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

N

Nelson

Jan 1, 1970
0
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?
 
W

William Sommerwerck

Jan 1, 1970
0
"Nelson" wrote in message
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?

Perhaps it indicates the polarity of diodes, LEDs, etc.
 
N

Nelson

Jan 1, 1970
0
100% correct!

Paul

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.
 
P

Paul Drahn

Jan 1, 1970
0
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.
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
 
Back when I worked with Tango (jurassic era) the pins had a name to match up with the pads in PCB. For non-polar components like resistors the pads were A and B. All the through hole footprints had 1 square terminal. The schematic component had the same name for the pins to match up with the pad name. Failing name matching would cause a net list error and you want NO net errors if you expect it to work.

 
W

William Sommerwerck

Jan 1, 1970
0
"Paul Drahn" wrote in message
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?

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

Nelson

Jan 1, 1970
0
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.

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

http://www.deejr.net/pbp/2013/08/21/PowerBoardFront.jpg
 
N

Nelson

Jan 1, 1970
0
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 :-#)#

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:

http://www.deejr.net/pbp/2013/08/22/PowerBoardBack.jpg

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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