Welp. Guess I'm not using this desiccant.
Bag melted all over my tray and leaked.
It said right on the pouch to recharge at 245F and that's what I had the oven set for :(
Welp. Guess I'm not using this desiccant.
Bag melted all over my tray and leaked.
It said right on the pouch to recharge at 245F and that's what I had the oven set for :(
Reballing fixture and 676 ball 1mm preforms came in.
I'll let the chip cook a bit more before reballing it as I'm not in a rush.
These are pretty cool and it's my first time using them although I've been aware of them for quite a while. Instead of using loose solder balls you just flux the entire chip and stick this preform on top of it then reflow upside down to attach the balls.
You then apply a bit of water to soften the carrier material and it comes off leaving perfectly positioned solder balls.
Definitely more expensive than doing it with a stencil and loose balls (I paid a few hundred bucks for the fixture and 25 preforms) but IMO worth it for salvaging pricier parts.
Ok, reballing time.
Quick visual inspection of the preform under the microscope to make sure nothing is missing. Looks good.
On the plus side I found another pack of desiccant in the office of all places. So i can still dry pack it.
After putting the preform in the fixture (ball side up) all I need to do is smear flux evenly across the lands on the package (no photos since my gloves were all sticky) and put the FPGA on top.
Then off to the oven.
Here goes.
I normally gauge BGA reflow by watching the solder turn shiny and the chip drop, but that's not possible in this setup.
So I squirted some SAC305 paste on a witness board next to the fixture and gave it about 45 seconds after that melted. Hopefully it was enough, we'll find out when it cools.
So apparently you shouldn't give your WES51 to kids under 3 because they might choke on it. TIL.
But if they're 3 it's totally fine, no worries of them setting the house on fire or anything.
@Lyude I made this over a decade ago and it's just as true today as it was.
I'm also going to experiment with putting a thermal pad underneath the DC-DC module in order to enhance heat dissipation from the underside of the module to the PCB.
The goal here is twofold: better cooling of the module (where almost all of the board's heat is generated), but also better thermal coupling from the module to the I2C temperature sensor, enabling more accurate self monitoring.
If things go well this should be the final module design, and I can go make a bunch of these to use for powering all of my future large instrumentation / networking projects.
Rev 0.3 of the 48V IBC board came in! Time to start assembling it.
This version has a few bug fixes like "thin trace where there should have been a fat plane" plus a dedicated low noise power rail for the shunt monitors, some lowpass filtering on the shunt outputs to remove the effects of ripple on the current measurements, and moving the 48V shunt out of the high dI/dt path.
On to my old nemesis from board rev 0.1.
I think I have it the right way around now? Pin 1 in the top left?
Solder paste print turned out fine. Not perfect, but more than adequate.
Placing the 48V current shunt resistor.
One of the prettiest resistors I've ever worked with (Ohmite LVK series). They're a little pricey but work great.
All done and going in the oven.
Me, in the middle of board layout: "Wow, that bypass cap is enormous. Did I accidentally grab a bulk cap or specify the wrong footprint or something?"
It was an 0402.
I can't be the only one who thinks this.
Given the circles I run in, often both meanings are equally plausible at first and I have to stop and think.
The now-very-crowded optics bench. I definitely need to spend some time over Christmas vacation tidying up the lab.
Absorbance spectrum (in ngscopeclient) of fluorescein based highlighter. Note negative absorbance at the 517nm fluorescence peak.
Getting ready to do a test run of my probing class for my first in person beta audience.
This will be my second test run of the lecture (first was a YT livestream a year or so ago) and the first time doing the labs.
There's still more meat I want to add especially towards the end of the class (e.g. the section on current probing is just a handful of slides, and there's no lab for it yet as i don't have any current probes here) but it'll be good to get feedback from a test audience on pacing and content.
Probably going to do at least one more test round early next year before I start doing it officially. Looking into getting registered with IEEE to provide approved continuing education / professional development hours as well.
Most of the board is just padding, to bring it up to OSHPark's minimum size for a flex PCB.
After hand depaneling with a pair of scissors and a scalpel, I get this, Might even trim a bit further.
Security and open source at the hardware/software interface. Embedded sec @ IOActive. Lead dev of ngscopeclient/libscopehal. GHz probe designer. Open source networking hardware. "So others may live"Toots searchable on tootfinder.
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