Screaming Circuits: December 2008

You Got Peanutbutter in My Chocolate...

FusionQuad No. You got QFN in my QFP...

I got a call the other day from a sales rep, at Practical Components, telling me about a new chip package coming out from Amkor. It's sort of a QFP, with pins all around the outside. But in the middle, it's just like a QFN with a center thermal/ground pad and one or two rows of QFN style lands. Amkor calls it VQFP or FusionQuad®. Pretty wild.

We haven't seen any of these yet. I'm not sure they are even being used by anyone, but it shouldn't be too much longer before they start to show up in microcontrollers and rf products.

[In case you aren't familiar with the two companies: Amkor makes packaging for IC's. Practical Components sells dummy components for test purposes.]

I expect that the layout and assembly challenges for this package will be similar to those of a QFP, a QFN plus a BGA. You'll have to deal with segmenting the solder paste layer in the center pad. You may need vias in pad. You'll have to escape the two center rows of lands out through or under the QFP pins. The QFP pins will come with either .5mm or .4mm pitch.

Like with QFPs, part care will be extra critical too. I expect that the package will be even more sensitive to bent leads than is a standard QFP. If the outside pins are bent too far down, it will be easy to get voiding or un-connected lands in the center. If the outside pins are bent up a bit, it will be easy to get un connected outside pins. Nothing really all that new, but it's a new combination. Fun.

I don't think these are out yet, but if they are, I'd love to hear from anyone that's used one.

Duane Benson
Clean up in aisle six, please

Back to Normal

Bgachip The snow is gone and it's 45 degrees and raining this morning. In other words, back to Oregon normal. We'll get the weather caused backlog out as soon as we can and just be rolling as usual.

And so it goes

Our office is open today (Tuesday, the 23rd), but we're still experienceing weather cause delays. Some of the shippers say they are getting in and out but we won't know for sure until they get here.

According to the weather folks, this is a 40-year record snow fall for Portland and the third most ever recorded for Portland. Brrr.

Closed By the Snow

Okay, this is getting pretty old, but we are closed by the snow today. In know you folks back in Chicago or Boston or wherever can deal with a lot more than we can out here in Oregon, but at least it's not just an inch any more. We have six to ten inches of snow, then a half inch or more layer of freezing rain-ice and now another four inches and growing of snow on top of that.

Late December snow storm SC sign 500 

We'd all much rather be in working those SMT machines, but it's just not safe to be out on the roads here right now. We're sorry for the inconvenience and of course, company policy dictates that I remind you that company policy says that a weather closure like this overrides our normal delivery guarantee.

I'd go build a snow man but it's too cold and I can't find my snow gloves.

Duane Benson

Flyback Diodes - a Question

Parallel caps A while back, I posted about putting caps in parallel. Sometimes it makes sense to do that either to reduce the effective series resistance (ESR) or to better respond to different frequencies of ripple, spikes or distortion.

But here is my question - Take a look at the schematic below. This is mostly for you motor control and power component folks, but anyone can take a stab at it.

MOSFETs typically have their own flyback diode built in. But it may not be fast enough or good enough in some way or other, so it's common practice to use external flyback diodes in parallel with the internal one. In this schematic, each leg of the H-bridge has three MOSFETs in parallel. It also has D7 and D8 as flyback diodes for the bottom legs. For the moment, ignore the fact that the top legs don't have any external flyback.

Barrier diode

Here's the question: Is is equally effective to have a single big flyback for the three parallel transistors as it is to have an individual flyback for each MOSFET?

Duane Benson
Is snow cold? Perhaps, but it's all relative.

All things are relative
All my relatives are things
My relatives took all my things

Weather Slowdown

It's getting better. The Canby schools are open today and so are we. Hopefully, we'll be able to get everything out on time. However, the Weather Service still has a winter storm warning for the Portland area in effect though.

We'll do our best to get everything out on schedule. But unfortunately because of the predicted winter weather, we still can not guarantee shipments right now. Weather related delays do not count toward your turn times.

I'll keep you posted.

Weather Shutdown

Please note that due to inclement weather, Screaming Circuits is shutting down today.

The snow and ice are causing deliver and shipment problems now. We have declared today (12/17) and tomorrow (12/18) to be snow-closure days. Unfortunately because of the weather, we can not guarantee shipments right now. Weather related delays do not count toward your turn times.

I'll keep you posted.

IMPORTANT BULLETIN: Weather Caused Delays


The snow and ice are causing deliver and shipment problems now. We have declared today and tomorrow (12/15/08 and 12/16/08) to be snow-closure days. We will still do our best to ship your jobs, but unfortunately because of the weather, we can not guarantee shipments right now. Weather related delays do not count toward your turn times.

I'll keep you posted.

End of Year Turn-Key Special

Icn-turnkey-w-orn Hey all - we're going to try and give you some help with your finances. For turn-key orders placed  and confirmed by 12/31/2008 [Through 1/31/09 - Update: Because of the snow, we're extending this through the end of January], we'll give you 35% off of our standard materials cost.

Save time by letting us source the parts and PCBs and save money with our end of year special too!

Order must be placed and confirmed by close of business on 12/31/2008. Discount is good on turn-key materials only.

Whether, weather everywhere, but not a drop to drink

Snow 12-15-08 My headline really doesn't make any sense, but with me, that just goes with the program sometimes. We did have some inclement weather here though and I wanted to update those of you that have jobs here. So far, despite the national headlines, we are still working and shipping as though it were a regular day. [UPDATE: We are having delivery problens due to the road conditions. Today has been declared a snow day and some jobs may be late. Weather related days do not count toward your turn-time.] I'll let you know as soon as I can if that changes. Unless it gets worse, Bob, the reindeer will keep on delivering.

I read a news headline that said "Two inches of snow shuts down Portland." It cracks me up. Anywhere else, it would be sometyhing like "thirty six inches of snow shuts down Boston" or "six feet of blowing snow, with 20 foot drifts, white out conditions, and temperatures of minus 45 degrees caused one fender bender in Minneapolis."

Of course, in our defense, it is a different kid of snow and ice here. I know. You always hear that and don't buy it. But the physics will back me up. Our snow and ice tends to happen real close to the freezing / melting point. I found this to illustrate my point:

"The Coefficient of friction for snow or ice is only 0.03 because due to local very high pressure the temperature of water -ice phase transformation is lowered and a layer of water is created. At low temperatures (-40 C and lower) the layer of water is not formed and the coefficient of friction rises to a value normal for two sliding solid surfaces, i.e., 0.7 to 1.2". Tadeusz, Burakowsk and Tadeusz, Wierzchon. Surface Engineering of Metals: Principles, Practices, Technologies. CRC Press, 1999: 143. Referenced from The Physics Factbook™ Edited by Glenn Elert -- Written by his students.

I've been saying "but it's a different kind of snow for thirty years, and finally, I found a reference to back me up. Cool! Also, they don't salt the roads here. We prefer to destroy our cars in one fast crunch (check out this funny from two years ago) rather than slowly rust them out winter after winter.

Duane Benson
Found: One chunk of salt-pork on roadway.

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