basic principles of x-ray inspection for bga’s. increased use of bga’s ball grid arrays - array...
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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– 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
image
Presence or Absence of Material
wedge objectx-rays x-raysdetector
imagedetectorlow density
high density material
x-raysx-rays
Differences in Material Density
X-ray tube generatesx-ray energy
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 high-resolution viewing
The image you see
How an X-Ray System Works
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
May be due to excess paste or flux
Improper rework implicated
Solder splattering due to poor reflow conditions
Defects Identified by X-Ray: Bridging
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
Can occur in manufacturing process
Usually due to mishandling
Missing Balls
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 lead-free solder
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
At 70 kV
Associated with camera used in many X-ray systems
As voltage increased, void artificially appears to expand (bloom)At 50 kV
Makes void appear larger than it really is
Glenbrook systems not subject to voltage blooming
Solder Voids & Voltage Blooming
Potato Chipping/Popcorning
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
Normal
Potato Chipping
Note distortion/ warpage of ball bonds lower right corner
View through Look-Under scope. Note package peeling away from solder ball
Potato Chipping/Popcorning
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
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
Specifications: RTX-113HV
Other Real-Time X-Ray Inspection Systems from Glenbrook TechnologiesJewelBox 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 AveRandolph, NJ 07869
Tele: (973) 361-8866Fax: (973) 361-9286
[email protected] www.glenbrooktech.com
Manufacturer’s RepAaron Caplan
1310 E. Maple AveSterling, VA 20164
(703) [email protected]
www.gsaservice.com
11 Emery AveRandolph, NJ 07869
Tele: (973) 361-8866Fax: (973) 361-9286
[email protected] www.glenbrooktech.com
Manufacturer’s RepAaron Caplan
1310 E. Maple AveSterling, VA 20164
(703) [email protected]
www.gsaservice.com