John,
I have never seen any recommendations as to how long people should stare at
a solder joint, nor, think I, that giving a time is possible - the time
required to inspect a joint is entirely in the eye of the beholder (or
Inspector) and depends on things like the eyesight of your inspector, how
quick he/she is at assimilating and interpreting what he/she is seeing, how
critical it is to have a completely defect-free joint and how difficult it
is to detect a particular defect visually. Such human variables and other
things in visual inspection are beyond the scope of most specs. They just
tell you what to do and how to do it - how long it takes is up to the
individual.
Having said that, it sounds like your inspectors are desparate to justify
their existence. If you have your suppliers well house-trained, it should
be possible to do away with further inspection operations and accept their
certification. Remember, you can't inspect quality into a job - it merely
catches some (note some, not all) defects and costs a lot of extra money
besides. If you're only getting one minor failure in 1000 units, I'ld
either move to batch sampling at in-coming inspection, or remove in-coming
inspection altogether until such time as you have problems with the product
again. Have you asked your inspectors why they feel they have to take so
long to inspect these boards so closely?
Pete Duncan
John Fahey
<jfahey@ECHEL To: [log in to unmask]
ON.COM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Sent by: Subject: [TN] Inspection Criteria
TechNet
<[log in to unmask]
ORG>
07/21/01
04:32 AM
Please
respond to
"TechNet
E-Mail
Forum.";
Please
respond to
John Fahey
Do any IPC standards (particularly IPC-610-C)recommend standard
magnification, distance, and time for inspecting surface mount solder
joints?
Some of our internal inspectors can spend up to 5 mins per small PCB assy
under 30x magnification to investigate and find minor fracture in solder
joint(say 1/1000 units)supplied by our CM's. These units have already gone
through 3 rounds on 100% visual inspection at the CM. These units pass
Functional test.
My worry is that our inspectors feel that they NEED to find visual defects
in order to show that they are doing their job effectively! Unfortunately,
finding 1 defect in a batch of 1000 assemblies under high magnification
with ample time to twist and turn the board under inspection, results in us
having to do 100% inspection on every unit from our CMs!
Does anyone have any input at all on this issue?
Thanks.
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