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January 26, 2011

Chip Component Moisture

Let's say we have moisture sensitive chip components that have been exposed to the atmosphere slightly beyond the specification allowed. They are then repackaged and sealed with desiccant and a humidity indicator card.

After about a week's time, would the card indicate humidity?

Could the desiccant alone remove the moisture in the chips, or is baking necessary?

Would vacuum sealing the bag make any difference?

E. R.

Experts Comments

Moisture Barrier bags are essentially designed for long term storage of dry parts. Properly vacuum prepared and sealed,they can effectively "stop the clock" but will not offer any predictablecomponent drying.

Baking has been the traditional solution, but it induces oxidation and measurably decreases wet-abilty. IPC/JEDEC specifications detailthe restrictionsand limitations on baking.

New, ultra-low humidity (<1%)desiccant cabinets are moisture vacuums that are able to "turn back the clock" with their revertive drying effects (adsorption), even at ambient temperatures.This drying can be accelerated with mild heating (<60 dgrees C).

The combination of ultra low humidity and milder temperature avoids the oxidationproblem but can acheivecomparable drying times to vacuum ovens andhigh temperature baking(ref: http://www.superdry.info/). In addition, components on reels or in tubes can be safely dried without damage to the packaging.

There is no substitute for a comprehensive MSD management process just as there is no substitute for a comprehensive ESD management process. And lead freeraises the risk even higher of not having proper systems in place.

Richard Heimsch
Protean Marketing
Now a director at Protean Marketing, Mr. Heimsch has worked in the electronics industry 25+ years in a wide variety of international sales, marketing and operations roles. Rich spearheads Protean's international business development, specializing in Brand Management and Strategic Communications.
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