Manufacturing process requirements of SMT processing template

1. What are the processing steps of SMT SMD Mark?
1. the handling method of Mark, whether Mark is needed or not, and the side of the template, etc.
2. Which side of the template the Mark graphic is placed on depends on the specific structure of the printing press (the position of the camera).
3. Mark stippling method depends on the printing press, including printed side, non-printed side, half-engraved on both sides, full-engraved and fully sealed vinyl, etc.
Second, whether the puzzle is made, and the requirements of the puzzle. In case of splicing, the PCB document of splicing should be given.
III. Requirements for inserting pad ring. Because the reflow soldering process is used for plug-in components, it requires more solder paste than for mounting components, so if there are plug-in components that need reflow soldering process, special requirements can be put forward.
IV. Requirements for the modification of the opening size and shape of the template (pad) by SMT. Generally, for pads larger than 3mm, in order to prevent the solder paste pattern from sinking back and preventing solder beads, the opening is “bridging” with a line width of 0.4mm, so that the opening is smaller than 3mm, which can be evenly divided according to the size of the pads. Requirements for template thickness and opening size of various components.
1. the printing quality of μBGA/CSP and Flip Chip with square opening is better than that with circular opening.
2. When no-clean solder paste is used and no-clean process is adopted, the opening size of the template should be reduced by 5% ~ 10%:
3. The opening design of lead-free process template is larger than that of lead, and the solder paste covers the pad as completely as possible.
4. Appropriate opening shape can improve the processing effect of SMT chip. For example, when the size of Chip component is smaller than metric system 1005, because the distance between the two pads is very small, the solder paste on the pads at both ends is easy to stick to the bottom of the component during pasting, and it is easy to generate bridging and solder balls at the bottom of the component after reflow soldering. Therefore, when processing the template, the inner sides of a pair of rectangular pad openings can be modified into sharp corners or bows, so as to reduce the amount of solder paste at the bottom of the component, which can improve the bonding of soldering sound at the bottom of the component when pasting, as shown in the figure. The specific modification scheme can be determined by referring to the data of “Opening Design of Printing Solder Paste Template” of the template processing factory.
V. Other requirements for SMT patches
1. According to the PCB design requirements, put forward requirements such as whether the test points need to be opened or not. If there are no special instructions for the test points, they will not be opened.
2. Whether there are requirements for electropolishing process. Electro-polishing process is used for templates with the center distance of openings below 0.5mm
3. Purpose (state whether the processed template is used for printing solder paste or printing patch glue).
4. Whether it is necessary to engrave characters on the template (you can engrave PCB product code, template thickness, processing date and other information, but not completely).
VI. After receiving Emil and fax, SMT SMD Template Processing Factory will send back the fax “Please ask the buyer for confirmation” according to the requirements of the buyer.
1. If there is any problem, please call or fax again until the buyer confirms it.
2. Check whether the size of the mesh frame meets the requirements, place the template flat on the desktop, press the surface of the stainless steel mesh plate by hand, and check the tension.
Screen quality, the tighter the screen, the better the printing quality. In addition, the bonding quality around the mesh frame should also be checked.
3. Lift the template for visual inspection, check the appearance quality of the template opening, and check whether there are obvious defects, such as the shape of the opening and the distance between adjacent openings of IC pins.
4. Use a magnifying glass or microscope to check whether the bell mouth of the pad opening is downward, and whether the inner wall around the opening is smooth and burr-free. Focus on the processing quality of the narrow-pitch IC pin opening.
5. Place the printed board of this product under the template, align the printed board pad pattern with the leakage hole of the template, and check whether the pattern is finished.
All aligned, with or without holes (unnecessary openings) and holes (openings of floor drain).
6. If any problem is found, we should first check whether it is our confirmation error, and then check whether it is a processing problem. If any quality problem is found, it should be fed back to the template PCB manufacturing and processing factory for negotiation.