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What are these round pads on the bottom of a PCB?

Can you place vias inside a QFN footprint?Designing footprint for LFCSP CP-8-13 what should be the pad sizeWhat are these exposed copper rectangles for on the mbed NXP LPC1768?Connecting top and bottom SMD component pads using viaIdentifying Feature on VGA PCBHow important is it to track from centre of pad in PCB routing?Copper dimension around the PCB component's hole (pad?)Some pads on a PCB are marked in clusters and I can't understand which one is which

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margin-bottom:0;

10

2

$begingroup$

What are these round pads on the bottom of a PCB marked ScX?

I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.

My best guess is that they're termination pads, but googling it didn't turn up many results so I can't verify that.

pcb

share|improve this question

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

asked May 7 at 22:51

fandorfandor

17611 silver badge1313 bronze badges

$endgroup$

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  What's a termination pad?
  $endgroup$
  – pipe
  May 8 at 9:35
  

  
  
  
  

add a comment
 | 

10

2

$begingroup$

What are these round pads on the bottom of a PCB marked ScX?

I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.

My best guess is that they're termination pads, but googling it didn't turn up many results so I can't verify that.

pcb

share|improve this question

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

asked May 7 at 22:51

fandorfandor

17611 silver badge1313 bronze badges

$endgroup$

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  What's a termination pad?
  $endgroup$
  – pipe
  May 8 at 9:35
  

  
  
  
  

add a comment
 | 

$begingroup$

What are these round pads on the bottom of a PCB marked ScX?

I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.

My best guess is that they're termination pads, but googling it didn't turn up many results so I can't verify that.

pcb

share|improve this question

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

asked May 7 at 22:51

fandorfandor

17611 silver badge1313 bronze badges

$endgroup$

share|improve this question

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

asked May 7 at 22:51

fandorfandor

17611 silver badge1313 bronze badges

share|improve this question

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

asked May 7 at 22:51

fandorfandor

17611 silver badge1313 bronze badges

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

edited May 8 at 11:54

pipe

10.5k44 gold badges2727 silver badges5959 bronze badges

asked May 7 at 22:51

fandorfandor

17611 silver badge1313 bronze badges

asked May 7 at 22:51

fandorfandor

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3 Answers
3

active

oldest

votes

30

$begingroup$

As mentioned in some of the comments, these are test pads designed for use with a pogo-pin test fixture, also known as a bed-of-nails test fixture. These fixtures have a specially-shaped array of pogo-pins which press down and make contact with the test pads on the board under test:

These test pads and the test points are probably used in different parts of the manufacturing process. For example, the test points may be used for board-level testing and the test pads may be used for system-level testing. Or, perhaps, the test pads are used for programming and/or debugging firmware, when the device under test is clamped into the bed-of-nails fixture.

share|improve this answer

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  +1; this answer is much more complete than mine. To the asker: also look at @ThomasWeller's answer, which explains why they might be labelled differently.
  $endgroup$
  – Hearth
  May 8 at 16:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Bed of nails isn’t as popular nowadays. Flying probe, wherein four or so pins attached to a robotic arm connect to the test points, is what is generally used.
  $endgroup$
  – user110971
  May 8 at 18:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @user110971 I don't know about popularity, but I know a LOT of places that still do bed of nails testing
  $endgroup$
  – DerStrom8
  May 8 at 21:50
  

  
  
  
  

add a comment
 | 

20

$begingroup$

They're called test points. They're places to stick your multimeter probes, or, more commonly, an industrial test jig.

share|improve this answer

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hm, I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.
  $endgroup$
  – fandor
  May 7 at 23:14
  
  

  
  
  
  


• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  $begingroup$
  They may be only for system validation by the manufacturer, whereas the ones labelled TP could be for maintenance purposes? They look exactly like the test points used on a number of boards I've seen and made, so I'd be surprised if they aren't.
  $endgroup$
  – Hearth
  May 7 at 23:17
  

  
  
  
  


• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  $begingroup$
  These are the eMMC interface debug points, to connect a custom-made pogo-pin test jig.
  $endgroup$
  – Ale..chenski
  May 8 at 2:59
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  Those are probably there to upload the firmware in the eMMC during production. So it isn't really for testing, but the principle is the same.
  $endgroup$
  – dim
  May 8 at 5:12
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  @fandor That information should have gone into the question. Now you can't accept this answer because it's not correct, while people have outdone themselves and not only written their alternative answers in the comment section, but in the comment section on a different answer! Good luck accepting those!
  $endgroup$
  – pipe
  May 8 at 9:39
  

  
  
  
  

add a comment
 | 

6

$begingroup$

I think SC could be short for "spring contact" (spring loaded contact), in which case the PCB will be mounted together with some other PCB, similar to a Arduino header, but a different connector type not using male and female pins.

share|improve this answer

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hm, interesting, so the pads would be designed for soldering the SMT spring contacts. It seems the most likely answer considering the size of the pads.
  $endgroup$
  – pipe
  May 9 at 8:23
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @pipe Not really, the pads look already plated, so they are there to be touched by the "pistons" of spring contacts mounted on a different board (or a bed-of-nails as mentioned in the other answers).
  $endgroup$
  – TooTea
  May 9 at 11:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @TooTea The plating looks like the standard ENIG that you can find on the other unsoldered copper on the board. They simply chose not to populate these pins.
  $endgroup$
  – pipe
  May 9 at 11:49
  

  
  
  
  

add a comment
 | 

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30

$begingroup$

As mentioned in some of the comments, these are test pads designed for use with a pogo-pin test fixture, also known as a bed-of-nails test fixture. These fixtures have a specially-shaped array of pogo-pins which press down and make contact with the test pads on the board under test:

These test pads and the test points are probably used in different parts of the manufacturing process. For example, the test points may be used for board-level testing and the test pads may be used for system-level testing. Or, perhaps, the test pads are used for programming and/or debugging firmware, when the device under test is clamped into the bed-of-nails fixture.

share|improve this answer

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  +1; this answer is much more complete than mine. To the asker: also look at @ThomasWeller's answer, which explains why they might be labelled differently.
  $endgroup$
  – Hearth
  May 8 at 16:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Bed of nails isn’t as popular nowadays. Flying probe, wherein four or so pins attached to a robotic arm connect to the test points, is what is generally used.
  $endgroup$
  – user110971
  May 8 at 18:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @user110971 I don't know about popularity, but I know a LOT of places that still do bed of nails testing
  $endgroup$
  – DerStrom8
  May 8 at 21:50
  

  
  
  
  

add a comment
 | 

30

$begingroup$

As mentioned in some of the comments, these are test pads designed for use with a pogo-pin test fixture, also known as a bed-of-nails test fixture. These fixtures have a specially-shaped array of pogo-pins which press down and make contact with the test pads on the board under test:

These test pads and the test points are probably used in different parts of the manufacturing process. For example, the test points may be used for board-level testing and the test pads may be used for system-level testing. Or, perhaps, the test pads are used for programming and/or debugging firmware, when the device under test is clamped into the bed-of-nails fixture.

share|improve this answer

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

$endgroup$

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  +1; this answer is much more complete than mine. To the asker: also look at @ThomasWeller's answer, which explains why they might be labelled differently.
  $endgroup$
  – Hearth
  May 8 at 16:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  Bed of nails isn’t as popular nowadays. Flying probe, wherein four or so pins attached to a robotic arm connect to the test points, is what is generally used.
  $endgroup$
  – user110971
  May 8 at 18:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @user110971 I don't know about popularity, but I know a LOT of places that still do bed of nails testing
  $endgroup$
  – DerStrom8
  May 8 at 21:50
  

  
  
  
  

add a comment
 | 

$begingroup$

As mentioned in some of the comments, these are test pads designed for use with a pogo-pin test fixture, also known as a bed-of-nails test fixture. These fixtures have a specially-shaped array of pogo-pins which press down and make contact with the test pads on the board under test:

These test pads and the test points are probably used in different parts of the manufacturing process. For example, the test points may be used for board-level testing and the test pads may be used for system-level testing. Or, perhaps, the test pads are used for programming and/or debugging firmware, when the device under test is clamped into the bed-of-nails fixture.

share|improve this answer

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

$endgroup$

share|improve this answer

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

answered May 8 at 11:12

DerStrom8DerStrom8

15.3k66 gold badges3131 silver badges6565 bronze badges

20

$begingroup$

They're called test points. They're places to stick your multimeter probes, or, more commonly, an industrial test jig.

share|improve this answer

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hm, I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.
  $endgroup$
  – fandor
  May 7 at 23:14
  
  

  
  
  
  


• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  $begingroup$
  They may be only for system validation by the manufacturer, whereas the ones labelled TP could be for maintenance purposes? They look exactly like the test points used on a number of boards I've seen and made, so I'd be surprised if they aren't.
  $endgroup$
  – Hearth
  May 7 at 23:17
  

  
  
  
  


• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  $begingroup$
  These are the eMMC interface debug points, to connect a custom-made pogo-pin test jig.
  $endgroup$
  – Ale..chenski
  May 8 at 2:59
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  Those are probably there to upload the firmware in the eMMC during production. So it isn't really for testing, but the principle is the same.
  $endgroup$
  – dim
  May 8 at 5:12
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  @fandor That information should have gone into the question. Now you can't accept this answer because it's not correct, while people have outdone themselves and not only written their alternative answers in the comment section, but in the comment section on a different answer! Good luck accepting those!
  $endgroup$
  – pipe
  May 8 at 9:39
  

  
  
  
  

add a comment
 | 

20

$begingroup$

They're called test points. They're places to stick your multimeter probes, or, more commonly, an industrial test jig.

share|improve this answer

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hm, I don't think these are test points - this board has some (not in the picture) and they're labelled with TP and the pad size and shape are different.
  $endgroup$
  – fandor
  May 7 at 23:14
  
  

  
  
  
  


• 
  
  
  

  
  11
  

  
  
  
  
  
  

  
  $begingroup$
  They may be only for system validation by the manufacturer, whereas the ones labelled TP could be for maintenance purposes? They look exactly like the test points used on a number of boards I've seen and made, so I'd be surprised if they aren't.
  $endgroup$
  – Hearth
  May 7 at 23:17
  

  
  
  
  


• 
  
  
  

  
  7
  

  
  
  
  
  
  

  
  $begingroup$
  These are the eMMC interface debug points, to connect a custom-made pogo-pin test jig.
  $endgroup$
  – Ale..chenski
  May 8 at 2:59
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  Those are probably there to upload the firmware in the eMMC during production. So it isn't really for testing, but the principle is the same.
  $endgroup$
  – dim
  May 8 at 5:12
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  @fandor That information should have gone into the question. Now you can't accept this answer because it's not correct, while people have outdone themselves and not only written their alternative answers in the comment section, but in the comment section on a different answer! Good luck accepting those!
  $endgroup$
  – pipe
  May 8 at 9:39
  

  
  
  
  

add a comment
 | 

$begingroup$

They're called test points. They're places to stick your multimeter probes, or, more commonly, an industrial test jig.

share|improve this answer

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

$endgroup$

share|improve this answer

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

answered May 7 at 22:52

HearthHearth

7,76311 gold badge1919 silver badges5353 bronze badges

6

$begingroup$

I think SC could be short for "spring contact" (spring loaded contact), in which case the PCB will be mounted together with some other PCB, similar to a Arduino header, but a different connector type not using male and female pins.

share|improve this answer

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hm, interesting, so the pads would be designed for soldering the SMT spring contacts. It seems the most likely answer considering the size of the pads.
  $endgroup$
  – pipe
  May 9 at 8:23
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @pipe Not really, the pads look already plated, so they are there to be touched by the "pistons" of spring contacts mounted on a different board (or a bed-of-nails as mentioned in the other answers).
  $endgroup$
  – TooTea
  May 9 at 11:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @TooTea The plating looks like the standard ENIG that you can find on the other unsoldered copper on the board. They simply chose not to populate these pins.
  $endgroup$
  – pipe
  May 9 at 11:49
  

  
  
  
  

add a comment
 | 

6

$begingroup$

I think SC could be short for "spring contact" (spring loaded contact), in which case the PCB will be mounted together with some other PCB, similar to a Arduino header, but a different connector type not using male and female pins.

share|improve this answer

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Hm, interesting, so the pads would be designed for soldering the SMT spring contacts. It seems the most likely answer considering the size of the pads.
  $endgroup$
  – pipe
  May 9 at 8:23
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  $begingroup$
  @pipe Not really, the pads look already plated, so they are there to be touched by the "pistons" of spring contacts mounted on a different board (or a bed-of-nails as mentioned in the other answers).
  $endgroup$
  – TooTea
  May 9 at 11:41
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @TooTea The plating looks like the standard ENIG that you can find on the other unsoldered copper on the board. They simply chose not to populate these pins.
  $endgroup$
  – pipe
  May 9 at 11:49
  

  
  
  
  

add a comment
 | 

$begingroup$

I think SC could be short for "spring contact" (spring loaded contact), in which case the PCB will be mounted together with some other PCB, similar to a Arduino header, but a different connector type not using male and female pins.

share|improve this answer

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges

$endgroup$

share|improve this answer

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges

answered May 8 at 15:24

Thomas WellerThomas Weller

40244 silver badges1616 bronze badges