EN2342QI Datasheet, PDF (21/23 Pages) Altera Corporation – 4A PowerSoC Voltage Mode Synchronous PWM Buck with Integrated Inductor

Design Considerations for Lead-Frame Based Modules
EN2342QI
Exposed Metal on Bottom of Package
Lead-frames offer many advantages in thermal performance, in reduced electrical lead resistance, and in
overall foot print. However, they do require some special considerations.
In the assembly process lead frame construction requires that, for mechanical support, some of the lead-frame
cantilevers be exposed at the point where wire-bond or internal passives are attached. This results in several
small pads being exposed on the bottom of the package, as shown in Figure 12.
Only the thermal pad and the perimeter pads are to be mechanically or electrically connected to the PC board.
The PCB top layer under the EN2342QI should be clear of any metal (copper pours, traces, or vias) except for
the thermal pad. The “shaded-out” area in Figure 12 represents the area that should be clear of any metal on
the top layer of the PCB. Any layer 1 metal under the shaded-out area runs the risk of undesirable shorted
connections even if it is covered by soldermask.
The solder stencil aperture should be smaller than the PCB ground pad. This will prevent excess solder from
causing bridging between adjacent pins or other exposed metal under the package. Please consult the
Enpirion Manufacturing Application Note for more details and recommendations.
Figure 12: Lead-Frame exposed metal (Bottom View)
Shaded area highlights exposed metal that is not to be mechanically or electrically connected to the PCB.
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February 21, 2014
www.altera.com/enpirion, Page 21
Rev A