[Official] PCBONLINE: PCB Stencil Manufacturing for SMT Assembly of Highest Accuracy

Overview of PCB Stencils

PCB stencils, also known as SMT stencils or solder paste stencils, are laser-cut stainless stencils used for PCB SMT assembly. This is how it works: a PCB stencil is placed in an SMT machine, and PCBs go past under it one by one. A scraper pushes the solder paste to pass SMT stencil openings to paste on PCB pads.
PCBONLINE manufactures SMT stencils while manufacturing PCBs. Creating PCB stencil openings isn't as easy as creating holes in the same size as PCB pads, especially for the pads of BGA, QFP, 0402/0201 components, USB, etc. With over 22 years of experience, PCBONLINE grasps all techniques and tips for PCB stencil manufacturing. Our PCB stencils ensure enough solder paste on all PCB pads.

Advantages of PCB Stencils

Why Choose PCB Stencils from PCBONLINE

• PCBONLINE adopts the laser cutting method characterized by high precision and easy to demodulate by trapezoidal opening.
• Our SMT stencil production is of little influence of objective factors, and accurate cutting is ensured
• Stencil holes are conducive to the release of solder paste because of the naturally trapezoidal aperture design (the upper hole is 1mil-5mil larger than the lower).
• Accurate data: PCB stencil hole size error is about 0.3, and the positioning accuracy is less than 0.12mil.
• Provide durable SMT stencils of thicknesses of 0.1mm, 0.12mm, 0.15mm, and 0.2mm.
• In SMT stencil design, we fully consider the mold release of solder paste, width/thickness, area ratio, tin connection, tin, etc.
• Solve stress concentration issues in PCB stencil design, which avoids a series of SMT soldering defects.

SMT Stencil - Manufacturing and Tech Specs

Process of SMT

SMT (surface mounted technology) is a series of processes to assemble components onto the bare circuit boards. The multiple phases are: stencil design according to the board > solder paste printing > component placement > reflow soldering > AOI optical inspection > maintenance (if needs) > sub-board.
An SMT stencil enables you to print the solder paste onto the board precisely and quickly by machine, and while the solder paste is still in liquid state, place desirable parts onto the solder joints also by machine. Then you get the PCBA and reflow to coagulate the solder paste so that the components are soldered tightly. Then is the AOI optical inspection, an automated visual inspection of printed circuit board to test for catastrophic failure and quality defects. If anything wrong is detected, you fix it. Finally, you cut or separate the boards ready for the final product assembly.
PCBONLINE has rich experience in the whole SMT process including but not limited to SMT stencil design and manufacturing. If you order PCB from us but want to assemble the boards by your own, it is suggested that you apply SMT assembly and buy SMT stencils from us. SMT enables fast, precise, and cost-effective assembling, and PCBONLINE, the PCB manufacturer, knows how to design and manufacture your stencils to be best, and we also provide suggestion in PCB assembly for free.

SMT Stencil Types

There are four types of SMT stencils. The most widely used types are the framed and framless SMT stencils, which are the main stencils produced by PCBONLINE. But still, you can get other types of SMT stencils from us.

1.Framed SMT Stencils

Framed PCB stencil is a laser cutting stencil process mounted permanently in the stencil frame with the help of mesh border to stretch the stencil foil tightly in the frame. Framed stencils come into design consideration for high volume screen printing.

Smooth aperture walls of framed SMT stencil are usable for less and equal to 16 Mil fine pitch as well as Micro BGS's. The permanent circuit board mounting offers maximum integrity levels and gives non-fading fiducial results.
2.Frameless SMT Stencils

Frameless PCB stencil, on the other hand, works with the stencil tensioning systems called reusable stencil frames. It also comes in a laser cutting stencil process category. This SMT stencil design is not glued permanently in the frame. They cost very less as compare to framed stencil and saves money by well maintain superior performance and quality.

The storage space is saved due to compact size. High engineering quality promotes maximum performance throughout the frameless PCB stencil life.
3.Prototype SMT Stencil

These are customized stencils designed in the CAD or Gerber to match the prototype PCB. They are solder paste frameless stencils explicitly created for printing manually.

Prototype SMT stencils remove the tiresome error-prone process of soldering the prototype circuit boards with hands.

The maximum efficiency and quick alignment reduce the assembly time of the prototype. It is cost-effective, requires no machine use, and is an easy-to-understandable circuit board printing process.
4.Electroformed SMT Stencils

This PCB stencil is nickel-based, made of electroforming foil mounted permanently in the stencil frame by using the mesh border to stretch the foil taut tightly. They have the best paste releasing characteristics. They are used commonly for excellent pitch SMT applications, Wafer Bumping (12-6 mil pitch), Flip Chip, and µBGAs.

About Solder Paste

The suspension of smooth solid particles in a flux vehicle makes a solder paste. In the electronic industry, it is commonly used in SMT stencil to SMD onto the printed circuits boards. The particle composition can be customized to produce a stainless steel paste of desirable melting consistency. Adding other metals changes the composition of paste depending upon application requirements. Shape, size, flux type, and metal content of particles vary to produce varying viscous paste.
There are three types of solder paste applications: 1. chemical etching, 2. laser cutting, 3. electroformed. The oldest, less expensive, and most widely practiced solder paste stencil method is chemical etching. Laser cutting and especially electroformed are used when precision is crucial.