What is an SMT Stencil?

At Millennium Circuits Limited (MCL), we’ve created a solid process for providing the best stencils on the market. As one of the most critical parts of the assembly process, we understand the importance of defect-free stencils for our customers. This value-added service helps many of our customers simplify their purchasing processes, ordering PCBs and stencils at once.

Why SMT Stencils Are Important

Before you can go into production, solder paste is printed onto the component pads of the PCB.

How can you make sure you apply the solder paste with precision exactly where it needs to go?

Stencils, or formally surface mount technology stencils, are the answer. Stencils are the medium used to transfer that solder paste onto the PCB.

Stencils consist of a foil made of stainless steel that is laser cut to match the places where surface mount devices will go on the board. Once you have the cut stencil,  solder paste is applied over the openings with a metal squeegee blade. When the stainless steel foil of the stencil is pulled away,  it leaves the solder paste perfectly placed on the board to receive your surface-mounted devices.

Can you apply soldering paste without a stencil? Yes, but because of the precision required, trying to apply soldering paste everywhere it needs to go on the board by hand can be an extremely time-consuming, painstaking process. Furthermore, you cannot get the consistency when applying soldering paste by hand that you will get using a single stencil. It’s important to consider that the chances of error are much greater when applying soldering paste by hand.

When applying soldering paste by hand, or trying to apply it without a perfect stencil you could face some very serious problems, like:

  • Short circuits
  • Voids in the soldering process
  • The desired printed result requires:
  • Smooth and burr-free sidewalls of the apertures
  • Flat, unstressed material
  • Uniform tension distribution over the entire surface
  • Precision in position and size of the apertures

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SMT Stencil Types Available From MCL

We offer the following stencil products:

Framed SMT Stencils

Framed SMT stencils, also known as glue-in stencils, feature a permanent stencil frame. A mesh border keeps the stencil foil stretched taut for optimum accuracy. These stencils have benefits such as:

  • Double-bonding for high-wear applications: Sturdy engineering resists intense use.
  • Superior print performance: Smooth and taut aperture design creates accurate prints.
  • Non-fading fiducial (marking) results: Screen-printing process makes long-lasting fiducial layouts.
  • Ability to withstand numerous uses: Permanent mounting offers high levels of integrity.
  • Availability for immediate use with an SMT printer: Preassembled product works in a screen printer right away.

Because of its durable engineering, a framed SMT stencil suits high-volume printing applications. We recommend this product for production runs that require long-term use. Consider choosing a framed stencil when you plan to assemble a large number of PCBs over an extended period.

Unframed SMT Stencils

Unframed SMT stencils consist of stainless steel foil without a permanent frame. They fit into reusable frames and can detach from them at any time. The benefits of using frameless stencils include:

  • Cost-effective price: Frameless stencils results in a significant price reduction from a framed design.
  • Reduced storage space: Compact size saves on space needed for storage.
  • Lower environmental impact: Use of fewer materials suits eco-friendly production methods.
  • Excellent print performance: High-quality engineering promotes top performance throughout stencil’s lifespan.
  • Compatible with screen printing and hand-printing: Versatile format allows for printing with a machine or squeegee.

Since frameless stencils last for a fair amount of time, they fit short-term applications. We recommend them for short production runs or prototype circuit boards. Choose an unframed stencil for lower volumes of PCBs produced in a short period.

Prototype Stencils

A prototype stencil features the design you specify using a CAD or Gerber file. The user places it over their PCB and uses it to print the design by hand. Prototype stencils offer these benefits:

  • Precise hand-printing: Alternative to hand soldering reduces the potential for errors.
  • Reduced prototype assembly time: Quick alignment and printing increase efficiency.
  • Eliminated need to use a machine: Hand-printing application requires no machine setup.
  • Ultimate cost-effectiveness: Efficient design results in affordable price.
  • Ease of use: Alignment tools allow for an easy-to-understand stencil printing process.

Prototype PCB stencils live up to their names — they suit prototype printing SMT applications. We recommend using them to test out your PCB design due to their affordability and ease of use. Add a prototype stencil to your order if you want to print a fast test product before creating a permanent design.

Prototype SMT Stencil Kit

Our prototype stencil kit comes with everything you need to print by hand. It includes:

  • Your custom prototype stencil
  • A squeegee blade that ensures precise application
  • Solder paste
  • Pick-and-place tool for careful handling
  • Temperature marker for accurate heating
  • A pair of gloves and alcohol wipes to prevent contamination

We suggest buying our prototype stencil kit if you plan to print a board by hand for the first time. It uses simple tools that create precise results.

Get started with an SMT Stencil from MCL

It’s imperative that the stencil be perfect to avoid the issues that could stop your assembly line in its tracks. MCL ensures perfection by utilizing the latest stencil technology and highly trained technicians.

At MCL, we provide top-of-the-line, 100% laser-cut SMT Stencils at competitive prices. Stencils can be shipped the same day from our east and west coast manufacturing partners.

Please contact MCL today to discuss your upcoming stencil needs. Our Customer Concierge team is standing by to discuss your PCB or stencil needs. Call us at 717-558-5975 or click here to contact us online.

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