an-994| Application Note
Application Note AN-994
Maximizing the Effectiveness of Your SMD Assemblies
by Gil Alivio, John Ambrus, Tim McDonald, Richard Dowling
Table of Contents
Page How We Measure Rth(JA) .......................................................................2 Thermal Characterization of Surface Mount Packages ........................3 Attachment to Board ............................................................................5 Solder Pastes.......................................................................................5 Reflow Soldering Heat Profiles.............................................................6 Rework .................................................................................................7
Herein is described the device mounting and heat sinking used and the test methods employed to measure Thermal Resistance of the various packages. Standard printed circuit boards were developed to which devices were solder mounted for measuring z thermal resistance. FR-4 material with 2 oz. Cu was used. Board dimension were 4.75 inches by 4.5 inches and backside of board had full metal pattern. Three different PCB metallization patterns were tested: one with 1 sq inch of Cu area, the second one with Cu trace minimized so as to cover only as much area as taken up by the Device Under Test (DUT) and necessary lead mounting pads (described as "modified minimum pattern"), and the last one is the "absolute minimum" pattern with the metallized area sized only as needed to mount each lead. This application note applies only to surface mountable type devices. Through-hole devices such as TO-220, TO-247, Full-pak, etc are excluded and not covered by this note.
AN-994
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