Actually Franklin, I think it is a valid idea that has already been
implemented at the assembly level of some high volume OEM's. I certainly
wouldn't want throw out the 'bed of nails' tester just yet. However, I do
think assemblers and OEM's will be increasingly open to a 'cost reduction
plan' that includes getting rid of test and inspection processes based on
yield. For example, if yields are so high that defects are around 20 DPM,
then the assembler would certainly benefit financially by paying less, and
getting less in return. This does not mean getting rid of electrical
testing on everything, but some things, certainly!
By the way, assemblers are faced with worse problems with electrically
testing high density circuits (Components like BGA's start to cover up
testable areas). So the concept of using AOI in place of electrical testing
is being discussed. Where it 'makes sense', AOI can completely replace
electrical testing. The hard part is convincing me it 'makes sense'!
Thanks
Ryan Grant
Advanced Technology Engineer
MCMS
(208) 898-1145
[log in to unmask]
> -----Original Message-----
> From: Franklin D Asbell [SMTP:[log in to unmask]]
> Sent: Friday, September 01, 2000 3:15 PM
> To: [log in to unmask]
> Subject: Re: [TN] Automatic Optical Test (AOT)
>
> Of course I agree with your and everyone else's comments and concerns,
> just thought I'd
> toss out the question. What the article discussed was using the AOI to
> 'enhance' the
> testing, I brought up instead of testing.
>
> Now let me ask you (and all assemblers and board buyers) this, if I showed
> you data, or
> had data available confirming the integrity of the vias and all through
> holes, had
> performed AOI to ensure all layers were as the gerber intended including
> of course
> being free of processing defects, opens, shorts, etc, would you waive test
> on the
> boards? ~grinning as all the engineers cringe at the thought~
>
> Franklin D Asbell
>
>
> Ian Hanna wrote:
>
> > As has been mentioned, AOI will not pick up interconnect defects. It
> would
> > also not be a reliable way of testing inner-layer functions on a
> multi-layer
> > product. I would submit that electrical test provides a much greater
> margin
> > of overall acceptability and functionality. Using a 'bed-of-nails' type
> > electrical test is also significantly faster than optical scanning,
> although
> > this technique is not feasible for fine-pitch work.
> >
> > Regards,
> >
> > Ian Hanna
> > Quality Manager
> > Lazer-Tech Ltd.
> > Voice: 416.291.7727.233
> > FAX: 416.291.0325
> > [log in to unmask]
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]]On Behalf Of
> > [log in to unmask]
> > Sent: Friday, September 01, 2000 2:21 PM
> > To: [log in to unmask]; [log in to unmask]
> > Subject: Re: [TN] Automatic Optical Test (AOT)
> >
> > Franklin,
> >
> > I have not read the article, but a user of boards. Here are my first,
> > knee-jerk,
> > questions. Perhaps the article answered them, and I should get a copy
> of
> > the article.
> >
> > On a twelve layer multilayer board, how would AOT verify compliance to
> the
> > IPC-D-356
> > net list that I provide?
> > Does the addition of Laser vias, buried and blind vias to the design
> change
> > anything?
> > Buried resistance?
> >
> > I think it sounds like an imaginative idea, perhaps reducing the Capitol
> > $$$'s required
> > for a board shop.
> > Still, I am standing here, wondering what to do with this bucket of cold
> > water.
> >
> > George Franck
> > Raytheon Company
> > Falls Church VA
> >
> > Franklin D Asbell wrote:
> >
> > > Just read an article in "The Board Authority" regarding Automatic
> > > Optical Test (AOT).
> > >
> > > Just wondering what you assemblers or purchasers of bare boards
> thoughts
> > > are on fabricators performing 'optical testing' (visual, AOI) instead
> > > of 'contact testing' (BON, probe)????
> > >
> > > An example: You state all boards to be electrically tested for
> > > opens/shorts, and instead of throwing the boards on our flying probe
> or
> > > bed-of-nails equipment I decide to put this on my AOI after setting it
> > > up to flag for opens/shorts, would you be satsified with this method?
> > >
> > > Franklin D Asbell
> > > Network Circuits, Inc.
> > > Irving, Texas 75061
> > >
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