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Topic: Got wrong pitch FQFP MCU - possible to make a save? (Read 2644 times) previous topic - next topic

harleydk

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 :-(

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.
---
My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

CrossRoads

Check the data sheet.
This package

34.4 32M1-A

has 5mm body, 0.5mm pitch.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

harleydk


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.
---
My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

CrossRoads

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

http://www.mouser.com/Search/Refine.aspx?Keyword=atmega328p-m
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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...

harleydk


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.
---
My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

JoeN

#6
Apr 09, 2013, 09:05 am Last Edit: Apr 09, 2013, 09:09 am by JoeN Reason: 1
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.
I have only come here seeking knowledge. Things they would not teach me of in college.

harleydk


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.
---
My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

harleydk


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 hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

westfw

Quote
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...

harleydk


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.
---
My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

westfw

heh.  I also recently acquired some "Earrings."

JoeN


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.
I have only come here seeking knowledge. Things they would not teach me of in college.

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.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

JoeN

#14
Apr 09, 2013, 07:48 pm Last Edit: Apr 10, 2013, 02:28 am by JoeN Reason: 1

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.
I have only come here seeking knowledge. Things they would not teach me of in college.

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