MIC45205 Datasheet, PDF (26/31 Pages) Micrel Semiconductor – 26V/6A DC-to-DC Power Module

Micrel, Inc.
MIC45205
Simplified PCB Design Recommendations
Periphery I/O Pad Layout and Large Pad for Exposed
Heatsink
The board design should begin with copper/metal pads
that sit beneath the periphery leads of a mounted QFN.
The board pads should extend outside the QFN package
edge a distance of approximately 0.20mm per side:
Total pad length = 8.00mm + (0.20mm per side × 2 sides)
= 8.40mm
After completion of the periphery pad design, the larger
exposed pads will be designed to create the mounting
surface of the QFN exposed heatsink. The primary transfer
of heat out of the QFN will be directly through the bottom
surface of the exposed heatsink. To aid in the transfer of
generated heat into the PCB, the use of an array of plated
through-hole vias beneath the mounted part is
recommended. The typical via hole diameter is 0.30mm to
0.35mm, with center-to-center pitch of 0.80mm to 1.20mm.
Note:
Exposed metal trace is “mirror image” of package bottom view.
Figure 17. Package Bottom View vs. PCB Recommended Exposed Metal Trace
April 15, 2014
26
Revision 1.0