AnsweredAssumed Answered

probing on smd pad's?

Question asked by ANDREL on Feb 10, 2011
Latest reply on Apr 5, 2012 by fritz001

Like • Show 0 Likes0
Comment • 3

Hi,
I have this board, that has smd on the bottom side (the first time i see this here). Now 6 nodes are inaccessible unless i probe on smd pads (resistors). Is this a good idea, who has done this?.

Regards,
Andre

No one else has this question

Outcomes

3 Replies

ANDREL Feb 10, 2011 11:29 PM
Mark Correct
Correct Answer
I found this on the internet:

Probing on components is a risky practice. The only way to probe SMT parts directly is to probe on the solder fillet. This presents (3) main problems:

   1. Solder fillets are not flat, causing the probes to side-load, which will quickly make them unusable.
   2. SMT parts often “move” from UUT to UUT making consistent contact a problem.
   3. Probing directly on components can damage the component and also can render a poorly soldered component “good” by forcing down a lifted pad.

Who has ignored this    ??, tell me your experience
Like • Show 0 Likes0
Actions
- fritz001 @ ANDREL on Apr 5, 2012 3:47 PM
  Mark Correct
  Correct Answer
  Let me start by saying if you have control over the PCB layout add a testpoint or a bead probe. I have not probed SMD pads of capacitors or resistors but I have been forced to probe the pads of SOIC devices. This was only possible because the pads were very long. The pads were 28mil wide and at least 25mil from the edge of the pad to the pin of the IC. Basically, a 28mil square testpad. So, if there is enough exposed metal it can be reliable.
  I took the following precautions. First, use 50mil probes with a pointed tip to reduce the chance of contact with the part. Second, offset the probe til it is only 13mil from the outside edge of the pad. Finally, use guided probing to protect the probes from damage from skewed components.
  Like • Show 0 Likes0
  Actions
adrianc Sep 14, 2011 10:37 PM
Mark Correct
Correct Answer
Hi,
Have you considered to use bead probes?
This is a small ball of solder printed on the trace what is so small that it does not affect the signal quality.
The beadprobe should be designed into the PCB by the pcb layout designer.
It will require the trace to be on the top or bottom layers of the pcb.
Attachments
- beadprobe2.jpg4.7 KB
- beadprobe.jpg6.4 KB
Like • Show 0 Likes0
Actions

probing on smd pad's?

Outcomes

Attachments

Related Content

Recommended Content