An SMT stencil is an important tool that is used in the electronics industry and PCB since it helps to provide accurate and effective solder paste deposition. An SMT stencil is a thin sheet that has accurately sized holes or apertures created with the use of different materials, like stainless steel.
These holes are medium-sized for accurately depositing solder paste on the pads of the board. Holes are important for the assembly process by providing proper solder paste deposition. Here we will cover different types of SMT stencils and their practical applications.
What is an SMT stencil?
- The PCB SMT stencil is basically a thin, pliable sheet that is made with stainless steel or aluminum. The stencil comes with small apertures that make a layout for printing on the board. The
- • The stencil is configured on the frame on the upper part of the PCB board, then solder paste is applied on the stencil. Solder paste flows through apertures according to the design applied on the circuit board.
- Small holes exist that control solder paste quantity and help to provide an accurate soldering process for the board.
Types of SMT
There are different types of SMT stencils, and they are used for different applications.
frame design SMT stencil
- based on framed. There are different types of SMT stencils, and each has its own uses.
framed SMT stencil
- It is good to use for high-volume screen printing on board. that comes with foil connected in aluminum frames and provides accurate solder paste applications. frame control solder paste volume and provide smooth aperture walls.
frameless SMT stencil
- This type has a reusable stencil tensioning system and a flexible and low-cost SMT process. You can use a single main frame and replace different frameless stencils there. It works like a framed stencil for low-volume prints like prototyping, and the output product is of high quality and works with a lower cost than framed stencils.
Types according to manufacturing process
An SMT stencil is defined through a frame also used in the manufacturing process. Here are some types based on the manufacturing process.
laser stencil
- It is made with the use of laser cutting of stencil materials and provides high accuracy. The laser makes accurate apertures in the use of solder paste through accuracy. This stencil is made for connection with the tensioning system of the stencil, which is strongly held at the time of printing.
- It is good to use for reliable and highly accurate SMT assembly, needed
ladder stencil
- This stencil is made for handling connected components on a board that has different dimensions and heights from the board. It comes with a special type of mesh that provides different levels for applications of solder paste. This stencil also has partial step-up and step-down parts that are confined on a steel sheet. It provides a smooth printing process over the stencil.
nano stencil
- It comes with nano coatings to provide good working performance. These nano coatings come with oleophobic and hydrophobic features. The nano coatings have resistance to water and oil and also provide smooth solder paste fluxes.
electroformed stencil
- This type of stencil comes with a trapezoidal stencil that helps with the easy release of solder paste as compared to an etched stencil. This stencil has electrolysis for depositing metal on molds. The steel mesh with good mechanical features resulted. This stencil is strong and tough in nature. It has features to handle high pressure and occurs at the time of manufacturing.
electropolished stencil
- This process makes steel with a mirror-like shiny surface, and the stencil apertures wall is smooth. Solder paste is easy to flow on the steel mask in the board pads. As a result, make clean solder paste applications. Electropolishing does not make spaces for blockage; as a result, each print faces repeated distribution of solder paste.
type according to text on stencil
- SMT stencils come with text that helps to provide an accurate assembly process, and these texts are made through laser use. There are two types of stencils based on text.
half-lasered text
- It is used usedfor fiducials and texts in solder mask stencils. As compared to a fully etched mark, half-lasered text is partially cut on the stencil, so it is easy to see. As a result, it is a good method since it does not affect the paste application on the board. Fiducials are etched marks that provide accurate positions for the system in assembly.
lasered through text
- Here clear yet made through cutting stencil materials, it is good to use for finding components on the stencil at the time of board assembly. Through the last text, there is accurate marking, and it provides completeness for using shape and strength. This provides stencil opening and comprehensiveness.
One-Stop PCBA and PCB Stencil Manufacturer
If you are searching for PCB stencil services for your PCB assembly, you can find the best SMT services at the JLCPCB fabrication house. That helps you to provide quality manufacturing. They are one-stop PCB and PCBA manufacturers found in China.
JLCPCB comes with a high-quality PCB stencil with PCB assembly features like BGA, via-in-pad, and CSP. They also provide framed and frameless board stencils in different dimensions.
They also offer all-in-one services with PCB manufacturing, board assembly, component sourcing, functional testing, thermal aging, etc.
JLCPCB also provides one-stop PCB/PCBA manufacturing from prototypes to bulk production.
JLCPCB also offers NON-FRAMEWORK (or frameless) and FRAMEWORK stencils. Frameless stencils are low cost and have less weight, which reduces delivery charges. A stencil was also ordered with the board to minimize the shipping charge, and only stencil order services are also available.
Types of Stencils Based on Solder Paste
Prototype Stencils:
- This type of SMT stencil is made for performing the manual solder paste printing process. Prototype stencils provide reduction of printing errors. It is made with CAD files or Gerber files.
Framed Stencils:
- It is a fixed type of stencil on a frame. that get the required force from the border mesh. A framed stencil used for bulk production. The framed stencil comes with smooth aperture walls and has good printing features.
Frameless Stencils:
- Over to framed stencil. These stencils do not allow for fixed mounting on the frame. These stencils are lower cost than framed stencils and used for prototype runs.
Benefits of SMT Stencils
PCB stencils provide high accuracy for the manufacturing of boards. The main features and advantages of stencils are.
- • A stencil is a low-cost option and used for continuous repetition.
- After using it, it is clean and used with the same accuracy.
- The use of an accurate stencil category removes errors such as short circuits and distributed pad position voids at the time of soldering.
- The PCB stencil helps solder paste to flow in apertures and not affect part of the board.
- SMT stencils provide zero errors and are also for automated board assembly or manual processes.
- Stencils come in handy to make production of PCBs in larger numbers.
How to Use a PCB Stencil
- If you are working with a frameless board stencil for hand soldering, apply solder paste on the unused part of the stencil and configure it with the board, and use a blade for pressing paste on board pads.
For the SMT line in the PCB assembly process, machine features are configured through CAM engineers to PCBA manufacturers and come with the strength, speed, and angle of the blade of the solder paste printing machine.
The framed board stencil is put in the machine; for the PCB stencil, the board is sent through the conveyor belt automatically to be printed with solder paste in a series of panels.
When solder paste printing is performed, there is solder paste printing inspection is performed before the connection of components on the board to avoid any error.
Polishing Process for PCB Stencil
Different methods used for polishing board stencils, such as
Mechanical Polishing:
- • The mechanical polishing process uses mechanical tools, like polished pads, that remove burrs on stencil material. This process is low cost and easy to perform, but it takes some time and does not have as high accuracy as other processes have.
Chemical Polishing:
- Chemical polishing uses chemical solutions, like alkaline or acid, for dissolving errors on stencil materials. This technique is highly accurate and makes a smooth surface finish but is high cost since it needs proper techniques to apply.
Electropolishing:
- This process uses current to dissolve errors on stencil materials. It is accurate and makes a smooth and constant finish surface but needs certain tools that are costly.
Stencil material:
- This process needed to support the stencil material used.
Required precision:
- The method used has features to make required accuracy and consistency
