Dry Storage of Electronics Components  [ Return towards  Applications  ]

Long-term storage

Storage of spare parts is required for strategic or obsolete components (military, aerospace, medical, and automotive markets). The storage period can be very long, especially in the aerospace / military or automotive industry. Storing these components in a dry, inert cabinet can eliminate the worries of moisture and oxidation damages over time. It also protects components from particulate, dust, or any physical shock.

 

Short-Term Storage

 

a) Moisture: The Enemy of Surface Mount Devices

 

The introduction of surface mount devices (SMDs) has contributed a significant amount to the advancement of the electronic components and packaging industry. However, moisture from atmospheric humidity can diffuse through the permeable plastic SMD package. If the moisture level inside the package reaches a critical point, the device may be damaged when exposed to high temperatures during the reflow process. These types of moisture-induced failures, also called ‘popcorning’, are of particular concern as they are often undetectable which eventually affects the product reliability.

 

These moisture-sensitive issues will become more prominent with the higher reflow temperature needed for lead-free soldering.

 

b) Dry Storage Option   

Traditional Method
PCB assemblers traditionally 'bake' or 'bake-and-bag' components that have exceeded their floor life as dictated by their IPC / JEDEC level. Baking, normally done for periods and temperatures varying from 24-hours at 125°C to 8-days at 40°C, removes the moisture that are absorbed from the ambient humidity. While baking prevents moisture-induced failures and 'popcorning', it also adds a non-value, timely and expensive step to the assembly process. Additionally, baking alters the component solderability, encourages growth of intermetallic layers, poses carrier compatibility, and creates bottleneck and logistic nightmares.

Moisture Management System

Another option to reduce baking significantly is to adopt a moisture management system. This comprises of a time tracking system and the use of dry cabinets. As compared to the traditional method, this is a pro-active step to deal with moisture. Experiments that are done to illustrate the effectiveness of a dry gas (nitrogen) environment, have proven that: a) it can prevent moisture absorption and b) it can dry or dehumidify components that may have absorbed some moisture. Till the day where IC manufacturers can fabricate truly hermetic packages, the best and simplest way to eliminate moisture-induced failure and popcorning is to prevent moisture from being absorbed by the components.

 

c) Air or Nitrogen

By using nitrogen, a reliable, clean and dry gas source, solderability is preserved over time. Nitrogen is also cleaner than most filtered and dried air and is gaining popularity as the atmosphere of choice for electronic assembly facilities. When nitrogen is used for soldering processes, its use can be extended to the dry storage of components. In all cases, nitrogen should be considered for its combination of properties: low dew point, inertness, cleanliness and atmospheric consistency.