Transcript Principles of X-Ray Inspection for BGA's

Basic Principles of
X-Ray Inspection for BGA’s
Increased Use of BGA’s
 Ball Grid Arrays - array of solder
ball connections underneath
component
 Provides many advantages over
leaded components
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Reduced component size
Increased I/O count
Smaller footprint
Increased performance
characteristics
The Problem with BGA’s
 How to verify a solder bond
that cannot be observed?
 Hidden joints - touch up not
possible
 Only way to test integrity of
joints
– Electrical test
– Look Under/Video Scope
– X-Ray
How X-Rays Work
Presence or Absence of Material
x-rays wedge object
x-rays detector
image
Differences in Material Density
high density material
x-rays
low density
x-rays detector
image
How an X-Ray System Works
X-ray tube generates
x-ray energy
The image you see
X-rays absorbed where
density exists in
sample - remaining
x-rays pass through
& strike the detector
Detector converts
x-rays to visible light,
video camera sends
image to processor
Image Processor
enhances x-ray
images for highresolution viewing
Solder Connections Under X-Ray
Analysis
 Main characteristic:
uniformity of the
connections
 If X-ray shows all
connections uniformly
circular & equal in area
- good indication of
complete/proper reflow
Nearly all Defects have “Signatures”
 Bridging, missing balls, large
voids obvious
 Other defects subtle
 Look for pattern in distortion of
size/shape of bond image
 Operator learns to identify
defect signatures, process
problems and quickly make
adjustments
Defects Identified by X-Ray: Bridging
 May be due to excess
paste or flux
 Improper rework
implicated
 Solder splattering due
to poor reflow
conditions
Look Under Scope Image
Misregistration
 Result of errors in component placement
 Possible issues with solder mask alignment
Insufficient Reflow
 More difficult to spot
 If package misplaced,
ball shape may be
elliptical (easier to
identify)
 Bond distribution not
consistent
Missing Balls
 Can occur in
manufacturing process
 Usually due to
mishandling
Cold Solder
 More difficult to identify
 Signified by jagged
irregular edge around
the perimeter of the
solder ball
Solder Voids
 Result of moisture in
BGA package – must be
thoroughly baked out
 Problems with solder
paste
 Huge issue with leadfree solder
Solder Voids
 Voids a process indicator,
not defect unless excessively
large
 Motorola Study - balls that
contain voids up to 24%
more reliable than those
without voids!
Solder Voids & Voltage Blooming
At 50 kV
At 70 kV
 Associated with camera used
in many X-ray systems
 As voltage increased, void
artificially appears to expand
(bloom)
 Makes void appear larger
than it really is
 Glenbrook systems not
subject to voltage blooming
Potato Chipping/Popcorning
Normal
Potato Chipping
 BGA’s outside edge lifts
up from a pad
 Center joints squashed
due to compression
under die area
 Caused by moisture in
BGA or excessive
topside temperature
Potato Chipping/Popcorning
 Note distortion/ warpage of
ball bonds lower right
corner
 View through Look-Under
scope. Note package
peeling away from solder
ball
Opens (require angled viewing)
 Ball smaller than
adjacent balls
 Pad shadow seen below
indicating no contact
between ball & pad
 Note two unattached
spherical shapes unlike
oval shapes adjacent to it
– indicate no contact
between pad & solder ball
RTX-113HV X-Ray Inspection System
 Features powerful 80 kV
X-ray tube
 GTI-5000 image processor
with auto-BGA analysis
software
 Sees through dense
multilayer PCBs & metal
capped BGAs
 Variable Angle Viewing
allows for 45 degree viewing
GTI-5000 Image Processing Software
 Provides analysis of BGA
defects: bridging, voids,
missing balls
 Measures BGA ball size,
ball roundness & void size
 Software identifies any ball outside of set tolerance
 Includes CPU, Frame Grabber, Software, Color
Monitor
Variable Angled Viewing
 Allows for 45 degree viewing
 X-Ray source is rotated
 Allows inspection for full
range of hidden BGA defects:
– Missing or mis-registered
solder spheres
– Misalignments
– Gross solder voids
– Non-wetting or non-contact
Specifications: RTX-113HV
Operating voltage: 120V, 50/60 Hz
Energy sensitivity: < than 15kV to >160 kV
X-Ray Tube – 80 kVA
Resolution: >20 line pairs per millimeter; can easily
resolve a 1 mil bond wire
 Magnification: 4 - 50x
 Maximum field of view: 1” diameter circle
 Maximum PCB size: 27” x 27” (685mm x 685mm)
with PCB manipulator
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Other Real-Time X-Ray Inspection Systems
from Glenbrook Technologies
JewelBox Series
 80 or 90kV
 5-7, or 10 micron Focal
Spot size
 7x-2000x magnification
 5 Axis, 360o Positioner
RTX-113
 35-52kV
 20 line pairs/mm
resolution (up to 100
optional)
 Variable Angle Viewing
option available
RTX-Mini
 40kV
 20 line pairs/mm
resolution
 Truly Portable – can
be hand carried or
shipped!
11 Emery Ave
Randolph, NJ 07869
Tele: (973) 361-8866
Fax: (973) 361-9286
[email protected]
www.glenbrooktech.com
Manufacturer’s Rep
Aaron Caplan
1310 E. Maple Ave
Sterling, VA 20164
(703) 731-8048
[email protected]
www.gsaservice.com
11 Emery Ave
Randolph, NJ 07869
Tele: (973) 361-8866
Fax: (973) 361-9286
[email protected]
www.glenbrooktech.com
Manufacturer’s Rep
Aaron Caplan
1310 E. Maple Ave
Sterling, VA 20164
(703) 731-8048
[email protected]
www.gsaservice.com