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Moisture Barrier bags

jtamagi

#19726

Moisture Barrier bags | 29 April, 2002

I have level 3 components per J-STD-20.

1) Are there any packaging methods which can be "zip locked" instead of heat sealed?

2) Do I need to evacuate the bag?

3) Do I need to purge with Nitrogen?

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#19736

Moisture Barrier bags | 29 April, 2002

Refer to J-STD-33 - Standard for Handling, Packing, Shipping and Use of Moisture/Reflow Sensitive Surface-Mount Devices. You can be downloaded it free from http://www.jedec.org

Assuming you want to meet expectations when selling your components to customers.

Q1: Are there any packaging methods which can be "zip locked" instead of heat sealed? A1: No. Zip-lock bags will not prevent moisture intrusion.

Q2: Do I need to evacuate the bag? A2: You don't have to evaculate the bag. You need to do what is necessary to meet the standard.

Q3: Do I need to purge with Nitrogen? A3: You don't have to purge with nitrogen. You need to do what is necessary to meet the standard.

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#19766

Moisture Barrier bags | 3 May, 2002

Dave is correct. I am including additional information that comes from a recent posting on another industry forum :

The proper guidelines for bag sealing are actually specified in the JEDEC standard EIA/JEP124 section 5.2.1 Packing moisture-sensitive components : "...Partially or lightly evacuate the bag to reduce packaging bulk and heat seal the bag as close to the end as possible following the heat sealing equipment manufacturer's guidelines. The bag should not be completely evacuated since this will reduce the effectiveness of the desiccant and possibly damage the content..."

As far as I know there are two technical reasons to explain this :

1. With a tight vacuum, the desiccant is squeezed between the bag and the stack of trays. There is no surface contact with any air that would allow it to pull moisture from everywhere inside the bag.

2. A high vacuum will slowly pull the outside air and the humidity that it contains through the bag. Over time the moisture content inside the bag will increase faster than with no vacuum.

I am aware of some experiments that were made by TI a couple years ago. It showed that when dry bags were opened, after 1.5 years, bags with low vacuum had less than 10% RH inside, while bags with high vacuum had 15% RH inside.

Of course you could use a vacuum sealer with very low vacuum but not all machine types can be set at low values. Many people use machines originally designed for the food industry and even at the lowest setting they will pull too much vacuum. Also I have seen that over time people tend to crank up the vacuum level (that warm and fuzzy feeling once again). And trust me, you can pull a high vacuum inside a dry bag. When you can read the marking that is embossed in your JEDEC tray you know you're in trouble...I personally think that it is safer to use a standard heat sealer and ask your operators to remove the excess air before sealing.

And yes I know, many suppliers are not aware of this very important specification. Feel free to point them to the right document.

Regards,

Fran´┐Żois Monette Cogiscan Inc. Tel : 450-534-2644 Fax : 450-534-0092 E-mail : fmonette@cogiscan.com www.cogiscan.com

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