Specification SIPLACE CA-Series2011版 - 第41页

41 Vision Sensor Technology PCB Position Recognition Description Different fiducial shapes prove to be optim al depend- ing on the condition of the surface. Particularly advis- able for bare copp er surfaces with little …

Vision Sensor Technology

PCB Position Recognition

Technical data

PCB fiducials

Local fiducials

Library memory f.

recognition of bad

panels

up to 3 (subpanels and multiple pan-

els)

up to 6 for the Long board option

(Optional PCB fiducials are output by

the optimization.)

up to 2 per PCB (may be of different

type)

up to 255 fiducial types per subpanel

Image analysis Edge detection method (singular fea-

ture) based on grayscale values

Lighting method Front lighting

Fiducial recognition

time

0.1 s

Field of vision 5.78 x 5.78 mm

Camera's field of view

Pixel

Ink spot, e.g. square

Evaluation window

Singular Feature

Description

SIPLACE has a number of

vision modules and a central

vision system to evaluate the

recorded image data, ensur-

ing high placement accuracy.

The PCB vision module is

mounted on the machine's X

gantry. It is used to find the

PCB's positioning-offsets

within the conveyor system.

This vision module is also re-

quired to measure the ma-

chine origin and/or the feeder

module positions on one side

of the table.

Each vision module consists

of a single CCD camera with

integrated lighting and

optics. The offsets in the po-

sition of the PCBs are deter-

mined with the help of at

least two but generally three

reference fiducials on the

PCB. When the PCB arrives

at the placement area the po-

sitioning system with its PCB

vision module moves to the

programmed fiducial. The

edge detection method

allows you to choose pre-

defined fiducials from a

menu (e.g. cross, circle,

square).

The size of the fiducial is pro-

grammed at the station com-

puter. From this time on form

and size of the fiducial is de-

fined and known.

With this data the PCB vision

module is able to search and

recognize the fiducial at the

predefined position on the

PCB or ceramic substrate

without further assistance.

For this reason it places sev-

eral small evaluation win-

dows at the assumed border

of the fiducial. Within these

evaluation windows the vi-

sion system looks for con-

trast transitions between

bright and dark. After finding

such contrasts the actual

position of the fiducial can be

assigned by comparison with

the predefined - and thus

known - shape and size.

The analysis operations can

be used to determine any off-

set with respect to the de-

sired position in the X and Y

directions and the angular

position. Alternatively, a fidu-

cial may be taught as a pat-

tern.

Additional functions of the

PCB vision module include

recognition of the position of

the feeder modules and ce-

ramic substrate (optional)

and recording of the machine

data including mapping.

The bad board detector

(GOOD/SCRAP scan) is also

moved over the ink spot us-

ing the PCB vision module.

Vision Sensor Technology

PCB Position Recognition

Description

Different fiducial shapes

prove to be optimal depend-

ing on the condition of the

surface. Particularly advis-

able for bare copper surfaces

with little oxidation is the sin-

gle cross. Maximum accura-

cy is achieved due to the high

information content.

Rectangle, square and circle

are less "informative" but

save space and can even be

used when oxidation is at an

advanced stage.

Advisable for tinned struc-

tures are circle or square be-

cause in this case the ratio of

the fiducial dimensions to the

presolder thickness is partic-

ularly favorable.

Fiducial criteria

Locate 2 fiducials

Locate 3 fiducials

X-/Y-position, rotation angle, mean PCB distortion

Additional: shearing, distortion separately in X and Y direc-

tion

Fiducial shapes Synthetic fiducials: circle, cross, square, rectangle, diamond,

circular, square and rectangular contours, double cross

pattern: any

Fiducial surface:

copper

tin

Without oxidation and solder resist

Warpage  1/10 of structure width, good contrast to sur-

rounding area in each case

Dimensions of synthetical fiducials (standard)

Min. X/Y size for circle and rectangle: 0.25 mm

Min. X/Y size for annulus and rectangle: 0.3 mm

Min. X/Y size for cross: 0.3 mm

Min. X/Y size for double-cross: 0.5 mm

Min. X/Y size for rhombus: 0.35 mm

Min. frame width for annulus and rectangle: 0.1 mm

Min. bar width / bar distance for cross, double-cross: 0.1 mm

Max. X/Y size for all fiducial shapes: 3 mm

Max. bar width for cross, double-cross: 1.5 mm

Min. tolerances, general: 2% of nominal dimension

Max. tolerances, general: 20% of nominal dimension

Dimensions of patterns

min. size

max. size

0.5 mm

3 mm

Fiducial environment Clearance around reference fiducial not necessary if there is

no similar fiducial structure in the search area

Vision Sensor Technology

Bad Board Recognition

Position Recognition of Feeder Modules

Ink Spot Criteria

Methods • Synthetic fiducial recognition

method

• Mean grayscale value

• Histogram method

• Template matching

Shapes and sizes of fidu-

cials/structures for

synthetic fiducials

other methods

For dimensions of synthetic fidu-

cials, see page 41

min. 0.3 mm

max. 5 mm

Masking material good coverage

Recognition time depends on the method: 20 ms -

0.2s

Description

In the cluster technology

each subpanel is assigned

an ink spot. If this is present

during the measurement via

the PCB vision module, the

corresponding subpanel is

populated.

It is also possible to accom-

plish the population of the

subpanel when the ink spot

is missing. With this function

it is possible to eliminate

costs due to unnecessary

population of faulty subpan-

els.

Inkspot files can be imported

with the optional software

module "iSkip".

Global Ink Spot

Each GOOD/SCRAP scan

takes some time, and the

time required is even greater

if there are a large number of

panels on a PCB. The global

inkspot helps to significantly

reduce these secondary pro-

cessing times.

The PCB vision module

searches at positions taught

before for the defined fidu-

cial. In case of recognition

there is no following evalua-

tion of subpanels. The sys-

tem allows the operator to

also choose the reverse in-

terpretation.

Position recognition of

feeder modules

Position recognition helps to

precisely pinpoint the exact

pickup position of the compo-

nents. The offset in position

relative to the stored ideal

position is determined on the

basis of fiducials on the feed-

er modules using the PCB vi-

sion module. With 0201

components, the position de-

viation is determined by the

component pocket detection.

This ensures a very high

pickup reliability from the

very first component.