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A Quick Introduction to Different Types of SMT Stencils

 Mar 09, 2020

Printed circuit boards have revolutionized the electronics manufacturing industry with their compactness and improved efficiency. They have helped electronic manufacturers automate the process of circuit assembly by reducing point-to-point wiring requirements. Today, PCB manufacturers use advanced machines for component placement and SMT PCB stencils for board assembly. These stencils allow them to deposit solder paste on the wiring boards to establish electronic connections. It is then followed by component placement. The stencil printing is performed using a stencil and an adhesive solder paste, which helps position the components during placement. Today, different types of SMT stencils are used during PCB assembly. They are differentiated based on the method of manufacturing, application of solder paste in SMT, and materials used for construction.

Types of SMT Stencils Based on Their Manufacturing

SMT stencils are made of robust materials and can be manufactured in different ways. The aperture can be formed on the stencil in any of the following ways:

  • Electroforming: The nickel is electroformed in this process to produce a stencil. It is also referred to as EFAB. There are high initial costs involved in the process. The process also requires high processing times than other manufacturing methods.
  • Laser Cutting: Apertures are created on a stencil foil using a laser machine. Laser cutting is a subtractive process, and it produces fine and accurate results, which is why it is favored over the other processes mentioned here.
  • Chemical Etching: As the name suggests, an aperture is created through chemical etching. The costs involved in the process are low; however, the results are much inferior to laser cutting process.

What Are the Different Types of Stencils Based on Solder Paste Application?

Stencils are divided into the following types based on solder paste application:

  • Prototype Stencils: These SMT stencils are designed for manual solder paste printing applications. Prototype stencils help eliminate printing mistakes. They are made from CAD files or Gerber files provided by the client.
  • Framed Stencils: These stencils are permanently fixed on the frame. They receive the necessary tension from border mesh. Framed stencils are used during bulk volume PCB production. Framed stencils feature smooth aperture walls, and they assure excellent print performance.
  • Frameless Stencils: Against framed stencils, these stencils are not permanently mounted to any frame. These stencils are comparatively affordable than framed stencils and are recommended for short runs or prototype runs.

An Overview of SMT Stencils Based on Material of Construction

The SMT stencils are mainly made of materials that can withstand harsh working conditions in the PCB shop. They are made of the following materials:

  • Stainless Steel SMT Stencils: Made of stainless steel, these SMT stencils are used during prototyping. They allow users to reduce mistakes and can easily meet the requirements of soldering. These stencils are of better quality than Kapton or Mylar stencil.
  • Mylar and Kapton SMT Stencils: These stencils are created by laser etching Mylar and Kapton materials. They are mainly used during prototyping and assure optimal performance during hand soldering. They are comparatively affordable than stainless steel stencils.

After understanding these SMT stencils, you may get confused on the type of stencil you should choose. This is where a trusted and experienced circuit board manufacturer can help. Accelerated Assemblies is one of the leading manufacturers of industrial printed circuit boards in the US. Their experts work with customers to understand their requirements and help make the right suggestions based on the application requirements.

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