Stencils thickness

Stencil thickness should be determined by the highest dot size needed to make contact with the part. In most cases, the dot height should be 1.5 to 2 times the standoff height. Mostpassive components require stencils that are at least 6-8 mils thick. Farge, small-outline ICs (SOICs) require stencils that are 10-12 mils thick. A specific example in the use of these guidelines is... 

Solder Volume. The inabiUty to apply enough solder paste to meet standard through-hole solder-joint acceptabUity criteria is one of the major shortcomings of pin-in-paste reflow. That is why this technique is usually relegated to boards <1.6 mm (0.063 in.) thick. Requisite solder volume is dictated by component pin pitch and the available printing space between component leads stencil thickness, which is generally limited by the smallest or finest pitch components on the PWB and PTH volume and associated component lead displacement volume. 

Aspect ratio considers the ratio between aperture width and stencil thickness. Area ratio considers the ratio between the opening of the aperture (the area of the PCB pad that will be covered with solder paste) and the... 

Pitch Pad Size Aperture Stencil Thickness Aspect Ratio ... 

FIG. 23 Shear strength testing of 0603/0201 capacitors for various land designs and stencil thickness of a) 0.1 mm and b) 0.12 mm. In general, the Sn-Ag-Cu alloy outperformed the eutectic Sn-Pb alloy. (Courtesy of Panasonic.)... 

---