BGABGA -- Ballball Gridgrid Arrayarray Inspectioninspection Workshopworkshop

BGABGA -- BallBall GridGrid ArrayArray InspectionInspection WorkshopWorkshop

Bob Willis leadfreesoldering.com Mixed Technology Assembly Processes

Adhesive Dispensing Component Placement Adhesive Curing Turn Boar Over Conventional Insertion Wave Soldering Inspection InspectionInspection TechniquesTechniques X-ray inspection procedures Optical inspection (Endscope) Destructive mechanical testing PBGAPBGA ReflowReflow CeramicCeramic BallBall GridGrid ArrayArray CeramicCeramic ColumnColumn GridGrid ArrayArray ChipChip ScaleScale ArrayArray FlipFlip ChipChip PackagesPackages FlipFlip ChipChip PackagePackage NoNo--flowflow UnderfillUnderfill LeadLead--FreeFree BallBall GridGrid ArrayArray OpticalOptical InspectionInspection SystemsSystems

ERSA OpticalOptical InspectionInspection SystemsSystems

METCAL OpticalOptical InspectionInspection SystemsSystems

KH Benz

Kaisertech OpticalOptical InspectionInspection SystemsSystems OpticalOptical InspectionInspection SystemsSystems XX--RayRay InspectionInspection SystemsSystems XX--RayRay InspectionInspection SystemsSystems VeryVery SkilledSkilled OperatorOperator

OperatorOperator underunder TrainingTraining DesignDesign && LayoutLayout DesignDesign && LayoutLayout SolderSolder MaskMask DefinedDefined PadsPads DesignDesign && LayoutLayout BGABGA WettingWetting IndicatorsIndicators BGABGA XX--RayRay AssementAssement ofof ReworkRework

BGABGA SolderedSoldered withwith SnSn/Ag/Cu/Ag/Cu BGABGA XX--RayRay AssementAssement ofof ReworkRework

BGABGA reworkedreworked withwith SnSn/Ag/Cu/Ag/Cu pastepaste BGABGA XX--RayRay AssementAssement ofof ReworkRework

BGABGA reworkedreworked withwith SnSn/Ag/Cu/Ag/Cu fluxflux gelgel AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment MarksMarks AreaArea ArrayArray AlignmentAlignment GeneralGeneral InspectionInspection ofof BGABGA SIZE OF BALL TERMINATIONS

Ball diameter should be equal to or larger than the original ball diameter on the BGA prior to reflow due to the addition of paste. In the case of high temperature lead/tin ball termination's which do not reflow there should be no change in ball size.

STANDOFF HEIGHT OF BGA PACKAGE.

Measure the difference in height between the board and the base of the BGA laminate on a minimum of two of the four corners. Compare the variation in height of the BGA by scanning along the length of the BGA on two sides. The height will be equal to or less than the original ball height. The stand off height will reduce due to the size of the device and its weight.

Variations in height between the centre and the edges of the BGA may indicate warpage of the fibre glass device or PCB. It can also indicate voiding in the ball terminations. This is more commonly noted if all termination measurements are taken. This technique is much simpler with X-ray as it can be automated. Warpage can occur up or down in the centre area of the part. Although uncommon warpage can even be seen on ceramic packages. GeneralGeneral InspectionInspection ofof BGABGA CHECK FOR SOLDER SHORTS

Scan along two adjacent sides of a BGA using light from the opposite side of the devices. There should be no restrictions to viewing each of the termination outlines. If light is restricted short circuits may be visible under the device. Viewing two sides ensures that shorts can be seen; viewing one side only shorts can be missed.

Check for complete reflow of solder paste and ball terminations on tin/lead or lead-free joints. In the case of high temperature balls on ceramic parts the ball will not become liquid. During soldering the paste will reflow and allow wetting to take place between the high temperature ball and the pad surface. There will be a distinct line between the ball and the solder at the interface. This is due to the different metal surfaces being joined.

CHECKING FOR CRACKING OR POPCORNING

BGA failures do occur for a variety of reasons, they may be component, printed board, process or design related. On some occasions both X-ray and optical inspection can easily provide the answer and that is when other techniques must be used. Microsections, dye penetrant and acoustic scans may assist is pinpointing the root cause. The essential aspect in all analysis is the experience of the engineer BGABGA CrackingCracking ““PopcorningPopcorning”” BGABGA CrackingCracking ““PopcorningPopcorning”” BGABGA CrackingCracking ““PopcorningPopcorning”” BGABGA CrackingCracking ““PopcorningPopcorning”” BGABGA CrackingCracking ““PopcorningPopcorning”” GeneralGeneral InspectionInspection ofof BGABGA INSPECTION OF BALL GRID ARRAY

Inspection of the solder joints should start at the centre of the BGA. This area is the most likely to be the last point to reflow during soldering. It is the most likely area to exhibit voids, non reflow or component delamination. If X-ray is being used after rework the whole area beneath the part should be scanned.

All BGA termination points should be broadly circular in appearance and consistent in size. Measurement of a ball under the centre of the BGA and four outer positions could allow confirmation of complete reflow. These measurements could be compared with historical data. BGA termination pads may include a wetting indicator. If this is the case it will make solder joint inspection easier to assess.

A wetting indicator is a minor change to all pad shapes or a track from the mounting pad which is left exposed. In each case the solder paste can wet away from the main pad in a controlled manner, wetting may then be confirmed by X-ray. Use of oblique angle X-ray views is ideal as it will often help the investigation of the joint interfaces by allowing a better observation of the interface, this might otherwise be obscured if the view is limited to top down. BGABGA ReflowReflow XX--RayRay GeneralGeneral InspectionInspection CriteriaCriteria

Inspection Criteria

The following provides a guide to inspection criteria for area array solder joints using x-ray and optical inspection. The basic criteria are provided for low and high temperature area array devices.

Ball Grid Array Devices

The ball termination should positioned on the centre of the land, they should not overhang the pad by more than 25%. The clearance between ball terminations after reflow should not be less than the minimum electrical clearance, ball to ball distance.

There should be no evidence of solder shorting under area array devices. Stand off height will be equal or less than the original ball termination. Measurements of stand off height during production will allow process limits to be defined for any group of devices.

Solder voiding on terminations should be less than 20% of the attachment area on the pad.

Evidence of complete reflow of solder paste should be seen. Complete reflow of high temperature balls or columns may not be visible. Solder joints on any one device should have uniform shape and size and surface appearance which depends on the process, materials and the soldering atmosphere. GeneralGeneral InspectionInspection ofof BGABGA Low temperature ball terminations will show evidence of complete drop of the ball and paste combining to form a ball shape appearance. High temperature balls will have a waist line/demarcation line between the reflowed solder and the ball. There should be some evidence of solder wetting under the high temperature balls There should be no evidence of damage to the balls or pads on either the component or printed circuit board.

Variations of ball size over 15% can indicate voiding or compression of balls due to PCB or package warp. Where present wetting indicators should show some evidence of solder flow. The distance criteria for process control can be defined during production inspection.

Column Grid Array Devices

All columns should be located on the pads, the columns should not overhand the pad surface. Slight deflection of the columns is allowed provided it is still positioned on the pads. There should be a solder fillet around the complete circumference of the columns. There should be some evidence of solder wetting under the high temperature columns. The solder should wet to a minimum height of 0.010” (0.25mm) DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad DesignDesign && LayoutLayout ViaVia inin PadPad Design & Layout Through Via Mounting Design & Layout Through Via Mounting ProfilingProfiling BGABGA BoardBoard AssembliesAssemblies

OneOne rowrow ofof ballsballs removedremoved toto thethe centrecentre ProfilingProfiling BGABGA BoardBoard AssembliesAssemblies LeadLead--FreeFree BGABGA withwith Tin/LeadTin/Lead PastePaste

BGABGA Reflowed,Reflowed, ballsballs diddid notnot reflowreflow

BGABGA compressedcompressed duringduring reflowreflow LeadLead--FreeFree BGABGA withwith Tin/LeadTin/Lead PastePaste

Balls have not reflowed paste has this is not clear on these images LeadLead--FreeFree BGABGA OpticalOptical InspectionInspection

Balls have not reflowed paste has this is very clear on these images LeadLead--FreeFree BGABGA OpticalOptical InspectionInspection LeadLead--FreeFree BGABGA withwith Tin/LeadTin/Lead PastePaste

Balls have not reflowed paste has wetted pads this is shown by the perfect circle of the x-ray image LeadLead--FreeFree BGABGA withwith Tin/LeadTin/Lead PastePaste

Balls have not reflowed but tin/lead paste has reflowed and wetted the joints PlasticPlastic BallBall GridGrid ArrayArray HighHigh TemperatureTemperature TerminationsTerminations CeramicCeramic BallBall GridGrid ArrayArray CeramicCeramic ColumnColumn GridGrid ArrayArray CeramicCeramic ColumnColumn GridGrid ArrayArray XX--RayRay InspectionInspection BGA CGA Chip Component J Lead Gull Wing Leadless Castellation XX--RayRay InspectionInspection

TheThe maximummaximum voidvoid sizesize inin anyany oneone terminationtermination willwill bebe lessless thanthan 10%10% ofof thatthat minimumminimum soldersolder jointjoint dimension.dimension. InIn thethe casecase ofof multiplemultiple voidsvoids thethe maximummaximum areaarea willwill bebe lessless thanthan 10%.10%. XX--RayRay InspectionInspection Bellcore GR 78 The maximum void size in any one termination should not exceed 1% (by volume) on average, with a worst-case incidence of 5% in less than one joint per circuit assembly. XX--RayRay InspectionInspection VoidsVoids upup toto 24%24% ofof thethe padpad areaarea hadhad nono effecteffect onon reliability.reliability. TheyThey improvedimproved thethe reliabilityreliability byby 16%16% whenwhen comparedcompared withwith voidvoid freefree joints.joints. IPCIPC 610D610D draftdraft InspectionInspection CriteriaCriteria PlasticPlastic BGABGA –– AlignmentAlignment

TargetTarget -- ClassClass 1,2,31,2,3 PlacementPlacement ofof thethe BGABGA soldersolder ballball isis centredcentred andand showsshows nono offsetoffset ofof thethe ballball toto landland centres.centres.

DefectDefect -- ClassClass 1,2,31,2,3 SolderSolder ballball offsetoffset violatesviolates minimumminimum electricalelectrical clearance.clearance. IPCIPC 610D610D draftdraft InspectionInspection CriteriaCriteria Plastic BGA - Solder Ball Spacing

Acceptable - Class 1,2,3 BGA Solder balls do not violate minimum electrical clearance.

Defect - Class 1,2,3 BGA solder ball spacing violates minimum electrical clearance.

Plastic BGA - Component Height

Acceptable - Class 1,2,3 Overall height CH) of the component does not exceed maximum specified.

Defect - Class 1,2,3 Overall height of the component exceeds maximum specified. IPCIPC 610D610D draftdraft InspectionInspection CriteriaCriteria

Plastic BGA - Solder Connections

Target - Class 1,2,3 The BGA solder ball terminations are uniform in size and shape.

Acceptable - Class 1,2,3 No solder bridging. BGA solder balls contact and wet to the land forming a continuous elliptical round or pillar connection.

Process Indicator - Class 2,3 BGA solder ball terminations are not uniform in size, shape, coloration, and colour contrast.

Defect - Class 1,2,3 No visual or x-ray evidence of solder bridging.

A "waist" in the solder connection indicating that the solder ball and the attaching solder paste did not flow together. Incomplete wetting to the land. BGA solder ball terminations have incomplete reflow of the solder paste. Fractured solder connection IPCIPC 610D610D draftdraft InspectionInspection CriteriaCriteria PlasticPlastic BGABGA –– VoidsVoids

AcceptableAcceptable -- ClassClass 1,2,31,2,3 LessLess thanthan 10%10% voidingvoiding inin thethe ballball toto boardboard oror ballball toto componentcomponent interface.interface.

ProcessProcess IndicatorIndicator -- ClassClass 2,32,3 1010--25%25% voidingvoiding inin thethe ballball toto boardboard oror ballball toto componentcomponent interface.interface.

DefectDefect -- ClassClass 1,2,31,2,3 MoreMore thanthan 25%25% voidingvoiding inin thethe ballball toto boardboard oror ballball toto componentcomponent interface.interface. MechanicalMechanical InspectionInspection MechanicalMechanical InspectionInspection

SurfaceSurface FibreFibre ContaminationContamination SolderSolder BallsBalls ExcessiveExcessive TimeTime andand TemperatureTemperature BGABGA OpticalOptical InspectionInspection BGABGA OpticalOptical InspectionInspection InspectionInspection ofof BGABGA BoardBoard AssembliesAssemblies

MeasureMeasure StandStand--OffOff HeightHeight InspectionInspection ofof BGABGA BoardBoard AssembliesAssemblies

MeasureMeasure StandStand--OffOff HeightHeight WeightWeight willwill depressdepress ballsballs TestingTesting BallBall GridGrid ArraysArrays TestingTesting BallBall GridGrid ArraysArrays TestingTesting BallBall GridGrid ArraysArrays OpticalOptical InspectionInspection OpticalOptical InspectionInspection SectionSection ViewView PriorPrior toto SEMSEM XX--RayRay ExaminationExamination ofof SamplesSamples XX--RayRay ExaminationExamination ofof SamplesSamples DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting DyeDye PenetrationPenetration TestingTesting PoorPoor PadPad SolderabilitySolderability OpenOpen CircuitCircuit BGABGA VoidingVoiding PCBPCB FinishFinish IssueIssue VoidingVoiding PCBPCB FinishFinish IssueIssue

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