- Ensure precise positioning and specification adherence. Strictly follow the specified method for opening to achieve high opening accuracy.
- Independent opening specifications should not be too large, and the total width should not exceed 2mm. For solder pad specifications exceeding 2mm, a 0.4mm bridge should be added in the middle to prevent affecting the strength of the stencil.
- Strictly control the tensioning process, ensuring that the opening range is horizontally centered.
- The openings on the underside of the stencil should be 0.01mm to 0.02mm wider than those on the upper side, forming a tapered shape to facilitate effective release of solder paste and reduce the frequency of nettoyage des pochoirs.
- Ensure smooth walls of the stencil openings, especially for QFP and CSP components with spacing less than 0.5mm, requiring the supplier to perform electro-polishing treatment.
- In general, the opening specifications and shapes of SMT components should match those of the solder pads in a 1:1 ratio.
Principes de conception des ouvertures spéciales :
- For 0805 components, it is recommended to open as follows: Each solder pad is cut inward by 1.0mm, then an inner concave circle is made with B = 2/5Y; A = 0.25mm or A = 2/5*L to prevent solder balls.
- For 1206 and above chip components: After each solder pad is moved outward by 0.1mm, an inner concave circle is made with B = 2/5Y; a = 2/5*L to prevent solder balls.
- For circuit boards with BGA, the opening ratio of the steel mesh is 1:1 for ball pitch above 1.0mm and 1:0.95 for ball pitch below 0.5mm.
- For all QFP and SOP components with 0.5mm pitch, the opening ratio in the total width direction is 1:0.8.
- For QFP components with 0.4mm pitch, the opening ratio in the total width direction is 1:0.8, and in the length direction is 1:1.1, with rounded corners on the outer side. The opening width for 0.65mm pitch SOP components is reduced by 10%.
- For PLCC32 and PLCC44, the opening ratio in the total width direction is 1:1, and in the length direction is 1:1.1.
- For general SOT packaged devices, the opening ratio at the large solder pad end is 1:1.1, and at the small solder pad end, the total width direction is 1:1.
