Specification_SIPLACE_F5_eng - 第25页

24 Description Various fiducial mark shapes prov e to be optimal depen ding on the condition of the sur face. In the case of bare copper sur- faces with li ttle oxidation, the si n- gle cross i s particula rly reco m- me…

Description

With the SIPLACE F

a number of

vision modules with a central vi-

sion system to evaluate the re-

corded image data ensure a high

placement accuracy.

At the machine’s X-gantry the PCB

vision module finds position off-

sets on the part of the PCB in the

conveyor system. This module is

also required to measure the ma-

chine and/or the feeders on one

side of the table. This vision mod-

ule consists of a single CCD cam-

era with integrated lighting and op-

tics.

The offsets in the position of the

PCBs are determined with the

help of at least two but generally

three reference fiducial marks on

the PCB. When the PCB arrives

the gantry with its PCB vision

module moves to the programmed

mark position. The vision system

compares the recorded video im-

age with the sample stored in the

PCB description.

With the help of the correlation

principle the vision system can de-

termine the correct position even

when fiducial marks are incom-

plete or damaged (actual struc-

tures). It does so by making com-

parisons with programmed

nominal structures. The mark con-

figurations are not fixed; they can

be taught without restriction.

Additional functions of the PCB vi-

sion module are recognition of the

position of the feeders and ce-

ramic substrate (optional) and re-

cording of the machine data in-

cluding mapping.

In addition, the bad board recogni-

tion unit is moved over “ink spots”

with the aid of the PCB vision

module.

Vision Sensor Technology:

PCB Vision Module

Technical Data

Reference marks

Local marks

Library memory

Recognition of poor panels

up to 3 (subpanels and multiple panels)

up to 2 per component

(may be of different type)

up to 255 types of reference marks

per subpanel

Image processing

Correlation principle based on

gray values

Illumination Front light

Recognition time

mark/ink spot 0.8 s

Camera’s field of view 5.7 x 5.7 mm

Correlation Principle

Target Low

Structure Correlation

Actual High

Structure Correlation

Description

Various fiducial mark shapes prove

to be optimal depending on the

condition of the surface.

In the case of bare copper sur-

faces with little oxidation, the sin-

gle cross is particularly recom-

mended because maximum

recognition reliability is achieved as

the result of the high information

content. Rectangle, square and

circle are less “informative”, but

save space, are rugged and can be

used even if oxidation is advanced.

In the case of tinned structures,

circle or square are recommended

because the ratio between fiducial

dimensions and presoldering thin-

ness is then particularly good.

Vision Sensor Technology:

PCB Position Recognition

Fiducial Mark Criteria

Determine 2 fiducials

Determine 3 fiducials

in addition

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

Shear, distortion in X- and Y-direction

Fiducial shapes

Freely definable via teaching, e.g.,

single cross, rectangle, square, circle

Fiducial surface:

Copper

Tin

Without oxidation and solder resist

Warp ≤ 1/10 of structure width, good

contrast with surroundings

Fiducial dimensions:

Single cross

Rectangle/square

Circle

Length and width: 0.9 - 2 mm

Stroke thickness: 0.3 - 1.0 mm

Edge length: 0.5 - 2 mm

Diameter: 0.5 - 2 mm

Fiducial surroundings

No clearance around the fiducial marks

necessary if there is no similar fiducial

structure within the search area

(5.7 x 5.7 mm).

Reference Fiducial

PCB Camera

Field of View

Fiducial to

be Located

Template

Window

Description

In the cluster technology each

subpanel is assigned an ink spot.

If this is present during the meas-

urement via the PCB vision mod-

ule, the corresponding subpanel is

not populated. Naturally it is also

possible to prevent the population

of the subpanel when the ink spot

is missing.

With this function it is possible to

prevent costs arising due to un-

necessary population of faulty

subpanels.

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f f

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eed

The pick-up position of the com-

ponent can be determined pre-

cisely with the aid of the position

recognition of the feeder. It is acti-

vated each time after a change of

feeder or component table. The

offset in position relative to the

stored ideal position is determined

on the basis of fiducials on the

feeder modules using the PCB vi-

sion module. This provides a very

high pick-up reliability even for the

very first component. This is par-

ticularly important with small com-

ponents.

Vision Sensor Technology:

Recognition of Faulty PCBs via Ink Spots

Position Recognition of Feeder

Ink Spot Criteria

Fiducial shapes

Single cross (recommended because

susceptibility to disruption lowest)

rectangle, square, circle, etc.

Masking material

Mat dark (light-absorbing)

Not recommended: white or shiny

Size or fiducial masking

Circular: Diameter ≥ 8.1 mm

Square: Edge length ≥ 5.7 mm

Fiducial recognition time

(travel > 100 mm)

Mark masked: 1.2 s

Mark not masked: 0.4 s