Moisture sensitive devices - Page 1
Forum section: electronics / beginners

author: Back2Volts
author_rank: Unknown
timestamp: February 07, 2017, 06:58:42 pm
content: I purchased some LEDs from Mouserhttp://www.mouser.com/ds/2/143/EAPL2835WA4-967961.pdfand the bag came with the warning label.Should I be concerned for manual hot air mounting? What about the pieces I do not use immediately.If needed, I can post pic of label

author: tron9000
author_rank: Frequent Contributor
timestamp: February 07, 2017, 08:06:00 pm
content: I know the label your talking about: it has 3 blue circles of differing darkness?If you read the label, it should tell you what to do, like "bake parts at 200oC for 30 mins"Personally I ignore it if I'm doing my own work. But if your product is destined for consumer usage and demands high reliability, take heed.

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2017, 12:13:37 am
content: Yeah this sort of thing matters if you're loading $300K worth of parts onto a big batch of boards, especially if some of the parts are expensive, but for building stuff yourself? I've never had any issues at all. I think if it were a $50+ IC I would be tempted to bake it as suggested if it had been opened, but LEDs? Who cares, just solder them on, on that miniscule chance that one popcorns just replace it.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: February 08, 2017, 12:31:58 am
content: Your risk depends on your environment. I have seen enough popcorning that I wouldn't dismiss it out of hand. I saw that happening in southern Arizona which is quite dry most of the year, but moist for a few months. If you do a little googling on moisture sensitivity and popcorning you can get a lot of insight into how much exposure to moisture it takes to cause a problem and what kind of devices are most susceptible. Another thing to consider is that popcorning is similar to ESD damage in some ways. It often does not cause complete failure of the part, just a shift in operating parameters, elimination of a subtle function or a reduction in reliability. In some cases it leads to intermittent operation. How concerned you should be will depend on how sensitive your application is to the stated performance of the part.If you decide you are concerned the solution is easy. Just go to the nearest thrift shop and buy a cheap toaster oven. You should be able to find one for just a few dollars. Then bake to the appropriate recipe for the part. The data sheet for yours says 60 deg C for 24 hours (on page 19). That resets the clock on the parts (for 168 hours at fairly moist temperature conditions, again according to the datasheet.)As a final aside, this also applies to rework. If you are repairing a board that has been out in the air for a while you will have the least risk if you bake it according to the recipe of the chips that will be removed or affected by your desoldering process. That sometimes takes some creative thinking to combine the various temperature and time recommendations.

author: Back2Volts
author_rank: Unknown
timestamp: February 08, 2017, 05:08:25 am
content: Thank you guys. I will wait to open the bag until I am ready to solder them and just place the few extras in a zip bag.

author: Ian.M
author_rank: Super Contributor
timestamp: February 08, 2017, 06:03:24 am
content: Cut tape, minireel, or full reel?The reel is packaged with a desiccant sachet and the clock starts when you open the foil barrier bag.If its cut tape or minireel (repackaged by Mouser) and the bag doesn't have a desiccant sachet, they are already expired and *should* be re-baked as per datasheet before assembly. If there's a desiccant sachet in there they should be fine.A Ziplock usually doesn't form an effective moisture barrier - you need to keep it in a hermetically sealed container with an active desiccant, or re-bake the spares before use.