TECHNET Archives

January 2002

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Lou Hart <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 3 Jan 2002 13:57:12 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (96 lines)
Olivia, Kathy, et al., what kinds of defects is inspection missing, and
what fraction of defects is it catching?  The inspector missed something -
so what else is new?  As we all know, visual inspection is typically said
to be 85% effective.  The few times (no more than 4) that I have been able
to check inspection effectiveness against true process performance, I have
calculated confidence intervals that included the 85% number.  My view is
that inspection can serve as a pretty good safety net, to catch a problem
of, say, a polarized capacitor installed backwards on each of 20 board, but
in finding needle-in-the-haystack problems its capabilities are limited.
 As the frequency of the occurence of defects decreases, the probability of
detection of any individual defect decreases, as one might expect and which
research result was reported by Malcolm Gladwell in the New Yorker a few
weeks back.  (That's why paying airport inspectors more won't make planes
safer.)

Also, I tell people our inspection instructions do not provide for any
"overlap".  The statement that "three inspectors missed it" is not true -
one inspector has the job of looking for, say, surface mount solder
nonconformances and no other inspector will even try.  Two people have a
chance to make a mistake - the person who installs the part and one
inspector.  Lou Hart

-----Original Message-----
From:   Olivia Mc Dermott [SMTP:[log in to unmask]]
Sent:   Thursday, January 03, 2002 10:01 AM
To:     [log in to unmask]
Subject:        Re: [TN] Final Audit/Inspection

We do have inspection points throughout the process. The problem is they
are
also missing defects and letting them through to final inspection.I
wondered
if there is a direct instruction on inspecting.
1. you do this
2. you do this.


>From: Kathy Kuhlow <[log in to unmask]>
>Reply-To: "TechNet E-Mail Forum." <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: [TN] Final Audit/Inspection
>Date: Thu, 3 Jan 2002 08:49:32 -0600
>
>I would first start with some in-process sampling so you can pinpoint what
>types of defects the process is currently producing.  Do you see more
>missing components from surface mount or do you have a problem withe
solder
>shorts on the solder side because of wave issues or snapping problems.
>All to many organizations use a final inspection as a safety net.  In my
>dream world I would have no one doing final inspection but bring it back
to
>the process and do the inspection at the process through auditing by both
>production and quality personnel so immediate feedback can be
accomplished.
>  Otherwise you get data that is out of date and you can't really take
>effective corrective actions, especially if your world is as a CM or small
>run lots.
>
>If you must do a final inspection then we typically start with a complete
>part verification (value, polarity, AVL check) than solder (quality,
>quantity, lead placement) and finally any specific customer
>instructions(labeling, rev add, etc).
>
>Kathy
><< TEXT.htm >>


_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com

------------------------------------------------------------------------
---------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET
Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases >
E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
------------------------------------------------------------------------
---------

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------

ATOM RSS1 RSS2