ATMEGA16U2-MU(R) / resistor packages

Schematic
1

Hello everyone !

I have a problem that has me struggling. I’m still developing my own Arduino Uno rev 3 and i’m adding footprints to the components ( for handsolder ). But there are 2 problems : the Atmega16u2-mu® and the resistor networks wich i both can’t solder because they are too small.

My question is are there slightly larger parts of them? like parts i can solder.
( For the atmega the pin layout has to be the same )

Greetings,

Jasper

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Is that the QFN or QFP variant?

  • QFP is easily solderable with a good solder iron and some flux. (The nominal density IPC footprint should be good enough here. A microscope or at least good magnifying glasses would help a lot.)
  • QFN might mean you would need a good heat gun (Maybe it is enough to increase the toe fillet. This could allow you to solder it using a solder iron.)
  • If they have a exposed pad then you might either need a good heat gun or you can make a large through hole pad for it such that you can solder it from the bottom side.

You did not specify anything about the resistor network. There are such networks out there that are basically a few 0603 imperial (or 0805 imperial) resistors right next to each other. Such packages can be soldered with nearly anything.

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this is one of the resistor networks on the arduino board : RES ARRAY 1K OHM 4 RES 1206
CAY16-102J4LF

And here is a picture of the atmega ( also including some resistor networks )

20180626_145655
20180626_1456551641×2918 2.33 MB

I’m not sure if ths is a QFP or QFN.

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QFP: quad flat package - is a gull wing component similar to SOIC (but with leads on all 4 sides.) So as we do not see the leads it can not be a QFP

QFN: quad flat no lead: This package has no outside leads. The connection points are on the bottom. Normally arranged on the border of the part (meaning if you look from the side you will see the metal connector) From the picture i would guess it is in fact a QFN. (I would however suggest you go for the QFP if you can. It is much easier to solder.)

RES ARRAY 1K OHM 4 RES 1206 CAY16-102J4LF

That is a huge part. So you would not need to worry about it with regards to handsolderability. You can still make your life easier by increasing the pad towards the outside compared to what industry standards suggest. (Use the R_1206_3216Metric_Pad1.42x1.75mm_Handsolder footprint as a guide)

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Thanks @Rene_Poschl I will look if i can find the QFP variant and have an eye on the footprint.

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I have found 1 company that has the QFP variant and found a larger footprint for easier soldering. :slightly_smiling_face:

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If you use a footprint you found somewhere on the net you might want to check it for correctness. Here a tutorial that describes one possibility of how this can be done: Tutorial: How to check footprint correctness?

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Changing the 33 pin QFN for another package could change the device ID. This Atmel part has to be programmed in situ.
It might be easier to use the FTDI FT232RL for a one off clone board, this is SOIC and much easier to solder

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Resistor networks can be a pain to hand solder, so you could drop those for standard packages.
QFN can also be very hard to solder, but can be made slightly easier with extended pad footprints.

Best to use QFP packages - the TQFP32 is probably the easiest, as it has a ‘large’ 0.8mm lead pitch.

if doing an Ardunio, you might want to look at the newest ones - a good image here :

Those I believe are going to have proper Debug included, so are a much better end user prospect. That means a slightly larger USB MCU.

What is the end use of your project ?

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