By so doing, we get six broad categories. Some of the steps can be grouped together to form a functional step. If the whole process was broken down into individual steps, we get about 32 steps. However, PCB silkscreen is a very sensitive, delicate, and sophisticated of the four main sub-processes. The process of solder masking also involves several sub-processes, such as PCB silkscreen printing. The production of a PCB involves multiple processes, which together make the finished board. Depending on your project, choose appropriately. It's now evident that the method you choose should help you save as much as possible on the overall costs and time. The only issues with DLP are the inability to produce readable text on silvery material, and the unreadable text that's usually produced when the text height is reduced below 0.02". This method's main selling points are the record short time it takes to print the board and the accuracy that surpasses the other two methods. The acrylic ink may produce illegible impressions on silvery finishes. Once done, the board is then exposed to ultraviolet light for curing and development. The printer inscribes the board with acrylic ink as per the commands the user inputs to the software. The method employs the same principle as an inkjet printer, but one guide by a CAD application. In case you really want to economize on the board space, you can sacrifice the long setup time associated with LPI.ĭLP is quite expensive as compared to the other silkscreen printing methods. You also need more ink for this process compared to the other two methods. White color is the most preferable in LPI. SILKSCREEN DEFINITION MANUALThis method has higher precision than the manual printing process, allowing for silkscreen application in boards with a lesser spacing. These plates are then allowed to cure, and the screen developed afterward. The laminate is then exposed to ultraviolet light so that the silkscreen sketch impression is transferred to the plate(s). The epoxy layer, in this case, has photodecomposition properties. Generally, the laminate is coated with an epoxy layer. If you're conversant with solder mask application, you may already know how LPI is done. If the minimum line width required is 4mil, LPI can be applied. Lastly, it takes long, typically years, to master the art of manual screen printing. Pad clearance is also bound to be troublesome in manual screen printing. First, the method requires bigger board spacing to accommodate the large text size. There are significant limitations, however. The main advantages of manual screen printing are the ease and low costs associated with this method. Next, the laminate is placed in the baking oven to cure the ink. A stencil made of text and traces is used to direct the epoxy ink through. SILKSCREEN DEFINITION REGISTRATIONHowever, this method is limited to line widths not less than 0.007", or when the registration tolerance is at 0.005". This is the oldest of the three methods and happens to be the least expensive. The common PCB silkscreen printing methods are: Each method has its uniqueness, which determines where that particular method can be applied. These methods differ in aspects such as overall cost, time to complete the printing, the available board spacing, and the printed circuit board material to be used. There are basically three common methods of PCB silkscreen printing. Logos and manufacturer or version numbers Reference designators for identifying the part's location The silkscreen is, however, not a functional part of a PCB. You can already guess what information the silkscreen provides. What information does PCB silkscreen provide? All components can be identified easily, and circuits efficiently traced. When applied as per standards, a detailed silkscreen makes the work easier for both the engineer and the manufacturer. For these reasons, the ink is usually available in a few colors, i.e., white, black, yellow. It is also necessary that the ink be non-conductive. The silkscreen employs a highly formulated epoxy ink. There are some PCBs you'll find with a silkscreen on the solder side. The silkscreen is mostly applied on the components side since it's economically more viable than if applied on the solder side. When it comes to Printed Circuit Boards (PCBs), the silkscreen is the ink layer that provides printed information to identify the various circuit points, components, marks, logos, warning symbols, etc. For a feature to be easily identifiable, there must be an accompanying name or standard symbol to denote it. We know that the various features are labeled on the map otherwise, it would make no sense to see the lines without a label. A simple analogy from which to observe a silkscreen would be observing a map, especially a countered map.
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