How about a cross section of the SJ?
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Tuesday, June 03, 2008 6:55 AM
To: [log in to unmask]
Subject: [TN] Intermitent contact on LEDs
Dear Technos,
I am investigating some returns from the field and can't really figure
out what the problem is.
On boards having 200+ TH LEDs we see 4 to 10 malfunctioning ones, but if
pressure is applied on the component it starts functioning. Under my
regular microscope I cannot see any problem with the joints and when
removed, the LEDs work properly. One unpleasant thing though is that the
LEDs were machine inserted and clinched to the board pretty tightly, so
the solder did not wick up on the leads too much, but if the joint was
somehow fractured, applying pressure on the component would only widen
the gap, since the bulk of the joint is on the opposite side of the
pressure point, am I right?
The PCB is a regular 0.062" thick 2 layer board, with the regular 1oz of
Cu on each layer, of pretty impressive dimensions, 22"x10". There is no
pattern in the disposition of the malfunctioning LEDs.
Besides cracked PTH, which we will investigate since I am preparing to
send out some boards for cross-sectioning, can it be anything else?
Thanks,
Ioan
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