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January 2010

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Subject:
From:
"Woolley, Mark D. (Mark)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Woolley, Mark D. (Mark)
Date:
Mon, 25 Jan 2010 08:44:19 -0700
Content-Type:
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Steve is correct.  The beam forms a cone so the balls at the edge of the
screen are being viewed at an angle.  This is very apparent when viewing
vias.  You cannot detect the density of the sidewall platings of the
center via, but as you move toward the edge of the display area the side
walls become more apparent.
In reality the physical magnification due to the proximity of the sample
to the tube varys slightly from the center to the edge.  This means the
locations of the balls and the diameters may be off slightly.  Normally
this is not too much of an issue since the variation is usually within
the cutoff limits of the acceptance criteria.

I never measure via diameter (for example) unless the via is centered in
the crosshairs of the system.  BGA measurements can be done across the
display, and I'm sure most x-ray systems have compensated for the
difference in physical magnification when they calculate the ball
diameters based on edge density.

Mark


Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave |
Westminster, CO 80234  USA |
|email: [log in to unmask] |

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of stephengregory5849
Sent: Friday, January 22, 2010 7:23 PM
To: [log in to unmask]
Subject: Re: [TN] X-Ray Inspection

You will have a "Fish-eye" effect with a lot of x-ray machines. Meaning
that 
when you are viewing the whole image, the image of the balls in the
center 
of the screen will appear to be a different diameter than the balls at
the 
edges of the screen. You should only concentrate on what you see at the 
center of the screen, and manipulate and move the BGA around so that you
can 
see all the balls in the center of the screen.

Steve

----- Original Message ----- 
From: "Paul Edwards" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, January 22, 2010 8:59 PM
Subject: Re: [TN] X-Ray Inspection


Are you x-raying a BGA with a metal lid?

Paul

Paul Edwards
Surface Art Engineering

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ashok Dhawan
Sent: Friday, January 22, 2010 11:22 AM
To: [log in to unmask]
Subject: Re: [TN] X-Ray Inspection

Bob

We are currently doing XRAY Inspection of BGAs. The XRAY TestEngineer
noticed that solder ball size on outer rows is different from the ball
size
on inner core areas.
"We are still seeing a bi-modal data distribution of ball volume between
the
middle and periphery balls? Is that normal for BGAs. "

I would appreciate your expert comments as there is not much XRAY
related
information on web.

Regards

Ashok Dhawan
Manuf. Specialist
Parker hannifin Electronic Controls
Winnipeg Canada
[log in to unmask]

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