msl

IPC/JEDEC Moisture Sensitivity Levels (MSL)

Different surface-mount package types have different sensitivity levels to moisture. The

problem with moisture absorption and retention inside the package is that the trapped

moisture will vaporize and apply tremendous internal package stresses when the device is

subjected to sudden, elevated temperature, such as during board mounting. Package

cracking due to such moisture-induced stresses is known as popcorn cracking.

In general, surface-mount devices (SMD's) are more prone to popcorn cracking because:

1) They are thinner and therefore has lower fracture strength

2) They absorb and retain moisture more easily

3) SMD board mounting also subjects the molding compound to the high temperature

experienced by the leads.

In identification of the varying degrees of popcorn cracking tendency of various package

types, IPC/JEDEC defined a standard classification of moisture sensitivity levels (MSL's).

The MSL's are expressed in numbers, with the MSL number increasing with the vulnerability

of the package to popcorn cracking. Thus, MSL1 correspond to packages that are immune

to popcorn cracking regardless of exposure to moisture, while MSL5 and MSL6 devices are

most prone to moisture-induced fracture.

Table 1 below illustrates the MSL definitions per IPC/JEDEC's J-STD-20

Cond Cond CondºC/ %RH ºC/ %RH ºC/ %RH

1 unlimited ≤ 30/85% 168+5/-0 85/85 n/a n/a

2 1 year ≤ 30/60% 168+5/-0 85/60 n/a n/a

2a 4 weeks ≤ 30/60% 696+5/-0 30/60 120+1/-0 60/60

3 168 hours ≤ 30/60% 192+5/-0 30/60 40+1/-0 60/60

4 72 hours ≤ 30/60% 96+2/-0 30/60 20+0.5/-0 60/60

5 48 hours ≤ 30/60% 72+2/-0 30/60 15+0.5/-0 60/60

5a 24 hours ≤ 30/60% 48+2/-0 30/60 10+0.5/-0 60/60

6 TOL ≤ 30/60% TOL 30/60 n/a 60/60

Table 1. IPC/JEDEC J-STD-20 MSL Classifications

Time Time (hrs) Time (hrs)

MSLFloor Life

Soak Requirements

Standard Accelerated

1) TOL means 'Time on Label', or the time indicated on the label of the packing. 2) The standard soak time is the sum of the default value of 24H for the semiconductor manufacturer's exposure time (MET) between bake and bag and the floor life or maximum time allowed out of the bag at the end user or distributor's facility. For example, an MSL 3 package will require a standard soak time of 192 hours, which is 168 hours of floor life plus 24 hours between bake and bag at the semiconductor manufacturer.

IPC/JEDEC J-STD-033 Bake Conditions Different packages have different levels of moisture sensitivity. The higher the amount of

moisture inside a package, the higher the thermo-mechanical stresses inside the package

during board mounting will be. These stresses are brought about by the rapid vaporization of

the trapped moisture, and can be large enough to fracture the package during board

mounting. Package cracking under such circumstances is known as 'popcorn cracking.'

IPC/JEDEC J-STD-020 defines the Moisture Sensitivity Levels (MSL) of surface mount

devices.

Moisture-sensitive devices are baked and vacuum-sealed inside a moisture barrier bag prior

to shipment in order to minimize their tendency to exhibit popcorn cracking during board

mounting. Users of such devices are likewise required to board mount the units within a

prescribed period after the bag has been opened. Failure to do so calls for a rebake of the

units prior to board mounting.

Table 1 shows the bake conditions recommended by IPC/JEDEC J-STD-033 at the user's

site if the out-of-bag time prescribed has expired prior to board mounting. Table 2 shows the

bake conditions required by IPC/JEDEC J-STD-033 at the manufacturer's site, prior to dry-

packing the parts.

Exposure Time > 72h

Exposure Time ≤ 72h

Exposure Time > 72h

Exposure Time =< 72h

Exposure Time > 72h

Exposure Time ≤ 72h

2 5 hours 3 hours 17 hours 11 hours 8 days 5 days2a 7 hours 5 hours 23 hours 13 hours 9 days 7 days3 9 hours 7 hours 33 hours 23 hours 13 days 9 days4 11 hours 7 hours 37 hours 23 hours 15 days 9 days5 12 hours 7 hours 41 hours 24 hours 17 days 10 days5a 16 hours 10 hours 54 hours 24 hours 22 days 10 days2 18 hours 15 hours 63 hours 2 days 25 days 20 days2a 21 hours 16 hours 3 days 2 days 29 days 22 days3 27 hours 17 hours 4 days 2 days 37 days 23 days4 34 hours 20 hours 5 days 3 days 47 days 28 days5 40 hours 25 hours 6 days 4 days 57 days 35 days5a 48 hours 40 hours 8 days 6 days 79 days 56 days2 48 hours 48 hours 10 days 7 days 79 days 67 days2a 48 hours 48 hours 10 days 7 days 79 days 67 days3 48 hours 48 hours 10 days 8 days 79 days 67 days4 48 hours 48 hours 10 days 10 days 79 days 67 days5 48 hours 48 hours 10 days 10 days 79 days 67 days5a 48 hours 48 hours 10 days 10 days 79 days 67 days

BGA package > 17mm x 17mm or any stacked die

package

2_6 96 hoursAs Above per

package thickness and moisture level

Not ApplicableAs Above per


Not ApplicableAs Above per


Thickness >2.0 mm ≤

4.5 mm

Bake Conditions for Drying Mounted or Unmounted SMD Package

Bake @ 125ºC Bake @ 90ºC ≤ 5% RH Bake @ 40ºC ≤ 5% RHPackage Body MSL

(User Bake: Floor life begins counting at time = 0 after bake

Table 1. IPC/JEDEC J-STD-033

Thickness ≤ 1.4 mm

Thickness >1.4 mm ≤

2.0 mm

Package Thickness MSL Bake @ 125ºC Bake @ 150ºC

2a 8 hours 4 hours

3 16 hours 8 hours

4 21 hours 10 hours

5 24 hours 12 hours

5a 28 hours 14 hours


3 43 hours 21 hours

4 48 hours 24 hours

5 48 hours 24 hours



3 48 hours 24 hours

4 48 hours 24 hours

5 48 hours 24 hours


Table 2. IPC/JEDEC J-STD-033

≤ 1.4 mm

≤ 2.0 mm

≤ 4.5 mm

Default Baking Times Used Prior to Dry-Pack that were Exposed to Conditions ≤60% RH

(Supplier Bake: ‘‘MET’’ = 24 h)

msl

Documents