Introduction And Classification of Stencils

Introduction to Stencils:

Steel mesh are also SMT templates (SMT Stencil). It is a special SMT mold. Its main function is to help the deposition of solder paste. The purpose is to transfer an accurate amount of solder paste to an accurate position on the empty PCB.

The development of SMT process:

SMT steel mesh (SMT template) is also used in the glue process.Steel mesh evolution Steel mesh was originally made of wire mesh, so it was called a mask at that time. It started with nylon (polyester) mesh, later due to durability, there were wire meshes, copper meshes, and finally stainless steel meshes. However, no matter what kind of wire mesh is, it has the disadvantages of poor molding and low precision.

With the development of SMT, the requirements for stencils have increased, and stencils have been produced. Affected by the cost of materials and the difficulty and ease of production procedures, the original steel mesh was made of iron/copper plate, but because of its easy rust, stainless steel mesh replaced them, which is the current steel mesh (SMT Stencil).

Steel Mesh Classification:

According to the production process of SMT steel mesh, it can be divided into laser template, electropolishing template, electroforming template, step template, bonding template, nickel-plating template, and etching template. Laser template/Laser stencil template is currently the most commonly used template in the SMT steel mesh industry. Its characteristics are that direct use of data files for production, reducing production errors, SMT template opening position accuracy is extremely high, the overall error ≤ ± 4μm , the opening of the SMT template has a geometric pattern, which is conducive to the printing and forming of the solder paste.

The following materials are required to make laser steel mesh:

1. PCB

2. The data file must includes PCB: the correct version, no deformation, damage, or fracture; Data file: CAD data formats: GERBER, HPGL, *.JOB, * .PCB, *.GWK, *.CWK, *.PWK, *.DXF, *.PDF; and the following software design data: PAD2000, POWERPCB, GCCAM 4.14, PROTEL, AUTOCADR14(2000), CLIENT98, CAW350W, V2001 . When the data is too large, it should be compressed and sent. Any compression format such as *.ZIP, *.ARJ, *.LZH can be used. The data must contain SMT solder paste layer (including Fiducial Mark data and PCB shape data), and it must also contain a character layer Data in order to check the front and back of the data, component category, etc.