Control the humidity to enhance paste integrity.

Possible causes: Solder paste.

Description. Solder paste, especially water-soluble versions, which are hygroscopic, tend to have limited stencil life because of moisture absorption.

Recommendations.

• Minimize exposure time.
• Printer temperature and humidity should be within recommendation.
• Try new lot of solder paste to verify paste integrity.
• Use coarser powder size if possible, as fine powder size has more oxides and tends to slump more readily.

Paul Lotosky is global director – customer technical support at Cookson Electronics (www.cooksonelectronics.com); This e-mail address is being protected from spambots. You need JavaScript enabled to view it . His column appears monthly.