Why be Concerned with Moisture?
Moisture is an invisible pest in the world of electronics manufacturing. Packages made from plastic are susceptible to moisture-related failure during board assembly. Excess moisture can turn to steam during reflow, creating defects and reducing production yields.
Moisture absorption and retention inside electronic packages could cause numerous problems. For instance, trapped moisture can vaporize and exert internal package stresses when the device is subjected to sudden elevated temperature during reflow.
Package cracking due to such moisture-induced stress is called popcorn cracking. However, even if the package does not crack, interfacial delaminating can occur.
Surface peeling between the die pad and the resin is caused by water vapor pressure during reflow. Surface delamination is likely, resulting in shear strain on bond wires and wire necking.
Micro-cracking can extend to the outside of the package. External cracking may appear on the sides, top and bottom of a component. Because the package wall is often thinnest below the die pad, bottom cracking is the most common and very difficult to detect visually.
Component damage due to moisture expansion
- • IC Packages
Reduce moisture related damage to all types of active devices from PoP, Stacked Die, BGA, QFP, etc.
- • Passive Components and Connectors
Prevent solder defects by reducing oxidation of leads caused by excessive moisture during storage and kitting
- • Circuit Boards
Maintain accurate board dimensions reducing board stretch and warp due to high moisture content
- • Silicon Wafers
Reduces contamination from particles suspended in moisture droplets. Anti-oxidation
- • Liquid Crystal Glass Board
Dehydration under ambient temperature after polishing
- • Lead Frames & Carriers
Controlled humidity increases the reliability of solder and wire bond points
- • Fiber Optics, CCD etc
Retards organic growth and maintains the condition of key fiber optics devices and components
Protection for Moisture Sensitive Devices (MSDs)
According to IPC/JEDEC J-STD-033B, SMD packages not sealed in a moisture barrier bag (MBB) may be placed in a dry cabinet, maintained at not greater than 5% RH. Storage in these dry cabinets are equivalent to storage in a MBB with unlimited shelf life.
In addition, storage of SMD packages sealed in cabinets maintained at not greater than 10% RH have limited shelf life. If the time limit is exceeded, these devices should be baked to restore the floor life.
In short, storing moisture sensitive devices in a dry cabinet maintained at not greater than 5% RH, offers unlimited shelf life without using MBB and removes possible re-baking costs which are much more than storage costs.
Most of our customers use Eureka Dry Cabinets for:
- • Preventing oxidation of PCBs while waiting for reverse side mounting.
- • Dry storage for MSD components levels 2 through 5a
- • Prevent effects of oxidation on electronic components
- • Dry and safe storage of film and other materials used in the manufacturing of PCB