John Gaudiuso explained in detail how the use of mesh in screen printing can be a cost-effective option.
With the size of screen printed electronics getting increasingly smaller, there is an increased need for finer features. This has brought on a demand for finer and sharper printing. Another important factor that has to be taken into consideration is that of cost-effectiveness. Excessive use means that dimensional issues occur faster. This is more common with stainless steel meshes as they tend to get deformed over a period of time.
There are several effective ways to deal with the issues such as dimensional stability and longevity while maintaining the sharpness of the print. The trampoline screen is one such solution that can be used very effectively to increase the longevity of a stainless steel mesh.
Features of The Trampoline Mesh
This mesh tends to have a rigidity that prevents it from regaining its original shape. The use of a trampoline screen permits the cuter mesh (which is a highly elastic polyester-like mesh), to expand more than the rigid inner mesh. This allows a larger number of print runs. Though this option is a good one, the method is largely time-consuming. It takes longer to fabricate a trampoline stainless steel mesh with a trampoline screen than it does to stretch a mesh onto a frame.
Using a V-Screen
Alternatively, a V-Screen, synthetic mesh can be used. It has a large number of advantages. The mesh is woven using Vecry fibre which is made up of a crystal-based polymer liquid core called Vectran. This core is sheathed with Pen which is a flexible polymer. V-Screen is very tensile (it has more strength than stainless steel does) and is abrasive-resistant. There is also no plastic-deformation when this material is used in printing, it also affords very fine and sharp line-printing and the fibres are also translucent. All these factors mean longer print runs and better edge definitions.
In Memory Lies Strength
The tensile strength of V-Screen affords larger areas to be covered with stronger mesh. It adds the property of “stretch” which goes a long way in reducing the screen’s snap-off distance which results in increasing the longevity of the screen. This particular property also helps in maintaining the proportion of the print over longer print runs as the mesh doesn’t have to stretch too much in the paste-transfer process. Vecry is essentially a synthetic material and has “memory”, similar to that of a memory foam mattress. Natural materials such as stainless steels lack this property and applying repeated squeegee-force to the screen will distort it. On the other hand, since V-Screen has memory, the distortion is very minimal.
The squeegee force that has to be applied in a printing process using V-Screen is less than that which is applied to screens made of other materials. This adds to the dimensional stability in longer print runs. Tension-loss in a screen leads to a change in the proportion and dimension change in the pattern. When a larger number of parts have to be printed, the V-Screen offers a tighter tolerance.
Higher Resistance to Abrasion
Its abrasive-resistant property is what makes V-Screen very durable. This property is a very critical one in the printing process as it means that mesh particles will not contaminate the paste that is used for printing. Particles from a disintegrating stainless steel mesh can mingle with the paste and will result in anomalies in the finished products. Since the V-Screen has wider open areas and finer threads, finer printing is possible and 50 micron line widths can be achieved very easily. To date, it has been possible to achieve a 30 micron print feature using an organic paste, under laboratory conditions. The surface roughness value (RZ) can be achieved due to these features as well. This is important as a strong gasket to screen bond means there will be less bleeding and the printing will be finer and more aligned.
Adhesion and Emulsion
The formulation of the emulsion is important to acquire finer screen-printing features. Though almost any emulsion works well with the V-Screen, the softer V-i version is specifically manufactured for use with it. It offers a sharper line resolution for finer detailing. Its soft texture makes it an ideal emulsion for use on surfaces of varying roughness. The translucent fibres afford greater emulsion adhesion. In meshes such as stainless steel ones, the emulsion does not coat the thread and thus a smaller area is held on during the printing process. On the contrary, the translucent V-Screen threads encapsulate the emulsion and the squeegee side also gets covered. Consequently, the emulsion doesn’t wear out too fast and longer print runs are possible. This creates better edge-definitions during the printing process. The longevity of the V-Screen translates into lower production costs too.
This article was written on behalf of Cadisch, an online store for all your screen printing products (http://www.cadisch.co.uk/search.asp?types=SCREEN+PRINTING+PRODUCTS)
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