Want mega8 MLF?

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Digikey has mega8 MLF chips (ATMEGA8-16MC) in stock!
And more models are on their way in....

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Hi AmPz,

They look very interesting, but quite a challenge to hand solder. To start with, the pitch (0.5 mm) is very fine. I've just built a board with a connector that had a single row of pins 0.5 mm apart, and it was difficult to get them aligned - I could hardly see what was going on. Secondly, most of the pin is under the device. This seems OK for soldering in a reflow oven, but a problem for hand soldering. There's only 0.2 mm (~7.9 mils) of pin exposed at the side of the device (dimension A3 on the drawing in the datasheet) for soldering to.

Have you got some good tips on how to work with these things? If you buy one and get it mounted, I'd be interested to hear how it's done.

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I have no trouble whatsoever mounting 0.5mm pitch TSOP and QFP packages with any number of pins. The largest one I've soldered was a 144 pin one, but I don't see any problems soldering 256pin 0.5mm pitch components with normal legs.
I actually think it's easier to solder 0.5mm packages than SOP packages, with 0.5mm packages you can solder all the pins on one side with just one move with the soldering iron, SOP packages you have to solder one leg at a time... Very time consuming.

I think the height, 0.2mm, is the same as the height of normal legs...
I don't see any problems with the slightly different legs of the MLF package, there is no need to solder the part of the "leg" that is under the package, assuming a clean bord and component, the solder will flow in under the component somewhat by itself. It doesn't have to solder the entire leg area to the board.

Mechanical stability is archieved by soldering the large pad under the component to the board, I'd say that can be done by putting a via at the center of the component, fill the via and pad with solderpaste and heat it from the other side of the board.

5 * 5 * 1 mm, gee, I could fit at least four of theese babies on my fingernail! :-)

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I haven't tried it myself, but Ulf@atmel.com has been saying for months that they're not hand-solderable.

I would've thought you could reflow the legs manually as well, but the pad in the middle sounds like a serious challenge. Let us know how it works out when you get them Ampz!

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AmPz,

I hadn't thought of soldering in from the other side of the board to get at the centre pad - that sounds like it might work. I guess the next trick is finding other components this small. E.g. with an MP3 decoder chip in this type of package as well, we could make an incredibly small MP3 player.

Good luck with it - I hope you can show us all some good results.

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I also read somewhere in atmels documentation that it's perfectly fine to just superglue the central pad to the board. However, that would decrease the total power rating of the part by 75% or something.

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The secret's in the flux. I typically use a liquid non-corrosive flux from GC electronics. It comes in a small bottle with a small brush attached to the inside of the lid or cap. With suface mount parts if the flux can be trapped under the chips then the flux needs to be non-corrosive. Solder pastes in a syringe like applicator work well too, but the flux in the applicators tends to be a water soluble corrosove type so you have to be careful how and where you use it.
I've ordered some MLF's from Digikey as I've been dying to try them for ages now in making really small robots.
I've recently been successful at mounting Analog Devices 32pin BGA MEMs Gyro devices onto a combo PCB I designed for Balancing Robots. (both the Gyro and Accelerometer are moutned together on one PCB). The 32 BGA pins are .020" in size with about a .015" spacing between pins. The pins are under the chip where you can't see them, so you either use some sort of IR reflow machine or a hot air rework station like I used. Some guys in the Seattle Robotics Club are very successful at using a simple Toaster Oven to do reflow soldering as well. BGA's suck as you can only test for shorts, you have to build up the entire circuit to see if it's working or not.
So this MLF will be a cinch to solder. Like the other guys stated you can solder the pins from the sides and let it reflow under. A simple small via under the the chip should work for the inside part.
I can't wait till I get the MLF parts, I'll be able to put all the parts I need now, onto a under 1" square PCB now.

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If anybody's interested www.pios.com (Pioneer) has a bunch of MLF Atmega128's for sale. Limited quantities though.
They have some Atmega8 MLF's as well.