In general which parts do you keep low humidity for baking? - Page 1
Forum section: electronics / projects

author: alank2
author_rank: Super Contributor
timestamp: March 23, 2015, 06:16:09 pm
content: Hi Everyone,In general which parts do you keep low humidity for baking?Thanks,Alan

author: Corporate666
author_rank: Unknown
timestamp: March 23, 2015, 06:34:00 pm
content: Usually those that come in sealed containers with dessicant packs and humidity indicators.Having said that, the ONLY components I've had issues with at Atmel microcontrollers in SOIC-8 packages. I get about anywhere from a 5% to 50% failure rate during reflow depending on how they are stored.Even if I stick to the recommended JEDEC profile and place/reflow them right out of the dry package, I still get about a 5% failure rate.Other MCU's and other brands I never have issues with.

author: Niklas
author_rank: Frequent Contributor
timestamp: March 23, 2015, 07:51:18 pm
content: Check the datasheets for Moisture or MSL ratings. MSL 1 is supposed to handle unlimited time without control, but paper tapes on reels might deform. MSL 2 and higher have limited time outside controlled atmosphere. We have an STM32 that has MSL 3 rating and that is stored in a dry cabinet with a log book for exposed time.

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 24, 2015, 12:49:51 am
content: A connected question. A data sheet I'm looking at does not have a MSL number, but it does have "Packing: Non dry". How would that translate to a MSL number ? The device is a Dual N-channel Small Signal MOSFET.

author: alank2
author_rank: Super Contributor
timestamp: March 24, 2015, 02:08:55 am
content: Quote from: Corporate666 on March 23, 2015, 06:34:00 pmDoes that mean you don't worry about keeping the other components in a low humidity environment and they are mostly fine?I'm thinking about all the resistors, capacitors, and other small parts I keep in one of those smd parts boxes. My home is probably usually 30-40% RH, would it only be the larger ic's you have had trouble with?Thanks,Alan

author: Monkeh
author_rank: Super Contributor
timestamp: March 24, 2015, 02:25:57 am
content: Resistors are a chunk of pretty much impervious ceramic with a layer of metal on the top. Ceramic capacitors are.. a chunk of ceramic.

author: Corporate666
author_rank: Unknown
timestamp: March 24, 2015, 12:51:25 pm
content: Quote from: alank2 on March 24, 2015, 02:08:55 amI do not keep...-Resistors-LED's-Diodes-FET's and transistors-Capacitors-Switchesin dry storage. Some of the parts, especially LED's, do come with dessicants and moisture indicators, but out of millions of LED's used over the past 10 years and stored in anything from unopened silver vacuum packs to stored in open air (for weeks or months at a time) in all weather ranging from humid to dry, hot to cold, I have had fewer LED's fail than I can count on one hand. With the transistors/FET's, I have the large size reels hanging off the pick and place and sometimes it will take a whole year to use some specific part, and again I've never had one fail.For parts like MCU's or other IC's, I try to generally keep them stored correctly, although again sometimes reels will sit on the PnP machine for days/weeks. The only part I've had an issue with is Atmel ATTINY chips. To the point that even when storing 'by the book' and following the JEDEC reflow profiles, I still get around a 5% failure rate. I even sent some back to Atmel for decapping and they blamed popcorning and our reflow profile or incorrect storage - which is bullshit, as sometimes my chips have shipped directly from Atmel to me and they failed during reflow even if strictly kept within JEDEC rules right from the time the package was opened.I have many hundreds of those little plastic tubs with everything from LED drivers, LED's, Op-Amps, shift registers and FETs to esoteric components that I bought for some specific project. Some of them have been in those tubs for 5+ years through all seasons and temperatures/humidity, and I've never had something fail that I remember when putting together a prototype board either with hand soldering or reflowing.

author: Gribo
author_rank: Frequent Contributor
timestamp: March 24, 2015, 01:13:35 pm
content: Certain sensors require non dry (>10%RH) environment, especially humidity and gas sensors.

author: alank2
author_rank: Super Contributor
timestamp: March 24, 2015, 01:31:13 pm
content: Quote from: Corporate666 on March 24, 2015, 12:51:25 pmThat is what I was looking to find out, thanks. Basically just IC's with some body to them then. I've reflowed maybe 25 tiny1634's and haven't had a problem, even for some that were stored in a parts box loosely for a couple of months.It sounds like there was something wrong with those soic's - did you try to dry any of them out using their technique of 48 hours at 105 or something?Thanks,Alan

author: Corporate666
author_rank: Unknown
timestamp: March 24, 2015, 06:22:05 pm
content: Quote from: alank2 on March 24, 2015, 01:31:13 pmI don't have a drying oven or want to invest in one just for that one part, not to mention I've received parts directly from Atmel sealed in original containers that were supposed to be appropriately dry and the issue still happens, around 5% bad. This has been going on for 10 years over hundreds of shipments from dozens of different batches of chips, although it is much worse with the thinner SOIC package in the ATTINY13A (-SSU or -SS7 suffix, IIRC).I have ATMega chips stored in plastic tubs for years and reflow them and never a failure. I have Cypress MCU's in SOIC, QFN and TQFP that I've had open for years also without any probelm. It is singularly the ATTINY's I have issues with.But @ 10,000 per year, 5% bad is only about $200 per year in extra cost, so it's not something I really put all that much thought into beyond considering Atmel to be a shit company with shit customer service and not designing their shit parts into my products anymore. Their loss.

author: alank2
author_rank: Super Contributor
timestamp: March 24, 2015, 06:26:18 pm
content: Quote from: Corporate666 on March 24, 2015, 06:22:05 pmYou sound like you've made up your mind.I appreciate the information!

author: Corporate666
author_rank: Unknown
timestamp: March 24, 2015, 10:59:02 pm
content: Quote from: alank2 on March 24, 2015, 06:26:18 pmYeah, it's just bitterness over the quantity of incidents we've had with their products and how they handled them. I've never dealt with a more "we don't give a shit" group of people than those at Atmel. And I'm easy to please and have had wonderful interactions with probably over a dozen other suppliers - Atmel stands alone in their utter lack of giving a shit about their customers. But that's just meGood luck with your projects... hope the info was helpful.

author: alank2
author_rank: Super Contributor
timestamp: March 24, 2015, 11:59:37 pm
content: Quote from: Corporate666 on March 24, 2015, 10:59:02 pmIt was - you answered exactly the question I had - thank you.