Baking conditions for moisture sensitive components

In order to ensure that the parts will not popcorn or de-lamination when passing through the SMT reflow oven due to excessive moisture absorption, general IC packaging components need to control the time when the components are exposed to ambient humidity according to the MSL standard. In this article, we will discuss what to do if MSL components are exposed to atmospheric humidity for more than the specified time?

In fact, there is only one treatment method after component moisture absorption, which is baking. Baking can remove moisture, just like the baking effect of the dishwasher or washing machine we use. The question is how much temperature and how much time should be used in order to be safe without harming the MSL components, or can use the least damage and the shortest time to remove moisture?

Different components packaging will produce different MSL levels. The more moisture enters the components, the higher the risk of the components expansion and peeling due to temperature. Basically, moisture sensitive components will be baked for a certain time and temperature before leaving the factory. It is then added to the vacuum packaging together with desiccant to achieve the lowest possible moisture intrusion.

Responsible components manufacturers will also declare what moisture sensitivity level (MSL) their parts comply with according to the J-STD-020 standard. The EMS and SMT factories must operate and bake moisture sensitive components according to another J-STD-030 standard.

The following Table 1 is IPC/JEDEC J-STD-033 Bake Conditions for Drying SMD's at the User Site.

Table 1 defines that different MSL require different baking conditions. For the same MSL parts, several different baking conditions are also provided, which can be used according to user needs.

Table 1:

Saturated @ 30°C/85% RH：

It means that if the moisture sensitive components are taken out from the vacuum packaging moisture barrier bag (MBB), and exposed to an environment with a temperature below 30°C and a relative humidity of less than 85% RH, regardless of the length of time, you can re-calculate its Floor Life after re-baking according to the temperature and time in the table above.

at Limit of Floor Life + 72Hr @ 30°C/60%RH：

It means that if the moisture sensitive components are taken out from the vacuum packagingmoisture barrier bag (MBB), within 72 hours, exposed to an environment with a temperature below 30°C and a relative humidity of less than 60% RH, if you re-bake according to the temperature and time in the tableabove, you can recalculate its Floor Life.

According to the above two conclusions, if the moisture sensitive components can not meet the environmental and time limits of “at Limit of Floor Life + 72Hr @30°C/60%RH” after unpacking, the other will apply "Saturated @30°C/85 % RH" to recalculate its Floor Life.

The following table 2 is IPC/JEDEC J-STD-033 Bake Conditions Prior to Dry Packing SMD's at the Manufacturer's Site.

Table 2 defines that when moisture sensitive components are shipped from their manufacturing plant, different baking conditions need to be adopted for parts with different MSL levels. Here, two baking conditions are provided for parts of the same MSL level, which can be regarded as user Need to adopt.

Table 2: