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I've been given the task of verifying a batch of ICs from a chinese broker, to see that the chips the company has bought are what the broker claims they are. The package we've received looks like this, and has this statement (amongst others) on it:

  1. "Parts should be used within 5 days after opening".

Why is this recommendation given? The shelf life of the ICs has to be much greater than 5 days right? And how critical is it for me to follow this statement?enter image description here enter image description here

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    \$\begingroup\$ That doesn't start until you open the seal... if it stays sealed it'll be good for a few years. The fact that you need to test samples from the batch long in advance of your production runs makes you responsible for the storage environment. The packaging is optimized for feeding large quantities into automated pick-and-place machines, not for using slowly over time. (For that, you'd want separately sealed short tapes of ICs... and then you'd still be rightly concerned that not all packs contain the genuine product) \$\endgroup\$
    – Ben Voigt
    Apr 25, 2023 at 23:16

3 Answers 3

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The parts can survive well beyond 5 days. However, the component is moisture sensitive. And if you don't store it well (in a well-controlled environment), it could cause SMT assembly issues such as dry soldering.

There are other methods that you can use if you have to use if after a prolonged period post opening the package to reduce such assembly issues. A common method is to do baking where you keep the component in a special oven at a set temperature for a certain duration. Temperature and duration depend on components. This can reduce the number of failures during mass manufacturing.

If you want to use it for prototyping using manual soldering, the impact will be less but if you are planning to use such components for mass manufacturing at an EMS, then better to consume fast once the package has been opened.

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  • \$\begingroup\$ As I understand it, it's not so much the component that is moisture-sensitive, but the soldering process. Components are shipped in a moisture-sensitive way because the moisture-sensitive soldering process (reflow oven) is by far the most common one. \$\endgroup\$ Apr 25, 2023 at 22:22
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    \$\begingroup\$ Moisture is absorbed by the package and then during soldering that moisture expands and can cause “popcorning” damage to the IC. See J-STD-033 for helpful background and information. If you don’t use the parts within 5 days you simply bake them at a temperature and time to remove moisture, then your 5 days restarts. Or, store them in a low humidity environment such as dry nitrogen. Counterfeit parts are rampant. You can x-ray and electrical test and compare to known golden units as first steps. \$\endgroup\$
    – 65Roadster
    Apr 25, 2023 at 23:22
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It's to do with Moisture sensitivity. When the components were packaged, there were done so in a controlled environment, particularly with regard to humidity (or lack thereof, you can see that bag was packaged at 20% which is pretty low). When you open the bag, the components are exposed to the humidity of your working area (which varies a lot, but my UK house is usually 50-70%), which probably isn't controlled to the same level.
Once this has happened, moisture gradually begins to enter the device, from the atmosphere. When you then assemble the boards,if you use an oven the package will be exposed to 200+ degrees, hand soldering presents much less of a risk. If excess moisture has entered the device, this change in temperature can cause damage as the moisture expands.
One mitigation is to simply bake the parts at a lower temperature prior to assembly to gradually remove the moisture.

https://en.wikipedia.org/wiki/Moisture_sensitivity_level#:~:text=Moisture%20sensitivity%20level%20(MSL)%20is,handling%20precautions%20for%20some%20semiconductors.

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    \$\begingroup\$ There should be a moisture-indicating card in there that will tell you if you need to bake the parts as it is a function of humidity and time. You can extend the shelf life by placing them in a sealed container with a bunch of desiccant packs (leave the card in there with the parts). There are specialized cabinets for keeping these parts dry; seeing as you have ~$5000 of parts on that reel, it might be a prudent investment. \$\endgroup\$
    – vir
    Apr 25, 2023 at 17:24
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I expect the original manufacturer should provide MSL Ratings and Reflow Profiles. See https://www.ti.com/lit/an/spraby1a/spraby1a.pdf as an example from Texas Instruments which:

This application reports explains the relationship of MSL rating to the customer production floor life and surface mount reflow temperatures for TI semiconductors.

65Roadster has already provided a reference to J-STD-033 for helpful background and information.

The above TI application report also references:

STD-020D.1: Joint IPC/JEDEC standard for moisture and reflow sensitivity classification for nonhermetic solid state surface-mount devices

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