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SMT Stencil

We can provide you with our quality Basic Stencil and framework so you can handle assembly from the convenience of your own worktable.

PCB_Stencil_About_3

About SMT Stencil

A SMT stencil (also known as a solder paste stencil) is a tool used in the manufacturing process of printed circuit boards (PCBs), specifically in the surface-mount technology (SMT) assembly process. It is used to apply solder paste to the pads of a PCB in preparation for mounting electronic components.

RAYMING offers high-quality, customized PCB stencils for SMT assembly, ensuring precise and consistent solder paste application across various components. These stencils are essential for both high-volume production and prototype runs, helping achieve reliable solder joints and high-quality assemblies. With fast production and expert design, RAYMING provides reliable performance for modern electronics manufacturing.

Stencil Technical features

1. Stencil type Framework Non-framework
2. Stencil side Top Bottom Top+Bottom (On Single Stencil) Top & Bottom (On Separate Stencil)
3. Thickness 0.08mm 0.10mm 0.12mm 0.15mm 0.2mm 0.25mm 0.3mm
4. Fiducial Mark No Fiducial Through Etched Half Etched

5. Size

370×470mm (Valid area 190×290mm)

370×470mm  (Valid area 190×290mm)

420×520mm  (Valid area 240×340mm)

450×550mm  (Valid area 270×370mm)

584×584mm  (Valid area 380×380mm)

550×650mm  (Valid area 350×450mm)

736×736mm  (Valid area 500×500mm)

400×600mm  (Valid area 220×400mm)

400×800mm  (Valid area 220×600mm)

400×1000mm  (Valid area 220×760mm)

500×800mm  (Valid area 320×600mm)

400×1200mm  (Valid area 220×1000mm)

400×1400mm  (Valid area 220×1200mm)

500×1200mm  (Valid area 320×1000mm)

500×1400mm  (Valid area 320×1200mm)

SMT Stencil Products

Prototype SMT Stencils

These frameless stencils are specifically designed to manually print solder paste onto printed circuit boards.

  • Printed circuit board stencils eliminates tedious hand soldering of PCBs
  • Reduce PCB prototype assembly time
  • Available with or without flaps

** The stencil kit comes with a squeegee blade and board holders.
** Using printed circuit board SMT stencils with a Toaster Reflow Oven will make your prototype PCB assembly job easier and save you time.
** We are backing that with a money-back guarantee program.

Stainless Steel SMT Stencil

Our stainless steel stencils were specially designed for the Maker’s market so everyone can have access to a high quality SMT stencil at a low price.

  • Eliminates tedious hand soldering of prototype PCB boards
  • Reduce PCB prototype assembly time
  • Better quality than a Mylar or Kapton stencil
  • Starts at $20

Mylar and Kapton SMT Stencils

These are very low cost SMT Stencils specifically designed to manually print solder paste onto printed circuit boards.

  • Eliminates tedious hand soldering of prototype circuit boards
  • Lower cost than stainless steel stencils
  • Cut with a UV laser for optimal performance

BGA Rework Stencils

Stencil are flexible solder paste stencils manufactured from a polyimide film with a high temperature adhesive covered with a release liner. They serve as both your stencil and alignment device.

  • StencilQuik comes in a pack of 10 BGA rework stencils
  • Allows you to replace your own BGAs or CSPs without special training or large capital equipment expenditures
  • Acts as an insulating barrier between solder balls as the solder paste masks adjacent apertures increasing placement reliability
  • Simplifies BGA placement as you can “feel” the device settle into the apertures of the Stencil

Quick-Turn Rework Stencils

These laser cut stencils are typically used to manually print a single component on a printed circuit board.

  • Maximum Size 2″ x 2″
  • Available with or without flaps (Flaps facilitate handling)
  • Mainly used for PCB rework but can used for prototype PCB assembly of simple boards

Rework Stencils

 greatly simplifies the ability to selectively print solder paste onto various areas of a PCB. Simply peel off the backing, place the StikNPeel™ onto the PCB and apply the paste.

  • StikNPeel comes in a pack of 10 stencils
  • This rework process overcomes many of the headaches of using metal stencils
  • Eliminates “smearing” of solder paste underneath the stencil
  • Co planarity between board and stencil is assured due to the adhesive backing on the stencil

Flip-Up Stencils

Flip-Up Stencils are single site stencils, used to apply solder paste onto circuit board pads of BGA’s, QFN’s, QFP’s, TSOPS, PLCC’s, etc.

  • Great for QFN’s where the pads on the board are larger than the pads on the component.
  • All Flip Up stencils are made from stainless steel and are reusable after a quick wash in an alcohol based cleaner.
  • All Flip Up stencils are custom made to order per your specification.

Frameless SMT Stencils

These laser cut stencils are designed to work with stencil tensioning systems also known as Reusable Stencil Frames like the Wizard Frame.

  • Reduces storage space requirements
  • Significantly less expense than framed stencils
  • Smooth aperture walls and can be used for 16 Mil pitch and below and for Micro BGA”s

** Frameless SMT Stencils are recommended for prototype printed circuit board assembly or short runs.

CPF Stencils

CPF Stencils (or Component Print Frame) are used to apply solder paste directly onto BGA and Leadless components.

  • A CPF stencil makes for simple alignment when pasting, and serves as an excellent tool for applying paste when boards are highly populated.
  • All CPF stencils are made from stainless steel and are reusable after a quick wash in an alcohol based cleaner.
  • All CPF stencils are custom made to order per your specification.

* Orders contain stencil only. Please see accesories

Framed SMT Stencils

These solder paste stencils are designed for high volume screen printing on printed circuit boards.

  • Foils are permanently mounted into aluminum frames
  • Provide optimum solder paste volume control
  • Large variety of standard frames for every printer

** Framed stencils have smooth aperture walls and can be used for 16 Mil pitch and below and for Micro BGA”s.

Framed Multi-level / Step Stencils

These Multi-level Stencils offer superior flexibility in achieving the right solder paste volume deposit for components with diverse paste requirement.

  • Provide optimum solder paste volume control
  • Eliminate co-planarity problems
  • Foils are permanently mounted into aluminum frames

Framed Ultra Stencils

An alternative to Electroform Stencil.

UltraSlic™ FG outperforms all other existing stencil technologies on the market today, and it can be shipped in 48 hours turnaround times.

  • Fine Grain stainless steel with superior fatigue strength, super smooth surface and elevated wear factor
  • Superior paste release below surface area ratios of 0.5
  • Higher performance and lower cost compared to electroform, the option of step stencils

Framed Electroformed Stencils

Electroformed stencils offer the best paste release characteristics available and are frequently used for fine pitch (20 mil to 12 mil pitch) SMT applications on printed circuit boards. They are also used for µBGA’s, Flip Chip, and Wafer Bumping (12 mil to 6 mil pitch).

  • The smooth trapezoidal sidewalls of an electroformed stencil allow for better paste release
  • Nickel has a lower coefficient of friction compared to stainless steel
  • Electroform foils are harder than full hard stainless steel of comparable thickness, providing for longer stencil life

Frameless Electroformed Stencils

Electroformed Frameless Stencils are nickel-based, electroform foils designed to work with stencil tensioning systems also known as Reusable Stencil Frames. They do not need to be permanently glued in a frame. Electroformed stencils offer the best paste release characteristics available and are frequently used for fine pitch (20 mil to 12 mil pitch) SMT applications on prototype printed circuit boards. They are also used for µBGA’s, Flip Chip, and Wafer Bumping (12 mil to 6 mil pitch).

Stencil Relative Articles

What is a SMT Stencil?

A SMT stencil is a thin sheet made from materials like stainless steel or nickel, with precisely cut openings that align with the pads on a printed circuit board (PCB). It is used to apply solder paste to the PCB before component placement. The stencil is placed over the PCB, and solder paste is spread through the openings using a squeegee, ensuring accurate and consistent coverage. This process is crucial for the reflow soldering stage, where the paste melts to form strong solder joints. SMT stencils help improve manufacturing efficiency, reduce defects, and ensure high-quality assembly in electronics production.

The main purpose of a PCB stencil is to accurately and consistently apply solder paste to specific areas on a printed circuit board where components will be placed.

PCB stencils are typically made from thin stainless steel or polyimide (a type of plastic). Stainless steel is more durable and precise, while polyimide is more flexible and less expensive.

  • The stencil is placed over the bare PCB, aligning precisely with the pads where components will be soldered.

  • Solder paste, a mixture of tiny solder particles and flux, is spread across the stencil using a squeegee.

  • The solder paste passes through the openings in the stencil, depositing onto the PCB pads.

  • When the stencil is removed, small, precise amounts of solder paste remain on the PCB pads.
  •  
  • Precision: Stencils allow for very accurate placement of solder paste, which is crucial for small components and fine-pitch devices.
  • Consistency: Using a stencil ensures that the same amount of solder paste is applied to each pad, improving soldering reliability.
  • Efficiency: Stencils significantly speed up the process of applying solder paste, especially for boards with many components.
  •  
  • Framed stencils: The stencil foil is mounted in a rigid frame for easier handling and alignment.
  • Frameless stencils: These are more flexible and can be used with automatic stencil printers.
  • Step stencils: These have different thicknesses in different areas to accommodate components with varying solder paste requirements.
  •  

The design of a PCB stencil is typically created from the same data used to design the PCB itself. The openings in the stencil correspond exactly to the pads on the PCB where solder is needed.

PCB stencils are widely used in surface-mount technology (SMT) assembly processes, both in large-scale manufacturing and in smaller prototyping or hobby electronics projects.

Understanding and properly using PCB stencils is crucial for achieving high-quality, reliable solder joints in electronic assembly. They play a vital role in ensuring that electronic devices are manufactured to high standards of quality and reliability.

How to Clean SMT Stencil?

Cleaning SMT stencils is essential for maintaining their effectiveness and ensuring the consistent application of solder paste. Over time, solder paste residue can build up on the stencil openings, potentially causing blockages or uneven paste deposition, which can lead to defects in the soldering process. Regular cleaning removes this residue, preventing issues like solder bridges or insufficient paste. Cleaning also helps extend the lifespan of the stencil, maintaining its precision and accuracy for future use. Proper cleaning methods, typically using solvents or ultrasonic cleaning systems, ensure that the stencil remains in optimal condition, contributing to higher-quality PCB assembly.

  • It's best to clean the stencil immediately after use to prevent solder paste from drying and hardening.
  • Use a dry wipe or squeegee to remove excess solder paste from the stencil surface.
  •  

a) Materials needed:

  • Lint-free wipes
  • Isopropyl alcohol (IPA) or specialized stencil cleaning solution
  • Soft brush (like a toothbrush)
  • Protective gloves

b) Process:

  • Put on protective gloves.
  • Dampen a lint-free wipe with IPA or cleaning solution.
  • Gently wipe both sides of the stencil with the dampened wipe.
  • For stubborn residues, use a soft brush dipped in the cleaning solution.
  • Pay extra attention to the apertures (openings) in the stencil.
  • Rinse the stencil with clean IPA or water (if using a water-soluble cleaner).
  • Dry the stencil thoroughly with a clean, lint-free cloth.
  • For more thorough cleaning, use an ultrasonic cleaner.
  • Place the stencil in the ultrasonic bath filled with appropriate cleaning solution.
  • Run the ultrasonic cleaner for 3-5 minutes.
  • Rinse the stencil with clean IPA or deionized water.
  • Dry thoroughly with compressed air or a lint-free cloth.
  •  
  • Many PCB assembly lines use automated stencil cleaning systems.
  • These systems often use a combination of spray cleaning, ultrasonic cleaning, and vacuum drying.
  • Follow the manufacturer's instructions for your specific system.
  •  
  • After cleaning, inspect the stencil under good lighting.
  • Check that all apertures are clear and free from residue.
  • A magnifying glass or microscope can be helpful for detailed inspection.
  •  
  • Once clean and dry, store the stencil in a clean, dry environment.
  • Use a stencil storage system or lay the stencil flat to prevent warping.
  •  
  • Regular cleaning during use can prevent build-up.
  • Consider using nano-coating on the stencil to reduce solder paste adherence
  •  
  • Always work in a well-ventilated area when using cleaning solvents.
  • Wear appropriate personal protective equipment (PPE) like gloves and safety glasses.
  • Dispose of used cleaning materials and solvents properly according to local regulations.
  •  
  • Clean the stencil after each use or production run.
  • For high-volume production, you might need to clean the stencil multiple times during a single shift.
  •  

By following these cleaning procedures, you can maintain the quality and longevity of your PCB stencils, ensuring consistent and accurate solder paste application in your PCB assembly process.

Stencil Design Guidelines

SMT Stencil FAQ

Stencils replace hand soldering of surface mount devices, and the inconsistencies created by hand soldering. They allow for direct placement of solder paste to the surface to be soldered. 

The stencil thickness is determined by the smallest component land pattern. If you are not sure, our design staff can choose the optimum thickness based on the data you supply.

Home base apertures are used to control solder balling and tomb-stoning of chip components such as 0603’s and 0805’s. The shape is generated by taking a percentage of the length of the pad, and percentage of the width of the pad to create a partial triangle where the points face toward the center of the component body. The resulting shape resembles a baseball "Home base" which is where its name is derived. The most commonly utilized percentage for length and width is 50%.

Trapezoidal Apertures are created by distorting the beam on the laser, creating a draft in the aperture wall. Trapezoidal Apertures are effective if you plan on a long dwell time between printing of solder paste and placement of components. The taper in the aperture wall causes the paste to sit on top of itself, rather than sliding out the sides. The shape of the trapezoid can be seen in cross section of the stencil opening. 

Fiducials are alignment marks consisting of a 1mm circle surrounded by a 2mm clearance. If your screen printer is equipped with a vision system, fiducials half cut (into the thickness) of the stencil will allow for the printer to automatically align the board with the stencil. If you are manually aligning the stencil with the board, you could either fully cut the fiducials through the stencil or just use any surface mount pad to align the stencil.

Yes, the coating will treat both the surface of the stencil, as well as the aperture walls.

No, the nano particles bond with the metal resulting in a thickness of only 2-4 nanometers. Trace elements of the coating would not be detectable in the flux with even the most sophisticated test instruments.

The coating can be tested by marking the surface of the stencil with a marker. If the ink beads up, the coating is present.

Introduction

SMT STENCIL

A PCB stencil is a thin metal sheet used to apply solder paste onto a printed circuit board during surface mount assembly. The stencil contains cutouts at the precise locations where solder paste is required to mount SMT components onto the board.

This article provides a comprehensive overview of PCB stencils covering their design, manufacturing process, materials, critical parameters, usage in SMT assembly, and key considerations for procurement.

What is a PCB Stencil?

A stencil is a thin sheet containing apertures or cutouts that allow solder paste to be deposited onto mating pads on a PCB in a controlled pattern. The key functions of a stencil include:

  • Transferring solder paste accurately onto select locations on the board.
  • Controlling the amount of solder paste deposited based on aperture size/shape.
  • Acting as a mask to prevent solder application on unwanted areas.
  • Ensuring consistent volume and thickness of paste across boards during high volume production.

Stencils enable high speed accurate printing of tiny solder paste deposits to mount SMT components like resistors, capacitors, transistors, LEDs, and integrated circuits onto printed circuit boards using surface mount technology (SMT).

laser stencil pcb
laser cut stencils

Benefits of Using a PCB Stencil

The use of a stencil in solder paste application provides the following advantages:

  • Precision – Cutouts match component footprint locations accurately.
  • Speed – Simultaneous paste printing for multiple components.
  • Consistency – Deposit repeatability across boards and batches.
  • Quality – Optimized aperture design prevents defects.
  • Efficiency – Automated alignment and print processes.
  • Reliability – Stencils are durable for long production runs.
  • Adaptability – Stencil designs can be modified based on process feedback

Typical Stencil Materials

smd stencil
framed stencils

Various materials are used to manufacture stencils. Common options include:

Stainless Steel

Most commonly used material due to durability and ease of cleaning. Typical thickness between 0.001″ to 0.012″. Laser cut and electroformed nickel plated. Good for fine feature printing.

Pros: Durable, moderate cost, high accuracy Cons: Limited fine feature capability, nickel adhesion issues

Nickel Plated Brass

Brass stencils allow very fine features down to 0.5 mil wide. Electroless nickel plating improves durability. Thickness between 0.005″ to 0.012″.

Pros: Finer features, flatness, economical for prototyping Cons: Less durable than steel, warp over time

Aluminum

Lightweight stencils etched or laser cut from aluminum alloy sheets. Used for larger low-mix assemblies. Typical thickness between 0.005″ to 0.060″.

Pros: Low mass, fast cut times, low cost Cons: Lower accuracy, limited fine features, short lifespan

Plastic

Made from chemically etched polymer materials like polyimide. As thin as 0.001″. Used for very high mix, short run SMT production.

Pros: Very low cost for prototyping Cons: One-time use, limited fine features, low durability

Nickel

Nickel stencils produced through electroforming over an aluminum or copper mandrel. Then the mandrel is etched away leaving just the nickel. Typical thickness between 0.002″ to 0.005″. Used for the finest feature paste printing.

Pros: Excellent fine feature capability Cons: Expensive, slower lead time, fragile, limited thickness

Key Stencil Design Parameters

Several stencil characteristics need careful optimization based on the assembly design and process requirements:

Thickness

Typical thickness ranges from 0.100 mm to 0.150 mm (4 to 6 mil). Thicker stencils give larger deposits but prevent fine features. Thinner allows smaller pads but risks smearing.

Strand Width

Strands connect islands together providing mechanical stability. Typical width is 0.20 to 0.25 mm.

Aperture Design

Aperture size, shape and position customized for each component pad. Allows controlling paste deposit volume.

Wall Angle

Laser cutting gives an angle between 5° to 20° for easy paste release. Electroforming allows vertical walls for small components.

Bridging Distance

Minimum distance between apertures to avoid bridging. Depends on material, thickness, and strand width.

Registration Marks

Fiducials and tooling holes to align the stencil to the PCB locate points. 4 to 5 fidicuals with 1 mm clearance typically used.

Frame Design

Stencil frame design based on support needs. Common options: framer, glue frame, and tension frame.

Careful optimization of these parameters prevents solder paste printing issues during assembly.

Stencil foil stretched and held to a frame by polyester mesh
Stencil foil stretched and held to a frame by polyester mesh.

PCB Stencil Manufacturing Process

Fabricating stencils involves specialized micro-machining technologies and precision processes. The sequence is outlined below:

1. Design

The stencil layout is designed based on the PCB assembly data. Apertures are added matching component pad geometries with optimized dimensions and positioning.

2. Data Output

Gerber data containing the stencil pattern is output to guide the micro-machining process (laser/photo etching).

3. Raw Material

The base metal material is prepared by cutting sheets into required stencil sizes and cleaning.

4. Micro-machining

Apertures are created through laser/photo ablation. Laser cutting gives better edge quality while photo etching offers finer features.

5. Surface Treatment

Post-machining processes like micro peening or electropolishing are done to improve surface finish, reduce drag, and ease cleaning.

6. Framing

The stencil foil is mounted to a frame which provides structural support. Common framing options are discussed later.

7. Cleaning

Stencils are cleaned to remove debris, oxides, laser slag, and contaminants from fabrication.

8. Packaging

After final inspection, stencils are carefully packaged to avoid damage prior to shipping to customer.

Working with an expert stencil manufacturer ensures high quality stencil patterning optimized for the SMT assembly process.

Usage of Stencils in PCB Assembly

In a typical SMT assembly line, stencils are used as follows:

Solder Paste Printing

The stencil is aligned over the PCB and solder paste is applied on top of the stencil. A rubber squeegee blade then traverses and presses the paste into the stencil apertures transferring deposits onto the PCB pads.

Optical Inspection

After printing, automated optical inspection validates paste application accuracy and detects any defects. Common defects include insufficient print transfer, clogging, bridging etc.

Component Mounting

The PCB then proceeds to the surface mount assembly machines. Components are precisely placed over the printed solder paste deposits.

Reflow Soldering

The solder paste is melted in the reflow oven to create permanent solder joints holding the components. The volatile flux residues evaporate away.

Cleaning

After production runs, stencils are cleaned thoroughly to remove all solder paste residues and debris using dedicated cleaners.

This sequence highlights the stencil’s vital role in high speed accurate SMT production.

 

Stencil Frame Designs

circuit board stencil
Circuit Board Stencil

Stencil foils require proper framing for mechanical stability and to prevent damage during handling:

Fixed Framer

Consists of a rigid metallic frame with the stencil tightly glued into it. Provides good stability for foils down to 3 mils thickness. Limited support for ultra-thin stencils.

Glue Frame

Involves gluing the stencil onto a plastic backing frame using adhesive strips. Allows easy removal and replacement of stencils. Recommended for fragile thin foils.

Stretch Frame

Uses four corner pins to place the stencil in tension within the frame opening. Best solution for ultra-thin foils below 2 mil thickness. Foils can be easily swapped out when worn.

Hybrid Frames

Some frames utilize a combination of fixed and movable segments. The central active stencil area is tension mounted while the external region is fixed for stability during handling.

The right framing technique must be used based on parameters like material, thickness, size, shape, and expected production volumes.

Key Considerations for Stencil Specification

stencil solder paste
Stencil Solder Paste

Below are some guidelines when engineering custom stencils matched to the assembly:

  • For fine pitch components below 0.4 mm pitch, use laser cut steel or nickel plated brass stencils around 4 to 5 mil thickness.
  • Match the stencil thickness to the print gap. A 4 mil foil typically gives best print performance at around 4 mil snap-off distance.
  • A general rule of aperture size is 1.5 times pad width for BGAs, 0.66 times pad width for QFPs, and 1.25 times pad width for other component types.
  • For apertures below 10 mils, use electroformed nickel stencils. For larger features, laser cut or chemical etch techniques can be used.
  • Stencil strand width can be 20% less than design rule minimum spacing. Typical strand width is around 5 to 6 mils.
  • Place 2 to 3 mil clearance between apertures for high density designs to prevent bridging.
  • For unstable small components, use “anchor prints” – oversized pads connected to main pads to anchor the part.
  • Add anti-collapse rings around apertures prone to sidewall caving due to excess paste volumes.

Early engagement with stencil experts aids optimization and prevents SMT defects during assembly.

Stencil Cleaning and Maintenance

Like PCBs, stencils accumulate solder, fluxes and pastes during printing. Regular cleaning after production runs is vital:

  • Use cleaners specifically formulated for stencil cleaning that quickly remove both organic and inorganic residues.
  • Clean the underside of stencils thoroughly to prevent micro-cracks degrading print performance.
  • Capillary flow undercut cleaning systems effectively remove residues hidden under components.
  • Monitor stencil condition and discard when wear, dents, stretching or chemical attack is visible.
  • Replace stencils after around 500 print cycles for optimal performance.

Proper stencil maintenance improves paste transfer efficiency, avoids print defects, and increases stencil longevity over production cycles.

Stencil Procurement Considerations

Here are some best practices when ordering custom stencils:

  • Engage early with design files to get expert DFM analysis on stencil design.
  • For high mix products, use stencils with removable windows to enable quick aperture changes.
  • Order foam lined shipping cases to avoid stencil damage during transit.
  • For offsite production, procure multiple stencils for frequent rotation to maximize life.
  • Insist on laser cut steel stencils for optimal quality rather than lower cost chemical etch options.
  • Require edge coating such as ProTek on laser cut stencils to prevent nickel corrosion/peeling.
  • Validate manufacturer qualifications – customer list, certifications like ISO 9001, IATF 16949, etc.

Careful procurement and engagement smoothens stencil fabrication and long-term usage in production.

Conclusion

The PCB stencil is a vital consumable component enabling accurate, high-speed solder paste printing during surface mount assembly. Investing in optimized stencil designs closely matched to products provides significant quality benefits over the production lifetime. However, expertise is needed to design and manufacture stencils tailored to the product characteristics. Working closely with specialized stencil fabrication partners allows OEMs to establish robust processes ensuring consistent, high-yield SMT assembly.

FAQ

What are the typical materials used for manufacturing stencils?

Common stencil materials include stainless steel, nickel plated brass, aluminum, plastics like polyimide, and nickel. Steel and nickel plated brass offer the best balance of durability, cost and process capability.

What are some key parameters to be optimized in stencil design?

Critical stencil design parameters include thickness, aperture dimensions, strand width, wall angle, spacing between apertures, registration marks, and frame type. These have to be matched to the PCB assembly design and process.

What defects can occur due to poorly designed stencils?

Common defects from sub-optimal stencil designs include insufficient paste deposits, bridging between pads, clogged apertures, smearing, poor release of paste, poor print definition, and positional offsets of prints relative to PCB pads.

How many prints can be typically done with one stencil before replacement?

Around 500 print cycles is a good rule of thumb for stencil replacement frequency. However, factors like material, aperture sizes, cleaning process, and operator care impact stencil lifetime.

How is stencil performance validated after fabrication?

Print tests are performed to validate paste deposit volumes match design needs. Automated optical inspection of paste printing detects any defects. Cross-sectioning can also be done to ensure good paste transfer into apertures. These ensure the stencil design and fabrication meet requirements prior to SMT production.