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Again: TQFP wrong Trace sizes

balczezzz 5 years, 4 months ago

Hi,

I am posting my problem as a new thread, since there is a problem in replying to existing ones. Just had the same issue with a 328P-AU 32 pin Atmega SMD TQFP microcontroller as mentioned here. I measured the chip and looks like it is in line with the datasheet specs from Atmel (see page 19). Designed, exported via Fritzing to pdf and then printed out -it comes out smaller (and I am printing 100% size from Mac). Please find the images attached below. Would appreciate if you could double check or point to where I am wrong.

Oh, almost forgot I am on a Mac SOX 10.7.5 Fritzing 0.8.0 b08d5 2013-06-12.



Jonathan Cohen 5 years, 4 months ago

Hi Balczezzz,

Thanks for taking the measurements. The part we have in Fritzing to match this (I believe) is the Atmega8U2 in the tqfp32-08 package. In Fritzing, the part is exactly 10mm sq which is a bit bigger than the measurements in your first image (basically, the pins are longer). However, the internal ceramic square is indeed very close to 7mm--a close match to your second image, and the third distance (width of pins?) also comes very close to your measurement of 6mm in the 3rd image.

So I can think of 3 possibilities here:

1. I am not using the same part, so the rest of this is probably irrelevant

2. it's a Fritzing bug

3. there is still a printer setting issue somewhere

Though it could be a bug that has crept in, we worked pretty hard to make sure that printing was accurate. So I would suggest placing the ruler part (at the very bottom of the parts bin) next to the Fritzing part in question and printing out the combination. In the printout, is the ruler distorted compared to a real ruler? If so, you might try a different route--rather than printing directly from Fritzing, export the image to pdf and try printing that. Do you get the same results? In the past we have found that some hidden or advanced printing option (like centering the image) is responsible for size distortion even when you select 100% as the main option.

Please let us know what you find.

Thanks.

- j