Tag Archives: Freescale

Using the Newest Gen Arm, Part III

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The continuing saga of the 0.4 mm pitch KL03 ARM microcontroller. If you haven’t yet done so, read part I and part II.

Today, I have a look at the good, the bad, and the ugly – or more accurately, the good, and the bad and ugly. As I expected, I was quite pleased with the job done here in house. The board is nice and clean, the parts are well centered, and the solder joints are solid. No surprise here.

Here’s a top view of one we did here in Screaming Circuits:

Next, I’ve got one that I did at home. It actually surprised me and came out better than I had expected. Here’s a top-down view of the one I did at home with home-grade tools (No, I didn’t intentionally make it look bad. The board surface is just a bit shinier than the one above.):

Of course, “better” is a relative term. I didn’t say good. I could call this both bad and ugly. I did manage to center the parts quite well — that took a lot of careful nudging with sharp tweezers and and an X-Acto knife blade.

All of those little round shiny spots are solder balls. That’s what happens when you get too much solder on the board, get solder off the pads, or have the wrong reflow profile. They might look harmless, but if there are too many under the chip, the connections could be shorted.

The fillets on the 0201 capacitor are a little lean on solder in the one I did, and there’s a solder ball on the right side, but, again, it looks better than I expected.

Next time, I’ll post the x-rays and show what’s under the hood.

Duane Benson
Carburetors, man.
That’s what life is all about

http://blog.screamingcircuits.com

Using the Newest Gen Arm Microcontrollers

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I’ve written a few times about the new Freescale KL03 ARM Cortex M0+ microcontroller. This particular part comes only in very small packages, with the smallest being a 1.6 x 2mm WLCSP (wafer level, chip scale package) 0.4mm pitch, 20 bump BGA. That’s a mouthful — albeit a very tiny mouthful. Maybe just a toothful.

On the left, here, I’ve got a pair of them on a US postage stamp.

For us, it’s not a particularly difficult part to assembly; just a garden variety 0.4mm pitch BGA, as far as we’re concerned. We place loads of them. But, it can be a very different story for a designer. Conventional wisdom says that a PCB designer has two choices with a part like this: a very expensive PCB, or don’t use the part.

Escape routing becomes very difficult (read: expensive) at 0.4 mm pitch. This part only has six connections that need to be escaped, but that can still be a problem. You can’t fit vias between the pads to escape out the back side. You can’t put vias in the pads unless you have them filled and plated over at the board house. That’s expensive in small quantities.

This blog post series is going to examine some possible ways to use these parts with more of a standard fab, such as Sunstone Quickturn. I’ve got three different process blank PCBs, each with four different land patterns.

I’ve been asked about home reflow too, so as a bonus, I’ve done my best to duplicate hobbyist conditions for one of the board sets.

Duane Benson
“Screaming Reflowster” not sold here

http://blog.screamingcircuits.com

VTP: Very Tiny Parts

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A while back, I wrote about a new ARM Cortex M0+ chip from Freescale. It’s not the first M0+, but I do believe that it’s the smallest. I’ve been checking stock off and on and finally found the smallest package to be in stock and available to ship. 

I actually bought a couple of different types. First, there’s the WLCSP 20. It’s got 32K Flash, 2K SRAM and an 8K bootloader. The real kicker is that the package is only 1.6 X 2.0 mm. I also got a few in the QFM-16 package, which is a bit more workable at 3 X 3mm.

Finally, I bought a Freedom development board with the 4 X 4mm QFN-24 package. The dev board is hardware compatible with Arduino shields, so that will make for some interesting possibilities.

Anyway, here at Screaming Circuits, I’m most interested in that 1.6 X 2.0mm package to see how easy (or difficult) it is to use – see if there are any particular layout challenges. The other stuff is just for after hours play time.

Duane Benson
I’m not a number. I’m a free development board!
(Free, as in named “Free…”, not free as in “don’t cost nothin”)

http://blog.screamingcircuits.com/

0.4mm Pitch BGA is Awesome

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I recently had a conversation with a friend about 0.4mm pitch BGAs. The specific part is the FreescaleFreescaleKL03KL03 ARM Coretex-M0+ microcontroller in a 1.6mm x 2mm, 04.mm pitch package. That’s a 20-ball wafer scale BGA form factor.

I don’t have an actual part to photograph next to a grain of sand, but trust me (or don’t), it’s really small.

Ti 0.44 pitch dimensionsThe challenge, and the reason I suggested a QFN form factor instead, is the costs involved. If you have the extra budget money for more expensive PCBs, then go ahead and use this form factor. You probably won’t be able to use this package in cost-constrained situations.

The simple reason is that you can’t escape route the inner six pins without using super small vias between pads, or in pads and filled and plated over. The page on the left is from a Ti doc, but any variations in geometry will be minor.

You can see that you can’t put a trace between the pads. Maybe a 2 mil trace, but maybe not. There just isn’t much room. The recommended method is to put microvias in the pads and have them filled and plated over at the board fab house. Never put a via in a micro BGA pad unless it’s filled, plated over, and flat.

Duane Benson
There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
But open vias in pads aren’t one of them

http://blog.screamingcircuits.com

A Sad Cure for Inventory Glut?

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If there is a silver lining from last week’s devastating earthquake in Japan, it could be that component inventories will be dwindled, thus relieving the industry of a possible oversupply problem.

Many chipmakers and others are saying the quake will hurt their ability to produce and supply parts for one to two quarters. TI, Freescale and Toshiba are among those who have closed or reduced production at their Japanese factories.

Research firm iSuppli of late has been warning of possible overinventory situation, and no one needs reminding of the pain involved to drain an oversupply glut. As of Dec. 31, semiconductor suppliers held 83.6 days worth of inventory (DOI), up 5.5 days sequentially. The last time the DOI was this high was June 30, 2008, or just before the last semiconductor downturn, iSuppli says.

It’s just possible, however, that the forced shutdowns could ease some pricing pressure and concerns for a correction as assemblers burn through existing inventories.

This much is clear: spot prices for memory and certain other parts are bound to rise in the near-term. If Japan can’t bring its factories back online soon, they may even stay there.