Hi Liu,

        A couple of methods come to mind:

Nondestructive:  (But, depends on design complexity)
        1)  Time Domain Reflectometry (TDR)
        2)  Acoustic Microscopy
        3)  Old standby of the Curve Tracer.
        4)  X-Ray sometimes provides info, but is subjective.  Requires
looking at shape of joint.

Destructive:
        1)  Cut the Assembly around the BGA being careful not to disturb the
solder joints.
        2)  Grin the Assembly board in the Z-axis toward the BGA, but stop
before layer one.
        3)  Visual inspection may reveal something at this stage.
        4)  If necessary, chemically etch the epoxy laminate.  Note, copper
may be etched as well depending on chemistry used.

You could always send one of the BGAs that you removed back to the vendor
for test.  That would confirm where it was failing, but not why.

Glenn

> -----Original Message-----
> From: lckang [SMTP:[log in to unmask]]
> Sent: Thursday, February 08, 2001 1:57 AM
> To:   [log in to unmask]
> Subject:      [TN] Locate the failure of component & SJ
>
> Hello Technetters,
>       It is a trouble before half of year.
>       Our boards cannot pass the electrical ICT test , and the problem is
> located on BGA or the solder joint,  and the vender of BGA component
> donnot agree the failure is his matter, and our compony process is always
> reliable, and assembly other or more complex board with BGA, the fail rate
> is much low than it.
>       We cannot low the failure rate although under very controlled
> process(PCB design, manufacture, printing, placement, reflow....).
>       Now only way is to replace BGA  with new one, then test , rework,
> again and again  until it works. But this BGA component is very expensive.
>       Our company have the X-ray machine(which can inspect bridge,Void,
> but cannot find out the open fail in the SJ).
>       Can you show me the good way  to locate that which is main failure
> cause between BGA component and SJ? and the analysis method?
>
> Thanks for your any input.
>
> Best Regards,
>
> Liu Changkang
>
>

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