Any significance to the shape of the solder pads on a PCB?

I am trying to create a schematic from a PCB and I notice each component has one square solder pad hole and one circular one. Is there any significance to that?

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Nelson
Reply to
Nelson
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Perhaps it indicates the polarity of diodes, LEDs, etc.

Reply to
William Sommerwerck

Commonly a "pin 1" designation, entered as part of the "footprint" artwork for the part in whatever PCB-design package was used to do the layout. You'll almost always see these used on IC footprint patterns (the through-hole ones at least). I imagine that in commercial PCB design packages, it's usually a convention to identify Pin 1 in any footprint where it's practical, since these footprints may be used both for polarized and non-polarized components.

Reply to
David Platt

100% correct!

Paul

Reply to
Paul Drahn

On Wed, 21 Aug 2013 15:54:13 -0400, Paul Drahn wrote (in article ):

But all the resistors are that way too :-) The board appears to have a plane sandwiched between the top and bottom. I'm guessing it is either a ground plane or a V+ plane. I thought maybe one or the other indicated a plated through hole that connected to the mid plane.

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Nelson
Reply to
Nelson

I thought you were referring to the silk screen art work. Are you saying you took all the components off the board and sucked the solder out of the holes so you can now see that some holes were drilled and some were punched with a square punch?

A properly soldered board will not show any hole if they are plated-through holes.

Paul

Reply to
Paul Drahn

Back when I worked with Tango (jurassic era) the pins had a name to match u p with the pads in PCB. For non-polar components like resistors the pads we re A and B. All the through hole footprints had 1 square terminal. The sche matic component had the same name for the pins to match up with the pad nam e. Failing name matching would cause a net list error and you want NO net e rrors if you expect it to work.

Reply to
stratus46

He's referring to the shape of the metal pad, not the hole.

Reply to
William Sommerwerck

On Wed, 21 Aug 2013 17:27:10 -0400, Nelson wrote (in article ):

Well, maybe not all the resistors, but quite a few of them. Here's a photo:

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Nelson
Reply to
Nelson

Those square holes are for the ground plane end of the resistor (and other similar parts). This is so the solder will wet properly and thus connect the leg of the device to the feedthrough hole. The feedthrough hole is separated from the copper plane mass except for four corners otherwise the copper plane will sink too much of the heat. More important on boards that are hand soldered instead of wave-soldered...

John :-#)#

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Reply to
John Robertson

On Thu, 22 Aug 2013 00:55:54 -0400, John Robertson wrote (in article ):

Thanks! I'm having a hard time visualizing this, however. I have researched "thermal relief" which is what I think you are referring to but I can't find any discussion of square pads contacting only at the corners. In particular, in this case, the ground plane or "copper flow" appears to be an interior layer. I can't visualize how the through holes connect to this or pass through without connecting.

Here is an image of the back of the board showing the embedded ground plane:

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As you can see there are quite a few square pads which don't appear to connect to the ground plane.

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Nelson
Reply to
Nelson

It may then be an artifact of the PCB CAD software - the first pin of a series (2 is a series in this case) is always square. I like the thermal relief term (thanks!) and for some parts it is probably still valid.

John :-#)#

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Reply to
John Robertson

SIL patterns invariably have one end with a square solder pad. This just helps you recognize which end is which when you turn your board over. I don't think it has a functional significance.

Reply to
ss.chelsc

The square pad is simply identification. Pin-1, Cathode, (+) etc.

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Jeff-1.0 
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Reply to
Foxs Mercantile

We never used that convention. They were either all square or all rounded.

NT

Reply to
tabbypurr

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