This is about assembling five PCBs yesterday that shared an IC and how, despite meticulous application of solder paste, reflow profile, yada yada, two of five didn’t pass FAT (final assembly test via a simple computer program and microprocessor). Late in the day a little light bulb glowed with faint neon letters spelling “popcorn.” This is the slang for when trapped moisture in an IC explosively changes to steam in the reflow oven, physically damaging the part. The part in question had been away from desiccants for months, the humidity in the shop is far from Arizona levels, etc. I don’ t have the equipment to determine if this damage happened, the budget involved can’t cover sending the board off to be studied, etc, so I just have to assume this is a “maybe” cause of my failures.
So I followed the specs for “baking out” the moisture and set up these chips with some others that need to stay dry or be in line for baking out and thought I’d share a snapshot. (Click on it to get a better version, and click on that for full resolution. The inner card color dots are distorted: they are actually blue). You know how we get desiccant bags and moisture card from places like DigiKey and toss them? I saved enough over the years to combine them with a cat treat container and Indian sauce jar to make a two level dry air environment. All the bags and some of the chips went through the bake out process (I used 125C for 12 hours). The outer card will let me judge how well the cat treat container lid fits and the same for the card inside the sauce jar with its tighter lid. Access is pretty easy and there is room for a “next gen” larger inner container down the road. The parts are in plastic boxes with labels facing out so I can quickly determine what’s there, and a few notations are on the box stickers to indicate their status wrt baking. (My parts database uses US town names starting with “A” for containers, thus the “AMORY” sticker).
I’m assembling several more of the same PCBs today and it would be nice if Whammy Central allows for pop-corning to have been the cause and the new boards to all pass FAT!
Years ago at one point I had maybe 200 cores of Sun Microsystems servers searching for gravity waves several days at a time through out the year as part of the “LIGO at home” project. Our Java release tests ran in waves and I could borrow the machines to use the troughs to crunch on this project.
Now there’s “Folding @ Home” that is for doing the very hard work of figuring out protein details or other life science computing, and apparently there is some work going on relevant to the virus pandemic. The link below is to an article about this and it contains a link for taking part in the last sentence. If this works the way the LIGO one did, the app automagically gets out of the way of you using your PC, such as running when the screen saver is active. I suspect it’s even more flexible now. So consider donating a bit of energy with your PCs to pitch in and make this go faster.
NC State, Centennial Campus Engineering Building One, Room 1007, 911 Partners Way, Raleigh, NC 27606 (same as IEEE/robotics/TAR meetings through May) Monday, Jan 13, 7-9PM. A map for finding the meeting and additional details here: https://triembed.org/meetings/at-ncsu/Agenda:
Problem of the Month: Paul MacDougal
Presentation: Charles Lord, an area embedded development professional and expert instructor, will go over RTOS fundamentals as well as providing heuristics and guidelines to help answer the question of how much "real time behavior" you need. (Charles will be giving a presentation in February too: stay tuned for details)
Show and Tell and general discussion: Including examples of two new OSH Park PCB service offerings to be passed around for close inspection: do it yourself, pro quality flexible PCBs and clear solder mask over ENIG traces on a black substrate (so cool you should bring your shades to look at it!) Also, you can see their latest improvement over the old "mouse bite" tab routing that is being delivered more and more often.
Door prize giveaways: Protocol highly variable!
(Prospective donations for the giveaway box always welcome!)
The Hakko FR-300 is a wonderful tool, but it does a very poor job of bending the unsoldered tab of a through hole potentiometer. While bending the tab forward the thought was clearly in mind “this is dangerous”. The tool slipped and while it was on the way to finger said finger was being withdrawn from the scene at warp speed, but not fast enough. You can even tell what size hole the tip fits.
(OK, I say tomatoe; my wife says tomahto. But out of respect, we don’t say we use Lienix, or Pythone, right? Although it took from 1991 to the late 90s, we did eventually stop saying Lienix, Leenix and Linooks.)
Chris Gammell, the expert interviewer half of The Amp Hour and long time KiCad supporter, organized a fantastic first KiCon conference in Chicago. Chris conducted some execellent interviews, including one of some of the KiCad developers, including project lead Wayne Stambaugh. Wayne is now employed full time to develop KiCad, a new milestone for this tool that seems to be on track to become the gcc of PCB CAD in coming years.
LoRaWAN™ – a Low Power Wide Area Network (LPWAN) specification intended for wireless battery-operated Things in a regional, national or global network. Join us as Charles Lord reviews the elements of LoRa and LoRaWAN, the advantages (and disadvantages) of this protocol, and the tools we need to develop IoT solutions that use LoRa – including building your own LoRaWAN hub. Charles will do a demo and show some examples of ways to build your own LoRa network for fun or commercial use. We will also look at how we can build our own LoRaWAN gateway using an inexpensive kit for both development and for deployment where a local LoRa provider doesn’t exist – and how to interface where we do have providers – like in the Triangle!
Charles J. Lord, PE is an embedded systems consultant and trainer with over 40 years’ experience in system design and development in medical, military, and industrial applications. For the last twelve years, he has specialized in the integration of communication protocols into clients’ products, including USB, Ethernet, and low-power wireless including ZigBee, 6LoWPAN, LoRa, and Thread.
The presentation slides are now in the meeting archive here.
Many different kinds of microbial metabolic processes generate free electrons that can be harvested, either to enhance activities like water treatment or hydrogen production or to be a source of electrical energy.
Join us at the next TriEmbed meeting to find out how simple-to-make microbial fuel cells can be used to power embedded systems for truly remote sensor applications.
As well as seeing the presentation, you’ll be invited to join in a brainstorming session to invent and explore different solutions to a practical problem involved with a specific project. There will also be a raffle for IOT and other gadgets and gizmos and embedded development supplies from the giveaway box. The last part of the meeting will be devoted to show and tell and general discussion.
In a recent edition of the Embedded FM podcast, you can listen to ideas for projects from a fire hose. This is a concentrated and amplified version of the sort of ideas regularly floated, discussed, and demonstrated every second Monday night in one of the NCSU engineering buildings during monthly Triangle Embedded Interest Group (TriEmbed) meetings.
If you’re a student hoping to find a killer internship or permanent job doing embedded development this summer, check out TriEmbed. Details are under the Meetings dropdown menu above.
We look forward to seeing and getting to know you there.