SMT steel mesh: The way we manage it before and after use is like this

I. Pre-production Stencil Inspection Requirements

1. Check stencil tension before mounting. The standard tension range is 35N to 50N. Insufficient tension causes printing offset and insufficient solder; excessive tension may lead to stencil tearing.
2. Verify stencil aperture dimensions against drawings (especially for ICs, BGAs, QFNs and tiny CHIP components) as well as stencil thickness. Excessive dimensional deviations result in abnormal solder deposition (excess solder, insufficient solder, bridging). Also inspect aperture edges for burrs, deformation and notches.
3. Confirm the solder paste model specified in the work instruction sheet. Allow the solder paste to warm up for 4 hours per standard procedures. Unwarmed solder paste has abnormal viscosity and easily clogs apertures. Prepare dedicated cleaning solvent for solder paste; mixing with other cleaning agents is prohibited.
4. Inspect both sides of the stencil for scratches, damage, deformation, residual old solder paste and dust. Clean and blow dry contaminated areas in advance. Fully peel off the protective film before mounting the stencil.
5. Check the stencil frame for deformation, looseness and dents. Frames with deformation cause uneven tension across the entire stencil and shall not be put into production.
6. Cross-check stencil model and product part marking to avoid mass defects caused by incorrect stencil usage.

II. In-production Stencil Operation Requirements

1. Manually level the solder paste on the stencil surface every 2 hours during production to prevent long-term static solder paste from drying and sticking to the stencil and clogging apertures.
2. Manually clean apertures for tiny components such as 0201, 01005 and BGA every 2 hours.
3. Immediately stop production and clean the stencil once insufficient solder, missing print or aperture clogging occurs to prevent defective products from flowing downstream.
4. Only lint-free cloths and soft squeegees with dedicated solvent shall be used for aperture cleaning. Hard tools such as utility knives and metal scrapers for harsh scraping are forbidden, as they deform apertures and create burrs.
5. Avoid prolonged exposure of solder paste to air during production; replenish new solder paste regularly to prevent drying and clogging.
6. Do not hit or squeeze the stencil with heavy objects or fixtures to prevent stencil damage and frame deformation.
7. When switching production batches or pausing production for over 30 minutes, scrape off all solder paste on the stencil surface and lightly wipe apertures to avoid dried and cured solder paste.

III. Post-production Stencil Storage Requirements

1. Complete stencil cleaning within 30 minutes after production. Solder paste cured after overtime cleaning will be hard to remove and may cause permanent aperture clogging leading to stencil scrapping.
2. Before cleaning, scrape excess solder paste off the stencil surface with a plastic scraper to reduce residue, lower cleaning difficulty and save cleaning solvent.
3. Follow the cleaning method (machine cleaning / manual cleaning) specified in the work instruction sheet. Clean both sides of the stencil and all apertures with dedicated solvent.
4. Thoroughly blow dry the entire stencil with a clean air gun after cleaning to eliminate solvent watermarks. Fully inspect both sides and all apertures to ensure zero solder residue and unobstructed apertures; re-clean if residual solder paste exists.
5. After drying and inspection, fully attach protective films to both sides of the stencil to block workshop dust.
6. Place stencils vertically on dedicated stencil racks. Laying flat, stacking or heavy compression are forbidden to avoid aperture damage and frame deformation.
7. Separate stencils for different product models with clear identification to prevent misselection.
8. For long-term idle stencils, conduct weekly re-inspection to check damaged protective films and dusty apertures. Re-clean and replace protective films when necessary.

IV. General Precautions

1. Store cleaning solvents in explosion-proof cabinets away from fire sources. Ensure ventilation during cleaning and wear complete PPE.
2. Immediately scrap stencils with cracks, large-area deformation, persistently unqualified tension or severely clogged uncleanable apertures; reworking and reusing such stencils are prohibited.
3. Hold only the frame when transporting stencils. Direct contact with the thin stencil foil is forbidden, as grease and dust from hands will adhere to apertures and impair printing performance.
4. Dispose of waste solder paste and waste solvent generated from cleaning in accordance with workshop hazardous waste management rules; random disposal is prohibited.