**PCB Screen Printing Specifications and Requirements**
1. All components, mounting holes, and positioning holes must have corresponding silk-screen marks. To facilitate board installation, each component, mounting hole, and positioning hole should be clearly marked. Mounting holes on the PCB are designated with labels such as H1, H2, …, Hn for identification.
2. Silk-screen characters should be aligned from left-to-right and bottom-to-top whenever possible. For polarized devices like electrolytic capacitors and diodes, ensure that the polarity markings are consistently oriented within each functional unit.
3. Silk screen should not be present on device pads or tinning tracks to ensure reliable soldering. The device position numbers should not be obstructed after installation. Ensure that the silk screen does not cover vias or pads to prevent potential loss of identification during solder mask application. Maintain a minimum silk screen spacing of 5 mils.
4. The polarity of polarized components must be clearly indicated on the silk screen, and polarity direction marks should be easily identifiable.
5. The orientation of directional connectors must be clearly marked on the silk screen.
6. A barcode position mark should be included on the PCB. When space allows, include a 42*6 mm barcode silk-screen frame on the PCB. Position the barcode for optimal scanning convenience.
7. The PCB board name, date, version number, and other finished board information should be clearly marked on the silkscreen layer. The PCB file must display the board name, date, version number, and other relevant information in a clear and eye-catching manner.
8. Ensure that all relevant information and anti-static signs for PCB manufacturers are complete.
9. Verify that the number of PCB light drawing files is correct, with each layer having accurate outputs and a complete set of layers provided. The device identifiers on the multilayer PCB must match the identification symbols in the BOM list.
Ink:
Viscosity: Viscosity measures the resistance between adjacent fluid layers as the fluid flows, with frictional resistance arising between them; unit: Pascal seconds (Pa.s).
Hardness: The ink’s hardness after pre-baking is 2B, after exposure is 2H, and after post-baking is 6H. This refers to pencil hardness.
Thixotropic: The ink appears gelatinous when standing but changes viscosity upon agitation. Known as thixotropic or sag-resistant, this property involves a decrease in viscosity when stirred and a rapid return to original viscosity when still. Effective thixotropy is crucial for high-quality screen printing, as it enhances ink flow through the mesh and ensures uniform application.
Dry film consists of three parts and ingredients:
1. Support film (Polyester film)
2. Photoresist Dry Film
3. Cover film (Polyethylene film)
Main components: 1. Binder (film-forming resin), 2. Photo-polymerization monomer, 3. Photo-initiator, 4. Plasticizer, 5. Adhesion promoter, 6. Thermal polymerization inhibitor, 7. Dye, 8. Solvent.
Dry film types are categorized based on development and removal methods: solvent-based dry film, water-soluble dry film, and peel-off dry film. According to their purpose, dry films are classified as resist dry film, mask dry film, and solder resist dry film.
Photosensitive speed: This refers to the light energy needed for the photoresist to polymerize and form a resistive polymer under UV light. With a fixed light source intensity and distance, sensitivity speed is expressed as exposure time; shorter exposure times indicate higher sensitivity.
Resolution: This indicates the number of lines (or spacing) that the dry film resist can form within 1 mm. It can also be expressed by the absolute size of the lines (or spacing).
1. All components, mounting holes, and positioning holes must have corresponding silk-screen marks. To facilitate board installation, each component, mounting hole, and positioning hole should be clearly marked. Mounting holes on the PCB are designated with labels such as H1, H2, …, Hn for identification.
2. Silk-screen characters should be aligned from left-to-right and bottom-to-top whenever possible. For polarized devices like electrolytic capacitors and diodes, ensure that the polarity markings are consistently oriented within each functional unit.
3. Silk screen should not be present on device pads or tinning tracks to ensure reliable soldering. The device position numbers should not be obstructed after installation. Ensure that the silk screen does not cover vias or pads to prevent potential loss of identification during solder mask application. Maintain a minimum silk screen spacing of 5 mils.
4. The polarity of polarized components must be clearly indicated on the silk screen, and polarity direction marks should be easily identifiable.
5. The orientation of directional connectors must be clearly marked on the silk screen.
6. A barcode position mark should be included on the PCB. When space allows, include a 42*6 mm barcode silk-screen frame on the PCB. Position the barcode for optimal scanning convenience.
7. The PCB board name, date, version number, and other finished board information should be clearly marked on the silkscreen layer. The PCB file must display the board name, date, version number, and other relevant information in a clear and eye-catching manner.
8. Ensure that all relevant information and anti-static signs for PCB manufacturers are complete.
9. Verify that the number of PCB light drawing files is correct, with each layer having accurate outputs and a complete set of layers provided. The device identifiers on the multilayer PCB must match the identification symbols in the BOM list.
Ink:
Viscosity: Viscosity measures the resistance between adjacent fluid layers as the fluid flows, with frictional resistance arising between them; unit: Pascal seconds (Pa.s).
Hardness: The ink’s hardness after pre-baking is 2B, after exposure is 2H, and after post-baking is 6H. This refers to pencil hardness.
Thixotropic: The ink appears gelatinous when standing but changes viscosity upon agitation. Known as thixotropic or sag-resistant, this property involves a decrease in viscosity when stirred and a rapid return to original viscosity when still. Effective thixotropy is crucial for high-quality screen printing, as it enhances ink flow through the mesh and ensures uniform application.
Dry film consists of three parts and ingredients:
1. Support film (Polyester film)
2. Photoresist Dry Film
3. Cover film (Polyethylene film)
Main components: 1. Binder (film-forming resin), 2. Photo-polymerization monomer, 3. Photo-initiator, 4. Plasticizer, 5. Adhesion promoter, 6. Thermal polymerization inhibitor, 7. Dye, 8. Solvent.
Dry film types are categorized based on development and removal methods: solvent-based dry film, water-soluble dry film, and peel-off dry film. According to their purpose, dry films are classified as resist dry film, mask dry film, and solder resist dry film.
Photosensitive speed: This refers to the light energy needed for the photoresist to polymerize and form a resistive polymer under UV light. With a fixed light source intensity and distance, sensitivity speed is expressed as exposure time; shorter exposure times indicate higher sensitivity.
Resolution: This indicates the number of lines (or spacing) that the dry film resist can form within 1 mm. It can also be expressed by the absolute size of the lines (or spacing).
