How to clean the solder paste left in the solder paste bottle?

Solder Paste Bottle Residue Cleaning Methods and Precautions

As a key soldering material in electronic manufacturing, the residue of solder paste, if not cleaned up in time, is easy to oxidise or absorb moisture, affecting the subsequent use of the effect.The following is a detailed cleaning guide that combines physical and chemical methods and safe practices to ensure efficient, safe and environmentally friendly cleaning:

I. Cleaning methods

1. Solvent soaking method (small amount of residue recommended)

Tools: Isopropyl alcohol (IPA), special washboard water (need to be compatible with the composition of the solder paste), soft brush, cotton swabs.

Steps:

Recover uncured solder paste: Tilt the bottle and use a plastic scraper to recover the uncured portion to reduce waste.

Solvent Soak: Pour solvent until it covers the residual area and let it sit for 5-10 minutes to soften the flux and metal debris.

Gentle brushing: Brush the inner wall and threads lightly with a soft bristle brush to avoid hard objects scratching the bottle; use cotton swabs to clean stubborn corners finely.

Rinsing and drying: After pouring out the waste liquid, rinse with pure water repeatedly, air-dry naturally or dry at low temperature (to avoid water stains remaining).

2. Ultrasonic cleaning method (stubborn residue applicable)

Tools: ultrasonic cleaning machine, water-based cleaning agent (environmentally friendly).

Steps:

Pre-treatment: preliminary scraping off large pieces of residue to reduce the burden of cleaning.

Setting parameters: cleaning agent liquid level did not pass the bottle, frequency set to 28-40kHz, temperature ≤ 50 ℃.

Start cleaning: run for 5-10 minutes, use ultrasonic cavitation effect to strip stubborn stains.

Post-treatment: remove and rinse with pure water, dry thoroughly and check the cleanliness.

3. Heating softening method (viscous residue applicable)

Tools: Warm water (50-60℃), hot air gun (low temperature gear ≤60℃), soft cloth or cotton swab.

Steps:

Heat to soften: Soak the bottle in warm water for 10-15 minutes, or low temperature hot air gun to heat the bottle evenly.

Wipe the residue: After the solder paste is softened, wipe the inner wall with a cotton swab or soft cloth, avoiding direct contact with the solder paste at high temperature (to prevent decomposition of the ingredients).

Cleaning and checking: After removal, rinse again with solvent or water to ensure no residue.

II, tool selection recommendations

Local fine cleaning: soft bristle brush, cotton swabs (suitable for bottle threads, corners).

Stubborn residue: ultrasonic cleaner (efficient and non-destructive, suitable for laboratory or batch processing).

Liquid residue: tin sucker (need to be heated and softened before sucking to avoid clogging).

III, environmental protection and safety considerations

Waste liquid disposal:

Waste liquid containing solder paste needs to be classified as chemical waste, contact professional organisations for disposal, and it is strictly prohibited to pour directly into the sewer.

If it contains lead solder paste, it needs to be disposed of according to the standard of hazardous waste.

Personal protection:

Wear N95 mask, goggles and nitrile gloves during operation to avoid contact with skin or inhalation of dust.

Ensure good ventilation when working with organic solvents (e.g. switch on exhaust fans or work in fume cupboards).

Resource Recovery:

Uncontaminated recyclable solder paste can be collected centrally and handed over to professional organisations for purification and reuse to reduce costs and waste.

IV.  the operation step summary

Recycling residual paste: Priority is given to recycling uncured solder paste to reduce waste.

Selection method: according to the residual amount and state, choose solvent immersion, ultrasonic or heating softening.

Auxiliary cleaning: with soft brushes, cotton swabs and other tools to refine the processing.

Thorough cleaning: Rinse with pure water and then dry thoroughly to avoid oxidation caused by water residue.

v. additional recommendations

Residue Prevention:

Scrape the top of the bottle immediately after each use and store tightly closed to minimise oxidation.

Dispense into small volume bottles to reduce the number of times the cap is opened.

Material compatibility:

Make sure the solvent is compatible with the bottle material (e.g. PP, PE) to avoid corrosion and deformation.

Prefer solder paste bottles with smooth inner wall or with anti-stick coating.

By using the above methods, solder paste bottles can be cleaned efficiently and their service life can be prolonged, while at the same time taking into account operational safety and environmental protection.If the residue is difficult to remove or the bottle is damaged, it is recommended to replace the bottle with a new one to ensure soldering quality.