Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Moisture Sensitive Devices

Dreamsniper

#22543

Moisture Sensitive Devices | 28 November, 2002

I'm in the process of generating work instructions for our stores and production process with regards to moisture sensitive devices.And I'm a bit confused. I found out that we have many TSOP's, QFP's and BGA parts in sealed bags that have not been opened but I noticed that the Bag Seal Date has lapsed or past the 12 Months Shelf Life in a Sealed Bag. Do I need to bake them before mounting and reflow? If I don't bake them then what will be the floor life of these parts? Does their Floor Life which was indicated by the manufacturers still apply despite exceeding the Shelf Life in Sealed bag? I have a baking oven for PCB but has no RH indicator. Can I bake them @ 40'C or 60'C under unknown Relative Humidity?

Please help....Thanks in advance for all your input.

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#22545

Moisture Sensitive Devices | 29 November, 2002

Here are the answers to your questions :

The shelf life in sealed bag as indicated by the seal date is calculated to be a minimum of 12 months, when stored in a non-condensing atmospheric environment of <40C/90%RH. The IPC/JEDEC standard J-STD-033A does not require that the components be baked when the one year shelf life is exceeded. The decision to bake parts should be made strictly based on the status of the Humidity Indicator Card (HIC) when the bag is opened. Ref : section 5.5.1 : "Excess humidity in the dry pack is noted by the HIC...regardless of the storage time, i.e., whether or not the shelf life has been exceeded."

When the bag is opened, provided the HIC is within the specified limit, then the floor life will be as indicated on the MSD label. Please note that the actual floor life will be modified by environmental conditions other than 30C/60%RH. Ref. section 5.2 and table 5-1.

As far as baking at 40C and 60C, the answer is that you are on your own when you deviate from the standard baking conditions specified in table 4-1. If you bake at 40C, the RH must be less than 5% and the duration will vary based on the MS Level, body thickness and saturation level. There is no specific duration at 60C although it should be somewhere between the 40C and 90C bake table. You can buy a cheap hygrometer to put in your oven to verify the actual humidity level.

I hope this is helpful,

Francois Monette Cogiscan Inc.

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Dreamsniper

#22546

Moisture Sensitive Devices | 29 November, 2002

Thanks monette. Its been very helpful.

best regards,

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