Pick and Place damage ?

[N Cook]

4 year old board covered in low power SMD.
Intermittant noise problem located to one 1206 format 3K9 resistor.
No solder problem , but resistor would appear to be cracked in its body,
can't see anything under 30x microscope, but measuring over the lands , can
be stressed towards o/c. Not yet removed it as a more urgent job begs.

How do you stress all such 1206 devices , safely, to check if there are
others similar, without causing the damage being sought?

 

[Smitty Two]

4 year old board covered in low power SMD.
Intermittant noise problem located to one 1206 format 3K9 resistor.
No solder problem , but resistor would appear to be cracked in its body,
can't see anything under 30x microscope, but measuring over the lands , can
be stressed towards o/c. Not yet removed it as a more urgent job begs.

How do you stress all such 1206 devices , safely, to check if there are
others similar, without causing the damage being sought?

Did you reflow the solder yet? Even at 30x, a crack could escape one's
notice. If the board was panelized and the suspect resistor is near the
edge, depaneling may have stressed it and/or the solder that holds it.

 

[N Cook]

Did you reflow the solder yet? Even at 30x, a crack could escape one's
notice. If the board was panelized and the suspect resistor is near the
edge, depaneling may have stressed it and/or the solder that holds it.

In main body of board , not been dropped or abused in use
I desoldered it and it is failure of the bond between the resistive film and
one of the lands but no crack in the body in the sense that it holds
together in normal handling.

I have a small adjustable automatic centre punch (spring loaded ratchet
release for easy centre popping of sheet metal). The minimum imulse setting
of that is 9Kg but found a couple of much weaker springs to try inside .
one gives range 1.5 to 2 Kg before the impulse, the other 2.5 to 3Kg range
of adjustment.

I was thinking of pinging at the 1.5Kg setting on all the 3K9 SM Rs on the
board after DVM checking and then DVM after pinging. Any opinions ?
Probably about 6 to 10 of that value on the board

 

[Smitty Two]

In main body of board , not been dropped or abused in use
I desoldered it and it is failure of the bond between the resistive film and
one of the lands but no crack in the body in the sense that it holds
together in normal handling.

I have a small adjustable automatic centre punch (spring loaded ratchet
release for easy centre popping of sheet metal). The minimum imulse setting
of that is 9Kg but found a couple of much weaker springs to try inside .
one gives range 1.5 to 2 Kg before the impulse, the other 2.5 to 3Kg range
of adjustment.

I was thinking of pinging at the 1.5Kg setting on all the 3K9 SM Rs on the
board after DVM checking and then DVM after pinging. Any opinions ?
Probably about 6 to 10 of that value on the board

If your objective is to test "without causing the damage being sought,"
I personally wouldn't use the center punch. Maybe a light tap from the
butt end of a dental probe. I know you enjoy the intellectual exercise
in these matters, but if you're really wary of the other resistors, why
not just replace them all since there's only a handful?

 

[N Cook]

If your objective is to test "without causing the damage being sought,"
I personally wouldn't use the center punch. Maybe a light tap from the
butt end of a dental probe. I know you enjoy the intellectual exercise
in these matters, but if you're really wary of the other resistors, why
not just replace them all since there's only a handful?

1.5Kg sounds worse than it is. Trying on the back of my hand is not painful
or self-mutillation.

 

[Michael A. Terrell]

1.5Kg sounds worse than it is. Trying on the back of my hand is not painful
or self-mutillation.

Your skin isn't brittle ceramic, either.

 

[N Cook]

Your skin isn't brittle ceramic, either.

Pinged, at 1.5Kg, the 7 Rs of that value, on the side rather than top as
that messed up the printing. No resistance variation before or after but if
it bounces back then I know what to check first.
The owner could not believe how tiny the miscreant was, lost in a minigrip
bag.