How to improve the precision of screen printing process in printed board production
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The screen printing process has been widely used in the production process of printed boards. It is not only the transfer of circuit patterns of single-panel, double-panel and multi-layer printed boards. Solder resists, character marks, etc. all accept the screen printing process. . With the growth of economic skills, it is increasingly required to improve the accuracy and pass rate of products, to ensure the amount of products, and to lower the cost, so as to obtain better economic benefits. Precision circuits have also been screen-printed for years and require high positional accuracy. In this paper, based on the resume in the screen printing process that I carried out, I will analyze the factors affecting the precision of screen printing in the screen printing process. How to improve the precision of screen printing? This article provides some insights on how to improve accuracy for cooperation.
First, factors affecting the accuracy of screen printing
Printed board graphic printing accuracy includes the following two aspects: First, the printed graphic line has a small amplitude distortion, and the line width is 0.05mm; the second refers to the high precision of the printed graphic position. When the graphic length is within 500mm, The location problem is <0.15mm, which affects the accuracy of the above two aspects. From the screen printing to the graphic printing production process, the following factors are important:
1. Screen plate material and printing material selection: including frame material, wire mesh material, mesh number, color and printing performance;
2. Screen printing equipment deployment, tooling: screen printing machine, positioning tooling, etc.;
3. The production process includes stretching, screen making, printing, etc.;
4. Environmental conditions: The temperature, humidity, cleanliness, and especially cleanliness of the event garden are important factors affecting the amount of product;
5. People are the most important factor affecting the quality of the project. Operators must have a high degree of responsibility and a high level of skill.
In this paper, we will focus on the principles of the influence of the factors in the first few aspects on the precision of printed graphics and the pace and essentials of improving the accuracy.
Second, the progress of the screen stencil quality is the condition for the fineness of the screen printing
Factors affecting the quality of the screen stencil include the quality of the photographic manuscript, the photographic, reticle, and dimensional stability of the photographic film. The production of screen stencils involves many factors such as frame, screen and stretcher, plate making and photographic materials.
1. The choice of mesh material is usually the same as LY12, LF2 and other hard alloy aluminum square tube profiles. The size is 20mm wide and 20mm thick. The four corners are made by argon arc welding or riveting. The metal frame is highly accurate and dimensionally stable.
2. The choice of wire mesh material is now the most used nylon mesh and polyester mesh. Nylon mesh has poor heat resistance, and it is easy to breed after heating to cause thermoplastic deformation, which makes the tension uneven and affects the quality of screen printing. Bonding stretch nets or screen stencils are not suitable for high temperature baking. Polyester mesh has good heat resistance and stable size, and the graphics are not changed due to changes in temperature and humidity. In order to ensure the fineness of screen printing graphics, it is best to use a monofilament polyester mesh. At the same time, the mesh with higher mesh size, thinner wire diameter and smaller mesh should be used. The color of the mesh is yellow or brown, so as to prevent vignetting.
3. Stretching the net is a key to avoiding. To produce high-precision printed graphics, the first requirement is that the stretch net meets the quality requirements. It is best to accept the pneumatic stretcher. The quality requirements of the stretch net are as follows.
A. The tension of the stretcher is consistent and symmetrical
It is not the better the tension, the tension is too large, and the elastic limit of the material is over, the screen will lose its elasticity, become brittle and even break. The tension is not soft, and the resilience is lacking. According to the rated tension, and then according to the operating conditions to give consideration, so that the tension on the entire screen surface is symmetrical.
B. The warp and weft wire is connected vertically
The latitude and longitude lines of the stretched wire mesh should be perpendicular to the edge of the frame. When the wire is stretched, the wire is stretched, that is, the force is the same as the wire. Second, the wire clamped by the net can stretch horizontally. mobile.
C. Prepare for relaxation
In order to reduce the stretched net over time, the screen will become loose or looser, and the tension will fall. It should accept the continuous pulling and repeating the tension of the stretch net, so that the tension of one department is relaxed before the fixed net. carry out.
4. The screen stencil making process is now used most directly to make the screen stencil. In this production process, the thickness of the fine sizing coating is consistent, and the key to dry control, exposure and development is strictly controlled, so as to obtain high quality. Screen stencil.
Third, control the influencing factors in the screen printing process, improve the screen printing fineness
In the process of screen printing graphic processing, the first requirement is that the printing performance is excellent, and secondly, the process factors such as printing setting equipment deployment, tooling, scraping, mesh distance, and printing pressure must be strictly controlled.
1. The printing material must have the following properties:
Good chemical stability; suitable drying rate; good adhesion to copper-clad board; viscosity, good thixotropy, color compliance;
Good printing penetration; easy to dry.
2. Set equipment deployment tooling
The acceptance of a screen printing machine with high printing precision can eliminate many unreliable factors, and the positioning tool can directly use the longitudinally adjustable positioning pin of the machine table to locate.
3. Other process factors
Scraper material, squeegee width, hardness, squeegee angle, edge state and mesh distance, squeegee pressure are all important. Polyester rubber should be used to make squeegee. Scraper width is appropriate, too wide and easy to cause distortion of the pattern, the hardness of the scraper is mostly within the scope of Shore A60-80, the scratch angle is 20-30, and the edge must be connected to the flat edge. The mesh distance is usually 2 - 4 mm and the screen is parallel to the table. The printing pressure is suitable for printing a clear pattern.
In summary, among the above process factors, the important factors affecting the accuracy of the line pattern include the printing material, the scraper hardness, the edge state, the printing pressure and the angle, etc., while the screen printing equipment deployment, tooling, mesh distance and scraping Important factors such as the width of the board affect the fineness of the position of the printed graphic, and high-quality screen stencils are indispensable for improving the printing accuracy.