Understanding PCB MSL Levels

20 January 2025

In PCB manufacturing, the moisture sensitivity level of components is a key indicator of whether the PCB can be durable. We will explain its levels and why it is a key indicator with the theme of pcb msl levels.

What is MSL?

Moisture Sensitivity Level (MSL) represents the sensitivity of semiconductor components to moisture during storage and use. The higher the MSL value, the more sensitive the component is to moisture. According to the IPC/JEDEC standard J-STD-020, components are divided into different moisture sensitivity levels, which determine the treatment of components before mounting and reflow soldering.

Importance of PCB MSL

Exposure to moisture can cause IC packaging to fail, such as expansion during reflow soldering, leading to component failure. Correct understanding of pcb msl levels can prevent component damage, enhance quality control and ensure product compliance.

List of PCB MSL levels

MSL levels range from 1 to 6, where level 1 represents the lowest sensitivity to moisture and level 6 represents the highest. Here is a detailed classification of each level:

Levels	Storage Conditions	Floor Life	Handling	Drying
MSL 1	≤ 30°C/85% RH	Indefinite	No special controls needed	Pre-bagging: Optional Desiccant: Optional Label: If >235°C
MSL 2	≤ 30°C/60% RH	1 year	Requires dry pack	Pre-bagging: Optional Desiccant: Required Label: Required
MSL 2a	≤ 30°C/60% RH	4 weeks	Requires dry pack	Pre-bagging: Required Desiccant: Required Label: Required
MSL 3	≤ 30°C/60% RH	168 hours	Requires dry pack
MSL 4	≤ 30°C/60% RH	72 hours	Requires dry pack
MSL 5	≤ 30°C/60% RH	48 hours	Requires dry pack
MSL 5a	≤ 30°C/60% RH	24 hours	Requires dry pack
MSL 6	≤ 30°C/60% RH	72 hours, Must be baked	Requires dry pack and baking	Pre-bagging: Optional Desiccant: Optional Label: Required

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