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Helpful ReplyHot!TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827

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daraga
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2017/10/27 00:58:49 (permalink)
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TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827

Hi to all,
 
I am working with PIC16LF1827 uQFN and I can not find any reference about if exposed pad should go connected to ground and if this pad could be the central ground of the microcontroller.
 
I have been reading different datasheets of other components with similar footprint and I did not find an answer.
 
Which is your experience about this question? Is it a big mistake to connect the exposed pad to ground?
Anyone knows how is connected internally the exposed pad on uQFN case?
 
Thanks in advance
daraga
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Nikolay_Po
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Re: TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827 2017/10/27 04:59:26 (permalink) ☄ Helpfulby Jim Nickerson 2017/10/27 06:08:30
+4 (4)
Submit a ticket for Microchip tech support. This is the best way to go. Then tell here about support answer.
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mbrowning
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Re: TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827 2017/10/27 08:04:56 (permalink)
+2 (2)
I just ohmed out the exposed pad on a pic18lf56k42 in 48-uqfn. The exposed pad is not connected to any other pins. I would recommend connecting it to GND, but the chip doesn't require it (unless you are driving so much IO current that you need heat sinking).
 
This is what I thought was true - the exposed pad is for mechanical connection with no electrical connection - but I wanted to get to work and measure before posting.
 
Of course this is a different device from yours but I believe this is pretty normal unless the datasheet specifically says to connect the pad to a certain net.
 
Interesting side - I got some samples from Microchip of the 56k42 which came in the usual little black ESD box. I also ordered some from Digikey - which came 10 transparent ESD bags packed into a bigger ESD bag. Each transparent bag had one bare chip in it - no tube or tape.
I am in the process of hand soldering one of these 0.4mm pitch QFNs onto a prototype board. I had to quit for a while when the solder station was needed for higher priority work, but I needed a break anyway. I finished one side and my nerves were shot (I'm sure the 5 cups of coffee didn't help).
post edited by mbrowning - 2017/10/27 08:10:18
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jack@kksound
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Re: TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827 2017/10/27 08:49:07 (permalink)
+2 (2)
Microchip has an application note, AN18.15, that discusses the QFN package pcb requirements. Possibly this may be of help. http://www.microchip.com/....aspx?appnote=en562787
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coffee critic
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Re: TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827 2017/10/27 09:54:31 (permalink)
+2 (2)
There is no electrical advantage to connecting the QFN pad to ground but it can provide some additional RFI shielding if this is a concern.  There can be a slight improvement to the thermal performance if the substrate has thermal via. There usually isn't much heat generated by a PIC.   

n_*$
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daraga
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Re: TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827 2017/10/30 00:31:27 (permalink)
+1 (1)
Hi to all,
 
Firstly many thanks to all for your replies. As I can realize this subject is a little bit dark because if the data of the component does not say anything about it..... all of us have our own theory.
 
I have found the "recommended footprint" for the PIC in the next link.
http://www.microchip.com/development-tools/resources/cad-cae-symbols
 
If I create the footprint it has not vias on the Exposed Pad. I think that it is quite significant. 
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marksullivan
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Re: TO GROUND EXPOSED PAD OR NOT TO GROUND - PIC16LF1827 2021/01/29 13:51:59 (permalink)
+1 (1)
This is old, but you never know.
 
Although AFAIK, all Microchip parts can have the die pad grounded, this is not a safe general rule.  I have run into more than one device where the pad was some other connection.  The first time it happened to me, it was a real mess as you can probably imagine.
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