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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Moisture Sensative Components

#27145

Moisture Sensative Components | 5 February, 2004

To All, I am looking for some feedback on the storage and handling of moisture sensative components. Mostly what people do for tubes and reels since most of these cant handle more than 60c.the ipc standard states that they can be baked at 40c.The only problem is that it requires bake for 5 to 67 days depending on thickness.

Thanks in advance

MrMaint

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#27149

Moisture Sensative Components | 5 February, 2004

There is the IPC/JEDEC J-STD-033 that addresses moisture sensitive components. Go to http://www.ipc.org for the standard. Your factory/storage area environment will dictate exposure times allowable. Be mindful of temperature and humidity changes- like overnight, as heat goes down RH tends to go up. The most popular method is to use a vacuum re-sealer to re-seal the IC package (tray, reel or tube) bag to limit exposure. Baking is another option, but less desirable as you must be careful on the lead finishes so they do not over oxidize, especially if you are using no-clean solderpaste. Water-soluble solderpaste is able to de-oxidize way better than no-cleans.

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#27150

Moisture Sensative Components | 5 February, 2004

Pete C We do bake our tray parts. I am familiar with the ipc specs. The problem is for example: a level 4 component can only be out a total of 72 hrs before rebake is required. If this is a tube or reel part, the 125c bake temp that is recommended will melt everything but the component.The real issue is what to do with tube and reel components after they have reached their saturation point.According to ipc specs we would have to bake this reel at 40c for 67 days.This low temp is to ensure no melting or deforming of the tube or carrier tape. Thanks

MrMaint

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#27151

Moisture Sensative Components | 5 February, 2004

MrM, Yes, here in lies the dilemma � �who the heck has 67 freaking days to wait for dry-out!� The only real way is to remove said parts from their carriers and put them into something that can handle the higher temp. I've seen people using those N2 cabinets as well to keep components dry and from oxidizing. The best measure is to prevent exposure - re-seal bags or store in N2 cabinets.

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#27153

Moisture Sensative Components | 5 February, 2004

Even with the best of intentions, some lots of components just last too long. Recognize that controlled environment storage is only a delaying tactic. So when the piper come to play and baking becomes inevitable, we "repackage" components in tubes and reels that can stand high temperature baking and throw the low temperature tubes and reels in the dumpster.

Search for sources for high temperature tubes and reels in the fine SMTnet Archives.

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Doug D

#27189

Moisture Sensative Components | 10 February, 2004

We have developed a product called HumiTel which will help you manage MSDs. We will exhibit it at this years Apex. It should make things easier for you. Doug D

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Doug D

#27190

Moisture Sensitive Components | 10 February, 2004

We have developed a product called HumiTel which will help manage MSDs on the factory floor. We will be at this years Apex, come and see us, the product should help you out. Doug

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Kevin McCarten

#27191

Moisture Sensative Components | 10 February, 2004

1st thing to be said; I work for a company that supplies Desiccant Dry cabinets to the electronics industry for the storage of moisture sensitive components. The answer here really lies in inventory management/control. Ultimately you want to avoid baking where possible, and this can be achieved with some kind of tracking system (automatic or manual, but this will be a necessity) and a dry storage cabinet. IPC/JEDEC J-STD 033a states; �4.1.2 Short Duration Exposure Previously dry SMD packages, which have been exposed only to ambient conditions not exceeding 30�C/60% RH may be adequately dried by room temperature desiccation using dry pack or a dry cabinet.�

So by controlling the total floor exposure time components are permitted (dependant upon their MS Level) and utilizing a dry storage cabinet, you can avoid baking altogether.

One of the suggestions in the posts above was to use Moisture Barrier Bags (MBB) with a bag of silica gel desiccant. There are a number of thoughts/concerns that come up here.

1)How fresh is the desiccant that is being used? And how will you maintain and verify it's 'activity'? 2)Can you guarantee that the bags will not be punctured or otherwise sealed improperly? 3)What is the propensity of the component carrier to absorb moisture, and how much �unplanned� moisture is going into the bag with the carrier? 4)Personal thoughts on a vacuum sealer�. I�ve seen set-ups where you can practically scan the barcode through the MBB the vacuum has sealed it so tight, and I wonder how there is sufficient space/pressure for the moisture to defuse out of the component to be captured by the desiccant.

Desiccant dry cabinets are able to maintain an RH level of less than 1%, they auto recycle their synthetic desiccant to ensure that it is always at it's most active. They are basicaly a "plug in and forget" type of solution for this problem.

If you are interested you can find a number of resources on this topic of MSD storage and handling as well as (of course) product information on our website, which is; www.drycabinets.com

As one of the posters mentioned above; We will also be exhibiting at APEX this year (2004), our booth number is 1417, stop by and see us.

Hope this helps.

Kevin McCarten

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Ventrista

#27203

Moisture Sensitive Components | 11 February, 2004

An obviously commercial post like that deserves a little equal time from the competition. I beleive you'll find Seika USA pioneered this technology and sell a great product:

http://www.seikausa.com/mcdry/dxu1001.asp

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