2-473

RF3133

Rev A4 030527

Thermal Pad and Via Design

The PCB land pattern has been designed with a thermal pad that matches the exposed die paddle size on the bottom of

the device.

Thermal vias are required in the PCB layout to effectively conduct heat away from the package. The via pattern shown

has been designed to address thermal, power dissipation and electrical requirements of the device as well as accommo-

dating routing strategies.

The Via pattern used for the RFMD qualification is based on thru-hole vias with 0.203mm to 0.330mm finished hole size

on a 0.5mm to 1.2mm grid pattern with 0.025mm plating on via walls. If micro vias are used in a design, it is suggested

that the quantity of vias be increased by a 4:1 ratio to achieve similar results.

Stencil Design Recommendation

The stencil aperture are typically designed to match the pad size shown in the PCB Solder Mask pattern and are

reduced for an overall 20 percent reduction in pad area for each pad. This has yielded good solder joint results based on

volumes assembled during product introduction phase.

Critical parameters to consider for successful solder paste application include:

Accurate registration of the stencil to the PCB during printing.

Good release of stencil from the PCB after paste applied. This is improved with laser cut trapezoidal openings.

Proper storage and handling of solder paste based on solder paste vendor guidelines.

Frequent cleaning of the solder paste stencil to remove residual solder paste.

Stencil material recommendations: 5mil (0.127mm) thick stainless steel, laser cut stencils with trapezoidal openings to

promote easy release of solder paste.

Vias

0.203 mm to 0.330 mm

Finished Hole

0.5 mm to 1.2 mm Grid

Figure 2. Thermal Pad and Via Design (RFMD Qualification)