Steve and other TechNetters,
We have a what is probably an "upper middle class", off-line, 2D x-ray unit.
It currently sits in our Materials Engineering Lab. We use it during
qualification of all new board codes containing BGAs. We run a few boards
out of the first lot of boards and then the production guys are off to the
races. It is great for solder balls, shorts and voids, but opens are indeed
a problem.
We also use it for looking for solder balls and metal slivers in other work,
examining bond wires in components, proper mating of male and female
connectors and other odds and ends.
We also provide these services to other sites so it doesn't sit idle. I
think it would be hard to justify for a small to medium plant's use only.
regards,
Bev Christian
> ----------
> From: Stephen R. Gregory[SMTP:[log in to unmask]]
> Sent: Friday, October 02, 1998 2:32 AM
> To: [log in to unmask]
> Subject: Re: [TN] : Assy: Xray Utilization
>
> In a message dated 10/01/98 6:25:26 PM Pacific Daylight Time, LonerLSZ
> writes:
>
> > Steve,
> > We do a percentage of lot inspection for ISO. If you are considering
> > becoming certified then you will need to do process control which will
> > require a need for inspection. BGA's can only be inspected by x-ray so
> how
> > else would you do it?
> >
> > Linda
>
> Hi Linda!
>
> How would I do it you ask? Easy, we got this guy workin' for us named
> Clark Kent and he...what?....not buyin' that are ya?...didn't think ya
> would...hehehe.
>
> Seriously, my logic is that when you're pumping out production boards, you
> should have your processes dialed-in.
>
> Production scenario: You've got your stencil tweeked, paste is just the
> stuff
> you want, and you know you can print 15 times and then program a cleaning
> cycle to keep the image crisp. You also know that each print takes 3-grams
> of
> paste, so you'll program a dispense cycle in every 30 prints to keep a
> nice
> roll of paste in front of the squeegee. You know your placement programs
> are
> dead on because they came from cad data, you also verified that on your
> first
> article. Reflow profile was created, plotted, and given a fine adjust for
> the
> first article, which was followed with the xray inspection. Now you're
> gonna
> run some revenue.
>
> You've got your people doing periodic, random, process checks and logging
> them
> after solderpaste print, placement, and reflow, and they're doing a great
> job
> making sure that happens. So you tell me, when should I fire up the ol'
> x-ray
> machine again? When would I r-e-a-l-l-y need to if what I described above
> was
> happening? See my point? Things normally don't all of a sudden go wacko
> for
> three boards and fall back in line again. If you have your process set and
> being monitored, I have a hard time coming up with a good reason to
> justify x-
> ray for anything other than initial process set-up and verification. If
> you
> find something during a production run, in my mind, it's too late. What
> would
> you do? Stop production and go back and x-ray all the boards that were
> built
> from the last time a board was
> x-rayed?
>
> Don't get me wrong, I'm not saying what you're doing is a waste, but these
> are
> things that I've been thinking about trying to really justify the expense
> of a
> x-ray. Will it really be earning it's keep while every other machine is
> producing something? Food for thought huh?
>
> -Steve Gregory-
>
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