The microelectronics industry is essential to the automotive, communication, medical, and test measurement industries. Each of these industries require precision screens for the printing of circuits and adhesives. Several factors affect the quality of electronic printing. Today we’ll review what you should know to make the right precision screen choice to achieve the best results for your printing application.
Mesh Count of Plain Weave
Quality screen printing starts with sensitized screens. Plain weave stainless steel mesh works best for precision circuit printing. The vertical wires (warp wires) are crimped to cross over and under the horizontal (weft) wires. The mesh count denotes the number of crossed wire pairs per linear inch. For example, a 200-count plain weave mesh would have 200 x 200 crossing wires, creating 40,000 openings per square inch.
Mesh Open Area
The open area in a screen is noted as a percent of the total screen area. Two factors contribute to this measurement: the mesh count and the wire diameter. MicroScreen provides mesh made with ultra-fine wire to increase the percentage of open area. The larger the open area, the more uniform the printing.
In theory, the thickness of the mesh is the diameter of both the vertical and horizontal wires. This is never accomplished, however, and a screen’s total thickness can reach up to three times the wire diameter. The key variable is the crimping heights of the warp wires.
MicroScreen's stainless steel mesh minimizes thickness differences within the same product roll, allowing ink-covered screens to maintain uniformity. During printing, the ink deposited through a screen appears as cubes. The wire diameter, mesh opening, and built-up emulsion determine the cube size. The cubes then flow together to form the image on the substrate. Any deviation in the wire diameter or weave thickness affects the deposited ink. To avoid variant ink droplets, MicroScreen uses special drawn wire and advanced electronic looms to create controlled, uniform wire cloth thickness.
The mesh can be mounted at 22.5°, 30°, 45°, or 90° angles. The best results come from 22.5° and 45° orientations. These angles work well for fine lines and odd-shaped images.
The orientation of the weft and warp wires to a frame is critical to achieving quality results and maximizing the life of a parallel-mounted mesh screen. Less screen fatigue occurs when the flexible warp wire is perpendicular to the squeegee movement and the weft is parallel to it. This is because the straight (weft) wire is more stable and less affected by the squeegee motion.
Mesh Tensile Strength
MicroScreen uses high tensile strength stainless steel alloy 304 wire. The wires are strong and can stretch more than other materials, allowing for a longer screen life. With precise dimensions and surface characteristics, the wire’s tensile strength has a yield point 20% higher than conventional wires. This provides a greater elastic reserve, reduces the wear on the screen, and enhances print quality. The wire also retains 0.5% +0.1% elastic elongation reserve to flex from the squeegee stroke.
Stretched mesh tension is noted in Newtons per centimeter. It is also expressed in mils of deflection in the center of the screen based on one pound of applied force. Deflection correlates to the size of the frame.
Screens with too little tension have greater deflection. This can cause poor print definition, image elongation, and mesh marks. The less tension, the slower the squeegee speed to compensate. Screens can get overstretched beyond their elongation reserve and become unusable. Problems also arise when the screen is under stretched.
MicroScreen’s Value Proposition
MicroScreen focuses on mesh specifications and the uniformity of the product. We know that consistency with each squeegee stroke is key to quality images. Of the many specifications we detail, these are the top three factors that drive quality:
- Ultra-fine wire mesh with a higher percentage of open area for more precise ink deposition
- Process control of mesh thickness for more precise print thickness
- High tensile strength mesh for longer screen life
Specifying these factors will allow you to create the best possible images, regardless of your fabrication. MicroScreen offers interwoven mesh screens of stainless steel and nylon. A light-sensitive emulsion coats the mesh. When you place the print layer image on the screen and expose it to UV light, the exposed emulsion hardens. The unexposed emulsion under your image will wash away, and in its place will be your print pattern on the screen. This is the area through which the squeegee will squeeze the ink onto the product you are printing.
Specifying Screens for Printing
Now that you understand how key factors like mesh count, open area, wire size, mesh orientation, and tensile strength impact the quality and clarity of printed images, you are better prepared to make informed decisions when specifying screens for your electronics and adhesive printing needs. You can learn more about our screen products on our website.