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Topic: Got wrong pitch FQFP MCU - possible to make a save? (Read 2551 times) previous topic - next topic

harleydk


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.
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My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

harleydk


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.


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.


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?
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My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

CrossRoads

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


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

CrossRoads

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.
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

#20
Apr 10, 2013, 08:40 pm Last Edit: Apr 10, 2013, 09:16 pm by JoeN Reason: 1


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.


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.


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?


Sure.  The way I have done it is actually I pre-tin the pads with regular solder and lots of flux.  I reflux the whole footprint and the IC and I melt the solder all at once with the hot air and place the QFN on top of that, it usually settles right in.  It will never settle between  the pads which is great but it can settle off a whole pad so have tweezers ready to give it a nudge if it does that.  The microscope is to check out if everything went OK and how all the heels look which is impossible to see with no or low magnification, at least for me.

Here is one I did with this technique.  This was taken through the eyepiece on the microscope so the quality is only OKish.



This is a Mega8U2.  Designed in DipTrace.  Manufactured at OSHPark.  Maybe I should have cleaned it before showing it off.   :smiley-eek:

DipTrace is free to hobbiests up to 500 pins.  You might want to give it a spin.  It's very easy to use.  I know Crossroads and a lot of other people like Eagle but the free version is limited and the pay version gets very expensive very quickly.  DipTrace has lowered pricing for hobbiests.
I have only come here seeking knowledge. Things they would not teach me of in college.

harleydk


Sure.  The way I have done it is actually I pre-tin the pads with regular solder and lots of flux.  I reflux the whole footprint and the IC and I melt the solder all at once with the hot air and place the QFN on top of that, it usually settles right in.  It will never settle between  the pads which is great but it can settle off a whole pad so have tweezers ready to give it a nudge if it does that.  The microscope is to check out if everything went OK and how all the heels look which is impossible to see with no or low magnification, at least for me.


You make it sound probably all too easy! :-) I was thinking along the same lines. I have some decent quality solder paste with lots of flux in it so that's what I'll pre-tin with. I also have a pair of surgical glasses with x20 magnification at hand :-) Thanks for describing your m.o.,


This is a Mega8U2.  Designed in DipTrace.  Manufactured at OSHPark.  Maybe I should have cleaned it before showing it off.   :smiley-eek:
DipTrace is free to hobbiests up to 500 pins.  You might want to give it a spin.  It's very easy to use.  I know Crossroads and a lot of other people like Eagle but the free version is limited and the pay version gets very expensive very quickly.  DipTrace has lowered pricing for hobbiests.


I hadn't noticed DipTrace until now. It looks mighty. Being a beginner hobbyist I'm a bit daunted by Eagle and all it's libraries. I like the notion of dragging a named IC or component from a library, but the one time I tried my hand at Eagle I came up short of a couple of components and had a bothersome time just figuring out how to fint a component with a similar footprint. That was the lure of Fritzing (well that and the breadboard view), that the components are anonymous until suppled with a value and a footprint of choice. Time and experience should weed those things out, of course, and of course it's a highly regarded piece of software with most. On your recommendation I'll make a point of trying out DipTrace before I try my hand at Eagle any further.
---
My hopefully helpful blog at technicalstuffhopefullyuseful.blogspot.com

JoeN


I hadn't noticed DipTrace until now. It looks mighty. Being a beginner hobbyist I'm a bit daunted by Eagle and all it's libraries. I like the notion of dragging a named IC or component from a library, but the one time I tried my hand at Eagle I came up short of a couple of components and had a bothersome time just figuring out how to fint a component with a similar footprint. That was the lure of Fritzing (well that and the breadboard view), that the components are anonymous until suppled with a value and a footprint of choice. Time and experience should weed those things out, of course, and of course it's a highly regarded piece of software with most. On your recommendation I'll make a point of trying out DipTrace before I try my hand at Eagle any further.


DipTrace does have some of these problems too, for example, the ATMega328P is not listed.  Do you might say to yourself why the heck not, it's one of the most popular uCs out there because of Arduino.  But the ATmega48 is in the list and has the exact same pinout - it's pretty much the same thing with 1/8th the flash.  So keep that in mind to look for other versions of the same chip.  Also, assuming DipTrace has an appropriate footprint (pattern in their lingo), it's really quite easy to map a pinout to a footprint and be using it in a few minutes.  I've done this for 100 TQFPs no problem, there is no provided component for the Altera EPM240 which I have used in a couple of project now (I LOVE CPLDS!).  You make your own library and throw all your random stuff in there and add it to the library list.  Very easy.

If you consider using DipTrace, I would recommend their getting started video.  It's fast-paced and shows you exactly the things you need to know to get a project done and nothing else.

http://www.diptrace.com/tour/
I have only come here seeking knowledge. Things they would not teach me of in college.

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