Obviously, there are many opinions and pro's/con's to xray that I've seen
in the recent string of emails.
I've seen some ultrasonic equipment advertised that looks quite interesting
and worth some evaluation.
Sort of a BGA-MRI if I understand it correctly.  Don't know the cost
implication, but if I were
concerned about the capability of xray and the cost/coverage it is
providing you, I would certainly
take a look at the sonic equipment and do the cost/capability comparison.

DT




At 08:33 AM 6/3/00 +0300, Gabriela Bogdan wrote:
>Let us return down to earth.
>If the BGA( or any other component )failed during electrical test or if it
>is a dummy,
>or if it is on a test board, you have all the time in the world to check
>it and do with
>it whatever you please. This is the case when the BGA was isolated as the
>sure culprit
>for the failure.
>If you get a board which failed "presumably" because of the BGA, you are
>in the dark,
>and limiting yourself to a few seconds is frustrating.
>Maybe a few seconds are enough for missing balls or shorts. Opens are
>harder to find,
>and cracks almost impossible.
>Frustrations are very common during X-ray inspection.
>Sometimes you check thoroughly the joints, only to discover later. that a
>bonding wire
>burned. But again, if this is the case , no harm is done because the
>component failed
>anyway.
>Our long discussion should focus on why and how to check presumably good
>assemblies
>that passed the electrical test, by  X-ray. Also, whoever is able to bring
>forward
>information and food for thought, please do it.
>Undoubtedly, for failure analysis it is one of the best tools.
>Thank you,
>Gaby
>
>joyce wrote:
>
> > the time is a fact for X-ray inspection.  If you set the contrast, tilting
> > angle correctly (provide you did enough cross section to know the few type
> > of failure mode: e.g. smaller balls, shorts, missing one, etc.) you can use
> > only few second to inspect using X-ray (if you are really good, fraction of
> > a sec.).  A lot of "leg work" has to be done prior to set up inspection in
> > order to minimize the exposure time.  (use dummy parts to figure it out
> > 1st...take few photo as bench mark example to train the operator,
> etc..it is
> > a massive undertaking)...
> >                               jk
> > At 12:59 PM 6/2/00 EDT, you wrote:
> > >In a message dated 06/02/2000 10:52:38 AM Central Daylight Time,
> > >[log in to unmask] writes:
> > >
> > ><<  I am using an equipment of max. 160 kV and until now I was very happy
> > >with it, inviting my friends to test BGA's with metal covers , their
> > >equipment being too weak.
> > >I don't know if we should be happy or not having this discussion, but
> I have
> > >a bad
> > >feeling. If there is something we don't know, research should be done. >>
> > >
> > >Hi Gaby!
> > >
> > >I've been searching to try and find something that talks specifically
> about
> > >possible damage from x-ray inspection and as Paul said; I'm hitting a
> silent
> > >wall. However, there's tons of information about radiation damage to
> > >electronics in space. From reading some of it, there's no question
> that x-ray
> > >radiation can degrade and damage electronic components. The question
> is how
> > >much radiation does it take to damage something. I don't have the kind of
> > >knowledge to know that...maybe somebody on the list that's a lot
> smarter than
> > >me knows?
> > >
> > >Below is a paste from a web page of an organiztion that's been
> studying the
> > >effect of radiation on solar panels. I think there's a few good
> statements in
> > >there that illustrate we should be a little concerned when using higher
> > >powered x-ray equipment.
> > >
> > >-Steve Gregory-
> > >
> > >Radiation effects
> > >
> > >The behaviour of solar cells in a radiation environment can be
> described in
> > >terms of the changes in the engineering output parameters of the devices.
> > >This approach limits the understanding of the physical changes which
> occur in
> > >the device. Since other environmental factors may need consideration, an
> > >understanding of a physical model provides a basis for estimates of the
> > >behaviour in a complex environment. In addition, solar arrays of the
> future
> > >will become more complex and may utilise materials which are affected by
> > >different aspects of radiation damage. For these reasons, one should
> be aware
> > >of the process by which radiation interacts with matter, and
> understand the
> > >physical models which describe the processes.
> > >
> > >Ionisation
> > >
> > >Ionisation occurs when orbital electrons are removed from an atom or
> molecule
> > >in gases, liquids, or solids. The measure of the intensity of ionising
> > >radiation is the roentgen. This unit is defined by a charge generation of
> > >2.58x10 -4 C/kg of air. The measure of the absorbed dose in any
> material of
> > >interest is usually defined in terms of absorbed energy per unit mass. The
> > >accepted unit of absorbed dose is the rad (100 erg/g or 0.01 J/kg). The SI
> > >unit of absorbed dose is the Gray (Gy), defined to be 1 J/kg. Through
> the use
> > >of the concept of absorbed dose, various radiation exposures can be
> reduced
> > >to absorbed dose units which reflect the degree of ionisation damage
> in the
> > >material of interest. This concept can be applied to electron, gamma, and
> > >X-ray radiation of all energies.
> > >
> > >The use of silicon dioxide as a surface passivation coating and dielectric
> > >material in silicon devices results in a wide range of ionisation related
> > >radiation effects. The development of trapped charges in the silicon
> dioxides
> > >can cause increased leakage currents, decreased gain, and surface channel
> > >development in bipolar transistors and increased threshold voltages in MOS
> > >field effect transistors (MOSFETs). Ionising radiation in silicon
> excites the
> > >electrons of the valence band to the conduction band, creating
> electron-hole
> > >pairs in much the same way that carrier pairs are generated by visible
> light.
> > >
> > >##############################################################
> > >TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
> > >##############################################################
> > >To subscribe/unsubscribe, send a message to [log in to unmask] with
> following
> > text in
> > >the body:
> > >To subscribe:   SUBSCRIBE TECHNET <your full name>
> > >To unsubscribe:   SIGNOFF TECHNET
> > >##############################################################
> > >Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> > >information.
> > >If you need assistance - 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 1.8c
> > ##############################################################
> > To subscribe/unsubscribe, send a message to [log in to unmask] with
> following text in
> > the body:
> > To subscribe:   SUBSCRIBE TECHNET <your full name>
> > To unsubscribe:   SIGNOFF TECHNET
> > ##############################################################
> > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
> additional
> > information.
> > If you need assistance - 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 1.8c
>##############################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with
>following text in
>the body:
>To subscribe:   SUBSCRIBE TECHNET <your full name>
>To unsubscribe:   SIGNOFF TECHNET
>##############################################################
>Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
>information.
>If you need assistance - 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 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################