Moisture sensitivity level

<h2 id="practical">Practical</h2>
<p>MSL-specified parts must be baked before assembly if their exposure has exceeded the rating. The approved degree of baking depends upon the thickness of the package, the exposure time to moisture, the relative humidity of the atmosphere it was exposed to and the MSL rating of the part, with thinner packages generally expected to need less baking time and at lower temperatures.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p><p>For example, an end user of a SOT-223, MSL 3 package (1.8 mm thickness) that has been exposed to typical ambient air conditions for longer than 72 hours would need to perform a 27-hour bake at 120° Celsius before soldering but under the same ambient conditions using a VQFN-24, MSL 3 package (0.85 mm thickness) that user would have to perform an 8-hour bake at the same temperature.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> It is expected that the user solders the part within a few minutes to a few hours after bake and cool down completes, as the part will commence absorbing moisture again as soon as the package cools. Baking at temperatures between 90° and 120° Celsius is generally not recommended to exceed 96 hours over concerns of promoting oxidation and/or intermetallic growth, however, baking at temperatures under 90° has no practical time limit.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> 
</p><p>Once soldered, moisture sensitivity is generally no longer a consideration. This is because the MSL rating is concerned with the process of soldering or desoldering, which introduces relatively rapid high-temperature stress to the part. During normal use, including when power is applied, the plastic package is unlikely to encounter temperature conditions similar to soldering itself.
</p><p>Though MSL standards are explicitly not meant to be applied during manual soldering and rework,<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> manual rework temperature rise conditions may approach that of reflow soldering over a portion of, or the entire, package. The user should evaluate whether ignoring MSL bake conditions is appropriate in their circumstances.
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<h2 id="external-links">External links</h2>
<ul><li><a href="https://www.ipc.org/TOC/IPC-JEDEC-J-STD-020E.pdf">https://www.ipc.org/TOC/IPC-JEDEC-J-STD-020E.pdf</a></li>
<li><a href="https://www.bourns.com/docs/RoHS-MSL/msl_mf.pdf">https://www.bourns.com/docs/RoHS-MSL/msl_mf.pdf</a></li>
<li><a href="https://electronics.stackexchange.com/questions/23044/ics-with-humidity-or-moisture-sensitivity-bake-recommendations">https://electronics.stackexchange.com/questions/23044/ics-with-humidity-or-moisture-sensitivity-bake-recommendations</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"Moisture/reflow Sensitivity Classification for Nonhermetic Solid State Surface-mount Devices". JEDEC. Retrieved 11 August 2022. <a href="https://www.jedec.org/document_search?search_api_views_fulltext=j-std-020" target="_blank">https://www.jedec.org/document_search?search_api_views_fulltext=j-std-020</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>[2] JEDEC J-STD-033D, Retrieved 6 April, 2025. <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>[3] JEDEC J-STD-033D, Table 4-1. Retrieved 6 April, 2025. <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>[4] JEDEC J-STD-033D, Section 4.2.7.1. Retrieved 6 April, 2025. <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
<li id="fn:5"><p>[5] JEDEC J-STD-033D, Section 1.3.4. Retrieved 6 April, 2025. <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li>
</ol>

Moisture sensitivity level open-in-new

Moisture sensitivity level