Screaming Circuits: October 2012


Let's Get Small, as in 0.3mm

Not long ago, I wrote about a 0.3mm pitch wafer scale BGA we received and were asked to place. The gist of that article was that those parts are very small and we d0n't yet have a process that we feel will give the quality, reliability and consistency that we want to deliver. That means officially, we don't, at the moment, support that form-factor.

However, as it turned out, we went ahead and built it and the x-rays all said it looked good. Whew! We still don't officially support it, but we're working on it. If you have one of these things, you can always give us a call and see if it's something our manufacturing engineers are comfortable with. If they say "sure, send it in", It will be a non-standard, essentially, experimental, operation so our normal guarantees won't apply. It will be "we'll do our best."

But that's not the point. The point is that there are still a number of unanswered questions with 0.4mm pitch, and now we have a smaller one??!!

I've only seen 0.3mm pitch in two places: some data from Amkor, and the data sheet for this part.The part in questions is a Maxim MAX98304 Mono 3.2 Watt Class D amplifier. The entire package is just 1mm x 1mm.

There is still a lot of difference of opinion on solder mask defined (SMD) vs. non solder mask defined (NSMD) at super small pitch like this. For BGAs 0.5mm and lager, the general consensus and IPC recommendation is NSMD. At 0.4mm, the Beabgleboard folks at Ti recommend SMD to reduce bridging. But I've had other folks say they get good results with NSMD. For 0.4mm, we've had best results with SMD. It's more than just that though, you also need to religiously follow the manufacturer's recommended pad sizes and such.

Shrinking BGA pitchFor this part, the datasheet shows the pad size (0.18mm), but doesn't cover the SMD vs. NSMD question. Instead, it refers to a Maxim app note (#1891) for that bit of information.

Of course, this is where it gets sticky. That app note, as of this writing, shows 0.5mm and 0.4mm, but no 0.3mm. It does reference IPC-7351, which is a very good thing, but I don't think IPC-7351 has 0.3mm pitch covered yet. Ugh. The 0.3mm part we placed used SMD pads.

Duane Benson
It's not just Facebook where you can designate something: "It's complicated."

 

Would You Like Parts With Those Frys?

In days of yore (last month), the PCB design process would more or less start with the schematic. (I'm ignoring all of the work that has to take place before the schematic) The bill of materials would typically come together during the schematic phase and get refined during PCB layout.

After that, it would be time to enter your bill of materials, a line at a time, into a parts website, upload your Gerbers to Sunstone Circuits for boards and then (hopefully) send the boards, parts and files to Screaming Circuits for assembly. If you're hand soldering, you might skip the last step. We hope you don't, but certainly understand if you do.

But here's something new:

At the Screaming Circuits website, you can now quote and order all three in real time.

  1. Quote the assembly labor
  2. Quote the cost of Sunstone PCBs
  3. Upload your BOM and quote parts

If it looks good to you, you can place the order right then and there. Of course, we still have folks to talk things through on the phone if you have questions or need non-standard services, but if you like what you see, it's a real quote and real order. No waiting for an email quote back. No going to three websites.

As always, we’ll happily build as few as one board or up into the thousands (or hundreds of thousands in our EMS division). Once we have your parts and boards, we can assemble it all in as little as one day.

BOM quote confirmation screen

 

Sharing With Sunstone

Sharing is what our partner Sunstone Circuits would like today - sharing your stories. We've been partners with Sunstone Circuits for a very long time. When we purchase boards turn-key, we go to them first. They even build a fair number of the boards that we don't personally order. We can tell by the labels on the boxes on our receiving dock.

Naturally, when I had some projects to build, (like this one) I went to Sunstone for PCBs. I've run a few other projects with their boards as well. The reason I bring this up is that they are running a design story contest right now (stories.sunstone.com). It looks to be a fun way to run a contest and you can make a game of it. They want you to submit a story involving their PCBs, share it and get your friends to vote for it. The contest ends December 16 of this year, so if it's the year 2015 and you're reading this in the archives; too late.

Personally, I would recommend that everyone vote for my story, except that I haven't submitted it yet. And, if I do end up submitting mine, I'll be like a third party candidate and steal votes from one of the true contenders. Being a Sunstone partner, I wouldn't be eligible for a prize, but I could still upset the whole balance of promotion by grabbing votes that would otherwise go to a more worthy candidate. So, if I ever do get my story uploaded, don't vote for me.

Duane Benson
I'm not red or blue. I'm sepia

It (.3 mm) Finally Happened

Back in January of 2012, I wrote about the possibility of 0.3 mm pitch BGAs being used here and there. I predicted that in a year, we'd see some 0.3 mm pitch BGAs showing up. I was about three month's off. Almost to the day.

I delivered a session at PCBWest last month and asked if anyone had used a part with that pitch yet. One hand went up. That actually surprised me. What surprised me even more was when one of them (a .3mm pitch BGA, not a hand) arrived on our shipping dock in a parts kit earlier this week.

0.3mm pitch trimFor comparison, the land pattern for an 0402 passive component is about one millimeter long. This specific part is just shy of a millimeter square. Even as small as it is, this part can supply 750 mA continuous. The olden days are so very long gone.

We do many, many complex parts and PCBs. We've put 5,000 parts on a single PC board. We've built boards to be shot up in rockets and dunked way down in the ocean. Some very crazy stuff has come though our shop, but we don't do everything. We don't do 01005 passive components at the moment. Our machines have the technical capability, but we don't rework them, which has to go along with the assembly capability, so we don't support that form factor for now. 0.3mm pitch components pretty much fall into that camp. Our machines can physically pick up and place the component, but until we've developed to process to assemble those parts with the quality people expect from us, we won't be supporting them.

I expect we'll be getting more and more requests for the form factor, so we'll be looking at it. Keep checking back. One of these days, we'll have the process down and reliable.

Duane Benson
It's (Huey mm, Dewey mm, and Louie mm)/10

Missing Mars Probes

Back in ancient times when multi-legged beasts ruled the earth, there were a lot more standards. Or maybe there were just fewer total things resulting in fewer total variations, which looks like more standards.

In any case, if you got a 7408 IC from one manufacturer, it was pretty much equal to a 7408 from any other manufacturer. Even connectors were more or less standard. If you plugged in one PCB mount DB25, you could plug in just about any PCB mount DB25. There were variations, just not as many as now. Today, though, there are a very large number of variations to a standard footprint. For example, while the pin footprint on most Ethernet jacks matches, I've probably seen a dozen different arrangements of mounting and alignment pins.

Another area that can throw monkey wrenches all over is the dreaded metric v. SAE units.

Metric vs imperial

This seems to pop up most often with connectors, as in this image, but it occasionally shows up on other types of parts as well. The footprint here is for a .1" (2.54mm) pitch connector. The connector has 2.5mm pitch. It would be fine for three pins, maybe four or five. But beyond that, it's just not going to fit.

I don't really understand the logic in 2.5mm pitch. If .1", which equals 2.54mm weren't such a ubiquitous standard, 2.5mm would make sense, but as it is, it's just too close. It's close, but they aren't the same. 2.5 != 2.54.

Duane Benson
It doesn't seem like much difference in mm, but in beard-seconds, it's 4,000* units off

*By some definitions, including the Google converter, it would be 8,000 units off

 

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