SMT solder paste printing scraper flatness control

In the SMT production process, the flatness of the solder paste printing scraper is crucial to the quality of solder paste printing. Scraper flatness control directly affects the thickness consistency and graphic accuracy of the solder paste, which has a significant impact on welding quality, production efficiency and product reliability.

1. The importance of scraper flatness

(1) Solder paste thickness uniformity

Insufficient scraper flatness may lead to uneven solder paste thickness, which in turn affects the mechanical strength and conductive properties of the solder joint.

(2) Graphic integrity

A scraper with poor flatness may not be able to completely cover the steel mesh surface, resulting in insufficient or excess solder paste transfer, and defects such as empty solder joints, cold solder joints or bridging.

(3) Extending the life of equipment and steel mesh

Uneven scraper will increase the local pressure on the steel mesh, causing excessive wear or damage to the steel mesh.

(4) Adapting to high-precision printing

As SMT develops towards high density and high precision (such as 01005 or micro-pitch packaging), the flatness requirements of scrapers have become more stringent to ensure that the solder paste distribution meets the needs of precision components.

2. Manifestations of scraper flatness problems

The scraper edge is worn, irregular or warped.

The solder paste is unevenly distributed, and the printing area is thin or locally accumulated.

The local area of the steel mesh is not completely scraped clean.

3. Scraper flatness control measures

(1) Material selection

Use materials with high hardness, corrosion resistance, and non-deformation (such as stainless steel or high-strength alloy).

For flexible scrapers (such as polyurethane materials), control their hardness and resilience.

(2) Regular inspection

Visual inspection: Observe whether the scraper edge is worn or warped.

Measuring instrument: Use a flatness tester or precision measuring tool to detect the flatness deviation of the scraper.

(3) Equipment maintenance

Ensure that the scraper mounting clamp is not loose or deformed to prevent affecting printing stability.

Regularly check whether the scraper installation angle meets the equipment parameter requirements.

(4) Scraper replacement and maintenance

Establish a scraper service life standard and replace it regularly according to the frequency of use and product requirements.

Avoid using hard objects to scrape when cleaning the scraper to prevent new wear.

(5) Optimize process parameters

Ensure that the scraper angle and pressure are set properly: excessive pressure may cause the scraper to deform, while insufficient pressure may result in incomplete scraping of the solder paste.

Set the appropriate scraper speed to prevent vibration or deviation caused by high-speed operation.

(6) Training and awareness

Provide professional training to operators to let them understand the importance of scraper flatness to printing quality.

Strictly implement the scraper inspection and replacement process to avoid using degraded scrapers.

4. Scraper flatness detection method

(1) Ruler detection method

Use a high-precision ruler to fit the scraper edge and observe whether there is an obvious gap.

(2) Interference detection method

Measure the flatness of the scraper edge by optical interference method, which is suitable for high-precision requirements.

(3) Thickness measurement method

Compare the scraper edge with the standard plane and use a thickness gauge to measure the edge deviation.

5. Factors affecting scraper flatness

Material degradation: Use inferior scrapers or use scrapers that have not been maintained for a long time.

Excessive printing pressure: Causes permanent deformation of the scraper edge.

Improper cleaning: using corrosive or hard tools to clean the scraper, damaging its edge.

6. The significance of improving scraper flatness

Improve product qualification rate: reduce solder paste printing defects and improve product one-time qualification rate.

Reducing production costs: reducing rework and material waste.

Extending equipment life: avoiding damage to the steel mesh and printing platform, reducing maintenance costs.

In general, scraper flatness is one of the key factors affecting the quality of SMT solder paste printing. Comprehensive control through material selection, regular testing, equipment maintenance and personnel training can significantly improve the stability and accuracy of solder paste printing, ensuring that the production process meets the requirements of high-quality electronic products.