PCB in which the screen printing process and precautions are explained in detail.

PCB in which the screen printing process and precautions are explained in detail.

The screen printing process in PCB (Printed Circuit Board) is an important part of the fabrication process, which involves printing the necessary markings, text, symbols, and other information onto the PCB board for subsequent component mounting, testing, and repair. The following is a detailed description of the PCB screen printing process and what you need to be aware of during the process:

Screen Printing Process

Screen Printing Preparation:

Make Screen Printing Plate: 

According to the design requirements, make a screen printing plate containing the required pattern.

Prepare Ink: 

Select the appropriate type of ink, such as epoxy resin ink.

Screen Printing:

Place the PCB board on the printing machine to ensure accurate position.

Apply the ink evenly to the screen printing plate.

Imprint the ink onto the PCB board by squeegee to form the desired pattern and text.

Ink Curing:

Expose the printed PCB board to high temperature or UV light to cure the ink and ensure it is firmly attached to the PCB substrate.

Inspection and Testing:

The silkscreen layer is inspected to ensure that all markings are clear and accurate.

Perform necessary tests, such as electrical tests, to ensure that the silkscreen layer does not affect the performance of the circuit.

Precautions

Silk-screen Location:

Ensure that the silkscreen is accurately positioned and does not cover the pads or areas to be soldered, as this may affect the quality of the solder.

The silkscreen should be placed in a location that is easy to see and not susceptible to mechanical damage.

Silk-screen Content:

Including component direction, polarity, pin number and other important information to facilitate the correct installation and maintenance.

For components with polarity, such as electrolytic capacitors, diodes, etc., the positive and negative polarity should be clearly marked.

Silk-screen Design:

Select appropriate fonts and sizes to ensure the readability and clarity of the silkscreen.

Avoid screen printing above high-speed signal lines, so as not to affect the signal quality.

Ink Selection and Curing:

Select the right type of ink and consider its compatibility with the PCB board and curing requirements.

Ensure that the ink is fully cured to prevent peeling or blurring during subsequent processing.

Pre-screen Printing Treatment:

Properly clean and pre-treat the PCB board before screen printing to ensure that the ink adheres well.

Quality Control:

Screen Printing Process

Design Preparation:

Before screen printing, the PCB design needs to be carefully reviewed to ensure that all the information to be printed has been included in the design file.

Screen Printing Plate Production:

Based on the design files, the appropriate screen printing plates are made. This step needs to be precise as the quality of the printing plate has a direct impact on the quality of the final screen print.

Ink Blending:

Selection of the right colour and type of ink. Usually, black epoxy inks are the most commonly used, but other colours are available to meet different visual or functional needs.

Screen Printing:

Fix the PCB on the printing machine and make sure the position is accurate.

The ink is evenly applied to the screen printing plate and transferred to the PCB by squeegee.

Post-processing:

After screen printing is completed, post-processing, such as cleaning and drying, may be required to ensure that the ink is fully cured and adheres to the PCB.

Precautions

Avoid Masking Important Areas:

Screen printing should not obscure test points, pads, or other critical PCB areas that could interfere with circuit testing and component mounting.

Screen Print Prity:

Ensure that the silkscreen content is clear and easy to read so that individual components and test points can be quickly identified during assembly and repair.

Protection of The Silkscreen Layer:

The silkscreen layer may require additional protective measures, such as covering with a clear protective film, to prevent abrasion or damage during subsequent PCB handling.

Environmental Factors:

Environmental conditions, such as temperature and humidity, need to be controlled during the screen printing process, as these factors may affect ink curing and adhesion.

Compliance With Specifications:

When designing and executing a screen printing process, relevant industry standards and specifications should be adhered to, ensuring product quality and reliability.

Through meticulous process control and strict adherence to precautions, PCB screen printing jobs can ensure that circuit boards are clearly and accurately labelled, thereby improving product maintainability and traceability, and ensuring the quality and performance of the final product.