LMZ12003EXT

SNVS663H – JUNE 2010 – REVISED AUGUST 2015

www.ti.com

Layout Examples (continued)

Figure 30. Bottom View of Evaluation PCB

10.3 Power Dissipation and Thermal Considerations

must see a thermal resistance from case to ambient of less than:

(15)

Given the typical thermal resistance from junction to case to be 1.9°C/W. Use the 85°C power dissipation curves

application it is 2.25 W

good estimate of the required board area covered by 1 oz. copper on both the top and bottom metal layers is:

Board Area_cm

θJC

(16)

As a result, approximately 31 square cm of 1-oz. copper on top and bottom layers is required for the PCB

design. The PCB copper heat sink must be connected to the exposed pad. Approximately thirty six, 8 mils

thermal vias spaced 59 mils (1.5 mm) apart must connect the top copper to the bottom copper. For an example

of a high thermal performance PCB layout, refer to the demo board application note AN-2024 SNVA422.

10.4 Power Module SMT Guidelines

The recommendations below are for a standard module surface mount assembly

•

Land Pattern – Follow the PCB land pattern with either soldermask defined or non-soldermask defined pads

•

Stencil Aperture

–

For the exposed die attach pad (DAP), adjust the stencil for approximately 80% coverage of the PCB land

pattern

–

For all other I/O pads use a 1:1 ratio between the aperture and the land pattern recommendation

•

Solder Paste – Use a standard SAC Alloy such as SAC 305, type 3 or higher

•

Stencil Thickness – 0.125 to 0.15 mm

•

Reflow - Refer to solder paste supplier recommendation and optimized per board size and density

•

Refer to AN Design Summary LMZ1xxx and LMZ2xxx Power Modules Family (SNAA214) for reflow

information

•

Maximum number of reflows allowed is one

20

Submit Documentation Feedback

Copyright © 2010–2015, Texas Instruments Incorporated

Product Folder Links: LMZ12003EXT