News - 10.26.2018

Stencils and Their Ultimate Influence

Surface Mount Technology, or SMT, is a method for producing electronic circuit boards where components are mounted or placed directly onto the surface of Printed Circuit Boards (PCBs).

Pete Anniss

One of the most effective ways to create these are through stainless steel stencils.

Why is the stencil phase necessary?

Stencil printing is the first step within the SMT assembly line. The stencil applies that material that will make every interconnection on the PCB, and is often regarded as the most important element within the whole process.

For over 20 years, Datum has provided stainless steel to produce metal masks and solder stencils for the SMT industry. Throughout that time, Datum has become the market leader because of our focus on the end application. We have developed an understanding to provide solutions to challenges throughout the production process.

As industry leaders, we know the ins and outs, ups and downs, of stencils.

The purpose of the stencil is to form the paste deposits on the PCB and can define the quality, productivity and profitability of the SMT line.

Bad printing will cause:

  • Defects, bad quality solder joints
  • Increased rework
  • Rework and replacements increase time and cost

Good printing will give:

  • Reduced defects
  • Improved throughput
  • Reduced overall product cost

What has Datum done to ensure good printing?

Datum examined the printing process and the influence of the stencil.

Here are the top four area that Datum continually addresses to provide positive impacts and innovations to stencils.

  1. Flatness

The stencil needs to remain flat after laser cutting (or etching). If the stencil is not flat it will cause misalignment or poor gasketing during printing, producing defects on the PCB.

Datum has ensured that our production specification gives an extremely tight tolerance on flatness of material. We have also implemented specific production methods to give a material with reduced internal stress. This results in a flatter material after cutting, which becomes more critical in areas of apertures with high density.

  1. Thickness control

Volume of paste deposits are crucial to the design and efficacy of the PCB and the components that will be placed on the board. Previous substrates that were being used (some are still used elsewhere) had a thickness tolerance of +/-10%.

Datum has controlled our manufacturing process to give thickness tolerances as tight as +/-1%. These controls ensure that the manufacturers are confident in what they can expect from the stencil.

  1. Paste release and cut quality

Datum has a consistent and controlled material. Our substrates have a homogenous structure with minimal impurities. There are many influences over paste release and cut quality that are in control of the stencil producers but, with the correct laser settings, our material has been shown to cut well with lasers and produce smooth aperture walls for good paste release.

  1. Continually develop

Datum has developed many premium products that provide benefits to the industry. We continually look at adding value to the industry and the tangible benefits to the end producers of PCBs.