Basic Principles of XRay Inspection for BGAs Increased

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 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 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 The image you see Image Processor enhances x-ray images for high -resolution 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 lead-free 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 k. V At 70 k. V § Associated with camera used in many X-ray systems § As voltage increased, void artificially appears expand § to Makes void(bloom) 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 area by moisture § die Caused 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 padtwo unattached §& Note spherical shapes unlike oval shapes adjacent to it – indicate no contact between pad & solder ball

RTX-113 HV X-Ray Inspection System § Features powerful 80 k. V 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

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-

Specifications: RTX-113 HV § § Operating voltage: 120 V, 50/60 Hz Energy sensitivity: < than 15 k. V to >160 k. V X-Ray Tube – 80 k. VA Resolution: >20 line pairs per millimeter; can easily resolve a 1 mil bond wire § Magnification: 4 - 50 x § Maximum field of view: 1” diameter circle § Maximum PCB size: 27” x 27” (685 mm x 685 mm) with PCB manipulator

Other Real-Time X-Ray Inspection Systems from Glenbrook Technologies Jewel. Box Series § 80 or 90 k. V § 5 -7, or 10 micron Focal Spot size § 7 x-2000 x magnification § 5 Axis, 360 o Positioner RTX-113 RTX-Mini § 35 -52 k. V § 20 line pairs/mm resolution (up to 100 optional) § Variable Angle Viewing option available § 40 k. V § 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 szweig@glenbrooktech. com www. glenbrooktech. com Manufacturer’s Rep Aaron Caplan 1310 E. Maple Ave Sterling, VA 20164 (703) 731 -8048 aaron@gsaservice. com www. gsaservice. com