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Subject:
From:
Werner Engelmaier /* <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 21 Sep 2009 19:17:41 -0400
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 Hi Guys,
The premise of the original question was by inference that completeness of the underfill coverage is necessary.
Would not be an underfill 'ring' covering the first 5 or so 'SJ squares' accomplish what is desired—better reliability? That would make this discussion academic.
Werner


 


 

-----Original Message-----
From: Vladimir Igoshev <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, Sep 21, 2009 6:47 pm
Subject: Re: [TN] Acoustic Microscopy for Under fill Coverage










C-SAM does do a beautiful work on flip-chip packages and of cause not in the 
transmission mode.

Regards,

Vladimir
SENTEC
SENTEC
11 Canadian Road, Unit 7.
Scarborough, ON M1R 5G1
Tel: (416) 899-1882
Fax: (905) 882-8812
www.sentec.ca


-----Original Message-----
From: "David D. Hillman" <[log in to unmask]>

Date:         Mon, 21 Sep 2009 17:30:36 
To: <[log in to unmask]>
Subject: Re: [TN] Acoustic Microscopy for Under fill Coverage


Hi Bev - I have attempted to use Acoustic Microscopy for underfill 
coverage on BGAs and as other folks have detailed, the number of 
interfaces and structures cause significant signal reflection problems 
making analysis very difficult. Some specific focused interface 
examination efforts can be conducted but are still very difficult to 
analyze.

Dave Hillman
Rockwell Collins
[log in to unmask]




Bev Christian <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
09/21/2009 05:16 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond=2
0to
Bev Christian <[log in to unmask]>


To
[log in to unmask]
cc

Subject
Re: [TN] Acoustic Microscopy for Under fill Coverage






John and others,
But wouldn't it be even worse trying to use transmission mode because of 
the nature if the circuit board underneath the component (copper 
barrier(s), glass fiber bundles and epoxy?

Nobody from Sonotek or Sonoscan on TechNet?
Bev

----- Original Message -----
From: John Burke <[log in to unmask]>
To: 'TechNet E-Mail Forum' <[log in to unmask]>; Bev Christian
Sent: Mon Sep 21 18:00:16 2009
Subject: RE: [TN] Acoustic Microscopy for Under fill Coverage


 Not a discontinuity as such just an interface, and you are right, the
signal reflections will be from every interface, so for a BGA (without a
lid) the interfaces will be as follows:

1    Liquid to top of package molding compound
2    Molding compound to silicon
3    Silicon to die attach
4    Die attach to substrate
5    4 or so interfaces in the substrate itself (copper to substrate
pre-preg)
6    Substrate to under fill (or NOT!)

Depending of the acoustic impedance between the Material travelling
from/Material travelling to, more or less ultrasound energy will be
reflected at each of the interfaces.

Of the layers above I believe that the strongest reflection will be from
level 6 above.

It is 30 years since I last played with non destruct testing using
ultrasonics, but I would bet from my experiences then that you would do 
far
better using through transmission for this scenar
io rather than reflected
signals due to Bev's comment, particularly due to the substrate interface
reflections masking the ones between the package and the under fill.


John Burke
(408) 515 4992


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Monday, September 21, 2009 2:07 PM
To: [log in to unmask]
Subject: Re: [TN] Acoustic Microscopy for Under fill Coverage

Since when can an acoustic signal punch through a BGA?  I know you can do 
if
for flip chips, but aren't there too many density discontinuities for CSPs
abd BGAs?
Bev

----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Mon Sep 21 14:40:48 2009
Subject: [TN] Acoustic Microscopy for Underfill Coverage

Anybody know a good lab in the North East that does acoustic microscopy? I
need to verify under fill coverage under BGAs.

Thanks,
Amol





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