Screen printing for the electronics industry (below)

Screen printing is especially important in screen printing. It must be suitable for printing materials, substrates, patterns, media, and work environment to ensure the quality of printed products. There are several major factors that can be summarized as follows.

1. Frame - The frame must be strong, strong, and absolutely flat to support high tension screens. The practice shows that for the application of the electronics industry, the essence of the network frame is not solid enough, so the basic use of aluminum mesh frame.

2. The choice of mesh-mesh is particularly critical and requires:

The diameter of the thread does not exceed one third of the width of the thinnest line printed.

The aperture of the screen is at least 2.5 times the size of the particles in the media to ensure good permeability and adhesion uniformity of the print media.

Selecting a large mesh with open pores, ie, a mesh with a low mesh number, can obtain a thicker dielectric deposition amount. But this will reduce the clarity of the print. The use of finer, ie, high-mesh, screen-printed images is clearer, but will reduce the ink deposition thickness.

Polyester mesh has good resilience, but its clarity and nesting accuracy is not as good as stainless steel mesh. Therefore, the stainless steel wire mesh is preferably used when the viscosity of the ink is high and the adhesion layer is required to be thick. However, the resilience of stainless steel wire mesh is not as good as polyester wire mesh.

The scope of application of screen printing is limited by the fineness of the lines that it can print. This limit is related to the fineness of the mesh.

The finest thread diameter is around 0\030mm, and when a screen of 195 to 120 mesh/cm is used, it is entirely possible to produce continuous lines of 70 to 90 μm thickness. Of course, this is related to the quality of the original document, the technical level of the producer, the accuracy of the screen, the type of the frame, and the tension of the screen.

In recent years, there have been further developments in the production of chemically-etched stainless steel nets, copper enclosures, etc., creating a good environment for print media, and making prints highly accurate and reproducible.

3. The type of photosensitive adhesive-photosensitive adhesive and the thickness of the coating are all critical factors. High-resolution photosensitive adhesives are used for fine level and high trimming force printing. Super-adhesive sensitized adhesive helps to increase the thickness of the ink. For thicker printing with a large area, a thicker screen, ie, a low-mesh screen, is used.

4. Template - To get a good screen quality, first have a good manuscript. Fortunately, the defects caused by hand-made originals are being eliminated through the use of digitized originals and imaging.

Screen printing equipment

Screen printers used in the electronics industry are usually planar, and need to be able to be multi-program adjusted or controlled by PLC programming to suit various printing applications.

The traditional printing cycle - loading the print job - printing - ink return - removes the work piece. At the end of the printing, the screen was covered with ink and ready for the next printing. The printing cycle of the UV ink - loading the printing workpiece - ink returning - printing - removing the workpiece, there is no ink on the screen after printing. This is because the UV ink contains finer particles than conventional inks. Therefore, if there is ink on the screen after a printing cycle, the ink will seep through the screen before the second printing. The ink layer is too thick, resulting in incomplete UV curing. The nature of UV ink means that the machine can be programmed to print in both directions.

The paste is printed using a reciprocating print head and the ink-removing knife runs behind the squeegee. The ink-repelling blade scoops up the solder to the ink blade when the end of the printing process, and brings the shovel back to the printing starting point and prepares for the next printing. The type of squeegee is also very important, because the paste needs to "roll over" the screen, so in order to obtain the desired effect, it is best to use a diamond-shaped squeegee. Composite type doctor blades can also be used, which have different flexibility in order to change the angle of printing.

Printing of the protective layer can be carried out in both directions, first of all, because the positioning is less important. Second, two squeegees can increase the thickness of the coating and provide better protection.

Although most of the printers used in the electronics industry are flat-screen printers, the use of roller screen printers has already been applied, which reflects the creativity of machine manufacturers. Printed conductive lines are primarily printed around cylindrical products used in the pharmaceutical, aerospace, automotive, and defense industries for heating or navigation purposes. Sometimes it is necessary to design a mold for a particular shape of the substrate, and then make the corresponding machine according to the shape of the mold. The electronics industry is a fast-changing industry that constantly brings new challenges to industrial screen printers. It seems that, with the screen printing process, a solution emerges that requires technological change and further innovation. However, this will continue to raise the level of technology in this area.

Although most screen printing in the electronics industry is invisible, it has a very important influence on our daily life. This fact is not necessarily accepted by the majority of the public, or it is recognized by the majority of the traditional screen printing industry.

Author: Mu Shaoping Source: Screen Printing