Many customers think of stencil rolls are commodities. They want the cheapest stencil roll they can get because they think there is no difference between the brands. However, there IS a difference in rolls, and cheap rolls can turn out to be very expensive.
Stencil printing is far more complex than many people think. There are over three dozen different stencil printing parameters that must be optimized on an SMT printer. Because of this complexity, the typical SMT line only runs at 90-95% yield. With proper stencil printing, SMT lines can run at 99%+ yields.
The key to better printing is to stop using alcohol during stencil cleaning. The alcohol leaves residue on the stencil that mixes with the solder paste and change its viscosity, resulting in a bad print. By eliminating the alcohol and only dry-wiping, it allows for faster production, higher throughput, higher yields, less scrap, less rework and fewer warranty claims, making your company more profitable and competitive.
However, most stencil rolls need to wipe wet because the paper is weak and leaves lint. A better answer is to use a stronger, cleaner stencil roll material that doesn’t need alcohol. Choose a better quality paper roll or opt for a fabric roll. They are stronger, more absorbent and can effectively dry clean stencils without leaving fibers or solder balls in the apertures. Using higher quality rolls help produce better-quality boards requiring very little rework.
Although the higher quality rolls cost more, many manufacturers are finding that they are wasting less time cleaning and spending more time printing, boosting throughput and productivity.
Benefits of Using Better Quality Stencil Rolls:
- Increases productivity: At a major PCB subcontractor, better quality rolls boosted production from 32 to 55 boards per hour – a 60% increase in productivity.
- Higher Yields: In a large-scale trial with five SMT lines switching to better quality rolls pushed the defect-free yield to 99.55% from an average of 97.25% — an 83% reduction in defects.
- Reduces defects: A large subcontractor in Europe found that improved rolls eliminated 35% of their SMT defects at functional test.
- Eliminates rework: A manufacturer in China made more than 2,000 boards without a single defect.