Aperture Area Ratio, and Determining Stencil Thickness

[Al Secchi]

When ordering a stencil it is important to request the appropriate stencil thickness to insure proper paste release from the stencil. The aspect ratio for rectangular apertures should be 1.5, and an area ratio of 0.66. It is best to evaluate the smallest apertures on the stencil to determine the proper stencil thickness.

You can use the following formulas to select an appropriate stencil thickness:

Aspect Ratio = Aperture Width (W) / Stencil Thickness (T) [should be 1,5]

Area Ratio = Area of Pad (LxW) / Area of Aperture Walls (2 x (LxW) x T) [should be 0.66]

(diagram attached)

[meli117]

When ordering a stencil it is important to request the appropriate stencil thickness to insure proper paste release from the stencil. The aspect ratio for rectangular apertures should be 1.5, and an area ratio of 0.66. It is best to evaluate the smallest apertures on the stencil to determine the proper stencil thickness.

You can use the following formulas to select an appropriate stencil thickness:

Aspect Ratio = Aperture Width (W) / Stencil Thickness (T) [should be 1,5]

Area Ratio = Area of Pad (LxW) / Area of Aperture Walls (2 x (LxW) x T) [should be 0.66]

(diagram attached)

Hello,

thanks , this was really helpful, but do these formulas go in any circumstances ? There are no exceptions ?

thanks

[Sal Hernandez]

This is a general formula for stencil thickness. Is there a particular exception you would like to discuss?

[nevertalk00]

Have your board fab house plug the via and then plate copper over it. They can plug with metal or a thermally and electrically conductive epoxy before the final plating steps."