, the bare copper surface should be lightly scraped with a knife without any dry film peeling off, otherwise it will affect the quality of the operation at all times.
5. The error between the dry film line width and the negative film line width should be controlled within -0.05mm.
6. Place the complex side of the circuit facing downwards to avoid residual film residue and reduce uneven development caused by pool effect.
7. Update the imaging solution in a timely manner based on the solubility of sodium carbonate, dry film load, and usage time to ensure the best development effect.
8. Control the levels of developer and clean water.
9. When blowing dry, the wind speed should be maintained at 5-6 degrees towards the inside.
10. The tank and nozzle should be regularly cleaned of scale to prevent impurities from contaminating the board and causing uneven distribution of developer solution.
11. To prevent the occurrence of jamming during operation, the rotating device should be stopped when jamming occurs, and the board should be immediately stopped from being placed. The board should be taken out and sent to the middle of the developing station. If it is not fully developed, secondary development should be carried out.High speed download
12. After development and drying, the board should be separated by absorbent paper to prevent the dry film from sticking and affecting the quality at all times.

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Quality confirmation:
Integrity: After imaging, the bare copper surface should be lightly scraped with a blade without any dry film residue.
Appropriateness: The edges of the circuit should not be jagged or show obvious thinning or curling. After imaging, the line width of the dry film and the film should be within 0.05/-0.05m.
Surface quality: It needs to be dried and there should be no residual water droplets.
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Etching and peeling film:
Principle: Etching is the process of uniformly spraying etching solution onto the surface of copper foil through a nozzle under certain temperature conditions (45 5). The solution undergoes oxidation-reduction reactions with copper that is not protected by etching inhibitors, resulting in the removal of unwanted copper and exposing the substrate. After film stripping treatment, the circuit is formed.
The main components of etching solution are copper chloride, hydrogen peroxide, hydrochloric acid, and soft water (with strict solubility requirements)
Quality requirements and control points:
1. There should be no residual copper, especially for double-sided panels, which should be taken into account.
2. There should be no residual adhesive present, otherwise it may cause copper exposure or poor adhesion of the coating
3. The timing speed should be appropriate, and it is not allowed for the line to become thinner due to excessive etching. The timing line width and total pitch should be the focus of this station's control.
4. The dry film on the solder joints of the circuit shall not be washed away, separated or broken
5. After peeling the film at all times, the board must not have any oil stains, impurities, copper skin warping or other poor quality.
6. When placing the board, attention should be paid to avoiding jamming and oxidation.
7. It should be ensured that the distribution of the medication is uniform at all times to avoid uneven etching of different parts on the front and back or on the same surface.Professional software download
Process control parameters:
Etching solution temperature: 45/-5 ℃ Solubility of hydrogen peroxide: 1.95-2.05mol/L
Film stripping solution temperature: 55/-5 ℃ Etching machine safe use temperature ≤ 55 ℃
Drying temperature: 75/-5 ℃ Front and rear plate spacing: 5-10cm
Specific gravity of copper chloride solution: 1.2~1.3g/cm3 for plate angle, guide plate, and upper and lower nozzlesswitchstate
Hydrochloric acid solubility: 1.9~2.05mol/L
Quality confirmation:
Line width: The etched standard line is. 2mm&0.25mm, and it must be within/-0.02mm after etching.
Surface quality: There should be no wrinkles, scratches, etc
Check for no residual copper using a transparent method.
The circuit cannot be deformed
Non oxidizing water droplets