Suspect Through-Hole Packaging

Surface mount components are carefully packaged up in strips, tubes or trays, because they’re machine-assembled. The assembly robots need order and organization to properly do their job.

Through-hole parts, on the other hand, are almost always manually inserted by actual human-type people. That being the case, the manufacturers and distributors are sometimes more lax with their packaging. They assume that, since a human is picking the parts, a jumble is okay. Sometimes it is, but not always.

In the case of these through-hole DB-25 connectors, the jumble was too much and lead to a number of bent pins. Slightly bent pins usually aren’t a problem, but some of these ended up a lot more than “slightly” bent.

To make matters worse, these pins are small thin-wall tubes, which are more susceptible to breakage when bent than are solid wire pins. For the connector on the bottom of the image, some of the most horribly bent pins may not be straightened without breaking. If they are, they’ll certainly be weakened.

The moral of the story is that through-hole parts need care too. We can’t toss them around just because they aren’t the latest technology.

Duane Benson
Spider-Pin, Spider-Pin,
Does whatever a Spider-Pin does

Packing Parts for Personal Manufacturing

Manufacturing, especially small volume one-time-only builds (like a prototype) is hard. It’s not wise for most people to actively seek out chaos, but that’s what we do, and we do it wisely. That’s what we’ve been doing since 2003.

We do it because it’s hard and because it’s necessary.

A big part of quality manufacturing involves risk reduction. Prototyping and quick-turns inherently add in a lot of risk. While we’ve designed our processes and systems around turning that risk into a quality product, there are a few things that you, the customer, can do to help reduce risk even further.

One of the best things you can do to reduce risk is to prepare a well organized kit, as shown in this video:

You can send us your parts in short, cut strips, like you get from Digikey or Mouser, long continuous strips, full or partial reels, tubes or trays. We machine place from all of those types of packages. What’s important is clear labeling and organization.

Individual, or mixed/loose components are not good, though. Pins get bent, leads get contaminated, values get mixed… Leave them in the strip, even if it’s short. If you’ve got multiple short strips of the same part, we can still machine place. Don’t tape them together. We can deal with them as is.

Duane Benson
Peter Piper Picked a Peck of Pickeled Manufacturing

http://blog.screamingcircuits.com

Freescale KL03 and PCB123 at 0.4mm Pitch

Small component packages seem to be a recurring theme with me. It’s understandable, I guess. Super tiny packages are becoming more and more common and we build a lot of product with them.

The smallest we’ve built is 0.3mm pitch. Those aren’t common enough to be considered standard — they’re still an experimental assembly — but not many chips use them yet. 0.4mm, on the other hand, is something we see on a pretty regular basis.

What’s so tough about that? The biggest challenge with these form-factors seems to be footprint design and escape routing. I can see why. There really isn’t room to follow any of the standard BGA practices. You can’t fit escape vias between the pads and you can’t put vias in the pads, unless they are filled and plated over at the board house. Filled and plated vias are the easiest way to go, but it can make for an expensive board fab.

KL03 WLCSP20 on a US Lincoln penny. One of my side projects involves trying to make the smallest possible motor driver. For this project, I’ve chosen the Allegro A3903 driver. It’s a 3 x 3mm DFN (dual flatpack no leads) with 0.5mm pitch pads and a thermal pad in the middle. The microcontroller will be the new Freescale KL03 32-bit ARM in a 1.6 x 2.0mm WLCSP (wafer level chip scale) package. It also comes in a 3 x 3 x 0.5mm pitch 16 pin QFN. Without an expensive PCB, that may be my only option.

Pick your CAD package. I’m using the newest version (5.1) of Sunstone Circuit’s CAD package, PCB123, but the principles here will apply to any CAD software. If you don’t already have a copy, download PCB123 V5.1 here.

If you’ve got fast Internet, you’re done now, so go ahead and install it. You’ll need the manual too, which you can get here.

I need to eat now, so stay tuned for Part 2.

Duane Benson
Nerfvana – It’s like Nerdvana, but with more foam darts.

http://blog.screamingcircuits.com/

The ESD Habbit, or An Unexpected Shock

Excitement is building here. In a little over two weeks from today, The Hobbit movie will be released to theaters. I’m sure everyone reading here knows the story, but in case you don’t I’ll spoil it for you.

It’s a story about Biblio who is, according to Spock, the bravest little hobbit of them all (google that if you don’t get the reference. You’ll be glad you did). Biblio is minding his own open source robotics business when the Wizard of Menlo Park (in CA, not NJ) invites 12 MCU designers over for a meal and discussion about the merits of hardware peripherals vs. bit-banged peripherals. The MCU guys convince Biblio to go with them to The Lonely Mountain Chip Fab and help them kill a terrible ESD Spike problem. Actually, it’s the Wizard that convinces the MCU guys that Biblio could help. The next day the MCU folks left early and Biblio ran out to catch up with them without even an ESD smock.

The ESD problem came from the North because it’s more humid up North and that tends to dissipate ESD. Our Terrible Spike didn’t like the idea of being dissipated without having first destroyed a few gold interconnect wires. The MCU guys need those gold interconnects to remain intact, so they brought a secret encryption key and enlisted help from the technician Biblio.

First though, they had to get past the TO-92 packaged parts that wanted to squash them into jelly or tacky flux. Fortunately, despite the bumbling of technician Biblio, the Wizard bought solder with no-clean flux which made the TO-92 parts stop moving once applied. After the TO-92 parts stopped working in daylight, they made a brief stop to inspect the last Homely Chip Fab in the Silicon Valley and see where the light sensitivity came from.

Passing over the Siskiyou Mountains on the way to Oregon and The Lonely Mountain Chip Fab, it started raining so they went into a cave and ate porc for dinner. Biblio ate so much that he fell asleep in the corner behind a chair where no one could see him and his buttons popped off. The missing buttons didn’t bother him too much because those ones had a de-bounce problem anyway. Luckily, the weren’t Grayhill switches or they would have hates Biblio forever, even if he used an achient gold Tolkien-ring network to bypass more porcs.

Biblio wasn’t the most skilled technician and he caught his pine cones on fire while trying to solder new switches into place, but the wizard was able to re-layout the board using Eagle CAD and an FPGA that could take many forms and would satisfactorily control the machinery and bears at the local honey production facility. But the FPGA brought them all into the murky world of Verilog and VHDL. That would have been fine except that the search engine spiders hadn’t crawled the eleven Wikipedia pages they needed to properly map out the clock routing.

The MCU guys got hungry and wouldn’t wait for Biblio to come back with pi so they rushed in causing so much in rush current that the lights went out with a snap. After eleven clock cycles in his new hall-effect switch, Biblio knew that the de-bounce problem would be gone except when he plugged the barrel jack into his Apple computer. But with no static guards to wine too, he had no choice but to use the Apple barrel jacks to get power to MCUs and switch open the flip flop made from a streaming-transistor logic gate.

Annoyingly, they split the story in two and the movie will end at this point. We’ll have to wait another year to see if Silicon Oakensubstrate is robust enough to kill the terrible ESD spike and pass final QC.

Duane Benson
One oven to reflow them all

http://blog.screamingcircuits.com/

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 datasheet for this part.The part in questions is a Maxim MAX98304 Mono 3.2 Watt Class D amplifier. The entire package is just 1 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.”

And Another Footprint Thing

 When you are creating a footprint in your favorite CAD program, or reusing someone else’s footprint, double check the zero orientation. This post discusses the IPC-7351 specified zero rotation orientation.

This picture on the left shows a library component with the improper zero rotation orientation. Your centroid file will never be correct if you start from the wrong point.

IPC-7351 states that the LED should be oriented horizontally and the cathode (pin 1) should be to the left. Obviously, vertical and cathode up is not the same thing as horizontal and cathode left. If it’s obvious, why do I feel the need to state it? I don’t know. I just do.

Duane Benson
Red is gray and Yellow white
But IPC decides which is right

http://blog.screamingcircuits.com/

Rain, Rain, Go Away

It’s almost June here in the Pacific Northwest. At least, that’s what the calendar says. I’m not sure I believe it at the moment. The weather is acting more like October. It’s a bit warmer than January, but every bit as wet. That pretty much equals October. We’ll just call it Junetober.

And what does Junetober have to do with electronic assembly?

MSD logo Moisture. That’s what it has to do with electronics assembly. Most of the parts running around in the world today have some level of moisture sensitivity. Despite my lament of the rain here, you have to consider component moisture no matter what your climate may be.

Looking at IPC-M-109, you can see the there are sensitivity levels MSL-1 though MSL-6. There are actually eight levels: 2A and 5A make up the extra two. If you’ve got an MSL-1 part, you really don’t have to worry about. I wouldn’t store it in your fish bowl, but the standard says you don’t have to bake it. Up at MSL-6, you have to bake the parts before use no matter what.

When you buy moisture-sensitive components, they should come in a moisture barrier antistatic bag with an indicator card and a little baggy of moisture absorbing desiccant. The best approach with these components is to leave them in the original, unopened bag. We’ll use what we need and properly seal up the rest just the way IPC-M-109 wants us to.

If you do need to open the bag and ship parts to us without the moisture protection, we may need to bake them for a while to make sure they are properly dried out before putting them in the reflow oven.

Duane Benson
Gore-Tex is a registered trademark of W. L. Gore & Associates.
http://blog.screamingcircuits.com/

Sales Up, Profits Down

Another round of EMS quarterly reports came out today, as LaBarge and SMTC provided their numbers. Now that the bulk of the major EMS companies have reported, the picture is pretty clear that first quarter revenues were up fairly broadly but profits took a hit.

This is unfortunate, of course, because the margin-sensitive EMS industry relies on leveraging higher sales to drive incremental profit gains.

Based on the consensus forecasts, expect second-quarter revenues to be generally flat, with pressure on margins because of higher component costs due to supply constraints.

Time to Panic?

Anecdotal reports indicate some manufacturers are purchasing larger-than-needed amounts of raw materials and certain components out of concern for supply availability in coming months. This is all tied to the shortages brought on by the earthquake and tsunami in Japan.

In the near-term, I expect analysts will be a bit confused as to what’s real demand and what’s over-ordering. Something to watch.

 

Drip. Drip. Drip. Drip. Drip …

Okay, water doesn’t have to actually be dripping down on to your parts to be a problem. I don’t know if you’ve heard or not, but water also comes in vapor form. Weird. I wonder if there’s a way to harness water in that vapor stage and do something useful with it. Hmmm. Ponder material for another day.

Here is something not so useful about vaporous water: It can get into your parts and make them unhappy. I was recently asked about opening and resealing moisture barrier packages for moisture-sensitive parts. This old post has a link to the IPC and Jedec standards document (J-STD-033B.1) covering this subject. It can be a complicated subject and the document is worth the read.

In sort, the best thing to do is just leave the parts sealed in their original moisture barrier packaging. If that’s not practical, look at the MSD classification. There are eight levels with one being least sensitive and six being most. (Levels are 1, 2, 2A, 3, 4, 5, 5A and 6). Most parts seem to be level 3, which can be open and exposed for a cumulative time of 168 hr. The actual safe time may vary based on your local humidity.

If you want to open and reseal, you’ll need the humidity indicator card that came with the parts, desiccant and a thermal sealing gizmo. Open the package, take out the parts you need, put the remainders, desiccant and card back in the package and reseal it. Sealing it with tape won’t do the trick. Then you would count the time that the components were in the open air toward the cumulative open time.

If there’s any doubt, just let the assembly house know that the parts need to be baked. It will probably add some time to your job, but it’s better to add a bit of time than have bad parts.

Duane Benson
Add walnuts and chocolate chips.
Two

http://blog.screamingcircuits.com/