PCB Soldering Inspection

PCB Soldering Inspection

Structured Highlight approach Structured Highlight approach

Structured Highlight method is applied to illuminating and imaging specular surfaces which

yields three dimensional shape information

This approach uses multiple point sources and images the resulting highlight patterns reflected

from the surface

Basic Geometric Relations Basic Geometric Relations

i r

Incident ReflectionReflective Surface

ri

k

Point source and

camera

• A fixed camera images the reflected light ray only if it is positioned and oriented such that it is admitted by the camera’s projective axis

•Once the reflected light ray is observed as a highlight in the camera image and the direction of incident ray is known, orientation of the surface element where light was reflected can be found

Solder Height Detection Solder Height Detection

kLEDv _

CAMv

kn

knv

X

Z

Y

Normal vector at highLighted point (i,j) is

_, ,

, ,

,

;LED k CAMi j i jk k

i j i jk CAMLED i j

v vn W

v v

rIZ CAM rIv kLEDji _

,

CAMCAMji vv

,

kLEDkLEDji vv __

,

Assumption:

Then:

Using total K imagesVector field is given:

,1

,

,1

Kki j

ki j K

ki j

k

n

N

n

Solder Shape SOLjiZ ,

,, 1, , x

,, , 1 , y

( )

( )

SOLi jSOL SOL

i j i j i j

SOLi jSOL SOL

i j i j i j

ZZ Z N

x

ZZ Z N

y

These can be rewritten as:

;) (

;) (

y,1,,

x,,1,

jiSOLji

SOLji

jiSOL

jiSOLji

NZZ

NZZ

PCB Soldering Inspection

Simulated Results Simulated Results Experimental Setup Experimental Setup

Sample PCB board images

Board Image

Processing • Find Normal vector• Vector Field• Solder Height• Depth Map

Full Depth Map

Selected Area

Reconstructed Solder Shape