eja january 2002 1 abab dust level control in phototooling basics eric janssensjanuary 2002

EJA January 2002 1 ab

Dust Level Control

in Phototooling

Basics

Eric Janssens January 2002


What is dust ?

Any material particles

that may have a negative effect on their environment


Sources of dust

Natural dust

Cosmic dust from outer space

Eruption of volcano’s

Sand, stone ... due to erosion by wind and water

Seeds, pollen

Humans

Man generated dust

Exhaust by industry and traffic

Generated by any friction

Human body tissue: hair, skin particle, sweat, ….


Dust generated by the human body

Calling generates 20,000 particles

Coughing generates 600,000 particles

Sneezing generates 1,200,000 particles

A man looses 1 hair every 15 minutes

A man looses 15 grams of skin tissue every day


Dust generated by peoples action

Writing on paper 30µm particles

Folding paper 60µm particles

Rubbing on a painted surface 90µm particles

Rubbing metal on metal 100µm particles

Putting on a screw 100µm particles

…..

By moving man make dust particles air born


Dust particles - Size distribution

Air born dust particles range in size from 0 to +/- 50 m

There are many small particles and fewer larger ones

Remark: dust particles may conglomerate


Dust particles - Size distribution


Definition Clean Room Class

Clean room class x means:

one cubic feet of air contains x particles of 0,5 m or smaller


The importance of clean room conditions

As long as dust particles are relative small compared to the lines and spaces they don’t cause much trouble

Stricter demands for PCB fabricationEver decreasing line and space widthsStricter tolerances for lines and spaces and padsMore layersHigher yield

Today the size of an average dust particles is ¼ to ½ of an average L/S

Today dust particles cause more defects

and the defects are more expensive


Dust particles in PCB production

Dust particles jeopardise image formation:

Phototool generation

Dust on the film while plotting

Dust in the light path while plotting

Dust on the plotter drum (fly off, out focus)

Dust on the film while processing

Primary imaging

Secondary imaging

Dust particles scratch phototools and resist


Dust measurement

Measuring/counting tools

Particle size Measuring device 2 - 100 µm Filter > 20 µm Petri dish


Petri dish


Pert dish


Dust measurement

Measuring/counting tools

Particle size Measuring device 2 - 100 µm Filter > 20 µm Petri dish

0.5 - 30 µm Particle counters with light* 0.1 - 5 µm Particle counter with laser light*

* does not measure the heavier dust particles

Remark

The naked human eye can see: 50 µm particles under normal conditions 25 µm particles under ideal conditions


Dust measurement: take care

We are fighting an invisible enemy


PCB production anno 2000

To remain competitive in the PCB industry

production is to be done in clean room conditions

where the dust level is well controlled


Clean room: the compromise

A clean room has to be

build correctly

and

used correctly

Find a compromise

Quality of the installation versus installation cost

Discipline applied versus comfort


Clean room: how to organise

No paper or card board (paper is compressed dust)

Limit access of people

Limit access of materials

Avoid transportation from one compartment to another (install hatch)

No cutting or punching of film in the clean room

No knifes,no scissors, nail files, no pencils

No posters, no photos, no radio

Use clean room certified tools and equipment

discipline discipline discipline discipline discipline discipline discipline


Clean room: how to act

No paper or card board (paper is compressed dust)

Clean feet

Dress correctly (overall, hair cap, over shoes, gloves)

Never ever enter in “out side” clothing, not even for just a second

Never ever leave the clean room in clean room clothing

No brief cases, no handbags

No food, no drinks, no smoking

Move slowly and as little as possible

Keep films in vertical position, use (humidity tide) envelopes

Clean the film as often as needed



Clean room: maintain dust level

Golden rule

Prevent dust generation

(people, production process, environment)

Prevent dust from entering the clean room

Remove dust


Clean room: maintain dust level

Implement cleaning programme

per batch, shift, day, week, month

what to clean, how to clean

Remark: after cleaning the dust level is higher as before

vacuum cleaner out of the clean room

Replace mats

Replace filters

Wash clean room clothing in special washing machine



Clean room: SPC programme

Dust level at all relevant locations

Cleaning

Pressure over the filters

Air flows

.…



The ideal phototool lab

Shoeshine

Hatch

Filmstock

Changing room

OverallsHaircapGloversOver shoes

Check

RetouchLabelMeasure

Copy onto diazo

Laminate

Climitisefilm

+

+++

++++

+++

Chemistry supply

Plotter

+++++

Dust retainingmat

Hatch

Lock

Package

++

Processor


Dust level control at Agfa

Agfa’s commitment

Production in class 1,000

Cutting and packaging in class 5,000

Special PCB packaging

Film safe


PCB packaging


Film safe

790 mm x 680 mm: FROJN

1179 mm x 870 mm: FROFG

1690 mm x 1480 mm: FPMM3


Conclusion

Working in clean room conditions

is

producing with well-focused discipline

in a well-monitored environment

in order to control defects


Conclusion

Dust level control in the PCB industry

is a question of

common sense and discipline!

but

it makes the difference

between making or loosing money

eja january 2002 1 abab dust level control in phototooling basics eric janssensjanuary 2002

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