Effect of moisture to IC - Page 1
Forum section: electronics / beginners

author: vaualbus
author_rank: Frequent Contributor
timestamp: December 02, 2014, 11:32:09 am
content: Recently I have mad sample request from maxim and take the max 5889 high speed dac. Today the sample is coming and the component is in antistatic bag and antic moisture bag. Now my question is how a ic can be moisture sensitive?Best regards, Alberto

author: Codemonkey
author_rank: Regular Contributor
timestamp: December 02, 2014, 11:36:27 am
content: The package can absorb moisture over time, then when the device is put through a reflow oven, the moisture boils out quickly and can cause the package to pop (known as popcorning). The problem can be avoided by baking the devices in an oven at a lower temperature over a longer period to drive the moisture out.

author: Wilksey
author_rank: Super Contributor
timestamp: December 02, 2014, 11:39:36 am
content: This is more for manufacturing, if you are hand soldering the part then I can't say I have had any issues.Having said that I have parts that have been opened for months, in the anti moisture bags, the litmus card has gone all sorts of shades, but they still reflow perfectly well, luck of the draw I guess.Depends on the environment, they have to warn you for worst case I guess, if it is kept in a relatively moisture free environment then you might not have an issue.When you send the devices to a CEM or if they buy them in and stock them, they would probably have humidity and temperature controlled storage for parts of such sensitivity.

author: Falcon69
author_rank: Super Contributor
timestamp: December 03, 2014, 06:23:45 am
content: I had thought about this as well. Last year, I ordered a bunch of 0603 LED's, and they also came in moisture sensitive packaging. Last month, I placed an order for some Schmitt Triggered Inverters, and they too came with the moisture sensitive packaging. I often wondered why?But this clears it up and makes sense. But, why wouldn't all the chips come that way then? Is there room for moisture to build up only in particular chips? Meaning, areas of air (or just open space) inside some IC chips and LED's that when moisture gets inside, they can pop like and ant under a magnifying glass? (FYI, I use to LOVE sitting on a park bench and do that in the middle of summer as a kid. Am I evil?)

author: coppice
author_rank: Super Contributor
timestamp: December 03, 2014, 06:37:03 am
content: As others have said, the package is affected by moisture. However, a much bigger effect of moisture is corrosion of the leads. ICs come with a use by date. That date is based on the expected worst case rate of lead corrosion within the supplied packaging. Beyond that point soldering becomes increasingly less predictable.All semiconductors and most passives are packed in moisture resistance packaging of one sort or another at the time of manufacture. If you have received devices not packed in this way, someone has removed the packaging. When you get small quantities this often happens.

author: Falcon69
author_rank: Super Contributor
timestamp: December 03, 2014, 06:47:38 am
content: ahh,Didn't think about the corrosion problem with leads. Makes perfect sense.

author: KJDS
author_rank: Super Contributor
timestamp: December 03, 2014, 09:24:52 am
content: I've worked in a place where the IC storeroom was sealed and filled with dry CO2

author: doctormord
author_rank: Regular Contributor
timestamp: December 03, 2014, 09:42:31 am
content: Quote from: coppice on December 03, 2014, 06:37:03 amNot all, depends on the moisture level, structure size, case size, case material etc. Packages with thermal pads are more sensitive to this.Corrosion, at most, is not an issue, that's what the flux is used for. (To break up passivation)Regards,Christian

author: coppice
author_rank: Super Contributor
timestamp: December 03, 2014, 11:01:12 am
content: Quote from: KJDS on December 03, 2014, 09:24:52 amWhy CO2? Isn't nitrogen more common for this?

author: Codemonkey
author_rank: Regular Contributor
timestamp: December 03, 2014, 11:11:40 am
content: Quote from: 3roomlab on December 03, 2014, 10:41:23 amI've seen it happen on a batch of boards that were not stored correctly / used outside of their "use by" date. It didn't happen to them all, but enough that we had to investigate the issue. In our case it was obvious since it was the PCB itself that was affected.

author: KJDS
author_rank: Super Contributor
timestamp: December 03, 2014, 11:53:51 am
content: Quote from: coppice on December 03, 2014, 11:01:12 amPossibly nitrogen, it's a long while ago and I never got that close to it.