Cantaloupes

But how about cantaloupes ?:-)

[snip the work stuff :-]

What we call cantaloupes aren't, they're actually some other melon, the name I can't recall right now.

Safeway is so-so for melons, just make sure they pass *both* smell and "press the stem button" tests ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

If you get tired of designing IC's, you could always be a 3rd grade English teacher.

That would be nice.

Musk melons, apparently:

Our Safeways is all ripped up now, the whole ceiling supported by huge jacks. They're converting it to a "Lifestyle" Safeway. The good part is that they now stock Perugina chocolates and the black Toberlone triangles, instead of Hershey and Cadbury.

John

No, it's this nasty little thing. Hard to solder, darn near impossible to probe:

John

[snip]

I dated a red-head in high school just to check that out ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Sno-o-o-o-o-ort ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Why's that any worse than any other 0.5mm plastic flat-package part? Not the smallest part around, pins on top, away from package, some room under the package, pins can be inspected...

What's painful is ICs using these small dimensions, but requiring a thermal/electrical solder connection to a pad underneath, like Analog Devices' new DDS chips, which have a 2mm square pad. We're using the ad9953, just finishing a PCB, and I'm not sure how to deal with it. See page 30,

and

--
 Thanks,
    - Win

--
And?
 
We like ours with our Blue Bell (from Brenham, Texas, "Where we eat
all we can and we sell the rest") Natural Vanilla Bean ice cream in
the cavity after the seeds have been removed.  Yum...

US8. The recommended footprint has 0.3 mm pads on 0.5mm spacing, so the clearance is 0.2mm (an RCH under 8 mils).

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Is that a micrometer in your pocket, or are you just glad to see me?

;-)

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

The proper way to deal with them is with paste and hot air. Then they are not so bad. For prototype quantities, some people put a giant via under the pad, so that they can solder it from the back side with a iron. If you want to have some fun, try some QFN's, or DFN's (same idea as the IC your using, only no leads out the side, they are flush to the package, stuck around the big pad in the middle, on the bottom!). They are, however, not too bad _once_ you get used to them. Or how about CSP's - some are 0.8 mm square with 8 or 9 solder bumps on the bottom - i.e. an 800 um BGA!

Jeff

Three words of advice:

1. The pad isn't really 2mm by 2mm. It's bigger. Yeah, the data sheet shows 2mm by 2mm, but do not route any traces/vias for 4x4mm or so around the center.

1. Just put a square via with a 1.5mm or 2mm or so hole underneath the part and solder through the via. I'm not sure exactly what hole size I used but choose something big enough to get the point of your not- skinniest solering iron through.

2. The AD995x do not run hot at all if you keep to under 400MHz. There are some experimenters running them at 800MHz plus, but I can't figure out why other than to make heat!

1. Split the A and D ground planes like they advise, tie them together where you've got the big bypass C.

2. Some of the AD datasheet/app notes show the PLL filter cap to be

0.01uF, others show 0.1uF. The small part is chosen entirely to make the PLL lock fast after recovery from sleep. Use the big part in all other circumstances.

OK, that was 5. (Nobody expects the spanish inquisition! We have three weapons at our disposal...)

This chip is fun and even a complete noob like me managed to use it. I even had two of my little kids running around in the basement while I hand-soldered it.

Tim.

In a full automated production environment. We have a hot-air system with preheat under, that we use for prototypes. But I don't know how much paste to put down under the IC, etc. I assume all the solder has to be melted at once to avoid stress after the part cools down.

This is after soldering the 0.5mm pins, right? When soldering to the middle pad through the via, how can one avoid permanent thermal stress after the part cools?

We haven't had too much trouble with these, hold in place, hot air directly on top, until they suddenly settle down onto the pcb.

--
 Thanks,
    - Win

Although I haven't used the device you have there, I have been using TIs parts with the equivalent (they call it PowerPad).

There's an excellent application note at:

Cheers

PeteS

Thanks, Pete, Analog Devices seems to have little to say about the subject, that I could see in 15-minutes of searching anyway. I was getting ready to search TI, ST, LTC and Fairchild, etc., next, and you saved me the time! That's a very useful app note.

--
 Thanks,
    - Win

Put a little dab of paste on the center pad (not too much or you will have to remove some, since the IC will not sit low enough for the pins to touch - push down on the IC, during reflow and a big solder ball should pop out if that happens), place the part, reflow it using hot air, and make sure it's centered on the pads using tweezers. When cool, solder the pins by hand. Thermal stresses should be less with this type of part, when hand soldering, since you now have the big pad sucking heat away from the die. The legs basically have a stretched Z shaped bend to absorb different thermal expansions. If it still bothers you, you can reflow it again after soldering the pins to relive any stresses.

Exactly

See above. You loose a little heat sinking ability if the center pad is not soldered first, but the large chunk of copper can keep it significantly cooler then a similar TSSOP without the copper pad, whose pins would be soldered the same way.

One thing that I haven't been able to find (haven't looked in the past

6 months) for QFN packages is the recommended solder paste stencil area for the die attach (paddle) pad. Linear Technology sent me the Carsem MLP Application note which, again, sidesteps the solder paste stencil area for the die attach pad. I have found that making the solder paste stencil area 70% of the die attach pad area has prevented the part from "floating" and causing shorts from pads to die attach area. I also use a checkerboard pattern as recommended in the Carsem application note.

--
Mark

Did you get a measurement?

--
Mark