IR3529

Page 21 of 22

February 12, 2010

Stencil Design

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The stencil apertures for the lead lands should be approximately 80% of the area of the lead lands.

Reducing the amount of solder deposited will minimize the occurrence of lead shorts. Since for 0.5mm

pitch devices the leads are only 0.25mm wide, the stencil apertures should not be made narrower; openings

in stencils < 0.25mm wide are difficult to maintain repeatable solder release.

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The stencil lead land apertures should therefore be shortened in length by 80% and centered on the lead

land.

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The land pad aperture should be striped with 0.25mm wide openings and spaces to deposit approximately

50% area of solder on the center pad. If too much solder is deposited on the center pad the part will float

and the lead lands will be open.

•

The maximum length and width of the land pad stencil aperture should be equal to the solder resist opening

minus an annular 0.2mm pull back to decrease the incidence of shorting the center land to the lead lands

when the part is pushed into the solder paste.