EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: blueskull on October 07, 2017, 01:36:10 am
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As the title stated, is there a particular recommendation when handling very old chips? Talking about date code 2010~2011 (LM393N and LM3671-ADJ from NSC, not TI).
Packages are all DSBGA bare chip, MSL1.
These don't come with desiccant nor humidity card, but since they are MSL1, I guess that's not a concern, right?
I never expect they are such old, I thought and gambled I would get some newer chips, though I knew I was buying overstock.
What kind of solderability should I expect? What kind of reliability should I expect? These are not cheap (totally 800+ chips) and I don't want to scrap them.
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As long as they haven't been stored in any adverse environmental conditions, I would simply ask: How do the solder points look?
I can't say anything more, since I've never worked with this package.
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So what you are really asking, is how to check or restore solderability, after exposing chips to HCl vapor?
Ouch. Bringing corrosive vapor emitting anything even into the same room as electronics is a bad idea. Guess you won't be doing that again.
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So what you are really asking, is how to check or restore solderability, after exposing chips to HCl vapor?
That was not what was said.
The story was offered in response to my comment about "adverse environmental conditions" - the point being that at that time those chips that were involved - which were stored still sealed in a tape reel - emerged unscathed. The inference being that these chips have also been stored still sealed in a tape reel ... and that such storage might offer significant protection from the environment.
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Lol, 2010 chips...very old? :-DD
I've used chips from the 70s and 80s that have been sitting fully exposed in a box in someone's basement/garage/whoknowswhere for decades and they still work fine. Just use a bit of extra flux and they'll be fine. :-+
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Lol, 2010 chips...very old? :-DD
I've used chips from the 70s and 80s that have been sitting fully exposed in a box in someone's basement/garage/whoknowswhere for decades and they still work fine. Just use a bit of extra flux and they'll be fine. :-+
That was my thought, too - I have a bunch from the mid 80s when I worked at National; they lived downstairs in my darkroom/workshop till about 2011, then migrated to the crawlspace behind the boiler during the house renovation.
Kids these days! :-DD
;)
-Pat
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Only thing that is bad about old chips is when they were stored in some moist place (basement, cellar....) and you decide to solder them by hot air => water expands inside the epoxy and you get popcorn. Same can happen with old PCBs, too. To prevent that, bake them in a oven at around 120°C for like 24h, so that the water can evaporate from the inside.
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Lol, 2010 chips...very old? :-DD
I've used chips from the 70s and 80s that have been sitting fully exposed in a box in someone's basement/garage/whoknowswhere for decades and they still work fine. Just use a bit of extra flux and they'll be fine. :-+
For personal projects or as a last resort? Sure. But sending it out to a customer?
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Drying them is easy as stated, and totally eliminates one of the two big risks. May or may not be necessary, but the only downside is a one day delay and lack of access to some oven for a day. You should be able to evaluate solderability with a microscope, or in the worst case, with a sample run.