Stencil's tensioning methods
We are ready to make a stencil for you for any method of its stretching. We have experience of cutting stencils for different stencil stretching systems used in different stencil printers.
Based on the experience of using different stencils, we recommend you to use a frames of pneumatic stretching stencils by compressed air. We are also ready to make your stencils with own aluminum frame of any size, with a stretched metal stencil on it.
Briefly describe the main methods of mounting the stencil on the frame for their subsequent use in the technology of stencil printing of solder paste.
- The stretching of the stencil for two sides
Stencils used for solder paste, may have attachment points for two or four sides.
Fig.1 Example of stencil stretching for two sides.
- The stretching of the stencil for four sides by means compressed air
Stencil stretched for four sides on the frame, has a lower distortion in flatness than for two-sides stretching. For stencil printing of paste for components with a pitch of 0.5 mm or less is better to use this type of stencil frames. They are more expensive than two-side frames, but more preferable because have less number of events with incorrect printing of solder paste.
Fig.2 Example of stencil stretching for four sides.
Stencil can be stretched on a frame by hand (cheap frame-printers for solder paste), mechanical stretching (stretching stencil frames and built-in stretching systems of some models of stencil printers), stretched by compressed air (special stencil stretching frames) or stretched on the mesh with own frame.
- The stretching stencil on the mesh with own frame
Stencils, stretched on a mesh, are currently being replaced by full-metal stencils for various stretching systems. Usually they are more expensive than usual stencils. because have own aluminium frame.
Fig. 5 Example of framed stencil with own frame from aluminum profile.
Such stencils has meaning to use then quantity of your products exceeds a few hundreds thousands copies, because they have a long service life than full-metal stencils for stretching frames.
Typically, the best uniform stencil stretching provides only frames with compressed air or framed stencils. This is due to the fact that only a compressed air is capable of simultaneously and uniformly stretch the stencil on all sides (in the systems for stretching framed stencils on the mesh also using special pneumatic cylinders for stretching for all sides). Production personnel can't do it by hand the same operation such quickly and accurately.
Examples of defects due to inaccurate stretching of the stencil
Fig.4 Example of formation of solder balls due to possible defects in the stretching of the stencil or expansion of the material from which stencil is made.
Good stretching of the stencil in flatness lets uniformly, without distortions to impose stencil on PCB, which will ensure even distribution of solder paste in all apertures and the absence of shift pattern of stencil apertures on the pads of the PCB.
If you plan to mass-producing of electronic products, do not regret for money on a stretching system for the stencils, it will save your time in the future and a lot of nerves when debugging process of production will have place.
Think about stretching system before you buy stencil printer!