Handling old chips - Page 1
Forum section: electronics / general

author: blueskull
author_rank: Unknown
timestamp: October 07, 2017, 01:36:10 am
content: 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.

author: Brumby
author_rank: Unknown
timestamp: October 07, 2017, 01:58:46 am
content: 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.

author: TerraHertz
author_rank: Super Contributor
timestamp: October 07, 2017, 02:43:47 am
content: 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.

author: Brumby
author_rank: Unknown
timestamp: October 07, 2017, 03:21:36 am
content: Quote from: TerraHertz on October 07, 2017, 02:43:47 amThat was not what was said.The story was offered in response to my comment about "adverse environmental conditions" - the point being thatat that timethose chips that were involved - which were stored still sealed in a tape reel - emerged unscathed. The inference being thatthesechips have also been stored still sealed in a tape reel ... and that such storage might offer significant protection from the environment.

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 07, 2017, 04:17:04 am
content: Lol, 2010 chips...very old?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.

author: Cubdriver
author_rank: Unknown
timestamp: October 07, 2017, 05:40:19 am
content: Quote from: Cyberdragon on October 07, 2017, 04:17:04 amThat 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!-Pat

author: MadTux
author_rank: Frequent Contributor
timestamp: October 07, 2017, 11:37:08 pm
content: 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.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 07, 2017, 11:50:04 pm
content: Quote from: Cyberdragon on October 07, 2017, 04:17:04 amFor personal projects or as a last resort? Sure. But sending it out to a customer?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: October 10, 2017, 02:40:06 am
content: 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.