|Ask the Experts|
June 13, 2019
Moisture Sensitive Components in Flooded Storage Facility
A storage facility was flooded and 10.000 packages of SMD/SMT electronic components and materials were exposed to moisture over 85% RH for several days. For high quality reasons the plan is to discard all these components. Is this the best solution? Do we have any alternatives?
|Expert Panel Responses|
Short answer, there are probably alternatives. Whether they are worth it depends on the value of the components, including their logistical value (may be low cost, but long leadtime). If stored properly in MBB (Moisture Barrier Bags) the high RH over the short term should have no impact on the components inside the bags. Biggest concern would be fungal growth on any outer packaging.
If not stored in MBBs, that's another matter. For parts that have MSL > 1, either they need to be baked, or discarded. Baking may have an impact on solderability particularly if the solderability was marginal to begin with. The high moisture environment can also encourage oxidation (micro-layers of water are present on surfaces at humidities > 85%). If the part cost is low enough and replacements can be obtained, then it's probably best to discard and replace any parts not stored in MBBs.
I'd take the approach of assigning risk level based on part cost/availability and MSL, recover what is easily recoverable with low risk, and also attempt recovery of components that are very high cost and/or difficult to replace, then discard the remainder.
I would ask the component manufacture. I know you can bake a lot of the different components in a convection standalone oven to remove the moisture. This is a common practice for some components. The amount of time and temperature used should be described by the manufacture of the part(s). In some cases, this might not be required. The component manufacture would have to provide this information.
Sr Fiald Applications Support Engineer
A possible solution is to bake the components in an nitrogen atmosphere at 100 deg. C for about 2 hours. Then run some of the components in their reflow process and see if they will survive the reflow regime.
Global Segment Manager
Air Products & Chemicals, Inc.
Depending on the MSL level, they could be baked out. This bake would take dedicated ovens potentially many weeks. This would reset the clock for floor life, but still would not address potential corrosion / oxidation issues. You will need to decide if the cost of the components outweighs the cost of baking and potential solderability issues in the future.
M.O.L.E. Line Product Manager
Electronic Controls Design, Inc. (ECD)
Unless the moisture exposure has damaged the component or the packaging mechanically or aesthetically, or there was direct contact between the component and the water that may have contaminated or oxidized the components leads, they can be "recovered" per the IPC.
J-Std-033 has a provision for "baking" the moisture from components whose exposure has exceeded the "floor life" time, which is a function of the component's Moisture Sensitive Level (MSL). The bake times and temperatures are listed in Table 4-1 of the standard, and it varies from hours to weeks, depending on the MSL of the component and the chosen bake temperature.
Now the value of the component, and the cost in time, effort and energy needed to "bake" them should be considered as well. It simply may not be worth the cost to bake some of the components. And since oxides have likely started on some of the component's leads, even after baking to clear the moisture from their interior, care should be take when soldered to make sure soldering is not affected, which may be as simple as using a different (more aggressive) flux/paste.
Senior Project Engineer
Electronic Controls Design Inc
The best thing to do would be to contact the component manufacturers for their recommendation.
If they do not provide a solution, you can try baking the components. But that would be quite a task to bake 10000 components.
Technical Support Engineer
Component use after plant is flooded and parts are over the 60 RH limit for 36-48 hours is usually the specification most abide to. As long as the components are not soaked in water humidity is still an issue yes but is usually fixed by drying in a vacuum drying oven for 24 hours at 125c or 36 hours for 36 hours. These are sold by oven manufacturers or failure analysis labs usually have them and can offer that service. Humidity when related to rework.
When Pcb's which are built come back to united states to be reworked at rework contractors or OEM's. these Pcbs are subject to similar issues if from Asia or Mexico. Asia humidity can be similar up to 90% at certain times of the year or Pcbs are stuck in trucks or in sea freight waiting to be shipped.
These are commonly dried to 100c for 8 ours but components are soldered to PCBS so slightly different specification as they can also be shipped in desiccator protected bags. Drying these parts should be Ok but tested by functional tester such as burn in tester to be sure its safe is my recommendation.
Advanced Applications Manager
OK, so we know that these components were exposed to excessive moisture for an extended period of time. My belief has always been rather be safe than sorry.
I cannot imagine how much baking time would be required to bring these components to a safety level acceptable to either your client, if you are a CM, or to your own spec if you are an OEM.
Hopefully you were fully insured because my opinion is take the money & run!
As the material were not stored in ambient condition for several days, It's always advised to discard such components, as those components will have observed too much moisture, which could lead to internal cracks, oxidation problem effecting solderability & reliability of product at later stage.
When a material exposure time exceeds the time stated on the Humidity Control Card, most industry refer J-STD-022 & J-STD-033 standard, but in this case the components are stored and packed in good conditions. Also, whether to use it or not will all depend on the application you use.
Don't discard. If they were in desiccant bags, you should expect no impact. And then there is option of baking. It is a little complicated subject but discarding these components should be considered only after you have explored some other options.
Ray Prasad Consultancy Group
From your question it appears that the components were not submerged with the flood waters. If this is the case then they may be salvaged by washing in a mild alkaline soap if no corrosion is present.
I have been contacted by companies over the years that have tried to salvage complete PCB assemblies that have had flood damage. Most of the time it is an exercise in futility.
Flood waters are filled with many types of pollutants. The enormous amount of storm water will overwhelm treatment facilities, washing chemicals and toxic substances into the mix, including raw sewage, crude oil, and pesticides. Personally if I were in your situation I would settle with the insurance company and discard them.
Technical Expert Sales Support
If the parts were flooded (e.g., exposed to 100%RH for several days via immersion under water) then my recommendation is to discard/destroy the parts permanently. A component risk mitigation strategy to salvage these compromised parts contradicts your "high quality" statement.
VP of Advanced Technical Operations
Your recommendation to discard the components is the best solution from my perspective. Exposure to high moisture will impact the solderability of the component, and will also be detrimental to the functionality of the components. The porosity of the component body may have been compromised and moisture within the component body would create problems during the reflow process.
This was found and documented during the introduction to the surface mount process back in the 80s. Depending upon the construction materials of the components, the moisture would change phases from a liquid to a gas, increasing the pressure within the component and during reflow process and would blow the bottoms (i.e. destroy) of the components reducing their reliability to another degree.
Using analogies, I would not buy a used car from Houston anytime in the near future and I would not buy those components. I would also suggest getting in touch with your insurance company as these may be covered under one or your company riders.
Vice President, Technical Director
Depending on the physical condition the components are in, a baking process might alleviate the moisture intrusion in the parts. Also for excessive oxidation (if that occurred) you might look at re-balling the BGAs and re-tinning the leaded components to avoid reflow issues (incomplete soldering, wetting issues, voids, contamination).
The analysis will have to be done case specific for each component as the baking times and temperatures will vary based on component structure.
Engineering and Operations Management
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