Reducing,Costs,With,Longer,Pri DIY Reducing Costs With Longer Print Runs

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John Gaudiuso explained how the choice ofmesh in screen printing applications could lead to cost savings. This is whatwas discovered. Screen printed electronics get increasinglysmaller so finer features are required. Cost also becomes important as screensare being used up more due to dimensional issues occurring faster. This is seenmore with meshes made from stainless steel because of its deformationproperties over print runs. There are different ways to combat screendimensional stability and longevity problems whilst also being able to printfine lines. One method is to use a trampoline screen to help improve thelongevity of stainless steel mesh. Stainless steel mesh is rigid and hasdifficulty returning to its original form. Using a trampoline screen allows thecuter mesh (a more elastic mesh-like polyester) to expand more than the inner,more rigid mesh, The outer mesh is more elastic and will return to form morethan the more rigid inner mesh, which in turn allows longer print runs.Although this option is a good option, it is still a more time-consuming methodto manufacture a trampoline screen with stainless steel mesh than it is tostretch a single mesh onto a frame. The second option is to use a syntheticmesh such as V-Screen, which has advantages over many other meshes. The mesh iswoven with a large open area and a fine thread comprising Vecry fibre; this hasa structure made up of a liquid crystal-based polymer core called Vectran, witha sheath of a flexible polymer called Pen. Some important features of V-Screenare its high tensile strength (stronger than stainless steel), almost noplastic deformation during printing, outstanding abrasion resistance, fine lineprinting and translucent fibres. All these features allow for longer print runswith better edge definitions. ABRASION RESISTANCE V-Screen has outstanding abrasion resistance, which is important for the durability of a screen. Abrasion resistance is also important so that the paste being used does not get contaminated with particles from the mesh. If particles from the mesh, especially stainless steel mesh, get .into the paste it is possible to see anomalies in the finished part with variances’ in desired results, so the yield will decrease:This is seen in stainless steel meshes because of the squeegee giving a rubbing motion across the stainless steel; the repeated friction causes the metal to abrade off the wire thread. With the larger open areas and fine threads of V-Screen, it is possible to print smaller features such as 50 micron line widths. The smallest feature achieved to date with V-Screen is 30 microns in a laboratory setting using an organic paste. Having larger open areas and fine threads also makes it possible to achieve a better surface roughness value (RZ), which is important for gasketing the screen to the substrate. When a good gasket is formed, less bleeding occurs and straighter printed lines can be achieved. STRENGTH MID PROPERTIES V-Screen’s high tensile strength allows fora stronger mesh with large areas, giving it the ability to stretch to hitensions which helps in reducing the snap-off distance of the screen, which inturn helps with the longevity of the screen. This feature also helps keepdimensions over long print runs because the mesh doesn’t have to deflect asmuch to transfer the paste. V-Screenhas almost no plastic deformation during printing, primarily due to itsphysical properties. Vecry is a synthetic material that has memory, much like amemory foam mattress, while natural materials such as stainless steel do not.After the forces of a squeegee are repeatedly applied to any screen, the screenwill begin to distort. However because of V-Screen’s memory, the distortion isminimal. Because of having a higher tensile strength, it is possible to achievehigher screen tension where less snap-off distance is required for printing.Consequently less squeegee force has to be applied to V-Screen when printingcompared to screens made with other mesh materials, thus further improvingdimensional stability over long print runs.V-Screen can hold its tensions over theselong print runs which allows for virtually no tension loss. Once tension on thescreen changes, pattern dimensions begin to change. Holding a tight toleranceis easier to achieve while printing more parts using the V-Screen. Figure 1shows the dimensional stability of a V-Screen’s dimensional accuracy over 5000prints. EMULSION AND ADHESION To achieve finer screen printing featuresand good line resolution, the emulsion used is important. Although any emulsionworks well with the V-Screen, one emulsion was made specifically to be usedwith it. The V-i emulsion is a soft emulsion that has great line resolution forfine features. As it is a soft emulsion it has the ability to form oversubstrates that have varying surface roughness, causing a better gasket whichleads to lower bleeding issues. Translucent fibres allow for better emulsionadhesion. In some other meshes, such as stainless steel, the emulsion does notencapsulate the thread; the V-Screen allows for light transmission through thethreads and encapsulates the emulsion around the thread, including on thesqueegee side. By encapsulating the thread in the emulsion, the emulsion has alarger area to hold on to during printing, which also helps with longer printruns because the emulsion won’t wear away as quickly. This also helps withcreating better edge definitions during printing.Using the V-Screen it is possible to lowerproduction costs due to the longevity of the screen, whilst its structures giveit the ability to print fine lines. V-Screen has a high tensile strength,almost no plastic deformation, outstanding abrasion resistance, line lineprinting and translucent fibres, all helping to give it a longer life. V-Screenis not going to cure the need to print finer lines than 30 microns, so atrampoline will be a good second option. John Gaudiuso is an Engineer for Dynamesh.