What is the Moisture Sensitivity Level Test (MSL Test)?

Humidity is one of the most important climatic factors to consider when testing products and materials. Humidity control is crucial in most tests, but some focus on specific moisture-related damage under specific conditions.

This is the case of the Moisture Sensitivity Level Test or MSL Test.

What is meant by Moisture Sensitivity Level?

The Moisture Sensitivity Level is calculated using a scale of values ​​ranging from 1 to 6, which indicate the level of sensitivity to damage caused by moisture absorption.

However, it is not a scale that applies to all moisture damage to all types of products and materials.

Instead, it is designed for a specific type of product, i.e. conductors and semiconductors, and calculates the damage of a particular moisture-related damage process.

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What is the Moisture Sensitivity Level Test Used For?

Semiconductors and electronic components can absorb moisture in varying amounts depending on how they are constructed and how they are positioned inside the device.

When moisture trapped inside the semiconductor is released, it can cause a variety of damage ranging from small cracks to full-blown semiconductor explosions known as the “popcorn effect.”

The MSL Test is used to establish the degree of moisture absorption of a component under examination and then assign it a value ranging from 1 to 6 on the sensitivity scale.

Depending on its value, the component will need periodic “baking” phases, i.e. cooking and dehumidification, in order to guarantee a longer life cycle.

But what is baking? 

Since it is part of the test itself, we will find out in the next paragraph.

How the Moisture Sensitivity Level Test Works According to J-STD-020

The procedure for the Moisture Sensitivity Level Test is defined within an internationally relevant standard, the J-STD-020.

The MSL Test consists of several phases.

The sample is initially subjected to a visual and microacoustic inspection under normal conditions. It is then baked for 24 hours at 125°C to completely dehumidify. 

It is then subjected to the reverse process of humidification and a series of subsequent releases of the trapped moisture are observed to finally assess how much damage it has suffered.

Depending on the result, the sample is placed on a scale from 1 to 6 and indicates its level of sensitivity to moisture damage.

The FDM Oven for the Moisture Sensitivity Level Test

As we have seen, the baking phase is central both in the MSL Test and in the subsequent periodic reconditioning to which the components will be subjected.

To bake semiconductors professionally and in accordance with international standards, there is no better tool than a laboratory drying oven.

FDM laboratory drying ovens are capable of performing the baking phase, the MSL Test and many other climatic tests that require reaching and maintaining extreme temperatures.

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Reference Standards

• IPC/JEDEC J-STD-020E — Moisture/Reflow Sensitivity Classification for Nonhermetic Surface Mount Devices
• IPC/JEDEC J-STD-033C — Handling, Packing, Shipping and Use of Moisture Sensitive Devices
• JESD22-A113 — Preconditioning of Nonhermetic Surface Mount Devices Prior to Reliability Testing
• JESD22-A118 — Accelerated Moisture Resistance — Unbiased HAST
• IPC-M-108 — Moisture Sensitive Components Handling

Authoritative Sources

• JEDEC J-STD-020 — MSL Classification Reference Standard.
• IPC — Association Connecting Electronics Industries.
• JEDEC — Joint Electron Device Engineering Council.

Frequently Asked Questions about the MSL Test

What are MSL levels and how are they classified?

Moisture Sensitivity Level (MSL) classifies electronic components based on their tolerance to ambient humidity during storage before reflow soldering. Eight classes range from MSL 1 (no limit—not sensitive) to MSL 6 (mandatory baking before each use). The most common: MSL 2 (1-year floor life), MSL 3 (168 hours), MSL 4 (72 hours), and MSL 5 (48 hours). Floor life is the maximum time in a standard 30°C/60%RH between opening the MBB bag and reflow.

How do you take an MSL classification test?

J-STD-020E procedure: (1) Pre-bake 24h at 125°C for dry-out; (2) Moisture soak in a climatic chamber according to the target level (e.g. MSL 3 = 192h at 30°C/60%RH, or accelerated 40h at 60°C/60%RH); (3) Triple reflow at lead-free soldering profile 260°C peak; (4) Inspection with SAM (Scanning Acoustic Microscopy) to look for delaminations, cracks, “popcorning”. If no defects after 3 reflows = classification confirmed.

What is the “popcorning” phenomenon?

During reflow at 260°C, moisture absorbed into the mold compound (plastic package) turns to vapor. The internal pressure exceeds the mechanical resistance and fractures the package with explosive expansion (hence the "popcorn effect"). Damage includes: die-compound delamination, cracked bond wire, internal moisture path cracks, and silicon die fracture. Visible popcorning is rare, but subsurface damage, detectable only with SAM, is more common and critical to reliability.

How to manage MSL in SMT production?

Best practices J-STD-033: (1) MBB (Moisture Barrier Bag) with silicagel and HIC (Humidity Indicator Card); (2) Floor life tracking with stickers and ERP logs; (3) Bake-out recovery RH); (4) Dry cabinet <5% RH); (4) Dry cabinet Dry cabinet RH per storage componenti aperti; (5) Work order <5% RH per storage componenti aperti; (5) Work order Work orders with an 8-16 hour limit between MBB opening and reflow. IPC-QPS-certified companies implement full MSL traceability for tier-1 automotive/aerospace customer audits. Dry cabinet a Work order con limite di 8-16h tra apertura MBB e reflow. Le aziende con certificazione IPC-QPS implementano tracciabilità completa MSL per audit clienti tier-1 automotive/aerospace.