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PCB manufacturing printed stencil thickness design

PCB manufacturing printed stencil thickness design

Printed stencil, also known as drain plate and stencil, is used to quantitatively distribute solder paste or patch glue. It is an important part of printed circuit board tin. The design of stencil reflects the quality of pcb assembly. Therefore,stencil is the key tool for ensuring printing quality. Stencil design is one of the important contents of PCB manufacturability design. The IPC 7525 (Stencil Design Guidelines) standard mainly includes nouns and definitions, reference materials, stencil design, stencil manufacturing, stencil installation, file processing/editing and stencil ordering, stencil check confirmation, stencil cleaning, and stencil life. This section mainly introduces how the thickness of the printed board stencil should be designed.

 


Print stencil thickness design

Stencil printing is contact printing, in which the bottom surface of the stainless steel stencil contacts the surface of the PCB, so the thickness of the stencil is the thickness of the solder paste pattern. The thickness of the stencil is a key parameter in determining the amount of solder paste.
The thickness of the stencil should be determined according to the assembly density of the printed pcb board, the size of the components, and the spacing between the leads (or solder balls). Steel plates with a thickness of 0.1 to 0.3 mm are usually used. When assembling high-density pcb, steel plates with a thickness of 0.1 mm or less can be selected.

However, on the same PCB, there are usually more than 1.27mm components with normal pitch and narrow pitch components. Components with a pitch of 1.27mm or more need 0.2mm thickness, and components with narrow pitch need 0.15~0.1mm thickness. In this case, the thickness of the stencil can be determined according to the condition of the majority of the components, and then the amount of the solder paste can be adjusted by expanding or reducing the opening size of the individual component pads.

When the difference amount of solder paste is required to be large, the stencil at the narrow pitch component can be locally thinned.

The above is the professional information provided by FASTPCBA.

Aug-15-2019

FASTPCBA