Dear Lum Wei Mei,
If you ask how to be sure of your results, I think that it also depends on
many other factors as circuit built up (internal copper planes, thickness),
height of solder joint (more material, more voltage), Image enhancement
(contrasts, others), and your ability to distinguish the location (which
interface and internal).
I understand your problem, as the results are not easy for interpretation.
You may see voids caused during your reflow process which ARE NOT CAUSED BY
IT.
If you check for voids in BGA balls as received , you may establish
criteria, but on assemblies after reflow it is another story .
In this case, establishing criteria may lead to errors.
Specific for one BGA, you may try to compare your results to a good cross
section on the same balls you checked by X-ray.
Hope this helps,
Gaby
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Lum Wee Mei
Sent: ו 13 ינואר 2012 09:29
To: [log in to unmask]
Subject: [TN] BGA X-ray baseline setting
Dear TechNet Buddies,
In IPC-A-600, the standard provides states the inspection magnification
requirement. For external observation : at 1.75x and progress to 40x if
acceptable condition of a suspected defect is not apparent. Such inspection
magnification requirement is not given in IPC-7095 for BGA x-ray. What is
the common industry practice on :
(a) Tube voltage
(b) Tube power
(c) Filter strength
(d) Averaging
I asked because I worry that I may unintentional set a 'wrong' tube voltage
that could result in the effect known as "Voltage Blooming'. I do not want
to cause false alarm due to my incompetency and result in wrong inspection
judgment on the void size.
Thanks and regards,
~wee mei~
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