SIPLACE 80 F4_EN.pdf - 第31页

30 Description Various fac tors contribute to the placement a ccuracy of the SIPLACE 80 F 4 machine, e.g ., the stationary PCB during the place- ment process. As no acceler ations are acting on the placed compo- nents, t…

Description

The optional coplanarity check fur-

ther enhances placement reliabil-

ity. This check is always con-

ducted right after the deviation of

position is ascertained with the

Fine Pitch vision module of the

Pick & Place head.

The coplanarity module is installed

next to the PCB conveyor along

with the Fine Pitch vision module

of the Pick & Place head.

One of the biggest problems in

Fine Pitch technology, the copla-

narity of leads, can be largely

eliminated by taking one additional

step during inspection. The copla-

narity module is employed to con-

duct a contactless, sequential ver-

tical scanning of the IC lead

structure on the basis of the laser

triangulation principle. The height

profile thus obtained for all of the

rows of leads is used to calculate

placement plane of the IC. The

programmed tolerance band based

on this placement plane then be-

comes effective.

If even one lead is outside this

placement area, the component is

excluded from the placement pro-

cess. It is gently placed back in the

Waffle Pack, entered on the repair

list and automatically repaired.

The component picked up by the

placement head may be crooked,

e.g., because one surface of the

package is not parallel to the row

of leads. The calculation of the

placement eliminates any influ-

ence this might have on

placement however.

As the result of extensive security

measures, the laser can only be

operated in the closed machine. It

then conforms to Safety Class 1

(not dangerous for eyes and skin).

Barring manipulation of the protec-

tive devices, the laser will not op-

erate outside the machine. Fol-

lowing impermissible tampering,

the laser complies with Class B.

On SIPLACE placement systems

the component which is picked up

is placed on the PCB immediately

after the coplanarity check. This

procedure ensures that no change

can occur after the check as the

result of any subsequent mechani-

cal influence. Unlike other designs,

with SIPLACE machines it is not

necessary to pick up the compo-

nent again or to transport it in a

special pick-up movement.

Vision Sensor Technology:

Coplanarity Module for the Pick & Place Head (Option)

Effects of coplanarity (lateral ben-

ding of leads) of a populated com-

ponent

Accuracy of the coplanarity module

Uncertainty of checking in case of real components

Dimensions

99.73

[µm]*

32 x 32 mm

55 x 55 mm

21.5

22.7

* Checking uncertainty of a single measurement with a confidence interval of 99.73%

(corresponds to 3

)

Description

Various factors contribute to the

placement accuracy of the

SIPLACE 80 F

machine, e.g., the

stationary PCB during the place-

ment process. As no accelerations

are acting on the placed compo-

nents, their position continues un-

changed. The PCB moves in and

out at a coordinated speed which

is automatically reduced just be-

fore the nominal position is

reached.

A further guarantee for long-term

high placement accuracy is the

position recognition of the axes of

the gantry and placement head by

means of optical scanning by in-

cremental encoders. Revolving

star and segments of the revolver

head are positioned by means of

high-resolution glass incremental

panels. The X- and Y-axes are posi-

tioned with the help of the metal

scales on each gantry axis.

To determine the placement accu-

racy on SIPLACE machines, highly

precision glass components with

mounted structures are placed on

a dimensionally accurate glass

mapping plate. The results are sta-

tistically evaluated and presented

as a Gaussian standard distribu-

tion. In the case of the 12-nozzle

revolver head the placement accu-

racy is ± 90 µm at a statistical reli-

ability of 4 sigma. In other words,

of one million placed components,

60 are outside the specified toler-

ance (= 60 dpm). If the accuracy

value ± 90 µm is divided by the

sigma value 4, the result is the

standard deviation S of 1 sigma =

± 22.5 µm.

A machine capability analysis is

conducted for each machine ac-

ceptance test.

Machine Criteria:

Placement Accuracy

Technical Data Gantry

Drive DC servomotors

Position measuring system (X/Y) Linear scales

Resolution of X-/Y-axis 2.5 µm

Speed of X-axis max. 2 m/s

Speed of Y-axis max. 2.5 m/s

Accuracy

X-/Y- and D-axis offset in optical component and PCB centering

12-nozzle revolverhead

Angle accuracy

Placement accuracy

± 0.525° / 3 σ

± 0.70° / 4 σ

± 1.05° / 6 σ

± 67.5 µm/ 3 σ

± 90 µm/ 4 σ

± 135 µm/ 6 σ

Pick & Place-head

Angle accuracy

Placement accuracy

± 0.052° / 3 σ

± 0.07° / 4 σ

± 0.105° / 6 σ

± 37.5 µm/ 3 σ

± 50 µm/ 4 σ

±75 µm/ 6 σ

Standard Deviation - dpm

-4

-3

-2

σσ

2700 dpm

60 dpm

P Point of Inflection

Description

t t

t R

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lili

lia

bili

iliili

ilit

Aside from correct positioning,

placement reliability also means a

gentle handling of the compo-

nents, so that these can be sol-

dered well later. Rework is mini-

mized or eliminated as a result.

On the SIPLACE 80 F

among

others this is ensured through a

number of control functions, e.g.,

the vacuum checks and compo-

nent vision test during the revolver

head sequence.

Unsuitable components are re-

jected, placed on the repair list and

automatically processed during a

repair cycle. An offset in the posi-

tion of the PCB relative to the con-

veyor system (PCB vision) and an

offset of the X-axis, Y-axis or rota-

tion of the component relative to

the midpoint of the nozzle (com-

ponent vision) trigger an immedi-

ate correction and thus placement

accuracy.

Thanks to the motionless PCB the

components remain in the exact

position they were placed. The

stationary component table pro-

tects, for example, the compo-

nents in Bulk Cases against dam-

age such as may occur due to

vibrations which are inevitable with

other placement concepts. Op-

tional add-on products ensure fur-

ther reliability: With the aid of the

component bar code scanner, the

correct placement program is

automatically sent to the station.

-u

p p

p e

All errors which occur between the

time the component is picked up

and the time it is placed on the

PCB are pick-up errors. They in-

clude:

No component in the tape

Component cannot be removed

from the tape.

Vacuum error

Vision error due to faulty com-

ponent

Vision error due to unrecognized

component

t t

t e

Errors which occur after the com-

ponent has been placed on the

PCB. They include:

Rotation error

Too many components on PCB

X/Y-offset

t t

t S

When used alone on the SIPLACE

80 F

the 12-nozzle revolver head

achieves a benchmark placement

rate of 10,000 components per

hour (cph). The Pick & Place head

places at a max. speed of 1,800

cph. These benchmark rates can

be verified on the demonstration

PCB at Siemens.

Factors such as PCB size, number

of components per board and their

layout have a certain effect on the

speed in actual practice. The

placement speed in practice can

be predicted using a calculation

program.

Machine Criteria:

Placement Reliability and Placement Speed

Placement Principle SIPLACE 80 F

Pick & Place Head

PCB Transport

Direction

Revolver Head

X/Y-Gantry

System

Fixed PCB

Fixed Component