bga inspection

BGA - Ball Grid Array Inspection WorkshopBob Willis leadfreesoldering.com

Mixed Technology Assembly ProcessesAdhesive Dispensing Component Placement Adhesive Curing Turn Boar Over Conventional Insertion Wave Soldering Inspection

Inspection TechniquesX-ray inspection procedures Optical inspection (Endscope) Destructive mechanical testing

PBGA Reflow

Ceramic Ball Grid Array

Ceramic Column Grid Array

Chip Scale Array

Flip Chip Packages

Flip Chip Package No-flow Underfill

Lead-Free Ball Grid Array

Optical Inspection Systems

ERSA


METCAL


KH Benz

Kaisertech



X-Ray Inspection Systems

X-Ray Inspection Systems

Very Skilled Operator

Operator under Training

Design & Layout

Design & Layout

Solder Mask Defined Pads

Design & Layout

BGA Wetting Indicators

BGA X-Ray Assement of Rework

BGA Soldered with Sn/Ag/Cu


BGA reworked with Sn/Ag/Cu paste


BGA reworked with Sn/Ag/Cu flux gel

Area Array Alignment Marks







Area Array Alignment

General Inspection of BGASIZE OF BALL TERMINATIONS Ball diameter should be equal to or larger than the original ball diameter on the BGA prior ball to reflow due to the addition of paste. In the case of high temperature lead/tin ball temperature termination's which do not reflow there should be no change in ball size. ball 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 height scanning along the length of the BGA on two sides. The height will be equal to or less than will the original ball height. The stand off height will reduce due to the size of the device and its to 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 the more commonly noted if all termination measurements are taken. This technique is much This simpler with X-ray as it can be automated. Warpage can occur up or down in the centre Xarea of the part. Although uncommon warpage can even be seen on ceramic packages.

General Inspection of BGACHECK FOR SOLDER SHORTS Scan along two adjacent sides of a BGA using light from the opposite side of the devices. opposite There should be no restrictions to viewing each of the termination outlines. If light is termination restricted short circuits may be visible under the device. Viewing two sides ensures that Viewing 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 leadjoints. In the case of high temperature balls on ceramic parts the ball will not become liquid. the 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 lline between the ball and the ine solder at the interface. This is due to the different metal surfaces being joined. surfaces CHECKING FOR CRACKING OR POPCORNING BGA failures do occur for a variety of reasons, they may be component, printed board, component, process or design related. On some occasions both X-ray and optical inspection can easily Xprovide the answer and that is when other techniques must be used. Microsections, dye used. penetrant and acoustic scans may assist is pinpointing the root cause. The essential The aspect in all analysis is the experience of the engineer

BGA Cracking Popcorning





General Inspection of BGAINSPECTION OF BALL GRID ARRAY Inspection of the solder joints should start at the centre of the BGA. This area is the 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 Xrework the whole area beneath the part should be scanned. All BGA termination points should be broadly circular in appearance and consistent appearance in size. Measurement of a ball under the centre of the BGA and four outer positions four 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. inspection A wetting indicator is a minor change to all pad shapes or a track from the mounting track 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 Xangle X-ray views is ideal as it will often help the investigation of the joint interfaces Xthe by allowing a better observation of the interface, this might otherwise be obscured if otherwise the view is limited to top down.

BGA Reflow X-Ray

General Inspection CriteriaInspection Criteria The following provides a guide to inspection criteria for area array solder joints using x-ray and array xoptical 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 land, pad by more than 25%. The clearance between ball terminations af ter reflow should not be less after 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 Measurements 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. attachment Evidence of complete reflow of solder paste should be seen. Complete reflow of high Complete temperature balls or columns may not be visible. Solder joints on any one device should have on uniform shape and size and surface appearance which depends on the process, materials and the the soldering atmosphere.

General Inspection of BGALow 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 temperature have a waist line/demarcation line between the reflowed solder and the ball. There and should be some evidence of solder wetting under the high temperature balls There temperature should be no evidence of damage to the balls or pads on either the component or the printed circuit board. Variations of ball size over 15% can indicate voiding or compression of balls due to compression PCB or package warp. Where present wetting indicators should show some show evidence of solder flow. The distance criteria for process control can be defined control during production inspection. Column Grid Array Devices All columns should be located on the pads, the columns should not overhand the not pad surface. Slight deflection of the columns is allowed provided it is still positioned provided 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 under temperature columns. The solder should wet to a minimum height of 0.010 of 0.010 (0.25mm)

Design & Layout Via in Pad











Design & Layout Through Via Mounting

Design & Layout Through Via Mounting

Profiling BGA Board Assemblies

One row of balls removed to the centre

Profiling BGA Board Assemblies

Lead-Free BGA with Tin/Lead PasteBGA Reflowed, balls did not reflow

BGA compressed during reflow

Lead-Free BGA with Tin/Lead Paste

Balls have not reflowed paste has this is not clear on these images

Lead-Free BGA Optical Inspection

Balls have not reflowed paste has this is very clear on these images

Lead-Free BGA Optical Inspection


Balls have not reflowed paste has wetted pads this is shown by the perfect circle of the x-ray image x-


Balls have not reflowed but tin/lead paste has reflowed and wetted the joints

Plastic Ball Grid Array

High Temperature Terminations

Ceramic Ball Grid Array



X-Ray InspectionBGA CGA Chip Component J Lead Gull Wing Leadless Castellation

X-Ray InspectionThe maximum void size in any one termination will be less than 10% of that minimum solder joint dimension. In the case of multiple voids the maximum area will be less than 10%.

X-Ray InspectionBellcore 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.

X-Ray InspectionVoids up to 24% of the pad area had no effect on reliability. They improved the reliability by 16% when compared with void free joints.

IPC 610D draft Inspection CriteriaPlastic BGA Alignment Target - Class 1,2,3 Placement of the BGA solder ball is centred and shows no offset of the ball to land centres. Defect - Class 1,2,3 Solder ball offset violates minimum electrical clearance.

IPC 610D draft Inspection CriteriaPlastic 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. specified. Defect - Class 1,2,3 Overall height of the component exceeds maximum specified.

IPC 610D draft Inspection CriteriaPlastic 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 coloration, contrast. Defect - Class 1,2,3 No visual or x-ray evidence of solder bridging. xA "waist" in the solder connection indicating that the solder ball and the attaching solder ball paste did not flow together. Incomplete wetting to the land. BGA solder ball terminations have incomplete reflow of the solder paste. Fractured solder connection connection

IPC 610D draft Inspection CriteriaPlastic BGA Voids Acceptable - Class 1,2,3 Less than 10% voiding in the ball to board or ball to component interface. Process Indicator - Class 2,3 10-25% voiding in the ball to board or ball to component interface. Defect - Class 1,2,3 More than 25% voiding in the ball to board or ball to component interface.

Mechanical Inspection

Mechanical Inspection

Surface Fibre Contamination

Solder Balls

Excessive Time and Temperature

BGA Optical Inspection

BGA Optical Inspection

Inspection of BGA Board Assemblies

Measure Stand-Off Height


Measure Stand-Off Height


Measure Stand-Off Height Weight will depress balls

Testing Ball Grid Arrays



Optical Inspection

Optical Inspection

Section View Prior to SEM

X-Ray Examination of Samples

X-Ray Examination of Samples

Dye Penetration Testing









Poor Pad Solderability

Open Circuit BGA

Voiding PCB Finish Issue

Voiding PCB Finish Issue

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bga inspection

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bga laminate

popcorning bga failures

bga termination pads

ball size

bga termination points

original ball height

general inspection of