Article Outline

1. What Is an SMT Stencil?
   • Definition and basic function
   • SMT stencil applications
   • SMT stencil classification
2. Terminology Related to SMT Stencils
   • Apertures, aspect ratio, and area ratio
   • Mesh, frame, foil, and squeegee
   • Fiducials and stencil printing terms
   • SMT, THT, BGA, CSP, and fine-pitch technology
3. Materials Used in SMT Stencil Manufacturing
   • Stencil frames
   • Mesh
   • Stencil foil
   • Adhesives
4. SMT Stencil Manufacturing Specifications
   • Aperture profile and dimensional tolerances
   • Stencil thickness
   • Aperture wall quality
   • Recommended applications
5. SMT Stencil Aperture Design Requirements
   • General design principles
   • Aperture design tips
   • Required design files and manufacturing data
   • Factors affecting solder paste release
   • Aperture designs for special SMT components
   • Adhesive stencil aperture requirements
   • Stencil thickness selection and aperture design
6. SMT Stencil Manufacturing Methods
   • Chemical etching
   • Laser cutting
   • Electroforming
   • Hybrid processing and step stencils
   • Comparison of manufacturing methods
7. How to Inspect the Quality of an SMT Stencil
   • Frame dimensions and mesh tension
   • Aperture appearance and defects
   • Aperture sidewalls and surface finish
   • Stencil-to-PCB alignment and aperture completeness

Introduction：

1. An SMT stencil, also known as an SMT template, is most commonly made of stainless steel and is therefore commonly referred to as a steel stencil. It is used in the first step of the SMT surface-mount process to print solder paste onto a PCB.

2. Before SMT component placement, solder paste printing must be completed. The perforated sheet used to print solder paste, which is a semi-liquid, semi-solid solder material, or red glue onto a bare PCB is called an SMT stencil.

3. A PCB stencil is a thin steel sheet with many apertures. These apertures correspond precisely to the positions of the solder pads on the PCB. The stencil is used with an automatic or semi-automatic component placement system. It is placed over the PCB, and solder paste, a viscous solder material, is applied with a squeegee. The solder paste passes through the stencil apertures and is deposited onto the PCB pads, while no solder paste is applied to other areas because the stencil has no openings there. The electronic components are then placed on the PCB, which is subsequently heated in a reflow oven to complete the soldering process.

4. When a PCB contains a large number of surface-mount ICs, resistors, and capacitors, a reflow soldering machine is generally used for automated assembly. Before soldering, solder paste must be printed onto the pads of the surface-mount components. This requires an SMT stencil with one aperture at each corresponding component-pad position. During solder paste printing, the paste passes through all of the apertures and is deposited onto the PCB pads. The components are then placed on the PCB, followed by reflow soldering. Any PCB containing surface-mount components generally requires an SMT stencil.

5. SMT stencil fabrication, commonly referred to as stencil opening or stencil making, is the process of manufacturing a stencil based on the Top Paste and Bottom Paste layers in a Gerber file, which is generally generated from the PCB design files.

6. SMT stencils are generally made from 0.12 mm-thick stainless steel sheet and may undergo laser polishing. The typical price is approximately RMB 500 per sheet.

Classification of SMT Stencils

By application: solder paste stencil, adhesive stencil, BGA rework stencil, and BGA ball-planting stencil

By manufacturing process: chemically etched stencil, laser-cut stencil, electroformed stencil, and hybrid-technology stencil

By material: stainless steel stencil, brass stencil, hard nickel stencil, and polymer stencil

II. Terminology Related to SMT Stencils

All terms and definitions used in this document comply with IPC-T-50. Definitions marked with an asterisk (*) are derived from IPC-T-50. Other specific terms and definitions that are important to the discussion of this subject are provided below.

2.1 Aperture

An opening or passage formed in the stencil foil.

2.2 Aspect Ratio and Area Ratio

Aspect ratio = aperture width / stencil thickness.

Area ratio = aperture area / aperture wall area.

2.3 Mesh

A polymer or stainless-steel mesh stretched around the perimeter of the foil. Its function is to maintain the foil in a flat and adequately tensioned condition. The mesh is positioned between the foil and the frame and connects the two components.

2.4 Solder Paste Sealed-Head Printing

A stencil printer head that holds, in a single replaceable component, the squeegee blades and a pressurized chamber filled with solder paste.

2.5 Etch Factor

Etch factor = etch depth / lateral etch length during the etching process.

2.6 Fiducials

Reference marks on the stencil or PCB that are recognized by the printing machine’s vision system for alignment and calibration of the PCB and stencil.

2.7 Fine-Pitch BGA / Chip-Scale Package (CSP)

A BGA, or ball grid array, with a solder-ball pitch of less than 1 mm [39 mil]. When the ratio of the BGA package area to the bare-die area is no greater than 1.2, it is also referred to as a CSP, or chip-scale package.

2.8 Fine-Pitch Technology (FPT)

A surface-mount technology in which the center-to-center distance between adjacent component terminations is no greater than 0.625 mm [24.61 mil].

2.9 Foil

A thin metal sheet used to manufacture a stencil.

2.10 Frame

A device used to secure the stencil. The frame may be hollow or made of cast aluminum. In one common configuration, the mesh is permanently bonded to the frame with adhesive to secure the stencil.

Some stencils can be directly mounted in tensioning frames that provide stencil tension without the use of mesh or a permanent fixture to connect the stencil and frame.

2.11 Intrusive Soldering

A reflow soldering process also known as the through-hole paste-in-hole process, pin-in-hole process, or pin-in-paste process.

2.12 Aperture Modification

The process of changing the size or shape of an aperture.

2.13 Overprinting

A stencil configuration in which the apertures are larger than the corresponding pads or annular rings on the PCB.

2.14 Pad

A metallized surface on a PCB used to provide the electrical and physical connection for a surface-mount component.

2.15 Squeegee

A rubber or metal blade used to roll solder paste across the stencil surface and fill the apertures. The squeegee is typically mounted in the printer head at an angle. During printing, the printing edge of the squeegee trails behind the printer head and the direction of squeegee travel.

2.16 Standard BGA Device

A ball grid array with a solder-ball pitch of 1 mm [39 mil] or greater.

2.17 Stencil

A tool consisting of a frame, mesh, and foil containing multiple apertures. The stencil is used to transfer solder paste, adhesive, or other media onto a PCB.

2.18 Step Stencil

A stencil whose foil has more than one thickness level.

2.19 Surface-Mount Technology (SMT)

A circuit assembly technology in which the electrical connections of components are made through conductive pads located on the surface of the circuit board.

2.20 Through-Hole Technology (THT)

A circuit assembly technology in which the electrical connections of components are made through conductive holes in the circuit board.

2.21 Ultra-Fine-Pitch Technology

A surface-mount technology in which the center-to-center distance between adjacent component terminations is no greater than 0.40 mm [15.7 mil].

III. Materials Used in SMT Stencil Manufacturing

1. Stencil Frame

Stencil frames are divided into reusable frames and fixed frames. With a reusable frame, the stencil foil is mounted directly onto the frame, allowing the same frame to be used repeatedly. A fixed frame uses adhesive to bond the mesh to the frame, while the stencil foil is secured to the mesh. Fixed frames make it easier to achieve uniform foil tension, generally ranging from 35 to 48 N/cm². The allowable tension for a standard fixed frame is typically 35–42 N.

Frame dimensions depend on the requirements of the solder paste printer. For example, the DEK 265 and MPM UP3000 solder paste printers use 29 × 29-inch (735 × 735 mm) aluminum-alloy frames, typically made from 1.5 × 1.5-inch frame profiles. Some semi-automatic solder paste printers use frames measuring approximately 22 × 26 inches (560 × 650 mm).

Common stencil frame sizes include:

• 20 × 30 cm
• 30 × 40 cm
• 37 × 47 cm
• 42 × 52 cm
• 50 × 60 cm
• 55 × 65 cm
• 23 × 23 inches
• 29 × 29 inches

Common stencil thicknesses include 0.05 mm, 0.08 mm, 0.10 mm, 0.12 mm, 0.13 mm, 0.15 mm, 0.18 mm, and 0.20 mm. Thicknesses of 0.05 mm and 0.08 mm are used less frequently.

2. Mesh

The mesh is used to connect and secure the stencil foil to the frame. It can be made from stainless steel wire mesh or polymer polyester mesh.

Stainless steel wire mesh with a mesh count of approximately 100 is commonly used because it provides stable and sufficient tension. However, after extended use, the stainless steel mesh may deform and gradually lose tension.

Polyester mesh, also commonly available at approximately 100 mesh, is less prone to deformation and generally offers a longer service life.

3. Stencil Foil

When selecting an SMT stencil foil material, factors such as rigidity, corrosion resistance, ductility, and coefficient of thermal expansion must be considered. These properties directly affect the stencil’s service life, including its resistance to corrosion, distortion, and aperture deformation.

Common stencil foil materials include phosphor bronze, stainless steel, and nickel-chromium alloys, with stainless steel being the most widely used. Copper foil, stainless steel foil, nickel alloy, and polyester materials may all be used to produce stencil apertures, depending on the application.

High-quality SUS301 or SUS304 stainless steel foil is commonly selected for stencil manufacturing. Its excellent mechanical properties help improve stencil durability and extend service life.

4. Adhesive

The adhesive used to bond the frame, mesh, and stencil foil plays an important role in stencil construction. Different adhesives may be selected according to the customer’s operating conditions and application requirements.

A suitable stencil adhesive should maintain strong bonding performance and withstand repeated exposure to various stencil-cleaning agents during complex cleaning processes.

IV. SMT Stencil Manufacturing Specifications

1. The apertures naturally form a tapered profile, with the top opening typically 1-5 mil larger than the bottom opening to facilitate solder paste release.

2. Aperture dimensional tolerance is approximately 0.3-0.5 mil, while positional accuracy is less than 0.12 mil.

3. The manufacturing cost is generally higher than that of chemical etching but lower than that of electroformed stencils.

4. The aperture walls are not as smooth as those of electroformed stencils.

5. The typical stencil thickness ranges from 0.12 mm to 0.30 mm.

6. This process is generally recommended for printing components with a pitch of 20 mil or less.

V. SMT Stencil Aperture Design Requirements

1. General Principle

According to the requirements of the IPC-7525 Stencil Design Guidelines, stencil apertures should be designed to ensure that solder paste can be released smoothly from the stencil apertures onto the PCB pads.

SMT stencil design factors:

Data format
Manufacturing process requirements
Material requirements
Material thickness requirements
Frame requirements
Printing format requirements
Aperture requirements
Other process requirements

2. Tips for SMT Stencil Aperture Design

1. For fine-pitch ICs and QFPs, rounded corners are recommended at both ends of the apertures to prevent stress concentration. The same principle applies to BGAs with square apertures and 0402/0201 components.

2. For chip components, inwardly concave apertures are recommended to prevent solder beading. This design can also effectively reduce the occurrence of component tombstoning.

3. When designing an SMT stencil, the aperture width should be sufficient to allow at least four of the largest solder particles to pass through smoothly.

3. Information Required Before SMT Stencil Design

The following information must be prepared before designing an SMT stencil:

• If a PCB layout is available, the following layers and information must be provided according to the component placement plan:

(1) The pad layer (PADS) containing the pads and fiducial marks for surface-mount devices (SMDs);

(2) The silkscreen layer (SILK) corresponding to the pads of the surface-mount components;

(3) The top layer (TOP) containing the PCB outline;

(4) For a panelized PCB, the panelization drawing must also be provided.

• If no PCB layout is available, a physical PCB sample, a 1:1 film of the PCB sample, or a scanned image must be provided. The information should include:

(1) Fiducial settings, PCB outline data, and the pad locations of the surface-mount components. For a panelized PCB, the panelization layout must also be provided;

(2) The printing side must be clearly specified.

SMT stencil manufacturers generally accept the following three types of data formats for stencil fabrication:

1. Design files generated by PCB design software, usually with the *.PCB file extension;

2. GERBER or CAM files exported from PCB design files;

3. CAD files with the *.DWG or *.DXF file extension.

The stencil fabrication data requested by most SMT stencil manufacturers generally includes the following layers:

1. PCB circuit layer, containing the complete data required for stencil fabrication;

2. PCB silkscreen layer, used to confirm component types and the printing side;

3. PCB paste layer, used to define the stencil apertures;

4. PCB solder mask layer, used to confirm the locations of exposed pads on the PCB;

5. PCB drill layer, used to identify through-hole components and the plated or non-plated holes that must be avoided.

4. Factors Affecting Solder Paste Release from Stencil Apertures

The aperture design should take solder paste release performance into consideration. Release performance is determined by three factors:

1. Aperture aspect ratio and area ratio: The aspect ratio is the ratio of aperture width to stencil thickness. The area ratio is the ratio of the aperture opening area to the aperture wall area. To achieve good solder paste release, the aspect ratio should be greater than 1.5 and the area ratio should be greater than 0.66.

When designing stencil apertures, other process-related issues, such as solder bridging and excessive solder deposition, should not be overlooked solely in pursuit of a suitable aspect ratio or area ratio. For chip components of 0603 (1608 metric) or larger, greater consideration should be given to solder bead prevention.

2. Aperture sidewall geometry: The aperture on the PCB side should be 0.01 mm or 0.02 mm wider than the aperture on the squeegee side, forming an inverted tapered opening. This geometry facilitates effective solder paste release and reduces the required frequency of stencil cleaning.

Under normal circumstances, the stencil aperture size and shape for an SMT component should match its corresponding PCB pad at a 1:1 ratio. For certain special SMT components, specific requirements apply to the size and shape of the stencil apertures.

3. Aperture wall finish and smoothness: Electropolishing should be performed by the stencil manufacturer, particularly for QFP and CSP components with a pitch of less than 0.5 mm.

5. Stencil Apertures for Special SMT Components

2.1 Chip Components

For chip components of 0603 or larger, the apertures should be designed to effectively prevent solder bead formation.

2.2 SOT-89 Components

Because the spacing between the smaller pads and the large component pad is narrow, solder beads and other soldering defects may occur easily.

2.3 SOT-252 Components

Because an SOT-252 package has one particularly large pad, it is prone to solder bead formation. The high surface tension generated during reflow soldering may also cause component displacement.

2.4 IC Components

A. For ICs with a standard pad design and a pitch of ≥ 0.65 mm, the aperture width should be 90% of the pad width, while the aperture length should remain unchanged.

B. For ICs with a standard pad design and a pitch of ≥ 0.05 mm, the narrow pitch can easily cause solder bridging. The aperture length should remain unchanged, while the aperture width should be 50% of the pitch, with a specified aperture width of 0.25 mm.

2.5 Other Conditions

When a pad is excessively large, typically with one side longer than 4 mm and the other side no shorter than 2.5 mm, grid-divided stencil apertures are recommended to prevent solder bead formation and displacement caused by surface tension.

The recommended grid-line width is 0.5 mm, and the grid size is 2 mm. The aperture may be divided evenly according to the pad dimensions.

6. Aperture Shape and Size Requirements for Adhesive Stencils

For simple PCB assemblies that use an adhesive process, dispensing is preferred. Adhesive may be stencil-printed for chip, MELF, and SOT components. For ICs, dispensing should be used whenever possible to prevent adhesive from being spread across the stencil by the squeegee.

Only the recommended aperture sizes and shapes for chip, MELF, and SOT adhesive-printing stencils are provided here.

1. Two diagonally opposite positioning holes must be created at the diagonal corners of the stencil. The fiducial marks should be selected as the aperture locations.

2. All apertures should be elongated slots.

Inspection methods:

(1) Visually inspect whether the apertures are properly centered and whether the mesh is flat and evenly tensioned.

(2) Compare the stencil with the physical PCB to verify that the stencil apertures are correct.

(3) Use a calibrated high-magnification video microscope to inspect the aperture length and width, as well as the smoothness of the aperture walls and steel foil surface.

(4) Verify the steel foil thickness by measuring the solder paste deposit thickness after printing. In other words, stencil thickness is confirmed through the printing results.

7. SMT Stencil Thickness Selection and Aperture Design

Controlling the volume of solder paste deposited during SMT printing is one of the key factors in SMT process quality control. The amount of deposited solder paste is directly related to stencil thickness and aperture shape and size. Squeegee speed and applied pressure also have some influence.

The stencil thickness determines the thickness of the printed solder paste deposit, and the two values are generally similar. Once the stencil thickness has been selected, the different solder paste volume requirements of various components can be accommodated by appropriately modifying the aperture dimensions.

Stencil thickness should be determined according to the PCB assembly density, component size, and spacing between component leads or solder balls. Generally, components with larger pads and wider spacing require a greater volume of solder paste and therefore a thicker stencil. Conversely, components with smaller pads and narrower spacing, such as fine-pitch QFPs and CSPs, require less solder paste and therefore a thinner stencil.

Based on practical experience, the amount of solder paste deposited on pads for standard SMT components should generally be approximately 0.8 mg/mm². For fine-pitch components, it should be approximately 0.5 mg/mm².

Excessive solder paste can result in excessive solder accumulation, solder bridging, and other defects. Insufficient solder paste can lead to inadequate solder joints and reduced joint strength.

The following table provides recommended aperture and stencil design solutions for different component types and may be used as a design reference:

Common aperture shapes include squares, rectangles, ovals, and circles, as illustrated below. The aperture shape should be designed according to the pad shape in the PCB layout and adjusted appropriately based on pad pitch.

VI. SMT Stencil Manufacturing Methods

SMT stencils are essential tooling in the SMT process. As electronic assembly technology continues to develop toward high-density interconnection, increasingly stringent requirements are being placed on SMT stencil manufacturing processes. Laser cutting is currently the most widely used method for manufacturing SMT stencils.

There are four main SMT stencil manufacturing methods:

1. Chemical etching, used to produce chemically etched stencils

2. Laser cutting, used to produce laser-cut stencils

3. Electroforming, used to produce electroformed stencils

4. Hybrid processing, used to produce step stencils

Electroforming is an additive manufacturing process, while laser cutting and chemical etching are subtractive manufacturing processes.

Comparison of SMT Stencil Manufacturing Methods

1. Chemical Etching Method

Chemical etching uses a corrosive chemical solution to remove the metal from the required aperture locations in a stainless-steel sheet. This produces apertures corresponding to the PCB pads and creates a stencil suitable for SMT assembly production.

Process Flow

Cut the stainless-steel sheet to the required size → clean the sheet → apply photoresist → UV exposure → develop and bake → chemically etch → strip the photoresist → clean and dry → inspect → mount the stencil on the frame → package

Characteristics

The process forms the apertures in a single operation and has a relatively short production time. It is also inexpensive.

Disadvantages

Chemical etching may produce hourglass-shaped apertures when the etching is insufficient, or oversized apertures when over-etching occurs. The results are significantly affected by objective and process-related factors such as operator experience, chemical solution conditions, and phototool quality.

The process involves multiple manufacturing steps, which can result in considerable cumulative dimensional error. Therefore, it is not suitable for manufacturing fine-pitch stencils. In addition, the process generates chemical waste and is less environmentally friendly, so it has gradually been replaced by other manufacturing methods.

Because chemical etching removes metal simultaneously from both sides of the steel sheet, the aperture profile may be tapered. Although the aperture walls may appear relatively smooth and vertical in some areas, incomplete removal of metal near the center of the sheet thickness can produce a constricted, hourglass-shaped cross-section. This profile is unfavorable for solder paste release.

For this reason, chemically etched stencils are generally not recommended for precision component assembly. In general, etched stencils should not be used for components with a lead pitch below 0.5 mm or for components smaller than 0402.

For larger components or components with relatively large pitch values, however, chemically etched stencils offer significant cost advantages while still meeting the production-quality requirements of many customers and SMT assembly manufacturers.

2. Laser Cutting Method (Laser-Cut Stencil)

Laser cutting is currently the most widely used manufacturing process for SMT stencils. More than 95% of stencils used in the SMT assembly industry are manufactured using laser cutting.

In this process, a laser is used to cut apertures at the required locations. The aperture dimensions can be adjusted directly in the design data, while improved process control helps enhance aperture accuracy. The aperture walls of a laser-cut stencil are generally vertical.

Laser-Cut Stencil Manufacturing Process

Process flow: Film preparation → PCB coordinate extraction → data file generation → data processing → laser cutting and drilling → grinding and electropolishing → inspection → mesh mounting and tensioning → packaging

Advantages:

• High data-processing and fabrication accuracy, with minimal influence from external factors;
• Trapezoidal apertures facilitate solder paste release;
• Suitable for high-precision cutting;
• Moderate manufacturing cost.

Disadvantage:

• Because the apertures are cut individually, the manufacturing process is relatively slow.

The laser-cutting principle is illustrated in the figure on the left below. The cutting process is precisely controlled by the machine and is suitable for producing ultra-fine-pitch apertures.

Because the apertures are formed by direct laser ablation, their sidewalls are straighter than those produced by chemical etching and do not have an intermediate constriction. This facilitates the filling of stencil apertures with solder paste.

Furthermore, because the laser ablates the steel foil from one side to the other, the aperture walls naturally form a slight taper. As a result, the aperture cross-section has an inverted trapezoidal profile, as shown in the figure on the right below. The dimensional difference produced by this taper is approximately half the thickness of the steel foil.

A reverse-trapezoidal aperture profile facilitates solder paste release. For pads with small apertures, it produces well-defined brick-shaped or coin-shaped solder paste deposits. This characteristic makes laser-cut stencils suitable for fine-pitch and miniature component assembly. Therefore, laser-cut stencils are generally recommended for precision SMT component assembly.

3. Electroforming Method (Electroformed Stencil)

Electroforming is the most complex stencil manufacturing technique. It uses an additive electroplating process to deposit nickel around a preformed mandrel until the required foil thickness is achieved. This process provides high dimensional accuracy and does not require post-processing to compensate for aperture dimensions or sidewall surface quality.

Process flow: Apply photoresist to the substrate → form the mandrel → electroplate nickel around the mandrel to form the stencil foil → separate and clean the foil → inspect → mount and tension on the frame → package

Advantages:

• Smooth aperture walls;
• Particularly suitable for manufacturing ultra-fine-pitch stencils.

Disadvantages:

• Difficult process control;
• The manufacturing process generates pollution and is not environmentally friendly;
• Long production lead time;
• Very high cost.

Electroformed stencils feature smooth aperture walls and an inverted trapezoidal aperture profile, providing optimal solder paste release. They offer excellent printing performance for micro-BGAs, ultra-fine-pitch QFPs, and small chip components such as 0201 and 01005 packages.

Owing to the characteristics of the electroforming process, a slightly raised annular ridge forms around the edge of each aperture, extending just above the surface of the stencil foil. During solder paste printing, this ridge acts as a sealing ring. It helps the stencil fit tightly against the PCB pads or solder mask, preventing solder paste from bleeding beyond the pad boundaries. However, electroformed stencils are also the most expensive type.

4. Hybrid-Process Stencil (Step Stencil)

A hybrid-process stencil is generally known as a step stencil. Unlike a conventional stencil, which has a uniform thickness throughout, a step stencil incorporates two or more thickness levels within a single stencil. Its purpose is to meet the different solder paste volume requirements of various components on the same PCB.

A step stencil is manufactured using one or two of the three stencil-processing methods described above. In general, many SMT assembly manufacturers first use chemical etching to obtain the required local foil thickness and then use laser cutting to form the apertures.

Step stencils are available in two types: step-up and step-down. Their manufacturing processes are essentially the same. The appropriate type depends on whether the thickness of a specific area needs to be increased or reduced.

For example, on a large PCB containing local fine-pitch components such as CSPs, most components may require a relatively large volume of solder paste, while fine-pitch CSP or QFP components require less solder paste to prevent bridging and short circuits. Clearance may also be required in certain areas. In this case, a step-down stencil can be used. The stencil foil is locally thinned at the fine-pitch component locations so that these areas are thinner than the rest of the stencil.

Conversely, a precision PCB may contain a small number of components with large leads. Because the overall stencil foil is relatively thin, the amount of solder paste deposited on their pads may be insufficient. Similarly, pin-in-paste reflow processes may require a larger volume of solder paste in the through-holes to meet hole-fill requirements. In these cases, the foil thickness can be locally increased around large pads or through-holes to increase solder paste deposition, requiring the use of a step-up stencil.

In actual production, the appropriate stencil type should be selected according to the types and distribution of components on the PCB.

VII. How to Inspect the Quality of an SMT Stencil

1. Check the stencil frame and mesh tension
   Verify that the frame dimensions meet the specified requirements and inspect the quality of the tensioned mesh. In general, higher and more uniform mesh tension helps improve printing quality.

2. Inspect the appearance of the apertures
   Check the apertures for visible defects, including irregular aperture shapes and abnormal spacing between adjacent apertures in high-density or fine-pitch areas.

3. Examine aperture sidewalls and orientation
   Use a magnifying glass or microscope to verify that the flared side of each aperture faces downward. Check whether the aperture sidewalls are smooth and free of burrs. Pay particular attention to the aperture quality in fine-pitch IC lead areas.

4. Verify aperture alignment and completeness
   Place the corresponding PCB against the underside of the stencil and align the stencil apertures with the PCB pad pattern. Confirm that all apertures are correctly aligned and check for extra apertures that should not be present or missing apertures that should have been created.

About NKEYTO

NKEYTO is the international brand of Shenzhen Xintu Precision Hardware Co., Ltd., a precision metal manufacturing supplier based in Shenzhen, China.

We provide one-stop precision metal manufacturing services, including chemical etching, precision laser cutting, stamping, CNC machining, electroplating, and other customized surface treatments. Our capabilities support the development and production of precision metal components for industries such as semiconductors, electronics, optics, medical devices, and industrial applications.

With engineering support and flexible manufacturing capabilities, we help customers develop customized metal parts from prototypes to small and medium-volume production.

For technical evaluation or quotation, please feel free to contact:

Luna
Head of International Trade & Pre-Sales Technical Consultant
Email: luna@nkeyto.com
WhatsApp: +1 213 221 9094
Phone / WeChat: +86 135 5470 8126