VER.3.0.0 MAR 2008

Vi Technology 3D Solder Paste Inspection Solutions

New Opportunities for Solder Paste Inspection

Demands of 3D SPI

Smaller and finer-pitch components like 01005 and flip-chipHigher popularity of components with invisible joints like CSP and BGAHigher opportunity of defect occurrence by lead-free solder paste (low wetting force, poor self-align characteristics, different aperture to pad ratio etc)Higher soldering quality required in mobile and security industry Approx. 70~80% of PCBA defects result from solder pasteRepair cost reductionDefect prevention by process control

Screen printing Component mounting Reflow soldering

Defect portion of total process

Repair cost per defect

X 1

X 1070-80%

10-20%0-10%

Effects of 3D SPI

3D SOLDER PASTE INSPECTION

REFLOW OVEN

Joint crackBridge

Solder bead Tomb stone & Skew

Final defects

PRINTER

Smearing

Root causes

Saving repair cost by earlier defect detectionPreventing defects by feed-back & control of screen printing processIncreasing long-term reliability of solder joint by solder volume control

Detecting solder paste level defects before reflow

Preventing defects by feed-back to printer

Through 3D measurement of paste volume, height, area and position

(Providing important predictor of good quality and long-term reliability of solder joints)

InsufficientExcess

Scraping Tailing

CCD

Viewing Lens

Projection Lens

White Light

Grating

PCB

Laser Diode

PCB

Slit Beam

Viewing Lens

CCD

Laser Triangulation Moire Interferometry

Koh YoungCyber OpticsCKD

Agilent TechnologyGSI LumonicsOrbotech

Flying Absolute Height Profilometry (FAHP)FAHP

FAHP

FAHP PRINCIPLE (Absolute Height Measurement)

2. Ø absolute = Ø + n • 2π (0< Ø < 2π)

1. Ø=f ( I ) (I= Intensity, Ø=Phase) Intensity

Phase

I

Ø

Intensity

Phase

I

Ø Ø + 2π Ø + 4π Ø + n • 2π

0 1 2 n

3. n = f (Ø1, Ø2)

Intensity

Phase

I

Ø Ø + 2π Ø + 4π Ø + n • 2π

PHASE 1 (Ø 1)PHASE 2 ((Ø 2)

0

6,000 um

n times wider measurement range

without degrading resolution.

h absolute = f (Ø absolute)

Ø absolute = Ø + n • 2π (0< Ø < 2π)

-1

ALGORITHM

Solder Paste

Reference

PCB

SURFACE PLANE WITH SLOPE

Solder Paste

Reference

PCB

COMPRISON W./W.O SLOPE

WITHOUT SLOPE COMPENSATION

WITH SLOPE COMPENSATION

INSPECTION SPEED SOLUTION

FAHP(FLYING ABSOLUTE HEIGHT PROFILOMETRY)

PSMI (PHASE SHIFT MOIRE INTERFEROMETRY)

REPEATED MOVE & STOP

Move ‘HEAD’

STOP ‘HEAD’

MOVE ‘GRATING’

STOP ‘GRATING’

Capture Image

Calculate Phase

Calculate Height

N TIMES ?no

yes

ON THE FLY

No Shadow effect

Zero % shadow effect by structured double light sourcesNo volume measurement error apart from pad orientation

Light source 1 Light source 2Detector 1ST SCAN 2nd SCAN

Shadow effect

(5-40% of Volume)

0% Shadow effect

Shadow’s Contribution to Volume Error

Assumption I. QFP BUMP CASE.(Parallelepiped Bump Shape)

L=2mm, W=0.5mm, H=0.12mm

L

H

W

0.12mm

0.3mm

Assumption II. CSP BUMP CASE.(Cylindrical Bump Shape)D=0.3mm, W=0.5mm, H=0.12mm

Detector

Light source

Object

Shadow

α

0°

45°90°

(1) Angle 0°

2mm

0.5mm

Shadow Area :0.18mm² (18%)

(2) Angle 45°

2mm

0.5mm

Shadow Area :0.16mm² (16%)

(3) Angle 90°

Shadow Area :0.45mm² (4.5%)

2mm

0.5mm

0.3mm

Shadow Area :0.027mm² (38%)

True Volume Measurement

1. 3D bare board measurement.

2. 3D total measurement of ROI. 3. Extraction of bare board geometry.

4. Solder paste volume only.

Measurement Description (1)

Stencil Area

from Gerber File

Reference value

1

2 3 4

6 7 8 9

10 11 12 13 14

15 16 17

18

5

Measurement

Summing all pixels of

solder paste area.

Equation

X SUM of

One pixel

dimension

Total pixel number

of solder paste area

Measurement object

Stencil AreaX

Stencil thickness

12 3 4

5 6 7 8 910 11

12 1314

15 16 1718

Top 50%

(Selectable range)

AreaSolder ),(),( )(AverageHeight ∈= jijih

∑∈ AreaSolder ),(

),(ji

jih

X

One pixel

dimension

Height of

pixel areaSumming each pixel’s

volume of solder paste area.Top 50%

(Selectable range) Averaging Top 50% height (AHR 50%)

Stencil thicknessMeasurement unit : 0.1

Area

Volume

Height

Item

SUM ( )

Reference value Measurement

Connectivity between neighboring solders

EquationMeasurement object

Convex solderVolume ratio of measured solder and convex solder

Bridge

Shape

Item

Bridge Length

hull)(Convex Volume(Measured) VolumeRatio=

Measurement Description (2)

Operation flow

Gerber based pad programming Teach & edit Inspection

Defect review Off-line SPC

Inspection tests

Insufficient or excessive height and volume

Position shift

Area

Abnormal shape

Bridge

Offline conversion of Gerber and CAD Data

On-machine defect review

Real-time process monitoring and alarm signal generation

Real-time SPC software for process monitoring and defect

analysis

3D Solder Volume Functionalities

Typical inspection speed @ zero shadow effect mode Satisfying most line cycle times in the market20 cm²/sec @ zero shadow effect mode

Perfect shadow effect eliminationStructured dual light source inspection mechanismNo volume measurement errors due to pad orientation

High repeatability< 10% GR&R for every solder pastes with 30-50% toleranceHeight < 1.5µm (3σ ) on standard certification target

High accuracy Height < 3µm on standard certification targetHeight Resolution : 0.1µm

PCB warp measurement & measurement compensationUpward 3.0mm / downward 3.0mm without z-axis control

3D Solder Volume Performances

PCB Warp Measurement

Note: Data collected from PDP PCB of S company

Fast Programming from Gerber & CAD

CAD file import.

Semi-automatic component information input

Link pads with component

COMPONENT LEVEL PROGRAMMING.(Typically 30 minutes)

Gerber file import

Automatic pad information input

Inspection parameters input

Debug & Automatic training

Start production

PAD LEVEL PROGRAMMING.(Typically 5 minutes)

OK ?

Off-line SPC StationChart Samples

X-bar / R Chart.

X-bar / S Chart.

Scatter Chart.

Trend Chart.

Raw Data List. Capability Chart.

Raw Data Expert. X-bar Distribution Map

Other Chart Etc.