July 16, 2014 | DATASHEET V3.3

20

IR3553

40A Integrated PowIRstage®

STENCIL DESIGN

 The stencil apertures for the lead lands should be

approximately 65% to 75% of the area of the lead

lands depending on stencil thickness. 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.

 The low power signal stencil lead land apertures

should therefore be shortened in length to keep

area ratio of 65% to 75% while centered on lead

land.

 The power pads VIN, PGND, TGND and SW, land

pad apertures should be approximately 65% to

75% 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. Solder

paste on large pads is broken down into small

sections with a minimum gap of 0.2mm between

allowing for out-gassing during solder reflow.

 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.

Figure 35: Stencil design

* Contact International Rectifier to receive an electronic PCB Library file in Cadence Allegro or CAD DXF/DWG format.