Moisture Sensitivity (as applicable to SMD's)
All Microsemi CMPG integrated circuits are manufactured using world class methods and materials and are designed to tolerate industry standard handling and board level processing without damage. However the solder mounting of devices onto boards can cause "pop corning" of certain types of surface mount packages if they have been improperly stored or handled. This package delamination occurs as excessive moisture within the package expands as a result of the rapid thermal changes experienced during solder mount operations. Adherence to proper storage and handling methods as described below will eliminate this risk. See "Soldering Profiles" for more details on soldering requirements.
Dry Packing
It is important that the moisture content of Surface Mount Devices (SMDs) is controlled in order to eliminate the possibility of this "popcorn" effect occurring during board solder processing. Microsemi CMPG addresses this issue by baking (where applicable) all moisture sensitive SMDs (those rated level 3) to remove any moisture and then sealing under vacuum into industry standard dry packs containing a desiccant. These dry packs also provide electrostatic protection during shipping and storage.
Floor Life
Floor life is the time allowed between opening any dry pack and subsequent soldering operations and is defined for packages according to the standard JEDEC J-STD-020. Recommended floor life for Microsemi CMPG dry packed products is indicated on the dry pack. Note that the safe floor life will be affected by the ambient environmental conditions.
Recommended floor life conditions are:
JEDEC level | Dry packed | Floor life at 30°C/60%RH |
1 | no | Unlimited |
3 | yes | 168 Hours |
A rebake is recommended if storage conditions exceed either 30°C/60% or the quoted floor life. The time and temperature of the bake depend on the package thickness as defined in the table below.
The floor life clock is reset to zero following the rebake. However if the ambient conditions still do not meet those defined the product should be used immediately following the bake.
Package Thickness |
Default Baking Times | Baking Times for Trays with <150°C Tolerance |
|
Bake @ 125°C | Bake @ 150°C | Bake @ 140°C | |
<=1.4 mm | 16 h. | 8 h. | 9 h. |
<=2.0 mm | 24 h. | 12 h. | 14 h. |
<=4.0 mm | 48 h. | 24 h. | 28 h. |
N.B. Product may be stored indefinitely once the dry pack is opened provided that the ambient humidity does not exceed 20% RH. Humidity controlled dry-air or dry-nitrogen cabinets are recommended for this purpose.
Reliability Assessment
The moisture sensitivity of all SMD families is assessed as part of Microsemi CMPG package qualifications. Devices are also preconditioned prior to certain stress tests carried out as part of our routine reliability monitoring programs. These provide us with confidence in the reliability of shipped product. Preconditioning conditions are chosen to simulate the worst case storage and soldering conditions experienced in use with exact conditions dependent upon the moisture sensitivity classification (as per JEDEC J-STD-020 & JESD22-A113). Preconditioning is applied as per JESD22-A113 prior to most stress tests, which include temperature cycling, biased damp heat and autoclave.
Typically, for dry packed SMDs (level 3) the preconditioning sequence includes a soak at 30°C/60%RH with a duration of 192 hours.
For SMDs which are not dry packed (level 1), the preconditioning sequence includes a soak at 85°C/85% RH for 168 hours.