What is basking in the sun in PCB screen printing?
There are many small operations in these two areas, let’s take a look
1. Steps for net pulling: net cleaning-level inspection-primer application-net pulling-tension-viscose-netting, sealing edge-storage how to do:
Due to the repeated use of the net cage, the residual adhesive, net yarn and other debris around the net frame must be cleaned to avoid affecting the adhesion of the net yarn and the net frame. Place the mesh objects on the platform (horizontal placement) for inspection Whether the mesh is deformed, if it is deformed, it needs to be cut off to clean the undeformed frame and gauze to be cleaned and evenly coated with a layer of Nanbao strong fat (no hardener required) to enhance the drawing The maximum degree of the rear mesh and the screen frame is about 10 minutes after the first gluing, put the mesh on the drawing net and adjust the relative position and height to select the mesh, loosen the surrounding nozzles, put the mesh on the box, and then Put the net yarn into the mouth evenly, without wrinkles, pay attention to the net yarn on the four corners, the clamp must be locked, and the gap between the clamp and the clamp (such as automatic lifting, manual pulling of the net)
Pull the net: first tension 26, let stand for 5 minutes to tension 24; second tension 28, let stand for 5 minutes tension 26; third tension 32, set the tension for 5 minutes to 30; fourth correction 5 point tension 32, in the glue Place on tension 30 for 20 minutes. After 15 minutes of glue curing, the net tension is 28. Allow 72 hours before using the screen (for example, take x beige as the standard).
Use a small brush to evenly brush the adjusted glue on the next surface of the net frame and the net yarn. Do not drop the glue into the middle part of the screen. After drying for 8 minutes, apply the glue on the coating surface with a spatula. It is completely suitable for about 10 minutes after the glue is completely dried (open air blowing should be used to strengthen the drying), press it to a position close to the contract, and then it can be lowered. Remove the excess mesh around the screen, and Write down the date in the mesh frame, the tension of the mesh and the net downwards (to observe the tension change) to prevent the white water from infiltrating the inner corners. Seal the mesh frame with red glue, and then use waterproof tape and the surface mesh on the mesh frame. Can prevent the potion from penetrating
2. Net drying
Washing the net: Use grinding net paste to wipe it to grease (new net), grind ghost paste to figure (old net), grind the powder remover into net paste, blue oil, wash the residue with anti-white water, and use detergent Rinse the net, finally rinse it with a high-pressure water gun, and finally clean it with pure water. The temperature of the grill-oven should be below 48 degrees Celsius.
Water-filled silk: Wash the clean net, and then wash it again with pure water. According to the project, Filin’s spelling graphics will increase by about 20% dissatisfaction, to choose water filin, press the water Filin end on the Internet with a triangular ruler, then use the triangular ruler to slowly level it, and then use a rubber scraper to scrape it lightly. Flat, towel dry excess water
Use mesh pulp: dry the mesh plate first, then make the pulp. Use a scraper box to scrape the mesh plate to the mesh. The green oil is three times the green oil (about once every 10 minutes or more). The surface oil comes next, and the orchid first Tear off the film on the 50K water silk, then scrape it on the mesh 20 times, three times each time (we have used an automatic pulping machine), after drying. Clean yarn selection of ordinary thread, green oil, machine oil, surface oil 120T, 100T, 110T mesh, carbon oil 51T, blue glue 24T photosensitive thread and thermosetting green oil 77T Filin selection thread made of 18K water silk (due to the use of Uneven mesh network without generating mesh pulp: dog teeth, fatty oil, wave oil), green oil, motor oil, surface oil selection mesh, carbon oil selection 50K water silk, and place the required engineering graphics Filin on the screen Select the position on the top, place it in the blasting machine for burst light, choose the time (3000W spotlight), the line is usually within 60-80 seconds, the green oil is within 80-100 seconds, and the bottom character oil is 40-60 seconds. Carbon oil, blue glue 350-400 seconds pressurized water rinse, dry. Seal the outer edges of the net with orchid oil (sealed net) and dry. Check and repair the network, write down the date of completion and each corresponding number, and record it for archiving and storage. Of course, this is just a general operation step. The ancients believed that it would be better to have no books. If the actual operation is carried out strictly according to this method, it is extremely unwise. We should learn to use it in order to continue to improve and make better products. ‘?/ r2 C” `. h
PCB screen printing specifications
PCB silk screen technology is a lot of specifications, which can not be done casually. These specifications promote the development of PCB silk screen intrusion technology. We will take a look at which specifications: all components, mounting holes, and positioning holes have corresponding silk screens to facilitate the installation of the board , All components, mounting holes, and positioning holes have corresponding silk screens, and the silk screens in the PCB mounting holes have H1, H2 … Hn logos. Screen printing characters should follow the principle of left to right and bottom-up screen printing characters as far as possible. Each screen printing character should follow the principle of left to right and bottom-up, which is used for each electrolytic capacitor. Diodes and other polar equipment functional units try to keep the same direction.
The equipment pads require tin tin but no silk screen tin, and the equipment tag number should not be blocked by the installed equipment. (Except for those screens with silk screens on higher density PCBs)
In order to ensure the reliability of the soldering of the device, the device pad requires no silk screen. In order to ensure the continuity of the tin, the tin of the tin is required, and the silk screen of the Wuxi tin is required. In order to facilitate the insertion and maintenance of the device, the number of the device after the installation of the device should not be Blocked by the device, the silk screen cannot be pressed on the through hole or the pad, so as not to lose the silk screen that penetrates the open weld and affect the training. The screen pitch of the screen is greater than 5 million. The polar component clearly shows the polarity on the screen, and the polarity direction mark is easy to identify. The PCB photographic drawing file has the correct number of sheets, each layer should have the correct output, and the complete layer number output. The identifier of the device on the PCB must be consistent with the identifier number in the BOM list. The direction of the directional plug-in is clearly indicated on the silk screen. The PCB should have a bar code position mark within the allowable range of its board space. The PCB should have a 42 x 6 bar code screen frame. The position of the bar code should be considered for easy scanning. The PCB file should have the board name, date, version number and other board information silkscreen, the location is clear and eye-catching. The PCB must have the complete information of the manufacturer and the anti-static mark.
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