Got wrong pitch FQFP MCU - possible to make a save?

Hello all,

I messed up my PCB design and now have a handful of PCB's where should go an atmega328 FQFP-32 0.5mm pitch size, but the only atmega328's I can find are 1mm pitch :frowning:

As I ordered and received a handful of atmega328 FQFP-32 1mm pitch (these: http://dk.mouser.com/Search/ProductDetail.aspx?R=ATMEGA328P-AUvirtualkey55650000virtualkey556-ATMEGA328P-AU) I'm looking for tips on how to make a save on this one... I've searched high or low for 0.5 pitch atmega's but no luck.

Any bits of inspiration are truly appreciated.

Check the data sheet.
This package

34.4 32M1-A

has 5mm body, 0.5mm pitch.

CrossRoads:
This package 32M1-A 5mm body, 0.5mm pitch.

Hello CrossRoads,

thanks for your input,

I did indeed notice that in the datasheet, what I meant to write was "I've been unable to locate the .5mm pitch MCU" (with either Mouser, Farnell or Digikey). I'll write them to them directly. Thanks again.

You are looking for
Atmega328P-MU, -MUR, -MN, -MNR
and not finding them?

http://www.mouser.com/Search/Refine.aspx?Keyword=atmega328p-m

You should pay more attention. For instance, there are no "1mm pitch" ATmegas. The LQFPs are 0.8mm.
Also, none of the packages are known as "FQFP" You've got your 0.8mm "LQFP", and 0.5 and 0.45mm "MLF" (leadless) packages...

CrossRoads:
http://www.mouser.com/Search/Refine.aspx?Keyword=atmega328p-m

Hello again,

and thanks for your help, it's much appreciated,

I can shed some light on what I was trying to do, via the attachment-picture: my PCB program of choice states the package-type of the IC that I dropped (in this case an atmega168), thus I went in search of that specific package-type, yet the units that I ordered, that fit the package-type, were too large for the footprint (I drew a dark red square to symbolize their body-casing size as compared to the white rectangle of the intended MCU).

The mouser-search that you kindly suggest lists a different package type, which finds me a bit confused - do you believe these are what I should be looking at?

Thanks in advance.

tqfp32-5mm.png

That's a 5x5mm TQFP-32 with 0.5mm pin pitches (example drawing: http://cds.linear.com/docs/en/packaging/TQFP_32_05-08-1735.pdf). The ATMEGA328P is in a 7x7mm TQFP-32 with 0.8mm pin pitches (datasheet: https://www.sparkfun.com/datasheets/Components/SMD/ATMega328.pdf page 436). So you chose the wrong footprint. I wonder if you couldn't force the 32-QFN 0.5mm version of the ATMEGA328P onto this footprint but I wouldn't count on it. And they are pretty hard to solder too, though not hardly impossible. The 7x7mm TQFP-32 isn't going to work out. You would need some sort of adapter to match it up.

I always print out my PCBs and make sure the components line up before I send them to be manufactured. Printouts from a laser printer are very accurate. It gives complete confidence you will be able to solder your parts correctly (assuming appropriate skill) so at least you can have some confidence there.

westfw:
You should pay more attention. For instance, there are no "1mm pitch" ATmegas. The LQFPs are 0.8mm.
Also, none of the packages are known as "FQFP" You've got your 0.8mm "LQFP", and 0.5 and 0.45mm "MLF" (leadless) packages...

Thank you for the suggestion that I pay more attention. I can assure you that the notion struck me the second I opened the box of MCU's to find that I'd wasted money on the wrong units. The "FQFP" was a spelling mistake - thanks for calling it. My PCB program lists a "TQFP32-5MM" package type, which led me to believe I should be able to find an atmega to fit the PCB foot-print. Riddle me this, is the pitch-sizes fixed for the various package types? (in which case I'll deem my PCB program to be rather confusing and poor).

Thanks in advance.

JoeN:
That's a 5x5mm TQFP-32 with 0.5mm pin pitches (example drawing: http://cds.linear.com/docs/en/packaging/TQFP_32_05-08-1735.pdf). The ATMEGA328P is in a 7x7mm TQFP-32 with 0.8mm pin pitches (datasheet: https://www.sparkfun.com/datasheets/Components/SMD/ATMega328.pdf page 436). So you chose the wrong footprint. I wonder if you couldn't force the 32-QFN 0.5mm version of the ATMEGA328P onto this footprint but I wouldn't count on it. And they are pretty hard to solder too, though not hardly impossible. The 7x7mm TQFP-32 isn't going to work out. You would need some sort of adapter to match it up.

I always print out my PCBs and make sure the components line up before I send them to be manufactured. Printouts from a laser printer are very accurate. It gives complete confidence you will be able to solder your parts correctly (assuming appropriate skill) so at least you can have some confidence there.

Hello JoeN,

thanks a lot for you input. I'm coming around to the conclusion that this board will have to go (though will try to fit a 32-QFN on there, might as well) - it's probably not worth the while to try and salvage it. A bummer, but a valuable lesson. Good tip on printing it out - in this case I ordered the PCB and components at the same time, next time I'll get the components first and the board later, as you do.

Thanks.

My PCB program lists a "TQFP32-5MM" package type

Ah. That's more understandable. But your PCB package is wrong, apparently. The 168 and 328 don't seem to come in that package at all! This is a problem with cad-package libraries that you haven't carefully checked, whether they be included from the software vendor, downloaded from a 3rd party, or created yourself...

westfw:
Ah. That's more understandable. But your PCB package is wrong, apparently. The 168 and 328 don't seem to come in that package at all! This is a problem with cad-package libraries that you haven't carefully checked, whether they be included from the software vendor, downloaded from a 3rd party, or created yourself...

Absolutely. A valuable lesson. At least I have some nice keychain-boards. Made me glad I put 3 designs on that 5x5 board, so I can cut off the bad parts and still have something to show for my PCB order.

heh. I also recently acquired some "Earrings."

harleydk:
Riddle me this, is the pitch-sizes fixed for the various package types?

The answer to this is no. There are some really common types and then a whole bunch of less common types and while I would call a lot of them common (e.g. 100-TQFP 0.5mm is very much the same over many manufacturers) I wouldn't call any standard. This is very different than the DIP days because with surface mount you don't use standard sockets, you are pretty much forced to make a PCB which means the manufacturers can say "do it our way because you have to get a PCB anyway and your PCB software has the flexibility to handle it." So there are some really weird things out there. I found these in my software:

But beyond that, there are various pin pitch sizes even within one type of package as you found out.

WeirdFootprints.png

Are you saying the 5mm, 0.5mm pitch parts I pointed out do not fit the 5mm, 0.5mm pitch pads on your card?

Atmega328P-MU, -MUR, -MN, -MNR

http://www.mouser.com/Search/Refine.aspx?Keyword=atmega328p-m'

Read the datasheet, take some measurements, compare to your board.

CrossRoads:
Are you saying the 5mm, 0.5mm pitch parts I pointed out do not fit the 5mm, 0.5mm pitch pads on your card?

Atmega328P-MU, -MUR, -MN, -MNR

http://www.mouser.com/Search/Refine.aspx?Keyword=atmega328p-m'

Read the datasheet, take some measurements, compare to your board.

Hey, I think Crossroads may be right on this. It's pretty close - the footprint is different but it looks like it is compatible. This is from DipTrace. This is the QFP32 7mm/7mm/0.5mm and QFN32 5mm/5mm/0.5mm footprints side by side. The problem here is that Diptrace doesn't show the exact outline of the package itself so if you imagine a worst case scenario here the QFN's pins might be just inside the radius of the QFP's traces. But it may be OK too.

A caviat is that QFNs are not as easy to solder as QFPs so keep that in mind. I hot air solder them myself and inspect them under a microscope.

I have use Atmel's QFN32 5mm/5mm/0.5mm packages. Too bad I don't have a PCB with a QFP32 7mm/7mm/0.5mm footprint on it otherwise I would see if it would work out for you.

CrossRoads:
Are you saying the 5mm, 0.5mm pitch parts I pointed out do not fit the 5mm, 0.5mm pitch pads on your card?
Atmega328P-MU, -MUR, -MN, -MNR
http://www.mouser.com/Search/Refine.aspx?Keyword=atmega328p-m'

Hello CrossRoads,

they may fit the board well, being rather the novice I remain merely hesitant for two reasons, the first of which is the labelling in my PCB program (which is Fritzing, by the way). If the footprint fits a so-called "QNF32" then why does it say "TQFP32". This a hugely complex, dedicated piece of software written by experienced people, so when I come across something like this I'm prone to declare myself the ignorant party before calling error on the program. Also the footprint has prolonged pads as indicates room for an MCU with spider-legs sticking out, yet the ones you link to have none of those.

I'm coming to the conclusion that I'd about to venture into my first foray into these leg-less MCU- that, and that I should probably start using Eagle as opposed to Fritzing.

Thanks for all your help, I'm very grateful - if I can get this leg-less MCU fixed on that board (although I shudder in horror at the thought I do have a hot-air station, so...), that's the save I was hoping for when I wrote the post.

JoeN:
Hey, I think Crossroads may be right on this. It's pretty close - the footprint is different but it looks like it is compatible. This is from DipTrace. This is the QFP32 7mm/7mm/0.5mm and QFN32 5mm/5mm/0.5mm footprints side by side. The problem here is that Diptrace doesn't show the exact outline of the package itself so if you imagine a worst case scenario here the QFN's pins might be just inside the radius of the QFP's traces. But it may be OK too.

Very kind of you to put that image up - thank you for that. By CrossRoad's help it's clear to me now that I'll have to try and get a QFP32 and try and solder it.

JoeN:
A caviat is that QFNs are not as easy to solder as QFPs so keep that in mind. I hot air solder them myself and inspect them under a microscope.

I shudder at the notion - I've never worked with them before. But there's a first time for everything. Hot air and paste at the ready, then.

JoeN:
I have use Atmel's QFN32 5mm/5mm/0.5mm packages. Too bad I don't have a PCB with a QFP32 7mm/7mm/0.5mm footprint on it otherwise I would see if it would work out for you.

Again, that's awfully kind of you - thank a lot. I might contact you in the case I need a bit of advice in regards to the soldering - would that be ok with you?

Fritzing - you get what you pay for. Not really an optimal design tool.

CrossRoads:
Fritzing - you get what you pay for. Not really an optimal design tool.

I'm inclined to agree with you, now more than ever because of my issue with the foot print obviously, but for those out there who're just starting out I'll hasten to add that it's a great visualizer for getting into electronics, with its combined breadboard/schematic/PCB view. I probably wouldn't have begun to design my own boards if it hadn't been for Fritzing. So good for beginners as an try point into the more serious programs like Eagle and such.

I've only seen it from the other side - poor "visualizer" of schematics, simple 'black boxes" for components with no clue as to functionality. To an engineer, a very poor tool.